Vacuum System

[stockbub]

OK, I have read a ton about the fein setup for vacuum holddown, but have a question, what is the science behind how the hold down works? Whast does the CFM matter? What about the mercury or whatever they call it? Would 2 regenerative pumps say 1 1/2hp work better then 2 feins. I will be cutting 3/4" plywood primarily and if possible would like to do it in one stroke.

[Brady Watson]

Buy the 2 Feins and be done with it. They are industrial vacuums that are made to run and run. Many of us (myself included) have used these for years with zero problems...I have run these sometimes for 20+ hrs straight.

In terms of performance, you will pull approximately 7" Hg and 280 CFM. These numbers can be misleading, but essentially they are inversely proportional to each other.

As far as a regen goes, you will be hard pressed to find one cheaper than the Fein with the same or better performance. The Feins are a proven setup.

-B

[richards]

Martin,
Your qualifier about cutting plywood - in one stroke - might eliminate the Fein vacuums. Also, what is the altitude of your shop? I'm at about 4,500 ft. My two Feins will not flatten a sheet of warped baltic birch. I've given up trying to cut anything in once pass. My standard method of cutting is to always leave a skin (0.020 to 0.050 inches thick) and then trim off the skin with a laminate trimmer or at the router table.

At this altitude, the two Feins will pull about 5: of mercury.

There is one condition that the Feins allow me to cut material in one pass. If I use a cut mask sealed off with AlL*Star tape, I can normally cut particle board, MDF and melamine coated particle board in one pass - if the parts are at least 100 square inches or so.

As Brady pointed out, if the choice is between two Fein vacuums and two 1-1/2 hp regenerative pumps, the Fein vacuums would be my choice. On the other hand, if you can find a 15 to 20 hp pump/blower, that would give about 15 inches of mercury while allowing a high air flow through the spoil board, then you would have something that could flatten a piece of plywood and allow one-pass cutting.

In my case, my small shop doesn't warrant a big hp blower. I just don't have room to stack fifty to one-hundred sheets of material, much less the parts that would be cut from fifty to one-hundred sheets of material - so getting the greatest efficiency out of my machine is not as important as it would be for a shop where per-sheet cycle times has to be in the sub-five minute range. Also, I am a one-man shop, so I'm not paying someone else to handle the material multiple times - I just force my old weary bones to act like they still have a little life left in them.

So, in my case, two Fein vacuums meet my needs. In fact, in most cases, I only use one of the two Fein vacuums. When I have to cut smaller parts and when I have to cut things in one pass, I make up a cut mask, apply some All*Star tape to eliminate leaks and then either use the Feins or my GAST 3/4 hp vacuum. (The GAST or a GAST-like vacuum, even a much smaller unit, will easily hold any non-porous material - if you eliminate air flow/leaks. My GAST pulls more than 20-inches of mercury. When I cut plaques from MDF, which leaks too much, I either seal the MDF with paint or shellac, or use shelf-paper to eliminate air flow through the MDF.)

[stockbub]

I live in Texas and my new bot will be here in 2 weeks. I am near the coast so I do not think elevation will be as big of a deal to me as it is to you. The pumps a friend of mine is looking at will be around $1600 for both 1 1/2hp blowers. With all the talk, I thought about getting 3 fein, but I did not know if you get to the point of too much with no benefit. I could cut in 2 passes if needed, although I have to still figure all that stuff out, but I will still have to cut all the way through. On a smaller piece say 8"x20" do you have enough power to hold it in place? THis would be for carving an onlay out of wood? I saw a post about an F16 with dble manifold. Would 2 or 3 feins pulling from a 2 x 4 area of a table hold the onlay piece that I mentioned above? I have room in my shop. Typically, I use around 15 sheets a day. Most plywood is 7 or 13 ply. MDF cuts that I do will mostly be for templets. I think brady is the botter who made his grid on the back of his spolier board? Is this better, especially if you are needing to only replace oneor so of your grids?How do you seal it where grid meets grid?

Thanks
Bubba

[rick_d]

I am trying another option mentioned on a previous thread. It is a vacuum pump from Grainger that seems to have better performance than the Fein. It is supposed to pull over 10" of mercury and blow 102 CFM. The cost is $258.00 . I bought mine a couple weeks ago and found it only pulled about 7"Hg but the factory rep I talked to felt the pump must be a defective one and we are going to try another one.
You will have to build an enclosure to house it in, its basically like a shopvac without the tank, but thats no big deal for anyone with a shopbot!
If I get the claimed performance out of the next one, I may install a second one to get better cfm which is what you need to pull a sheet flat or to maintain holding power once you cut through your material.
None of these systems will work well if you are going to cut through your workpiece. They simply don't have the power. If you are wanting to cut through plywood in one pass, you need to start looking at good old horse power, and I'm thinking over 10! Now you are talking 3phase power supply and thousands of dollars. The cost of production.
For the rest of us, we use tricks like onion skin, tabs, and gasketing with our relatively low power vacuums. And it works pretty well. Others do well with clamps screws and nails. Find what works for you and don't worry about what someone else thinks is the perfect answer. There isn't one.
Just my opinion.

Good Luck
Rick

PS Here is a link to the blower I bought;
http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611764155&ccitem=

[robert_cheal]

Rick,

One question about the Granger vacuum how is the noise level? The Fein is said to be very quiet but I like the idea of the Granger vacuum.

Thanks,
Robert

[rick_d]

Robert,

I haven't used a Fein, but I'd say this compares with a normal Shopvac. I wouldn't call it quiet at all, but with my dust collector and Porter Cable router running on my bot, I'm already wearing earplugs! If I can ever afford to move up to a spindle I will move the dust collector and the vacuum outside, but until then a quiet shop is just a fantasy!

Rick

[Brady Watson]

Rick,
The Fein does not compare to a 'regular' ShopVac. It offers approximately 2 times the suction to my large Ridgid shopvac and it is only 58 decibels compared to at least 70 dba with the Ridgid.

The Porter Cable is LOUD compared to a spindle, and the dust collector is most definately louder than 2 Feins.

-B

[patricktoomey]

Brady, I have an older model Fein and a Rigid shopvac. The shopvac pulls more vacuum (5") than the fein (4.5") so I'm thinking I need to get a newer Fein. What model are you running? I'm not even sure what model mine is but it's probably from the early 90's It is quiet and it runs very cool but I need to upgrade to something with more static pressure.

[danhamm]

Here..in canada..the Fein cost over 500.00 for whatever reason..way above the exchange rate diff.
So it makes one look to different "offerings" I have been using a builtin vac sys..for awhile, when ..R.Ball..started using 4 "shopvacs" I tried a 3hp..that I had in the garage..and started learning about shopvacs..I found I could make it run cooler..by relieving the vac impeller, by drilling holes..and without comprimising suction..also found that I could improve the suction by closing the clearences..between impeller and the suction housing..but the housing is plastic..and heat is generated..so end of story...getting bac to my..builtin..it supposedly has 140 "vacuum (H20 sealed)..I cut a fair amount of Melamine for a local shop..and onion skinning is out as it leaves a bad edge that is easly chipped just from handling..so I made a spoilboard of cheap melamine one side...particul board..with 90 degree vbit cuts ..3/4 of the way through and then drilled with 1/16 bit the rest...the logic is it provides more direct suction..but also provides a tapered hole for the cuttings to shut off the path...and maintain the vacuum..it works
untill you get down to the really small part sizes ..cheers...Dan

[paco]

Dan, I bought my Fein T III from Woodcraft and saved a bunch of dollars. They shipped the box for little less than 20.00$usd through postal, customs are very low. I did took about 2 weeks to get here though...

[danhamm]

I think I'll stay with what I have for the time being..
According to the spec's I have found..Fein= 99in.w.c. shop vac + 60in w.c that Grainger blower Motor was 140 in. w.c. my Builtin vac..is 140 in w.c it is also 230 volt and I have outside..but lose a little in the piping...I can see it flex..when I put a 4x8 piece on the table..Thinking back...I used to have a Drilling Bussiness..Gopher Drilling services..was the name of it sold it in 1995..and retired..bought a ULS Laser..and started Burning Impressions..was fun..but I had a Screw Compressor on the one of the drill rigs..750/350 750 cfm/350 PSI..it collasped the suction line one winter as ice had built up in it..1/4in. steel line 8in. dia..Now this is aimed at "Brady" I think it was you that made a water pump for a outdated Vehichle..How about designing a 3 stage alum..housing for 3 stainless 10 in.impellers..about 7 hp..worth..cheers..Dan

[Brady Watson]

Patrick,
What is the model number of the Fein in question? Has it had the snot beat out of it and used pick up dust and debris? As a general rule, you don't use the Fein as a shopvac...It is ONLY for vacuum hold down and nothing else! When someone talks about using a Fein vac, they are talking about the 9-77-25 Turbo III unit, which is more powerful than the Turbo I or II. This is an important little tidbit of info for those looking to buy one. You only want the Turbo III.

Martin,
To answer your 2nd question (since it is your post), you will want to make an accessory vacuum plenum that you can plug the Fein into for those small parts OR devise a system of gaskets/masks that direct the vacuum under that 8X20" area. Practically speaking, you can't have too much vacuum. Have a look at my web column for hints & examples.

In terms of using vacuum motors from Granger etc...Yes, that is a good alternative. I am currently working on a setup that uses multiple vacuum motors to allow either 9" Hg and 200 CFM OR 15" Hg and 100 CFM. Turn a few knobs and you can switch between either 'mode'. This is something that I am going to feature in a vacuum video in the (hopefully) near future. It is not too far off some of the $6000+ vacuum setups in terms of performance, AND it can be built for the same price as a single Fein...I've been working on this setup for about a year off & on...Details when they develop.

-B

[danhamm]

Series..or parallel valve switching sounds like to me..thas funny...I know someone else that is playing with it..cheers...Dan

[donchapman]

I'm doing fine with my Fein vacuum hold down using one small Fein model 9.11.20 I got from Woodcraft in a closeout sale for about $150 last spring. It pulls only 78" water which is about 5.7" mercury (Hg) and has held everything I've needed it to hold from 4x8 sheets of MDF to 10"x4"x1/2" pieces of solid oak.
It's been running an average of 8hrs/day for the past 14 days holding down 1" Finland Birch plywood pieces from 1-4 square feet for several hours at a time. My minimalist vacuum hold down system which cost less than $300 makes me think most vacuum systems are overkill, at least for my budget.

[stockbub]

What is the difference in HG and CFM? Which one is more important? Which one does the majority of holding? I was listening to the Shopbot video last night, is that your voice brady? If so, do you think I can get an autographed copy of the cd?

[richards]

Martin,
The inches of mercury (HG) is the important rating for hold down. The CFM is mostly a rating of 'how fast' the vacuum can evacuate air in order to create a vacuum. (That's not exactly right, because the Fein and large vacuums - in general - work on the principle that they will be able to hold down the material even when part of the spoil board is uncovered.)

My 3/4-hp GAST vacuum does a much superior job of holding down material with its 20+ inches of mercury than my two Fein vacuums; however, if the smallest leak occurs, the GAST quickly looses all vacuum and the part pops loose. On the other hand, the Fein vacuum(s) with only 5" of mercury at my altitude, can often hold a large sheet of material securely even when half of the table is uncovered. (It works better if I lay down some plastic or scraps of material to cover all of the table - but often I just turn on the vacuum, give the part a hard shove and if it stays in place, I start cutting.)

So, in a nutshell, if a vacuum is rated to hold 13 inches of mercury while passing 200 cfm, that means it will hold about anything through a spoil board without exotic masking. If a vacuum is rated at 20" of mercury OR 10 CFM (like my GAST), it means that it will have an incredible amount of holding power as long as there is NO leakage. If a vacuum is rated at 100" of water OR 100 CFM (which, I believe) is the rating of the Fein), it will have moderate holding power and still be able to sustain SOME leakage through the spoil board.

[Brady Watson]

Martin,
Yes that is my voice on the CD...somebody's gotta narrate it! Send it to me and I'll autograph it for you.


I'll add and paraphrase a litte to Mike's excellent explanation. In the context of using vacuum suction for workpiece/material holding on a CNC machine, both CFM or airflow, and sucking power rated in inches of mercury (Hg) or inches of water are equally important.

First, a vacuum device must have enough airflow to quickly evacuate a vacuum chamber. This is the 1st area where CFM is important. In our case, it must get all of the air out of the vacuum grid and as it does this, it starts pulling the material tight to the bleeder board. Provided that there are a minimum of leaks, as the vacuum evacuates the vacuum chamber, it starts to suck the material down with greater force. Actual airflow past the vacuum motor decreases AS vacuum suction or Hg" increases. The suction will increase until the vacuum reaches it's maximum suction capacity, providing that air does not leak out of the plenum, hoses or any other part of the system. It is *very* difficult to achieve a 100% leak-free system as Hg" increases. The CFM plays an important role in helping the system 'self-seal' against the bleeder or gasketing if you are using any. Low CFM/high Hg" pumps struggle or fail in all but the most leak free setups.

So you have your Fein vac(s) holding down a full sheet of 4X8 plywood and you zero out the tool and start cutting. One thing you want to really think about here is chipload, and ultimately the amount of force that the bit is going to exert on the workpiece. This is not as much of a concern if you are not cutting all the way thru the parts to the bleeder, as the vacuum suction will be maintained. But...if you cut all the way thru the sheet like I do, you really want to pay attention to how many 'open kerfs' you have as vacuum will start leaking out in these areas. This is the 2nd area where CFM is important. The greater the CFM rating, the greater the vacuum's ability to absorb those leaks and maintain a good working level of suction. Just because you have a vacuum system, doesn't rule out that you may have to suppliment the vacuum with strategicly placed screws, tabs/bridges or both. It depends greatly on the shape and number of open kerfs in the sheet layout. Tool geometry is also important. An upcut spiral will fight against the vacuum and exert more vibration into the mix than a straight tool will. Experiementing with different tooling will pay off.

The actual theory of vacuum as it relates to CNC work holding is essentially this: The vacuum device evacutates air UNDER the workpiece. As it does this, it is essentially allowing the entire column of air from your material on top ALL THE WAY UP TO THE EDGES OF SPACE...to get 'shifted down' and apply pressure to the top side of your material. In a perfect vacuum (29.92" Hg), there is 1 Atmosphere or 14.7 PSI of pressure PER square inch of force on the top of your workpiece. Since none of us have the loot for a 29"Hg+ pump that moves 1,000 CFM, we'll have to use what we can afford. I'll use a single Fein as an example. A 9-77-25 Fein T3 pulls down a 4X8 sheet of plywood. It is rated at 126 CFM (at zero Hg") and 7.3" Hg (at zero CFM). Let's say we have a perfect system with NO leakage. To calculate the actual force being applied per square inch, we need to do a little math. Our vacuum max Hg" / perfect vacuum Hg" X max vacuum force in PSI (with perfect vacuum) = OUR psi

So...it breaks down like this: 7.3"Hg / 29.92"Hg X 14.7 psi = 3.6 psi

This means that the total force being applied with perfect vacuum on our 4X8 is an astonishing (48" X 96" X 3.6psi) 16,588 POUNDS of force over the entire piece! To bring this number down to earth a little, that equates to roughly 518 pounds of force per square foot with our single Fein Turbo III vac running full bore with no leakage. (why hasn't our table crushed under the weight? Because for every force there is an equal & opoosite amount of force. This force also pushes up against the table cancelling out the force of the vacuum...it gets complicated...anyway) As we start to cut all the way thru the material, leakage occurs. Vacuum suction or psi force on the top of our material begins to decrease from that 518# number and vacuum CFM begins to take on an important role of helping the vacuum to maintain decent pressure/suction while this is happening. If leakage becomes too great, holding power suffers and parts will move as our inversely proportional vacuum scale starts sliding down from 0 CFM and 7.3" Hg to 126 CFM and 0" Hg. This is where a second Fein would help to cope with the vacuum bleed off and maintain suction by doubling CFM. (just using this as an example could be brand XYZ) With 2 Feins, you would have @ 250 CFM, but still the same 7.3"Hg max suction power. The 3.6 psi of force that they exert is more than adequate for most materials that you cut on a CNC router. Only when you get into severely warped or irregular panels (and very small parts that require gasketing) do you have the need for higher Hg". The Fein has an excellent balance between CFM and Hg", and it's this proportion that is what to look for when considering a suitable vacuum device. As a side note, keep in mind that if you implement a weaker vacuum next to a stronger vacuum, that there will come a point where the stronger vacuum beings leak thru the weaker vac's housing, limiting your max Hg" suction power. If you ran a Fein with 7.3"Hg and a regular ShopVac with 3.5"Hg, your highest Hg" would be 3.5"Hg...so be careful not to do this. There are a few tricks to get around this, but I'll save that for another time.

One more thing I want to add...a high Hg"/low CFM vacuum device, such as the 27"Hg+, 4CFM Gast pump that I have are NOT suitable for CNC work holding UNLESS you are cutting non-porous materials like plastic, AND you have employed suitable gasketing. These pumps are very hard to get 'over the hump' and evacute the air from underneath the workpiece without solid gasketing. They DO work once you have eliminated leaks, and are excellent when you need to hold small parts using a dedicated vacuum fixture. I have a small fixture for doing lithophanes and this works quite well. However, trying to use this setup with a conventional bleeder board cutting plastic is futile, as the pump cannot evacuate the air fast enough to seal it's own system.

All of that was a mouthful & a 1/2...but I hope that it took some of the mystery out of vacuum systems for some of you.

-B

[stockbub]

Actually it all makes a lot more sense and surprisingly my thougths were on line with the physics of what was taking place. That was the reason for 2 or 3 fein pumps or 2 feins and a small VP (Still under $6000.00). As I cut through the plywood, openings start and the air leaks. THe more cabinet parts cut from a sheet the more openings, where the additional vac could come in handy. No matter what these vacs will only pull a max of 7.3 hg (perfect no leaks. Which is why I thought of the VP. REmove air with the Feins and then increase holding with the VP. Another downside of the table I purchased (5x8) is that 1 x 8 of the table will be open and increases the possibiliteis of leaks. Will put that on a different zone and keep it shut off most of the time. My arverage (smalles part will be1' by 3' for upper cabinet side. Bottoms could be smaller. and I did not know id brace pieces, usually 1 1/4" by leangth of cabinet could be heald, but I can always bring those to table saw. I guess what makes the single phase roots so good is the ability to suck air out and the the 14 HG of preassure for holding. My overall thoguth was to get to that point. I know that it is not practical to think that I will get things set up right the first time, but I really really want to get close and that is where everyone else experences comes in.

[gene]

Martin, I think you are on the right track . I have a 7.5 single ph on a alpha 4x8 and it does good for what i do. That being said i think that a lot of people are not understanding the concept of vac holddown . I thought by spending the $ on the roots blower it would solve all my holding problems ( WRONG ) your holddown devise should match the part being held. If i am cutting 4 x 8 sheets then yes crank up the blower, but if i am cutting bird house fronts then a jig and a fein vac works so much better, not to mention quieter. If you are cutting small parts then a jig or puck with a fein is the way to go. Dont think if you buy the blower you can just throw a small part on the table and its going to stay there, NOT Match the part to the job. after all you dont use an 8 lb hammer to put up trim. sometimes if i am cutting a 1/2 sheet i close off 1/2 of the table with the valves but you will be supprised at how much vac is lost thru the sides so i lay a scrap piece of wood beside the good to help prevent the vac loss. hope this tid bit helps someone

[Brady Watson]

Gene,
"... Dont think if you buy the blower you can just throw a small part on the table and its going to stay there..."

Very good. I am suprised by the number of people that never grasp this concept.

-B

[harryball]

Questions first, what do you use to connect to the vacuum manifold? i.e. I don't want to use the full vac hose and I don't want to cut it up. What shorter hose have you found that will plug into the front of the fein?

Next, where do I get a vacuum gauge and which one? HD doesn't seem to carry those.

My twin fein setup is all installed. I replaced the 4 shopvac heads due to noise levels and finally my cash level reached enough to get the feins. I gave $300 each for turbo III's.

Now that they are installed I can hear vacuum loss and track them down :-) I would say the table is now 99% vac sealed. I pressure fitted all the PVC and taped the joints. I've used a quart of shellac and the zones are lined with double back tape and the bleeder board applied. I can route both vacs to any single zone.

I read Brady's post this morning and realized I'd done the practical experiment.

With the full table on I have less airflow but "seem" to have more suction. I have a specific test sheet of potato chip board. With the 4 shop vac heads it would quickly snap to the table with just a little weight but with only a little pressure I could relift it. When I first tried to pull this sheet down with the twin feins, I had to really push on it and hold it to the table... however, as soon as the pitch changed and the feins took hold it went flat. It takes considerably more force to relift it from the table. Once the relift starts and the vac breaks it pops up from the table all the way, previously it would not peel as far back.

This was not unexpected, the feins pull about 280 cfm on the entire table, but the shop vacs pulled 400 cfm or more (440 cfm if you believe the posted numbers). However, the shop vacs pull about 4" of vac with the feins pulling 7" or more.

Working with one zone is a different story. With both feins pulling one zone I have 280cfm + 7" vac instead of 110 + 4" vac. When placing a 1/4 sheet over that zone... SNAP and you are not moving it.

Of course, I'm not factoring in lost cfm due to piping resistance. That's one reason I want a shorter connection from the vac to the manifold instead of a 10' winding hose.

The sound reduction, even over the shopvacs in their enclosures, is impressive. I'll start real cutting this week with the new setup.

Robert

[rick_d]

I bought a nice oil filled vacuum gauge from Grainger for about 30 bucks, but the problem I have is that I can't see it easily from anywhere in the shop. So I came up with an idea of using a length of clear rigid tubing stuck in a reservoir of colored water and connecting a vacuum line from my table plenum to the top of the tube.
I haven't actually tried it yet, but I think it will work slick! It also occurred to me that if I could determine the minimum safe amount of vacuum required, I could install some sort of a switch at that point on the tube that would act as a stop switch.
My biggest problem is that if I can get the advertized 145" H2O out of this blower, my shop ceiling is only 120"!

[Brady Watson]

Robert,
I just keep the Fein hose on the vacuum and either plug it in my 2.27" vac jig intake hole or use a rubber pipe connector to attach it to rigid PVC. I sincerely doubt that you are going to lose any noticeable airflow between using the factory hose and rough inside cast PVC pipe...It would be one thing if it were being used on an intake manifold on a racing engine...

You can get a vacuum gauge at any auto store. I got mine from www.summitracing.com (http://www.summitracing.com)

Where did you buy the Fein T3 for $300?!!

-B

[gene]

Rick,
Drill a hole in the ceiling and install a chimney pipe. ( just picking ) That sounds like a good idea. If you loose vac the machine shuts off , Why couldnt you use an air flow switch in the line that if too much air is passing thru the line it would flip a switch and kill the machine

[rick_d]

Sounds like an airflow switch would work, but I don't know anything about them. It would be cool if they were adjustable so you could set your threshold to suit the application.
The main problem that I have trouble with is when I am cutting a sheet that has a little bow in it and it breaks the seal during a cut because of all the through cuts dropping the vacuum level. Its tricky to know where that critical level is going to be because there are so many variables but I think it would be nice if the machine would stop before you lose vacuum and ruin a piece.

[rick_d]

Brady, I did a quick search and found a Fein III for $289.99 on Amazon.com

http://www0.epinions.com/Fein_9_77_25_Turbo_III_Portable_Vacuum_Shop_Tools/display_~latest_prices

[Brady Watson]

"The main problem that I have trouble with is when I am cutting a sheet that has a little bow in it and it breaks the seal during a cut because of all the through cuts dropping the vacuum level."

Just put a couple of screws in the sheet. This will help to keep it down. To be sure that your bit isn't going to run into the screw(s), program drilling holes in PW and make a drilling toolpath.

-B

[Brady Watson]

Rick,
If you actually follow the link all the way thru, it is $349, as it has been for a while now. The epinions page must be old.

-B

[rick_d]

Do you screw through your bleeder board into your table? My half inch bleeder board doesn't have much holding power for screws.

[rick_d]

Brady, You're right about that Fein price, I'll keep looking for a better deal!

[Brady Watson]

Rick,
Yes & No. I use a removeable Trupan bleeder of my own design. I can take it off the spoilboard if I want, OR just screw right thru it and into my spoilboard residing below.

-B

[harryball]

Brady, I picked the feins up at the Atlanta Woodworking show last weekend. Kentec was there and had 2 damaged boxes. As I had no interest in using the box for anything... we reached an agreement :-) The guys there were great. What sold me was NOT hearing it running when I walked up... I had no idea the demo was on until I put my hand over the hose.

We were some of the first people to walk through the door Friday. I also purchased a delta lathe 46-715 for $299. I returned the last day of the show, last few hours and picked up a few other good deals.

I learned from being in trade shows the best times to make deals is being there as the show opens and as it closes. I bought my shopbot the first day of the IWF... if I'd waited until later that day or the next I feel it would have been sold already.

Robert

[Brady Watson]

Robert,
You certainly got a GOOD deal!!!

-B

[harryball]

I feel like I got a VERY GOOD deal!

Do any of you use a lathe? This is addictive, I enjoy it almost as much as the bot... now I'm looking at the indexer. Funny thing is, my wife actually bought the lathe. She has wanted to turn pens for several years and finally decided I'd never buy her a lathe so she got the good deal on it. I can't sit here and let her have all the fun!

Back on topic, Brady, you don't think the hose will cost some cfm? I don't have a way to test cfm but I know there is a formula for calculating cfm loss from Oneida for their dust collector. The loss is much higher for flex hose than for smooth duct work. I had it in my mind to eliminate as much flex hose as possible. I even used street 90's and Y's for the PVC in my design. These are the ones for drainage, long turns, fewer joints etc...

Probably overkill, but it can't hurt.

Robert

[gene]

Rick
When i have a bowed sheet i will screw thru into the table to help hold it down. Make sure that you do a drill screw location in pw first so the screw dont get cut . every so often you replace the spoilboard co i dont feel that running a small drywall screw thru it will hurt much. Besides its about getting good useable parts anyway. Good luck

[Brady Watson]

Robert,
A dust collector suited for the type of work that we do moves about 1200 CFM. That much air moving thru ribbed tubing, bends, 90's and other connections not perfectly smooth, can affect airflow when you are moving that much air. When it comes to a vacuum system, yes...you may sacrifice a few CFM when the vacuum level is at ZERO Hg", but once vacuum starts building, the airflow goes way down, as well as the air's velocity and bends are not an issue.

-B

[beacon14]

Robert,

I had an old shop-vac, pretty sure it was a Craftsman, going bad at about the same time I was trying to hook up my Feins to my new table. It had a flexible 2 1/2" hose that was almost smooth on the inside and outside. Well the hose ends fit perfectly into the Fein inlets, so I cut the hose in half and what do you know, the hose fits perfectly into the 2" PVC fittings. It's a nice, snug fit.

I did a search on the Sears.com web site under shop vac hose and came up with a few options but the photos are not clear enough to say for sure whether it's the exact same hose. I'm not even 100% sure it was a Craftsman vac. But I'm thinking it's a standard 2 1/2" shop vac hose, so it might be worth the $20 or so to try one.


7110

[harryball]

First... blue painters tape is air tight, white masking tape is not.

David, your setup looks great. I couldn't get any of my shop vac hoses to fit into the feins I have. They go in about 1/4" and won't go any further. Did you glue all your PVC joints?

I'm still not completely happy with the performance. I hope it's getting air from somewhere, that means I can fix it. I discovered that the plastic molded part for the hose where the black meets the orange leaks air on both feins. I taped that up.

Before I do anymore I'm going to get a vac guage of some kind and check full vac on each zone and go from there.

The issue is I just don't have enough airflow to keep a full sheet on the table. The table is fully surfaced and the same as with the shop vac heads. The plywood is 1/2" ACX and as flat as it comes. It raises less than 1/4" on one side and easily presses to the table.

In my previous test the situation I was using the open grid, no bleeder board, just doing a comparison. As I mentioned, once the vac breaks the board more easily come off the table than before. With the bleeder installed it's just not holding down the sheet as well. It takes a little effort but once an gap occurs, even the size of a fingernail... the vac is gone and the board is free.

Like I said, need to get a gauge and work the problem.

Robert

[Brady Watson]

Robert,
You can use a rubber/hose clamped adapter from the plumbing dept. to securely plug the hose into 2" PVC. The connection will be air tight.

The plywood should be put on the table crown UP. On some boards it is hard to tell which side is better. Put one side down and pull vacuum. If it is not tight, flip it and try it again. ACX is a bugger any way you slice it. If your vacuum grid is not machined close to the edges, then you will not get vacuum pull at the edge. I pushed my grid out to 1/2" all the way around and sealed the edges. The default SB grid pattern leaves a good 1-1.5" border around the grid. It needs to be moved out a bit.

Run DUCT tape around the entire edge & periemter of the bleeder, especially where the bleeder meets the spoilboard/table base board. Painters tape doesn't have an aggressive enough adhesive to be reliable. Look underneath the table for holes from you drilling/screwing thru the table. Cover them up or fill them.

-B

[harryball]

Thanks Brady, I'll have to increase my vac table grid. As for the ACX... the outside is the A side and has to go down with all the machining on the inside. I've never had a problem getting the A side to stick with the 4 heads running so I'm hoping I find an issue somewhere to fix. Once I get the vac gauge in I should have a very good idea when things are and are not working.

I have a big roll of duct tape ready to go.

What do you do when you place a 4x8 sheet on a 49x97 table top? I've been using tape to cover the exposed edge on one side. It so happens the edge that lifts is on the inset side of the spoil board by 1" I have blue tape over it now, going to change to duct tape and see if that helps.

well... going to drink some hot tea, each some lunch, take a nap then get back to work.

Robert

[Brady Watson]

Robert,
You can also use foil tape to 'edge band' the bleeder. You *should* have enough CFM to overcome that little gap of air around the perimeter. Heck...I cut ACX with ONE Fein...you've got 2!

You have each Fein going into it's own zone, right? You may have issues running 2 thru a Y pipe if it is only 2" PVC.

-B

[harryball]

Each vac drive a manifold, all 4 zones are connected to each manifold with valves, 8 valves total.

Here it is, not as pretty as some other folks...


7111

The vac plenum is sealed with several coats of shellac and double sided tape is around the outside of each zone.

The sheet good is shifted to the X=0 and Y=49 side of the table. The slight lift issue is on the Y=0 side.

I've tried running with all zones open and with both zones open on the Y=0 side.

Brady... from what I've seen with the shopvac heads I should be able to pull this sheet down along the suspect side and hold it because my setup is much the same, one vac per zone. The difference is the piping... I can't hear significant vacuum escaping. (Local supply for vac gauge didn't pan out, going to have to order one)

Must be the phase of the moon, pulling the sheet off the table too hard.

Robert

[Brady Watson]

Robert,
I'm looking at your grid and it looks like there isn't any vacuum getting to the Y0 - Y2.5 area at all...you might want to machine another grid or two in the front. This is keeping your edges from pulling down...Also, where is your bleeder? The bleeder (ideally 1/2 or 3/4" double skinned Trupan) really makes a big difference in keeping the vacuum in the plenum. It serves as a medium to slow down the velocity of any air that might escape and helps to distribute the vacuum better.

The manifolds look real purdy


-B

[davidallen]

One way to track down vacuum leaks is to clamp a board down to the table then blow air into the system. You can feel air escaping easier than a vacuum leak.

If you can find a smoke generator, fill the plenum before pressurizing it and you might be able to see the leaks.

da

[steve4460]

Nice pictures of the manifolds, but where is the purpull primer ?.that you need to glue the pips together so that the glue works right .

bot on

sv

[patricktoomey]

Robert, maybe I missed it above but what is the thickness of your spoilboard after surfacing both sides? I've noticed that if I just take the skin off of 3/4 Trupan on both sides, the sheet is still too thick to allow enough airflow to pull down warped sheets. By taking it down to a little under 1/2 inch thick it starts pulling down sheets better. Once they're stuck down either thickness works fine but the thinner my spoilboards get the better warp handling I seem to have.

[harryball]

The photo is at an "in progress" stage and seen from the X=96 end of the table, head is on the other end. I agree, the grid needs to be machined a little further over on the far sides. The photo is a dry fit. However, I did not glue the joints, they are all taped with a vinyl type of duct tape. I checked those joints closely for leaks by stopping the end of the pipe, the vacs really pitch up and the few leaks I did find were easily sealed.

My spoilboard is down to just over 1/2" right now. It's ultralight MDF and is the same board I was using with the shop vac heads.

The edge of the board that won't pull down is on the side of the table where the plenum is about 7/8" wide. The board itself is shifted over 1" from the edge of the table so it is fully over vac plenum. I have taped the exposed 1" of spoilboard.

If I run a piece of tape along the edge of the sheet itself and seal the gap between the edge of the sheet and the spoilboard the board will pull down and stay. When I just hold them down the vacs pitch up and take hold... when I let go the board slowly rises as the vacs pitch back down and the vac is lost... takes about 3 or 4 seconds.

I'm going to wait before I do anything else until I get my vac gauges. I will think very differently if I see a full vac of 7" of Hg with the pipes plugged. I can prove the vacs and pipe are good or bad and move forward.

Good idea with the smoke, I think I can find something that'll do the trick.

Robert

[danhamm]

I am using a little diff idea for a spoilboard just for that reason..couldn't get quick enough air through the spoilboard..so used 1 sided melamine...melamine down particle board up..with 90 degree 1in. cones 3/4 of the way through then used a dremel to drill 1/16 holes ..a zillion..the vacuum coming through the holes is quick..and when you cut over them it attracts the cuttings closing them off from losing to much vacuum..works very well cutting melamine and mdf.. \image {} \image {}

[danhamm]

try again.. \image {spoilboard}
7112

[danhamm]

closeup
7113
7114

[paco]

Interesting bleeder board adaptation Dan. Since it's a problem to get Trupan here in Canada (don't know about your end).

Does it clog?

Can you/do you remove it sometime for specific task?

Is it stable? Is it glued up?

[harryball]

Perhaps with ultralight MDF... the cones alone would be enough if the bottoms left the bottom skin at 1/4" or so. I noticed an accidental plunge on the spoil board that didn't go all the way through does allow alot of air flow.

Now you got me thinking...

Robert

[danhamm]

Its not permenently attached with the melamine bottom it sucks down quite nice..have had no problems with leakage between the boards..cutting melamine..whitch is slippery..and if you don't cut right through you have to deal with the hard edge thats left..and it damages the edge real easy ..so I cut right through using the cuttings as a seal..

[mziegler]

WOW! Dan like your idea for an universal vacuum table. How do you clean the cones? With a shop vac? That probably would work OK. So I think that you leave the cones plugged for product runs and then clean them when you run a different part? Do you load only full sheets or is the table zone to hold partial sheets? What kind of pump do you have? How do you clean the table? By blowing the sawdust, don’t that fill the other cones with dust? Sorry about all the question, but I would like to know. Thanks in advance, Mark

[danhamm]

Mark..the front or operational side I have a vice..for doing verticle edges..I keep a piece in there as a backstop..the other end I have corner pieces for locks..thats it..I lift it and blow the table clean with a air hose..both the plenum and the bleeder..I am "playing" with various devices for vacuum..but my main unit is a old commercial builtin vacuum..I have removed the motor and fan unit..and have it mounted outside of the building..It is supposed to draw 140 inches WC..and in the next few days I will find out..what it does..for real, as we are at the 3000 ft level here..I did test a shopvac, and it only did 42 inches..mind you my test is very primitive..a clear plastic hose, in a bucket of water.."well I did say primitive"..

[harryball]

I have the vac gauge installed and with the valves closed it pulls 6.5" of Hg. With any one zone open and a sheet of material on top I'm pulling 6" of Hg. With the entire table open and a sheet of material on top with the edges taped I'm pulling 5" of Hg or a little better. No audible leaks, no leaks I can feel and from what I've been reading 5" is pretty good.

When I untape the edges of my working sheetgood the vac holds about 5" and then slowly drops to about 4" as the edge of the sheet raises up slightly. Then it stays around 3.5" to 4". I can reseal the edge of the sheet and the vac goes back up and the sheet pulls down... it would SEEM I have insufficient airflow in cfm but plenty of vac.

Opinions, ideas?

Robert

[Brady Watson]

Robert,
I think part of your problem is that you have not secured the bleeder to the grid. The bleeder will actually lift & break vacuum if the force of the spring of the material is greater than the vacuum can hold. I run a thin bead of GLUE (notice I did NOT say silicone) around each zone and the perimeter of the entire grid. Then pull vacuum on the bleeder to hold it in place until the glue kicks. When it is time to replace the bleeder, just CR down to the tops of the grid and replace. Screws just don't work out very well AND glue keeps the bleeder flat to the work with or without vacuum on.

-B

[harryball]

Interesting... I used double back tape between zones but I have noticed the bleeder still lifting and added screws as before. Did you just use yellow glue?

I also found some round foam weather strip, it's about 1/4 in diameter... laying it right on the table next to the sheet does the trick. I have not run the vac with bleeder board only... I should do that and see what I get.

Robert

[Brady Watson]

Robert,
I use titebond III, but you can use any wood glue that you think will do the trick. The tape doesn't always work out as expected...It either gets cooties on it from the wood sheets and it fails, or it leaks out thru the sides. Gluing it down gets things nice & flat and you only have to deal with small paper-thin leaks if any. AFTER you have glued down the bleeder, you can follow up with just about any type of caulk that you think will seal the very thin gap between the bleeder and the grid.

-B

[danhamm]

Robert..what is the "sheetgoods" your using..plywood..?

[harryball]

I'm using 1/2" ACX plywood, it's very good so far as being flat, I've not had a sheet yet that was more than 1/4" off the table anywhere and I can press it to the board with 1 finger. I just finished cutting my 2nd sheet on the new setup, I run about an hour a sheet with all the grooves. Using the small round bead of weather stripping down the edges workd like a champ.

Brady, on the spoilboard only I'm pulling about 1.5" Hg. I'll be replacing my spoilboad before too long with a sheet of Trupan and I will glue the next one down.

In my current setup as I make cuts the vac drops from 5" to about 3.5" when the cuts are finished... but the board stay put so I'm happy.

I suppose I could get 2 more feins and just run one per zone :-)

Robert

Robert

[Brady Watson]

There are a few guys running 4 Feins in production environments & it works quite well.

The 1.5" Hg with open bleeder is good. That's what you want.

-B

[fredtoo]

Woodcraft at Springfield, VA has their annual 10% off sale February 17 and 18. That puts a Fein III at about $333 plus tax, comparable to Amazon. Seems timely for this topic.

[rick_d]

I posted earlier in this thread about the Grainger Vac not living up to its claims and, for anyone who might be interested, I got the results back from Ametec Lamb. They claim the pump is working perfectly. However, it only pulls about 7" Hg, which is about the same as the Fein. I don't have a good way to test the airflow, but I suspect it is less than the Fein. It is certainly a lot noisier, but it costs about a hundred dollars less so maybe not a bad deal after all.

Just my results.

[andre]

Can someone advise me on whether to get the pvc kit from shopbot or to build one myself. My shopbot prsalpha will be here end of march and I am still not sure. If Ibuild it on my own where can I get those pvc open close valves that I keep seeing and do I need a vac gauge? I am planning on using two feins. and another question, would you create one zone per vac or would the two vacs share the whole zone?

[harryball]

I can't see buying the PVC kit from shopbot myself. I got all my parts from Home Depot. Spend a little time laying it out and cutting, do a dry fit before gluing.

I would suggest you have both vacs able to pull on any one zone. I have a sled that covers my first zone for board hold down. With both feins running on that one zone it's like it's glued down, screwed and nailed. Doesn't move.

The vac gauge is cheap enough, mine was $12.00 from an autoparts store. It is very useful to test and verify your setup is working but I've found myself looking at it time to time to check my potential holding power.

I placed a sheet on just yesterday and couldn't get comfortable with the way it looked... sure enough the vac gauge shows 2.5" of Hg... I located a large knot gap allowing the far side to lift slightly. I added a couple of feet of painter's tape over the gap and checked again, 5" of Hg and it was solid.

Robert

[bleeth]

I got all my parts to do my own from the local Home Depot. Any plumbing supply department or store has it all. Some valves are smoother to operate than others so you will want to check that out. The advantage, to me, of doing your own is to set it up the way you want for your needs. For the second question: Most guys split the vacuums into "North" and "South end of the table. Another reason for doing your own "custom" design.

[richards]

I bought the PVC valves from Home Depot. It's been awhile, but I think that cost somewhere in the $10 - $15 range.

A vacuum gauge is helpful. I use mine everytime I put a piece of material on the table just to make sure that it is being held down properly. On my machine, 5" of mercury is good suction when I'm cutting MDF. A quick glance at the gauge shows whether everything is working or whether I've got something trapped under the material.

On my machine I have four zones all sharing all the plumbing with my two Fein vacuums. When I use just one Fein, I have to disconnect the other one from the plumbing and cap off the connection, otherwise the vacuum that is off leaks too much air.

[ed_lang]

Allow both vacs to work together. I plug one Fein in the the other and set for automatic operation. that way when I turn on one, the second one (or more of them) will also turn on. When I turn off the first one, the rest turn off. By doing it this way you will double your CFM air flow. Remember, you will NOT double your vacuum. Both must run together or do as Mike does above, cap off the unused port. I always run both.

My pipe, fittings, valves and glue all came from the local Lowes store. If you know a plumber, get him to buy it for you and save even more.

If you have any further questions, just ask.

Ed

[andre]

Thank you everyone. that answers some questions.
My next question is what size pvc should I use to maximize the use of 2 feins. Wouldn't 2 feins equal double cfm therefore require bigger pipes to take advantage?

[ed_lang]

I ran 2". When the material is sucked down, you should not have much air flow. If you do, you need to fix the leaks. You are looking for max vac and min flow.

[andre]

Thanks Ed
So from what ihave learned so far is ontop of the table base goes the plenum, ontop of that goes the sacrificial top of 1/2" trupan. the bleeder and the sacrificial top are the same correct? The plenum mustbe sealed both sides and all edges sealed.
This forum is great!
I will post some pictures once I have things running.

[ed_lang]

Andre,

Sounds like you have it all right.

[andre]

Is there a need to use grounding wire on the pvc pipes? as you would on a dust collection system, I would think you should. Am I right?

[steve4460]

Hi Andre

I would deffenetly ground it on both ends of the PVC pipe . The better you ground your bot the less comuniction losses will happen .

Bot on

[ed_lang]

Not saying one way or another but mine is not.

[Brady Watson]

It's probably not necessary as the SB table itself should be grounded. Vacuum hold down does generate a significant amount of static electricity in many materials. While you already know about the 'zappy zappy' part of that dance, I will remind you to wear your safety glasses when taking parts off of the vacuum table. In my experence PVC & aluminum are expecially nasty with a very high affinity for eyeballs. The chips actually fly up in your face when the material is lifted off of the bed with everything shut down...AL in the eye is not fun...PVC isn't nice either! Be sure to get a set of glasses with side-shields. You may look like a dork...but you will greatly lessen the chances of an eye injury. I'm still trying to understand the electro-mechanics of static, vacuum hold-down and how high voltage is stored in cut materials. It laughs at Static Gaurd spray...

-B

[wcsg]

Would running two feins have enough vacuum for holding down small plaques say 8"x8" and letters 4-12" tall? Or will double stick tape work better?

[donchapman]

Erik. I use one small Fein and and have been able to hold down anything I've tried down to about 40 square inches, so long as vacuum is not lost by cutting all the way through any of that area, and there is not a lot of vacuum loss outside the hold down area.
I leave about .02" of skin on the bottom of the material to maintain vacuum, then thickness sand or trim the skin off with a utility knife, rotozip tool, router, etc.
The rule of thumb for me is that it takes about 80lbs of downward force to keep the lateral force of the ShopBot bit from moving the material. Since I get about 2+lbs/sq.inch of vacuum from my one small Fein, I've got at least 80lbs holding down a 40 sq. in. piece of material.

[harryball]

Erik, That would not be enough to hold what you are describing on an open table. For the square you'd need laydown mask board right up against it then it should hold. For letters you need to have tabs or leave a skin.

Another method would be a vacuum mask when openings in a thin material behind the parts you want to hold and using vacuum mask tape. Brady has some information about a vac mask in Brady's Tricks on the ShopBot home page.

Robert

[wcsg]

Bummer, I couldn't really use a thin skin for acrylics and alum. Guess I'm sticky tape for life

[donchapman]

Are you sure, Erik?
I've cut no acrylic nor alumimum using vac hold down, but it only takes the thinnest skin to hold the vacuum, and it seems like there ought to be a way to leave that and cleanly trim it after CNC routing. But maybe not or maybe it's too much trouble. All I know is that I used a lot of carpet tape in the past and would try most anything to avoid having to use it much again.

[wcsg]

Tell me about it, peeling that tape off everytime is a pain the the ass. BUT, at least it's a good hold down method.

That is also why most of the time for anything thinner than 3/16" I've converted over to down spiral, less tape and headache of peeling.

As for leaving a thin skin it would be too time consuming for me for clean up and more chance of getting a break off in acrylic.

So for hold down of individual letters and plaques this where you need a 7k system then huh?

[carlcnc]

Erik
try putting application tape on your plex,then the double stick tape,
when you pull your parts off the application tape they will come off clean,
Carl

[wcsg]

I use to do that but that's just too much, paper masking then application tape then double stick tape. 3 Layer dip

[bill_l]

Calling all vacuum experts,

Are there any adverse consequences to using 2 vacuum holes for one zone? I'm creating an 8 zone system and the centers of two of them fall directly over one of the cross members. Would one offset to miss the cross member be sufficient or would two,(one on either side) be better?

Another question I have is; would 1.5 inch instead of 2 inch PVC plumbing make a difference. I'll be using 2 Fein vacuums to do the job.

Bill

[ed_lang]

I would run just one hole where it fits best. I would not be too unhappy with using 1.5" but would feel better with 2".

[bill_l]

Ed,

Thanks. Not to question, just to understand ... why 2" vs 1.5"? Is it volume?

Bill

[Brady Watson]

Yes...CFM = Volume & your Fein dust hose is already 2.25" in diameter. Going down in size would increase velocity but reduce CFM. The CFM is more important than the velocity of the air.

-B

[bill_l]

Brady,

Thanks. By chance, you wouldn't have any photos of your system would you?

Bill

[Brady Watson]

Bill,
I invented a system of using a inverted grid that combines the vac grid & plenum in one removeable board. This allows me to accomodate both materials that can be vacuumed as well as those that need to be bolted down, by simply applying or removing the 'BradyVac' plenum. You can check out the concept by going to my column 'Tips & Tricks' on the ShopBot website. You can also download the BradyVac virtual tool courtesy of Bill Young & ShopBot in the ShopBot Labs section of the website.

At the moment I use a single Fein, but am experiementing with other vacuum sources as well. In my experience, creating a system with more than 6 zones is usually overkill and of diminishing return. Having more zones can actually reduce performance rather than enhancing it...but everybody has the freedom to play the way that they want with their machine & their own R&D.

-B

[ed_lang]

Bill,

Brady said it all. I didn't want to restrict my system more than the Fein's hose was.

I have some pictures at

http://www.kc4ylx.smugmug.com/gallery/1459437#69597957

I now run two Feins.

Feel free to look around the site for other "stuff"

ed

[andre]

Is 1/2 trupan best for your bleeder board.?
I have heard of people using the plenum turned upside down as the bleeder. The only down side I see with that is that you would have to remill a plenum evrytime your bleeder wore thin.
Any thoughts on which method is best?

[elcruisr]

Been using 1/2 trupan for 6 years over my plenum. No complaints so far. I do run a 15 hp regen blower though.....

[Brady Watson]

Andre,
If you cut the same types of parts out everyday, like full 4X8 sheets for cabinet parts, then use the conventional vacuum grid & Trupan bleeder setup. If your cutting & material varies, where you need to screw down or tape some parts, and vacuum others, use the 'BradyVac' setup where you machine the grid into it and flip it. Yes, you will eventually have to replace the entire thing, but if you use the 18mm Trupan and mill the grid 3/16" deep with a 1/2" bit, it goes a long, long way before you have to replace it.

-B

[andre]

Brady thanks
I still have not memorized the metric system. whats 18 mm again? 3/4?

[3imoh]

Andre-

18 millimeters = 0.708661417 inches

Here is a trick...type "how many inches in 18mm" in Google:

http://www.google.com/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&channel=s&hl=en&q=how+many+inches+in +18mm&btnG=Google+Search (http://www.google.com/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&channel=s&hl=en&q=how+many+inches+in +18mm&btnG=Google+Search)

-Howie

[conceptmachine]

andre-

here's a simple way to convert mm to inces.
18(mm) divided by 25.4= .708...or to go from inches to mm .750 x 25.4= 19.05 mm

[lex]

I couldn't stop thinking about hold downs:P
So I drew a quick one in ACAD lite for comments.
this is 48" x 48" and has 4x 3" holes seperating it into 4 major zones with internal "valves" for control of 16 seperate areas of 11.5" square each. the internal "valves" could be relieved on the edge for an o-ring. The vacuum should pull it flat to the bottom of the board but you could use another gasket there if you really wanted to.

I added the ACAD file if anyone wants to mess with it.


holdown

7115 (44.5 k)

[lex]

Bah had to edit because of size...
7116

[Brady Watson]

Lex,
What do you plan on cutting?

-B

[lex]

Plaques, Kids toys, boat parts, some cabinet fronts, a sign or two, maybe some furniture here and there. Mostly wood but some Penski board, high density foam, or honeycomb board. I also want to be able to do UHMW and lexan.

I was just thinking about this thread and how there should be more flexibility to hold different sized and shaped items.

[Brady Watson]

Lex,
I use a single Fein & hold down everything from full sheets to parts as small as .625 X 1". It comes down to how efficiently you can use the vacuum. I have a few vac plenums that I use for specifically sized parts. Some use gasketing, others are just Trupan with a grid machined in it and flipped. Sized jigs give you much more control over what you are doing than a big zoned grid, in my experience, if you are cutting a variety of sizes.

-B

[lex]

Perhaps my intent is good but not practical for the most part. What I was intending with this was to enable variable vacuum zones according to needs. For instance you need just one square foot of vacuum: close all ports but one....Say you need two feet square: open the 4 adjoining ports and you have it....Then say you are doing a full cut out in the center of a 48" x 48" piece: Open all the outer ports and close the inner ones to prevent vacuum loss. It can be one large gride or any combination of smaller grids based on what ports you open or close.

[Brady Watson]

In theory, the 8+ zone table works...in reality, you will find that it is not as efficient as an accessory grid/plenum that you can add/remove from the table. You get more holding power & control from purpose built setups than the one size fits nobody big grid...All of this is of course just my opinion & what I have derived from my own R&D. So, don't let me discourage anyone from trying out their own stuff & coming up with what you believe will work for you. Just keep in mind that Fein vacs are good, but they aren't as tolerant to leakage and open kerfs as a 15hp Regen or Roots. Therfore you have to ensure that you don't have any leaks and make sure you plan your cuts to make the most of the vacuum.

-B

[paul60]

Is this idear pratical. I use a four zone vacuum
board sealed both sides. and a 3/4 mdf spoild board.
would it make a difference to my vacuum. if i was to replace my spoilboard using another 3/4 mdf sheet,
sealing it on the bottom then drilling 1/2 holes through the sheet every 3 inches.
would there be a higher concentration of vacuum in those areas?
i am using a lamb 2 stage vacuum.
thanks paul

[Brady Watson]

Paul,
Your best bet would be to use a sheet of trupan as the bleeder. Simply drilling holes in the spoil/bleeder does nothing to slow down and retain some of the vacuum when you cut all the way through a part & expose those holes to atmosphere. The MDF might be OK as it is IF you skin both sides of it. You would probably do best to skin it to about 1/2" thick, but MDF varies in resin content & I have seen MDF bleeders skinned all the way down to 1/4" thick and it still doesn't bleed. If you want to try the hole method, go grab a piece of pegboard & try it...a bleeder is more than just a porous board; it slows down the vacuum & reduces leakage when open kerfs break the vacuum seal. Holes work well with a gasketing perimeter around a specific shape...but I think you will be disappointed if you do it on a 4X8...even with zones.

For those who cannot get Trupan near them, you can order a few sheets of it here: http://www.woodworkerswholesale.com/Spoilboards_s/787.htm

-B

[paul60]

thanks brady will try the peg board and see how it goes i use my shobot to cut 8x4 sheets of plywood]
for cabinet parts.

[henrik_o]

Very interesting thread.

I am currently looking at the universal vaccums offered by Shopbot.

The 15hp Roots PD Blower (14”Hg at 330CFM) seems like much better bang for the buck than the 16.9hp Regenerative Blower (13”Hg at 140CFM) -- more than twice the flow volume for the same cost.

I understand the noise issue, but it's not a concern for me since I can put the vacuum in an insulated room away from the shopbot and other work areas.

Is there something I'm missing?

[bleeth]

Lex: My system is set up with an 8 zone table with valves on each zone under a bleeder of mdf. It works great. I currently am using a 7.5HP blower. Most of the production work is on plywood or mdf and we have never had a part break loose. I have carved parts smaller than one zone by simply dropping some scrap over the balance of the zone.

Dave.

[andre]

brady
I have shopped wwwholesale
They have alot to offer. But Trupan at $119 a sheet! Whoa!
I have a supplier here in mpls that sells it for $37 a sheet for 1/2
http://www.industriallumber.net/CATALOG/MDF.htm
Don't know if they ship but it is worth it to do some digging in your area before shelling out 119
try looking at smaller home centers who offer eco freindly products

[Brady Watson]

Andre,
I only posted that link for guys who are in places where they can't get Trupan...YES by all means try to source it locally or take a road trip. I think one reason it is so expensive (besides needing to be shipped via truck) is that they crate them up. For a lot of businesses, the cost is of minor significance...when you need it, you need it. For smaller shops, a road trip is in order


-B

[harryball]

Brady... on this topic related to Trupan. I learned from you that all Trupan is not created the same, there is regular and ultralight I believe. When you use the generic term "Trupan" as it relates to making a good vacuum table do you mean the regular and/or ultralight?

I'm going to need a vac table top since I decided to see what happens if you zero on the table then run a file designed to zero to the material. I can get Trupan locally for $25/sheet but I believe it is regular stuff. Will that work or should I go with the other brand of ultralight?

Robert

[Brady Watson]

Robert,
I always refer to the ultralight stuff...that seems to be all my supplier carries & the closest place for me to get it is 100 miles away in one of the rudest places on earth: Bergen County, NJ.

I would imagine that the regular stuff would be good as well since it is still Radiata pine. I would like to hear how well it works for you. Regular MDF works too...not as well as Trupan and it is a gamble what resin content you will get with regular MDF. I'm curious to hear if the regular grade stuff pulls vac thru it or if it has resin content issues like MDF.

-B

[harryball]

I'll be sure to let you know, provided the local supplier has stock I'll have it next week. If he doesn't I may have to go "other brand" again.

---
one of the rudest places on earth: Bergen County, NJ.
---

LOL... I've been there, had an uncle that lived there. However, I always been told France was the rudest place on earth... Paco?
;-)

Robert

[woodworkseb]

Here is what you all are searching for. A system that will cut small parts, with no spoilage board an it won't break the bank. Check out our "little puck'r" at http://www.oriontechproducts.com
Feel free to drop me a note at my e-mail address in my profile or click on "contact us" on the web page.

[elcruisr]

Henrik, that roots blower is a fine hold down pump. I have a 15 hp regen and it works well but I's swap it for more cfm any day! If you are going to put it in another room I'd talk to the manufacturer about pipe diameters. Using 4" pipe on a long run like that will mean CFM loss. We looked into something similar and discovered we needed 6 to 8 minimum or the loss would degrade performance too much. The price of the pipe and valves that size dictated that the pump reside under the table. Noise isn't much of an issue with me. I run a good sized wood shop and you need hearing protection anyway!

Remember, hold down systems are not just about vacuum but also flow rates!

[henrik_o]

Eric, thanks for the info. What were the distances you were looking at? As can be seen in this sketch (http://members.arstechnica.com/x/hiphink/shopbot-shoprender01.jpg) I have two options for routing the vaccum; either to an exterior bay or an interior sound insulated area (where there's also a large compressor, dust collection etc).

It would be nice to have the vaccum blower away from the work area, at least if I obtain the 92dB roots blower. That's a hellish amount of noise. The 82dB regen would be less of an issue.

[elcruisr]

Henrik,
a 2 meter run might be acceptable but on my regen they said any more than that and I had to start increasing pipe diameter to keep up flow rates. I wanted to look at one option for me that was an 8 meter run and the technical guy just whistled! Started talking about 8 to 10 inch pipe! That would also require a surge tank at the machine, etc, etc. The shorter the run the better it seems.

[fleinbach]

Brady,

I purchased some light weight MDF from Russel Plywood in New Castle Delaware for my bleader board and it works great. They told me the name is Tafisa and it cost about $26.00 a sheet for 3/4 inch. When I first put it on my plenum board and turned on the Fein vacuum it worked so well unsurfaced that I applied it and only surfaced the top to level it out.

[andre]

Brady
I figuered you had yourself covered, I was just voicing to everyone else. I asked my distributor if this was the ultra light trupan and he said yes. I hope he is right. I will find out. I just ordered 2 feins and am excited to try them out.

[hershberger]

Anybody know where to get 16th inch ball nosed bits??

Thanks email: Rayscraft@juno.com (mailto:Rayscraft@juno.com)

[jo_mosis]

www.msc.com (http://www.msc.com)