BT32 Vacuum System

[plimandri]

Hi Guys

I am brand new to this I have a background 17+ years in real estate. I would love to find someone who has a BT32 with vacuum system so I can see photos of the set up. I have had quite a few people tell me how to do this unfortunatly without seeing it for myself I just cannot get a clear understanding of how the system comes together. I really appreciate any help and maybe photos to get me started.

Thanks

Phil

[garyb]

Phil there is tons of information and photos here on the forum, just do a search
Under Variations and Modifications check out Brady's 9-15 open source should help you a bunch

[Brady Watson]

Phil,
Hang tight. I have a new Buddy on the way & will be constructing a vac system specifically for the BT line of tools within the next several months.

-B

[plimandri]

I appreciate it seems strange shopbot has files for all the other models to cut the table for vacuum except this one. When attaching the plywood to the aluminum plate how much should I recess the bolts so no damage is done to the bit when I shave the table flat? By the way is it a good idea to just use regular plywood for the main base.

Thanks for all the help :]

[gigdog]

Brady:
I have a Buddy on the way the 16th of May. I would like to build a vacuum plentum like the one ShopBot has on their's (they don't have any plans on how to build one like theirs). Have you designed and built yours yet?

[Brady Watson]

Raymond,
I designed & built the one that ShopBot has on their training machine. I had hoped to do a web column on the enhancements that I have made to my machine, but workload and other stuff has kept me too busy to do a proper write-up. If you look at my last web column on the ShopBot.com site, you'll see me standing next to my truck at SBHQ getting ready to drive back to NJ with the BT48 'under wraps'.

Here are a few pics of the setup so that you can get some ideas for yourself. There are currently 4 'BradyVac' BT vacuum hold down systems in use on machines around the country...but it isn't exactly a product that you can buy off the shelf at the moment. This system requires a 2" hole to be bored into the 1/2" BT AL table, a 3X1" AL tube, some PVC fittings, a sheet of suitable plastic or sealed plywood & a sheet of Trupan as the bleeder. With a Fein T3 it holds amazingly well. I made mine removable so that I can employ BradyVac Masks, which direct vacuum ONLY under parts to be cut, with no gasketing required for 99% of the parts that I do (down to about 1" wide parts).

So...here are the pics. You'll notice that I mounted my VFD for the spindle up @ eye level so that I don't have to change RPM like a caveman...and I've added a laptop arm to hold the laptop at a comfortable distance (don't ask me where I got it...It came with another CNC I bought) After taking these pics, I came up with a self-managing solution for the dust collection hose. Now EVERYTHING on the entire Buddy is 100% completely unpluggable and portable, PLUS completely functional with no interference with the soon to be released PowerStick option for these tools. The VFD plugs into a 230v extension cord, the control box & computer operate off of a 110v one. The Fein hold-down vac plugs right into the back, as well as the dust collection hose. The machine can be rolled from one end of the shop to the other without affair. I added another secret squirrel goodie - a spindle fan override switch, which lets me have the control box on, and the spindle fan off while using the ShopBot probe...More on all of this later. I would have liked to get some of these pics up a few weeks ago...but life happens...

On a side note, this tool is an absolute TANK! It is rock solid and stable. With a little bit of VR tuning I've been able to cut up to 10 IPS reliably with no problems. This is a FAR cry from my original PRT which would jog at a max of 3 IPS under DOS software...Hurray for progress



-B


BT48 Standard with 2HP spindle 'All Kitted Out' as they say...

5278


The grid

5279

Back of machine showing manifold & fittings etc

5280

Caulking up the manifold with gutter seal

5281

Grid & 18mm Trupan Bleeder

5282

[dana_swift]

Brady- that is a really nice general purpose hold-down for big stuff. I presume you put gasket material in the channels at the edge of your part?

Good work-

D

[phil_o]

Are the chrome things around the perimeter bolts holding the trupan to the table?

[Brady Watson]

Dana,
Thanks. No, actually. The idea is to keep the grid itself in pristine condition. The purpose of the Trupan bleeder is to bleed vacuum thru it's porous interior matrix and function as a universal vacuum solution. Several years back I devised the BradyMask, which is a purpose built vacuum jig that sits on top of the grid, and below the material to be cut, directing vacuum to only the areas that need it - maximizing the efficiency of the vacuum source. You use the Trupan when you want to slap a sheet of plywood on the machine and cut out relatively large parts (let's say 8" square or larger). It's a good general vacuum solution, but there is a performance hit when you use a bleeder. A mask is more efficient, but you have to make one for each job, and that isn't always practical. I never liked the 'gasket in the channel' method personally, although some find it useful when cutting square parts. Gasket durometer becomes critical when using that method.

Phil,
No. The bolts you see only hold down the plastic grid to the AL table. The Trupan 'floats' on top & is held in place by nothing more than vacuum. When using the bleeder in a production setting, a quick once-around with some foil tape secures & seals the seam between the plastic grid & Trupan and keeps in from getting knocked out of position.

-B

[phil_o]

Thanks Brady,
now I have to ask what type of plastic is the grid made of?

[gigdog]

Brady:
I am totally new to this CNC, CAD stuff. I have been woodworking for years and build guitars and cigar box guitars as a hobby. To say I can justify buying my BT would be a streach. I'm sorry to be so naive but I assume the Trupan is the brand name for the MSD board? What is a "bleeder" and a "VDF"? Do you plan to publish any plans for the Brady Vac with specs. in the near future for us Newbies?

[Brady Watson]

Ray,
Trupan is a unique ultralight MDF (Medium Density Fiberboard) sheet product, perfect for a vacuum bleeder. A bleeder distributes vacuum across its entire face. A VFD is a Variable Frequency Drive that controls RPM on a spindle.

No plans at the moment.

-B

[phil_o]

Brady,

have you experimented with different thicknesses of Trupan. Such as 1/4", 1/2", 3/4". It seeems to me that thinner material would provide greater air flow and therefore better vacuum.

[Brady Watson]

Phil,
There is little difference in flow between 1/4" & 3/4" Trupan. I don't have an answer as to why this is. The 3/4" (18mm really) is stable, lasts many table flattening routines & is the most widely available thickness around.

-B

[beacon14]

Once you have reached full vacuum there is (or should be) relatively little airflow. The vacuum pressure inside the 1/4" bleeder and the 3/4" bleeder will be pretty much the same, therefore the holding power is the same. The difference comes when you start cutting through the workpiece or have too much leakage. The thicker board does a better job of keeping larger quantities of air from rushing in through small openings/leaks and therefore seems to maintain a vacuum better than the thinner board. Plus it needs to be replaced 1/3 as often. I start with 18mm and end up retiring it when it gets down to 3/16" or so (the old too-thin spoilboards get used for templates or crating).

[tim_mcknight]

Please excuse the newbie question but ... lets say that you have a small block of hard wood, 1-1/2" W x 6" L x 3/8" thick, that you want to profile and do machining on, can you lay that part directly on top of the bleeder and will the vacuum coming through the bleeder be ample to hold that part secure while machining it? If not, how do you use vacuum to hold that individual part?

[dana_swift]

tim- If you are going to make a lot of those blocks, it may be worth your while to make a dedicated fixture perhaps holding many blocks of wood simultaneously. The secret is gasket tape, check out:

http://www.allstaradhesives.com/

D

[bill_lumley]

Brady , I am intrigued by this comment 'with a little bit of VR tuning I've been able to cut up to 10 IPS reliably with no problems' . This is not an Alpha you are talking about correct ? What kind of cutting are you doing that you can get this kind of speed from . My application is cabinet parts from MDF and Particle Board and I generally cut at 3"/second with a 1/4" compression bit on my PRS Standard.

Thanks Bill

[mikek]

Tim, I think you might need a lot more vacuum to hold those small pieces if you are cutting all the way through and not leaving tabs or a thin skin. Look at this pump. http://www.joewoodworker.com/veneering/EVS/concept.htm
It can give you 18 to 24 inches of Hg at small volume (CFM) and hold small parts with the right gasketing.
These links can give you some food for thought. Look under "Vacuum Clamping/Bagging/Materials".
http://www.shopbottools.com/resourcelist.htm

[Brady Watson]

Bill,
Correct. It is a Standard. I have cut Gatorboard and HDU at 10 IPS, but it isn't often that I run it that fast. Hard maple is run at 1.5 IPS or less...mostly less. The material, cutter and strategy set the speed limit on your CNC.

Tim,
No. I would not use a bleeder setup to hold a part that small with a Fein. I would unplug the Fein after making a 'BradyMask' type vacuum fixture, and remove the bleeder. Then attach the mask to the grid & use a high Hg" pump, like the ones Mike has listed. I came up with a device that allows you to use both the Fein or 9-15 setup in conjunction with a high Hg" vac to 'have it all'...to a point. More on this later.

On a side note, vacuum isn't the end all, be all - so do look into using clamps, carpet tape or screws if they prove to be the path of least resistance.

-B

[tim_mcknight]

Thanks for the advice guys. I have a vac system on the way from Joe. Brady, do you have a picture of using the BradyMask in conjunction with a vac clamping fixture. I am not clear on how to use the mask.

[Brady Watson]

Tim,
I'm on the road consulting at the moment...so no pic - But, the idea is to remove your Trupan bleeder, exposing the grid. Then take a cheap 1/4" sheet of MDF, Luan etc and offset your parts to be cut at least .08" to the inside. Cut those offsets out all the way thru the 1/4" sheet. Foil tape the mask to the grid sides. Place your material on the mask, pull vacuum & make some parts.

Make sense?

-B

[kenakabrowncom]

Brady,
My BT48 arrives today (yipee!) and I want to follow these suggestions on the vacuum system. I will be alternate using your mask and bleeder method.

Can you elaborate a bit on the vacuum manifold shown above. This is a 3x1 alum tube... correct? I see where you attached the elbow to the manifold but I am not clear how the attachment was made and how you sealed the ends of the alum tube.

Thanks for the valuable info!

Ken

[kivimagi]

Here is another version of a hold down system. Similar, but different from Brady's style. I'm not much of a metal worker so I went with PVC.

http://s305.photobucket.com/albums/nn230/ryankivi/shopbot/BT48%20Hold%20Down/

It seems to be working well, but I'm still tinkering. I have a whoping $7.48 invested in the plumbing.

[erik_f]

Ryan...nice work...the only problem I can see is the 1" pipe. I don't know the inside diameter of your pipe...so I'm going to assume it is .75". Area would be .375 x .375 x 3.14= .4415 square inches. This is ok for a high vacuum but not so great for high cfm. The 1x3" aluminum measures .75 x 2.75= 2.062. So the only problem is area. You would need 5 of the 1" pipes to give you as much area as a 1x3" square aluminum one. I think the 1x3 will work well but I'm going to use two of them I think on either side of the table. This way I will have better cfm as well as a mini two zone. Way to think outside the "box" though! For less than $8 I sure its been worth the investment.
Erik

[kivimagi]

Yes was concerned about the CFM, but it works well enough for me that I'm going to pursue it.. We'll see how it holds up.

p.s. I'm curious about the efficiency of a pipe versus a square tube. I imagine the corners of the tube become useless, and the air flow ends up rounding in practice. Not a dynamics expert

[erik_f]

If you don't do a lot of cut through it shouldn't really matter. I'm no expert on either subject...only talking from what I have seen. I was thinking about your idea and thought it would be possible to run 5 one inch pipes next to each other into a single box fixed to the end of your one inch pipe this box would feed into the hole in the table and then T them together into larger pipe.

[john_how]

Brady, I just ordered a Fein T3 to go with my buddy and would like to build a plenum like the one shown above. Curious about what kind of suitable plastic you used. Other than that is seems pretty straight forward.
Thanks very much for you fantastic ideas!!!

[Brady Watson]

John,
Any type of expanded PVC works well and is relatively affordable. Komatex, Sintra, Excel etc.

-B