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bstern
03-03-2009, 10:12 AM
Decided to upgrade my vac system when I moved my shop. Upgraded to a Becker VTLF250 from a 10hp Fuji. I cut 3/4 melamine almost exclusively.The fuji had done great at about 7"mg and degradation to about 5.5" after cuts on most sheets. The only problems I had was on very small pieces, ie 12"X3.5" toe-kicks.

The problem I am having now is very quick loss of vacuum. All plumed up and cutoff valve closed I get 24". With a full sheet of melamine loaded it drops to 8". I have 4 zones. If I open only 1 zone I can maybe get to 10".

The worst part is when cutting vac drops rapidly.

I know that I must have some serious leaks. I have resealed the edges of the spoil board with caulk.
I have gone around with burning incense (saying all sorts of incantations) and seeing no major leaks.

How much should I normally see with a full sheet?
(On the fuji the relief valve kicks in.)

How much should it degrade with cutting?

Any notorious places to look?

BTW my plenum is made of Azak so sealing there should not be a problem. Spoilboard is caulked to the plenum.

Thanks
Bob

carlcnc
03-03-2009, 10:56 PM
BOb
I just went thru this with my new table
first you want to isolate if it is plumbing or plenum/spoilbd
I would tape some visqueen over entire table,
plain masking tape works well.
then see what you get with all valves open,no valves. work your way thru opening and closing each valve/zone. If each zone by itself gives you the same reading[low] then it has to be connection at the azek. or around whatever you used to fasten azek to machine.??
vacuum leaks are a pain to hear over other noises,.
Carl

terryd
03-04-2009, 10:27 AM
I had this problem when the vacuum release valve would kick open to protect the pump and then bounce continuously. Resetting the pump (valve)with a corrected guage eliminated the problem.....Took a lot of beer and staring at the 'bot' to get to root of the problem

Brady Watson
03-04-2009, 12:00 PM
Bob,
What is your vacuum Hg" reading with the bleeder board completely uncovered & all zones open - as if you had a 4X8 on the table? If your bleeder is not bleeding enough, this would be the culprit.

-B

ken_rychlik
03-04-2009, 01:39 PM
In my previous life as a mechanic, I would take a piece of old garden hose about 3 ft long and use it to find vac leaks on engines. Hold one end right up against your ear and take the other end of the hose and "hunt" for the leak. It gets loud in your ear when you get close. You can find leaks even with the engine running and background noise, so I think it will work fine for a vac leack on a table also.

Kenneth

rb99
03-04-2009, 02:44 PM
Why not go around the areas in question with a lit cigarette? If there are no drafts it should show the leaks...

RB

rb99
03-04-2009, 02:44 PM
Why not go around the areas in question with a lit cigarette? If there are no drafts in the room it should show the leaks...

RB

dubliner
03-04-2009, 02:59 PM
I think that what the incense was for...

rb99
03-04-2009, 03:02 PM
I am incensed I did not read more carefully...

RB

bstern
03-04-2009, 04:56 PM
The incantations were no help either!

OK - I removed the old spoilboard and put a cap on each zone at the plenum holes.
got about 20" hg at each hole. (the relief valve is set at 23". So there is some loss.

After installing a new spoilboard and carefully sealing all edges (2 times) I am up to 14" with all valves open.

With only 1 valve open I get 18" open 2 it goes to 15.5 open 3 14.5" and all 4 14".
Seems to be the same no matter what order I open the valves in.

We are going to a test cut in the morning and see what it drops to.

erik_f
03-04-2009, 07:07 PM
Maybe I'm thinking about it backwards, but wouldn't you want to see a lower vacuum number with all valves open and only you bleeder board covering your plenum? I'm no expert so I'm sorry if I'm only confusing things.

bstern
03-04-2009, 07:18 PM
Sorry - testing with a full sheet of melamine on on the spoilboard!

Brady Watson
03-04-2009, 07:58 PM
Bob,
It sounds to me like your bleeder board is not porous enough. You should look into getting some Trupan Ultralight or Ultralight MDF. Before you seal it or do anything else to it, slap it on top of the grid and open all table zones. You should be pulling no more than 5"Hg with NOTHING on top of the bleeder.

I remember consulting with a client that had trouble holding material down with thier 1200 CFM/25hp vacuum pump using 5X12' MDF. They skinned the stuff down to 3/8" thick, flipping in between surfacings in hopes that it would bleed. No dice. It was pulling 13.5"Hg with nothing on top of the bleeder & the system maxed out at 14"Hg.

Get some Trupan or Ultralight MDF on that puppy & the Becker will hold darn near anything down. Remember, if you pull over 5"Hg with nothing on top of the bleeder, then that material will not work as a bleeder - sent it back and try to find the right stuff. Ideal bleeder resistance is somewhere between 2 & 4"Hg.

-B

ken_rychlik
03-04-2009, 10:35 PM
I don't think bob said what his spoilboard was. He said he replaced it and he had a full sheet of mel on top of it. What are you using Bob? It finally got my light weight mdf (Tafisa) on my machine and it surely is day and night difference in holding power.

bstern
03-05-2009, 08:38 AM
ULMDF - no trupan available in our area (Charlotte NC)will post open pressures when I get to the shop this morning!

This worked fine with the Fuji.

BTW - we tried the hose and cellophane as suggested - no luck.

bstern
03-05-2009, 10:04 AM
OK - open spoil board 1" hg.

Going to do some test cutting. If we start at 14 and only get to 7" I will be happy.

bstern
03-05-2009, 02:21 PM
No Go - starts at 14 and drops below 4 at the end parts are moving. VERY FRUSTRATED!!

I need to get back to making sawdust.
Any other suggestions?
I may have to install the Fuji soon. This will entail allot of electrical work


Help!

Brady Watson
03-05-2009, 07:28 PM
Bob,
Something is not right. Clearly you are not 'green' in your abilities, so something must be faulty here. If you bought the Becker used, be aware that it has replacable vanes that wear under normal use in the pump. I believe that they are about $800 to $1000 to replace the entire set. It might be a case that as the vac heats up, tolerances expand and the pump starts cavitating.

I would run a simple test to see if this is the case:

Close ALL zones and run the pump for as long as you ran the cut file, all the while keeping an eye on the vac gauge. See if that 18-20"Hg number drops over time. If it does, it's probably time for new vanes - or time to hook the Fuji back up until you get the ducks to service it.

-B

bstern
03-05-2009, 07:42 PM
Hi Brady

I talked to Becker tech support. I checked the vanes, they are at about 10% worn. They do make allot of noise. They said that would go away or I would need to hone the pump walls.
They said if I closed the valves and the pump is drawing 24" with the relief valve opening, the pump was operating correctly.

This really makes no sense to me. I'm sure it something small but I need to get back to making sawdust, so I reinstalled the Fuji for now.

We are going to get caught up and then try again.
Any suggestions are appreciated.

bstern
03-05-2009, 07:47 PM
Brady, I have run the pump for a half hour while with the valves closed. The tech support guy said this would help re-seat the vanes.
No change in pressure. Also done with melamine on top and valves open, no drop.

harold_weber
03-05-2009, 08:49 PM
What is the model number of the Fuji pump you are using? The only 10 Hp Fuji pump I see is Model VFC80. The factory spec I see for the Becker pump says its rated at 8 HP and the wide open flow of the Becker is a little less than half the flow of the Fuji VFC80. If this is correct, I can send you a chart that explains what is probably happening.

bstern
03-06-2009, 10:26 AM
Hi Harold, I am not in the shop today so I cant verify this but, I believe VFC80 is correct. Specs are about 400 cfm max and about 8"mg max., if I remember correct.
The Becker is a VTLF250 10hp rated at 25"mg max and about 175 cfm max.


I was under the impression that the Becker was the big dog. Most report running in range of 18" to 20" at the beginning of the cut and end up down at 11" to 12". Anyone running one? Brady what are your experience running sheet goods?

Finishing at 9" would be a dream come true for me. I love the Fuji but, at 7.5"Hg, even though I skin everything, small toe kicks and hanger rails sometimes move.

FYI, Fuji's next pump up at 20hp does not increase Vac only cfm.

harold_weber
03-06-2009, 11:48 AM
This figure is the best I can do with the Forum restrictions. You should be able to make out 4 curves.


7953

Imagine a whole family of curves like the blue and green ones. These curves represent the flow through certain hole sizes as you vary the suction pressure. You can think of the millions of tiny holes in the exposed portions of the spoilboard (plus any leakage paths in your system) as adding up to a certain hole size, and this size will increase the more you cut through parts and expose additional spoilboard.

Lets first look at the blue curve. The intersection of the blue curve with the red curve is where you would run if you hook up the Fuji pump and have a total open hole area equivalent to a 3/4 inch diameter hole. So for this case, you would pull about 105 inches of water.

Now if you substitute the Becker pump for the Fuji pump, you would move to the intersection of the blue curve and the black one. Looks like you could pull about 220 inches of water. The Becker pump is best for this amount of bleed hole area.

As you continue to cut and expose more spoilboard, the answer changes. Once you expose enough spoilboard to have enough open flow area equal to a 1-1/8 inch hole, you move to the green curve. For this case, you would only pull about 80 inches of water with the Becker pump, and the Fuji pump could around 100 inches of water.

So the summary is that once you have enough spoilboard exposed that the flow exceeds about 130 SCFM, the Fuji pump will provide higher vacuum.

Hope this is clear.

harold_weber
03-06-2009, 12:24 PM
I forgot to mention that your original post says the the Fuji pump's inlet pressure had degraded to 5.5"mg (inches of mercury gage?) at the end of your cuts. This is 13.6*5.5 or 75 inches of water. You can see from the graph that the red curve crosses 75 inches of water at about 230 SCFM, this is far above the capacity of the Becker, so its no wonder you are having problems with the Becker pump.

bstern
03-06-2009, 04:05 PM
Thanks for the great explanation.

Looks like I am starting with a little over 3/4" hole start with. If I can find most of that, it looks like I might be better with the Becker.

A little background on my cutting might help.
I cut closet parts. My software cuts the smallest parts on a sheet first. Usually the smallest parts end up on the fist few sheets to fill in from the biggest parts, usually sides. The sides are quite large and don't need much to hold them down. So if I can start with anything above 10 and end above 5 things would work quite well.

The last sheets cut are usually the shelves and most are at least 3 sq ft.

I guess I'm trying to figure out if I am working with the wrong pump or do I have problems in my plenum system that needs to be taken care of?

carlcnc
03-06-2009, 05:04 PM
Bob
probably stating the obvious;
Can't you get software to cut with onion skin?
I sometimes edit a file to leave 10-30thou at the bottom,then rerun the file at full depth.
really helps with a marginal vac.
Carl

harold_weber
03-06-2009, 05:50 PM
Simple diagnostic procedure for the case where a relief vacuum valve is installed::
1. Disconnect the Becker from the vacuum table.
2. Plug the line from the vacuum table and install a vacuum gage.
3. Turn on the Becker. It will not overheat if your relief valve is opening. The Becker people said it should pull 24 inches. Does it? QED

bstern
03-06-2009, 06:04 PM
Runs at 24". Also runs 24" with relief valve open when all 4 valves closed.

With full sheet of melamine on table then open one zone 18"... see above. This is where I came up with guess that I am starting with about a 3/4 hole.

Can't seem to find that hole.

You've go me wondering if the pump is the right one for my application.

All parts cut with onion skin.

Brady Watson
03-06-2009, 11:36 PM
Bob,
Question: How large is the tube coming out of the Becker & how large are the ones going to each zone, in diameter? Is this the same plumbing that you used for the Fuji?

-B

bstern
03-07-2009, 09:20 AM
The same size pipe out of the pump to the filter, 3" PVC out of the filter, reduce to 2" or 2.5" (will have to look) before the valves, the same to the plenum.

I think the whole setup was very similar to shopbot's standard 4 zone setup. I chose pipe size based on that.

Brady, What do you get with a full sheet on a 4X8 setup?

Do you ever cut sheet goods like cabinet parts?
If so, what do you start at and what is the lowest you get to? Assuming its not all small parts.

I am still trying to decide if this is the right pump for my application.
If not, I need to quit spending time and money on it.
If it is the right pump,I will throw more resources at it.

Brady Watson
03-07-2009, 12:35 PM
Bob,
Depending on how porous the sheets are, I pull down around 17-20"Hg and if I have a lot of kerfs, it will typically settle down around 12-14"Hg. So...this is why I said that something doesn't seem right with your setup. Without seeing it in person, it is hard to pin-point. Are you cutting MDF by chance?

-B

harold_weber
03-07-2009, 06:28 PM
Brady, the second sentence of Bob's first post in this thread says he cuts 3/4 melamine. Is it possible that air can leak through a brand new sheet of melamine?? Never cut any of this stuff myself.

Bob, maybe you should try replacing an uncut sheet of melamine with a sheet of visqueen?

wberminio
03-07-2009, 06:45 PM
Can I ask?
What is visqueen?
Never heard of it.


Erminio

erik_f
03-07-2009, 06:46 PM
I would think melamine would bleed a lot more than MDF. I usually cut MDF and I can feel my zero plate stick to it when holding MDF with vacuum. He should try cutting the same file with 3/4" MDF. I think Harold has explained a lot. Bob is looking for his 3/4" hole and it is on top of his table. Take some garbage bags and put them on top of you 3/4" melamine and see if you vac pressure goes back up.

jerry_stanek
03-07-2009, 06:52 PM
I think the Plastic surface on Melamine would keep the vac from flowing though it. Erminio Melamine is a partical board based product that has afinish on it. the stuff that knock down furniture is made of.

wberminio
03-07-2009, 07:05 PM
I know what melamine is.
I just never heard of ity referred to as "visqueen"
Thanks for clearifying.

Erminio

harold_weber
03-07-2009, 08:03 PM
Erminio, simply Google Visqueen. Its 3 to 6 mill polyethylene sheet that is sold at building supply houses and is normally used for vapor barrier in home construction. I suggested that Bob try that to see if he gets higher vacuum with it. If he does, then the melamine sheet is bleeding air.

As Eric has suggested, plastic garbage bags can be used instead.

gabepari
03-07-2009, 08:26 PM
I highly doubt that melamine would leak. I usually achieve my highest vacuum readings when cutting melamine.

Gabe

erik_f
03-07-2009, 08:33 PM
Maybe I'm wrong but I think of melamine and partical board as the same thing. I guess that is where the confusion came in...so if melamine always has a plastic coating I'm sorry for confusing things.

wberminio
03-07-2009, 10:16 PM
Thanks for the explanation.
I'm always learning


Erminio

myxpykalix
03-07-2009, 10:23 PM
When you hear the term "melamine countertops" or "formica countertops" actually the base is the particle board and the thin veneer covering is the melamine or formica. At least thats what i think.

bleeth
03-08-2009, 09:08 AM
Melamine is a hard plastic impregnated paper that is applied to a substrate in an extremely thin layer. It can be purchased typically on particle board but can also be bought on mdf. It is also available in many colors and patterns and is usually used for cabinet interiors or really cheap office furniture (and lots of closet systems). Formica is a brand name of High Pressure Laminate that is applied to any substrate. It consists of a layer of solid phenolic, a layer of paper, and then a protective plastic coating.
A full sheet with melamine or HPL on your table should yield the highest vacuum you can get.
Particle board and mdf without any laminate will yield some of the lowest.

Back to the thread subject: If there are absolutely no other changes other than the Fuji and the Becker when you went from one to the other and the Becker was not operating as it should than either the connection from your line system to the Becker has a problem or the pump has a problem. That 10% wear you spoke of earlier could mean you are simply not getting the volume you should. It sounds like as pressure builds up the vane is changing shape inside the unit and degrading performance.

bstern
03-08-2009, 01:09 PM
I should clarify on the wear of the vanes. When measured only 10% of the tolerance from new to worn out has worn off. i.e. There should be 90% of the life left in them.

Thanks for so much response! I find most of these difficult issues come to to something small that is common sense "once you find it."

I am just going to list some facts that I know so maybe someone can spot something to look at.
I am open to all input.

The pump - used 1999 Becker vtlf-250
Makes some screeching sounds that I am told by Becker to be seating of the vanes. They told me it would go away or I will need to hone the walls of the pump. I was also told this would not effect the performance of the pump. The pump will pull up to 24" hg and at this point the relief valve is open and sucking air. Becker said, if it pulls 24" the pump is operating properly. I would try new vanes but they are $1000 and according to my description to the Becker folks they look fine.

The pump is hooked up to a 30 KVA transformer to go from 230V to 460V(or 480 don't remember exactly, let the electrician figure that out). OK, I know it not very efficient but it was free and plan on getting a better matched 15kva later,

The pump is also driven by a properly matched square D soft start.
I have talked to engineers at SqD and they do not see how it could effect the pump in the manner it is. I will remove this from the circuit when I try again. Its fairly easy to do and eliminates the starter as a question.

Harold has pointed out the Becker is a lot less tolerant of air leaks than the Fuji. I will try covering the table with garbage bags. I think of melamine as completely non porous. But, I am obviously have some false assumptions or I would not be having problems.

I come up with 2 basic categories of problems
pump based or plenum based.

Pump based plan:

Remove soft start.

Check behind electrician on wiring.

Harold, I have a rubber coupler between the pump filter and the PVC. What to you think of putting a plate over the end with 3/4" holes in it to see if it matches the polar curve of the specs? I see that as 220" water or 16"hg.

Plenum based"

Cover spoil board with garbage bags.

I have tried: Smoke, listening with a garden hose, replacing and resealing the edges of the spoil board,going around all possible leak points with cellophane wrap to see if it gets sucked in.

Any other trouble shooting methods welcome.

Thanks for all the mind power thrown at my problem!

harold_weber
03-08-2009, 05:07 PM
Bob, you are free to try using a 3/4 inch hole to check the vacuum, but I suggest you try the same exact text on both pumps.

I'm not sure why you are spending more time on the pump itself. Your very first post says that the Fuji was giving you 5.5 inches mercury vacuum at the end of cutting a sheet of parts. Just look again at the Fuji and Becker performance curves. 5.5 inches mercury corresponds to 75 inches of water and 225 SCFM. The Becker curve shows that it is not capable of flow above 175 CFM, so it will not do the job for you unless you reduce leakage flows.

I think you said you have checked to make sure that there are no leaks around the perimeter of the melamine sheets where they meet the spoilboard. Maybe you should post a few photos of your setup and something might show up to someone.

bstern
03-09-2009, 08:26 AM
Harold, as I started early, I believe I have missed something. Something I am assuming is wrong. I did troubleshooting for a living for years. One big thing I learned is that when you get to the point of having checked everything and everything looks good. You have made a wrong assumption. You need to go back and retest everything, in a different way if possible.

I do not want to pull production down again with out a compressive plan to retest both parts of my system, pump and mixer/plenum.

If the pump is the problem, it is ultra sensitive to air leaks. It would be nice if I could test it to see if follow the manufacturers curve.

If I cap the end of the pump with a 3/4 hole and a vac gauge. Should I see 16"hg? Will this fully confirm the pump is working as designed so I can look elsewhere with confidence?

harold_weber
03-09-2009, 04:08 PM
Bob, yes. I've attached the same graph I posted earlier, but added the factory curve for the Lamb Ametek Model 117123 vacuum blower. You can access the Ametek test data points and curves from the Lighthouse Enterprises website, (but I think only with Internet Explorer). I think you can also get to them from the Ametek site. The Ametek curve crosses the 3/4 inch orifice curve at a vacuum of 66 inces of water. Ametek reports that they obtained that point during their test by using a 3/4 inch orifice, so it works for them.......

I recommend that you keep the orifice at least a foot or so away from the actual pump inlet, this will give the flow time to even out after passing through the 3/4 inch hole. This measuremt will not be acceptable according to ASME test codes, but it should get you to within 5% or so....

I cannot recall if I mentioned this in a previous note: the 3/4 inch hole needs to have its edges as sharp as possible, but must not have any burrs.


7954

Gary Campbell
03-09-2009, 06:01 PM
Bob...
I have been lurking on this thread for a while...Here are my observations, based on your information and that provided by others.

1) If you have 24" with all valves closed, your problem is beyond the valves

2) According th the Mgfr data chart provided by Harold, if you only have 8 inHg with a sheet on the table you are flowing (leaking)around 130 cfm. Coincidentally, this is right around where the graph lines from the Fuji and Becker cross.

3)Spread across 4 zones this is about 30-35 cfm per zone... in my opinion too high for a well built well sealed plenum/spoilboard combo with a sheet on top. (assumes full table coverage or good mask)

4) You can expect to flow another 35 to 60 cfm PER ZONE when cutting thru parts. That is why the Fugi worked and the Becker failed.

5) We cut with the "measely" little Ametek over there in the corner, we make this work by using one per zone. We will start cutting near 10 inHg and finish around 7 inHg. This is also backed up by the chart.

6) You should also check to see how well the spoilboard flows (as per Brady above) as this will reduce the vacuum available to the part.

Take your spoilboard off the table and working on one zone at a time, find the leaks. This may be at the plumbing to table/plenum connection, thru the plenum bottom or sides, the plenum to spoilboard seal or thru the sides of the spoilboard. You may even be testing with a warped sheet that wont seal. I recommend a sheet of 1/4" plexi to cover a zone and some fine sanding dust or smoke to find the leaks. Dont take anything for granted, assume there are leaks. They are there.
Good Luck, Gary