vacuum

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Brian Shannon
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vacuum

Postby Brian Shannon » Wed, Sep 14 2005, 2:48PM

What vacuum pressure should I be getting with my 15 HP Busch on a Model 40 w/ 5X8 table? What are other shops seeing?


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Nick M Singer
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Postby Nick M Singer » Thu, Sep 15 2005, 12:12AM

The pressure could really be no more than atmosphere, the crucial issue is rather air removal. Your pump is plenty strong enough, I am using a 10HP unit on a bed bigger than 9 x 6 and all but the smallest stuff stays put. My unit will develop near perfect vacuum but as I said the key is the volume of air it can move because your vacuum is compromised by bleed which gets worse as you cut up the sheet. Are you having a problem with your unit? What is the flow of the unit in cubic feet per second?

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Postby Brian Shannon » Thu, Sep 15 2005, 4:38PM

The displacement on the pump is 330. The vacuum guage reads over the max 30 (in. Hg) with the gate closed. With the gate open and nothing on the table but a 3/4\" ultra-light MDF spoilboard and a 1/4\" MDF wasteboard I'm getting a reading of 8-9 (in. Hg). Add a full sheet of 5/8\" Melamine and my vacuum reading is still 8-9 in. Hg. This may be normal. I am just have some small ( 4\" wide top web pcs.) move slightly. Maybe I just need to surface or flip my wasteboard more often. I didn't use a 1/4\" mdf wasteboard untill I talked to Ryan at the Thermwood booth in Las Vegas. He had no explanation but said that by adding a 1/4\" mdf wasteboard the vacuum seems to hold better. I was just curious if I am getting what I should from my pump.


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Postby Bill OConnell » Thu, Sep 15 2005, 6:59PM

Check the actual composition of the MDF that you are using. I know that there are a number of kinds of MDF and some people use the definition loosely. From Jason Susjnara:

The spoilboard that comes with the machine is 32 lb density and the wasteboard is 48 lb density. If you are not machining 5 x 10 sheets, you can use a 4 x 8 wasteboard. I belive that we have to machine both the spoilboards and the wasteboards here to the correct dimensions because we order it oversize. Hope this helps.


I specifically asked my salesman if the 1/4\" wasteboard he could supply was actually 48lb density. He confirmed that it was and I bought it. My guage reading doubled from about 8 to 16. I also purchased a roll of plastic film that I will use when I am cutting smaller parts to seal off that part of the table where I don't have parts. We have a CS45-510 but most of what we cut is 4'x8'
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Postby Forrest Chapman » Thu, Sep 15 2005, 8:34PM

Hey Bill,

Are you useing 5x8 wasteboard? We have a 5x12 table and have just recently found a local dealer with 5x8x1/4. Its really nice for machining 5x material and even 4x, it gives us an ear to grip for pulling the sheet off the table. Also its less to move around when we are machining 5x12x3/4 mdf. We also found that when we replaced the spoilboard with 48# mdf it seemed to hold better. Definatly cover your open table with plastic or laminate scraps. As for the vacuum pressure, I'm not sure what the 15HP should have as I have a 40HP. Even so I still occasionaly have small parts move.

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Postby Brian Shannon » Thu, Sep 15 2005, 8:47PM

Thanks Guys,

I am using a 5x8 spoilboard and a 4x8(49x97) wasteboard. I will have to ask my supplier about the density. It sounds like the 48# makes quite a difference. Ryan from Thermwood also told me to remove the rubber gasket that seals around the bottom of the spoilboard. I haven't tried that yet.

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Postby Forrest Chapman » Thu, Sep 15 2005, 9:01PM

Brian,

I'm not sure what removing the gasket will do, but another thing is to edgeband your spoilboard. It seals off leakage from the edge.

Seems like the gasket thing would be counter productive.

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Postby Brian Shannon » Thu, Sep 15 2005, 9:51PM

I don't understand the gasket thing either. He said that it is not really needed with universal vacuum where you are sucking through a spoilboard. The edgebanding makes a lot of sense. I'll try it. It can't hurt. Thanks for the tip!

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Postby Bill Rutherford » Fri, Sep 16 2005, 6:10AM

Brian,
We are running the 15 HP Busch pump and I use regular Nordboard MDF for the spoil board. I tried some ultra-light and was not impressed (don't recall the manufacturer). Also as for the edge banding, Forest is right it will help to seal the edge but you need to balance the cost of one or two parts moving against the cost of banding such a large piece. This will also depend on how often you change the spoilboard. We have never used a wasteboard as I have been very pleased with the hold down against the spoilboard. We cut a fair amount of small parts and if the parts are really small then cut a couple of extra.

Just my 2 cents

Bill R

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Postby Jason Susnjara » Fri, Sep 16 2005, 8:12AM

Hi,

If you have small parts that are moving on you, make sure that you have a double pass set for those pieces. Also make sure that your spoilboard and/or wasteboard is clean and that you have as less cuts as possible on the surface. This will cause small parts to move.


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