View Full Version : 1st Vacuum Hold Down

07-05-2006, 07:30 PM
A couple of quick questions for you boters that have a Fein with a vacuum hold down system.

1. Does the Fein get hot when running. I received mine today and the motor gets very hot after 10-15 min.

2. I have a one zone system using Brady's plenum on bottom and spoil board on top method. While it holds acrylic, gatorboard, aluminum and most non-porus items; what has been the groups experience in how tightly these are held.

3. I do plan on masking off the unused portions of the table with corex to keep the vacuum at a high level, but after experiencing how this one zone system works, I may just opt and go for a 6-8 zone. Have any of you started with a one zone and moved to multiple zones? Did you notice a big increase in holding power by just using 1 or 2 zones?

Thanks in advance for any comments. I'm beginning to think, like many of you, that vacuum hold down is a tricky system. There are probably as many variations as their are people with ShopBots.

07-05-2006, 10:27 PM
Hi Mike,
I will give you a short answer here and more to follow.
I started with the high vacuum and gasketing. Pods, pucks or dedicated vac jigs. All work great. Then I wanted to hold items without making a jig so I bought a Fein Turbo III. I have a 4 zone system on my 4'X 8' PRT Alpha. I am very happy with it. I do plan to put a second Fein on the system for the extra volume of air flow, no more vacuum. I have used plexiglas, plywood and trash bags to mask off the un-needed areas in my 4 zone system. This morning I was cutting 3/4" MDF making doors that were 17" X 21" and I had no trouble holding them and doing any of the cuts. Even the outside profile cut that has no tabs. I have cut little 6" starts out of 1/2" ply as test parts with no movement. With my system this morning, when I went and placed the z zero plate on top of the 3/4" MDF I could feel good resistance to moving it as the Fein was pulling through the bleeder 3/4" MDF and the 3/4" MDF I was making the doors from. With the trash bags I found out real quick that having one zone open does not mean that there is little to no vacuum in the rest of the bleeder board! The entire surface should have a mask in my opinion. I also used silicone sealer around the edge of my bleeder. I hope this helps some to tide you over till more is posted. Best thing to do is try it. It, whatever it is, just might work out good.

I am sure I'll be using gasketing for something again but for now, I like just laying something on the bleeder and turning on the Fein then pushing the "green" button.

Have fun

07-05-2006, 10:49 PM
Thanks Ed. I too am trying different masking techniques to see what is the best for the application I am running. Trial and error, but hopefully just more trial.

Any comment on the heat issue with the Fein motor?

07-06-2006, 06:46 AM
With my Henry vacuum you HAVE to make sure there is a flow of air through the motor to keep it cool - is thisd the same with Fein?

07-06-2006, 07:27 AM
The Fein Turbo III is a good choice because it does not use the air that is drawn through the hose to cool the motor. So running it with the air flow almost still will not burn up the motor on the Feins.

I do notice a rise in temperature in my 28'X42' shop when I turn on the Fein. I also understand that the Roots Blowers generate a lot of heat as well so heat is to be expected.

I will try to remember to take a reading on the temperature of my Fein Turbo III the next time I have been running it for a while and let you know the temp on the surface of it.

It may be warm, but it sure is quiet!

Running my PC 7518 router at 10,000 rpm is nice too.

07-06-2006, 11:11 AM
I have two Fein vacuums and a four zone system based on Brady's design; however, most of the time I remove one of the vacuums and cap the secondary connection to the system. The Fein vacuums get moderately warm, but certainly not hot, even when they've been on most of the day. My system with either one Fein or two, pulls 5-inches of mercury (altitude here is about 4,500 feet), which gives me about 2-1/2 pounds per square inch. That holds large pieces very well, but small parts, even 16x20 inch panels sometimes slip.

I've stopped trying to find a way to hold partial sheets with my Fein vacuum(s), choosing instead to leave a 0.020 to 0.050 inch skin of uncut material, rather than risking ruined cuts. I can make that cut in one pass using a 3/8-inch downcut spiral cutter. (For small parts, I set up a GAST vacuum and pods.)

As for the difference between a one zone and a four zone system, I've found that I get better control with the four zone system. My plenum/spoil board is also zoned off with AllStar gasketing tape into four zones. Even with the gasketing tape, there is some bleed between zones, but not nearly as much as there is in a one zone system.

Short recap: Fein works perfectly on full sheets if a 0.02 to 0.05 skin is left (other users have had better luck, but I assume that they're at a lower altitude). Four zone system with gasketing between zones works better than one zone. GAST type vacuum with pods works best for small parts.

07-06-2006, 11:39 AM
I have a 4x4 table with two vacuum zones and a Fein III. To cover up unused areas of the table to prevent vacuum leaks while cutting or routing, I found some clear flexible vinyl roll material at my local hardware store (Orchard Supply Hardware). It is very flexible and molds very well to the top of the table (spoilboard) under vacuum. It reminds me of clear vinyl used for upholstery in cars and home furniture (thinking back to the 50's here). The vinyl was used to cover the fabric and prevent soiling and wear to the fabric. I think the hardware store had three different thicknesses - I chose the thickest and it is still very pliable. Works great.

07-06-2006, 12:06 PM
And others using a Fein vac sucking thru bleeder board;

Obviously 2.5 pounds per square inch of pressure pulling smooth melamine against semi smooth MDF does not produce a great deal of friction when pushed. I have used an aerosol product called plasti-dip; it dries to a rubbery surface. What would happen if you were to spray a very light coat of this onto the spoil board after surfacing it? It dries very fast and I tend to think it would noticeably increase the hold on melamine. I don't presently use a bleeder board vacuum setup or I'd try it myself.

07-06-2006, 12:45 PM
Thanks for all the terrific feedback!

My one zone system works well for large pieces as Mike Richards indicates, but the smaller the piece the more likely the slippage. After reviewing a variety of systems, I probably will change my system and go with a 6-zone system. This would work well for me.

Re the Fein and the heat issue. I guess I was overly concerned about the motor itself. All motors run very warm at hi RPMs, the air discharge around the collar of the Fein is warm, not hot. I ran the Fein a couple of hours today and it seems to do fine.

I am also using a product I bought at a local hardware store that is used under a hardwood floor to reduce vibration and noise. When I laid the stuff on the bleeder board with the vacuum on I was surprised to find that it was relatively porus and thus I can lay boards on it and they get sucked down. Its like having a gasket material on top of the bleeder. I'll let everyone know how this works out with a variety of substrates. I'm thinking it would be great for gatorfoam because I won't have to contend with the ugly "MDF dust" issue when cutting large letters.

07-06-2006, 01:36 PM
re: Double Fein ...

I put a high quality vacuum guage on my vacuume table manifold (4-zone). I have a Fein Turbo III.

With all valves Closed: 6" Hg Suction
With all valves Open with 4x8 Melamine: 5.5" HG Suction
With all valves Open just the bleeder board: 5" Hg Suction.

A 2nd Fein vaccuum will only increase volume of air, not suction. With the experiments above, and others I don't think masking off the unused exposed bleeder board with plastic would help much and I don't think a second Fein would do anything. I think ONE Fein vaccuum is suffecient.

With this setup I'm able to safely hold about 40 in^2 of melamine. Cutting .25 in deep at 3IPS


07-06-2006, 06:58 PM
What if you had one Fein tied to 2 zones and another to the other 2 zones. Wouldn't you get better suction if you then opened all zones with both Feins running? This would give more suction for large sheets that are cut up into smaller sizes. Just a thought...

Re the porus pad I mentioned earlier. I cut acrylic and gatorboard (1/2") today and the pad worked great. Held the acrylic without moving on a 11 x 40" piece cut all the way through. The letters I cut on the gatorboard were very clean, no dust except for some "gator dust" which is to be expected. I did leave a .005" skin on the letters because they were only 2.5" high. The vacuum held the gator very well. I didn't use my dust collector because it would have sucked the letters into it. So there was quite alot of black foam powder, but it cleaned off the pad quickly with my Shop-Vac and my MDF bleeder board was still pristine.

I'll get the name of this pad and leave it on this thread tomorrow.

07-07-2006, 04:47 PM
Mike, I have an 8 zone table and have a Fein and a Shopvac, each one powers 4 zones with a crossover valve that lets me run all 8 zones on one vac or just 4 zones with two vacs depending on the situation. I do get much better hold down on full sheets of plywood by using one vac per 4 zones. On warped pieces, one vac won't hold all 8 zones but running both at once does the trick (usually). Holding Corian seems to work fine with one vac since it's so smooth and heavy.

As for the heat issue, I run the Fein 8 hours at a time with no issues yet. The exhaust air is plenty hot but that's due to the secondary fan that cools the vacuum fan so the hot exhaust is good news. The ShopVac I have seems to maybe have a secondary cooling fan too because it seems to run about like the Fein. I had another older ShopVac that died after about a week of 8 hours per day. This newer one has been fine for a few months now.

I am going to be switching to a more industrial set of blower motors though... http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?xi=xi&ItemId=1611764155
Those were discussed in another thread on here a few months back but I don't know if anyone actually bought one to try it out. The specs look very good and I just don't have the power needed to run a big vac system. My shop's main breaker already hums since I added A/C to the shop this year. I'm thinking of venting the exhaust of those pumps outside so I'm not re-heating the air that I'm paying so much to cool, maybe quieter that way too if I'm lucky.

07-07-2006, 06:07 PM
The only thing that would worry me about the Grainger motor is the life... 700 hours. At 8hr/day, that would last around 3 mo. Sort of expensive @ $228+shipping.

Thanks for the info on the dual zone. I probably will go with that with my 6 zone system - 3 and 3.

Re the porus pad. The name is SoundSolution and it is an acoustical underlayment. It is manf by Healthier Choice (www.healthierchoice.com (http://www.healthierchoice.com)) It is sold by larger home centers. I purchased mine @ Menards in IL for $50. It is a 36" x 33' pad that can be cut to length and reused until it looks 'ratty', then cut some more. It is .085" thick (just over 1/16")
It is remarkable that it lets air through because it is waterproof. Air molecules smaller than water. I guess you could hose it off after use, but that's an extra procedure I don't need.

Anyway, for me is works great and as an added bonus it has an anti-skid surface so if the vacuum is a little sparse on an area of board it would still hold because of the friction.

07-07-2006, 06:35 PM

I thought the same thing about the 700 hour life and I couldn't figure out why it would be so low. I talked with a Grainger rep who put me in contact with a rep for the manufacturer. He told me that the 700 hours is more of a measurement of the life of the brushes. The brushes are only a few bucks and can be changed in minutes. Then you would have another 700 hours. Based on where the units are being used now and the life they're getting out of them, I think I can probably easily get a few years out of them by changing brushes a couple of times a year. I run 8 hours a day on and off, probably an averagle of 20 hours a week with the vacs on, the rest is cut using other hold down methods.

Thanks for the info on the porous pad, I'm going to check that out, it sounds really interesting.

07-19-2006, 08:19 PM
Previously in this forum I had mentioned our compressed air powered vacuum clamps as a viable alternative to large pumps. We now have a couple of new additions that will be of interest to those who need a ready made solution to vacuum hold downs.
Our VC5 clamp will hold itself down to a surface, and then hold a workpiece on top. It has two low consumption vacuum generators built in. The faces can be configured to hold down almost any shape, and no moving parts inside to wear out.
Link http://www.vac-clamp.com/vc5.htm

The other product is a face plug for the VC4 or VC5 vacuum clamp. This is a shim or packer that clips into the face of either clamp. It elevates your workpiece by 3mm to allow you to cut through the workpiece, but not damage the clamp face.
Link http://www.vac-clamp.com/vc%20cnc.htm