Planning my vac system.

[gundog]

I have been reading through the archive on vacuum hold down systems but I have a couple questions. When I built my SB table I constructed it as follows 1 - 3/4" x 8' x 4' piece of plywood bolted to the frame and then another 3/4" x 8' x 4' piece of plywood screwed and glued to the first sheet using a 12" grid for the screws. I then glued a 3/4" piece of MDF on top the bottom of the MDF is not planed just glued then planned for level on top. That is what I am working with.

I have been reading Brady's articles on vac hold down and I am planning to buy a Fein Turbo III or 2 of them. I want to buy some Tru Pan to machine a grid into and make 4 main grid areas with manifolds and valves as shown in many of the posts.

The questions for now I am sure there will be more but what should I do with what I have on there right now? Should I mill off most of the MDF or just cut my vac holes right in what I have there now and seal everything with varnish or some other product?

I am also not sure if using the Feins is the best way to go I like the fact they are quite. I machine sheets of UHMW and HDPE plastic. I machine UHMW in pieces starting out 1.25" thick by 48" by 32". I make several different parts from this it is rather slick will the Vac system hold down good enough? I machine to a .050" skin and trim out my parts with a laminate trimmer now. The HDPE is .500" 54x96" and I also have been leaving a skin on that. The plastic is very slick and I am just hoping I will get enough hold down power. I do not push the tool real fast on any of it no more than 1" per sec. I am just trying to figure out if vacuum hold down will work for my use and if going with the Fein vacs is my best bet.

There is actually so much info on Vac hold down it is hard to filter through it. I have looked at the systems that use other built in vac motors but I don’t want that level of noise. I am not trying to make a real elaborate system I want it simple and fast to construct.

Any advice will be welcomed.

Thanks Mike

[joewino]

After attending the ShopBot Camp in Austin this past weekend I have decided to go ahead with my plan to build a vacuum hold down. Instead of using MDF or other wood product for the plenum I will use 3/4" solid PVC. It is a little more expensive but there is no need for all that sealing.

After hearing all the success stories using a Fein, I'm confident that it will be more than enough for my needs.

Now I have a used sheet of MDF as a sacrifice table and it has been milled twice. I plan on just milling it down to the 3/4" plywood underneath and attaching the PVC to that.

After having my machine for over two years it is just about time to make it work more effeciently.

[Gary Campbell]

Mike...
I am sure others will chime in, but here is my 2 cents worth.

Regular MDF will make a better plenum than Trupan or other ULDF. If you have enough clean thickness available, use what you have. Make sure the sheet is glued down well before you cut the plenum into it, and seal it well, including the edges.

The Feins should work if you use a good mask to cover the area outside the parts (including taping part edges) and you are not located at a very high altitude. Your cut speeds are conservative, but cutting plastic results in high vibration, especially when near the end of the file.

I would be tempted to use a very thin gasketed "pallet" that is custom made for each parts batch. Like you say, the plastic is slippery, and when you combine no lateral friction with vibration and even minimal side force you will have movement. That being said, many others out there have developed workable solutions with a single Fein. IF you keep after it, you will succeed.
Good Luck!
Gary

[bernott]

I'm with Gary on this subject 3/4 ply, reg MDF for plenum and Trupan as spoil board. BUT and a very big But I'm also with Raymond & Brady if you want a table that is stable in all weather condition and you can afford it go PVC.
I built mine about a year ago (ply,MDF,ULDF) because CNC machining is (was) new to me and I really did not know what set up I would need or want to change later, after the learning curve screw-ups I'm glad I have waited to go PVC.

The feins will do you just fine.
Keep reading the SB Forum there is a lot of great knowledge here!!

[erik_f]

This may or may not be of any use to you. I built a simplified version of the 9-15 "vacuum pump" using two of the suggested motors in the open source vacuum thread. In theory, running two of these motors in parallel should pull 9" of vacuum and max out at 200cfm. It was pretty simple to build and I believe I spent about $300 on the parts for the pump. I didn't put any of the valves in to run the pump in series...so my pump is parallel only, but from what I remember this set up will still pull more vacuum and higher cfm than two Feins for about half the price. I used HDPE for my Vacuum plenum and ULDF for my spoil board.

[gundog]

I have been running my machine for about a year and have been screwing everything down. If I have this straight the PVC would be laid down and the vacuum recess paths and zones machined into it then one UDLF or trupan sheet would be put on top of that as a spoil board. For now though if I choose to wait on the PVC I can machine the vacuum grid and zones right into the MDF I have on there now seal it good and get some UDLF or trupan to use on top as spoil board. Do you attach the spoilboard or just let it hold down from the Vacuum pressure?

Mike

[gundog]

Erik,
How loud is your setup? Can you tell me where you bought the motors? Did you use a muffler? I remember reading about these vac systems a year ago when I got my machine. I really don't have time to consturct all the boxes and such but I saw some in my latest search where they did not build everything in a box.

My business is a side line for me and my time is limited so a time consuming project right now is not going to work I am having a hard time keeping up with my orders.

I found a post by Ed Lang that looks as simple as it gets so I am thinking copying this configuration. Scroll down the thread to Ed's post.

Mike

http://www.talkshopbot.com/forum/messages/28/27390.html

[erik_f]

Michael,
Its not too much louder than running a shopvac...I am using a muffler...which you could make yourself (if you want to try I can tell you my thoughts later). I actually contacted Ed Lang and he was very helpful...and helped me through my set up. I can send you some pictures of my set up...and even the cutting files if I can find them. VBTST6460VM is the one I am using. I will try and post some pics of the set up. I would say doing it the way I did it took a 3 or 4 hours working on it on and off to get it done, but that includes all the plumbing and shopping for parts. I felt making the boxes was way over kill for my situation and just wanted to see how well vacuum worked for me. If I wanted to build a more elaborate set up later on I could do that and just change the motors over. As of right now I find no reason to change anything. I can give you more info tomorrow or you can email me if you like and I will be glad to try and help. http://www.centralvacuummotor.com/imperial.htm

[gundog]

Has anyone tried using primer sealer for the MDF plenum and edges of the spoil/bleeder board followed by some latex paint? I have some of this left over from some house painting we did and it seems latex paint would seal really good.
Mike

[tkovacs]

Mike,
No valves, no boxes:

http://www.talkshopbot.com/forum/show.cgi?tpc=28&post=69798#POST69798

This has worked well for me.

Terry

[gundog]

I decided to try and build a simple vac system. I ordered 2 of the 220V motors and 2 mufflers from Light House today.

Mike

[ed_lang]

You will be very happy with your system.

Make sure you size the pipe and clears in the plenum so you can get maximum air movement.

[Gary Campbell]

Mike...
If you purchased the Ametek 117123 240V motors, I strongly reccommend only an air parallel system. I tested these particular motors using a air series configuration, and even tho I could get awesome results, the heat was a concern to me. See this post: http://www.talkshopbot.com/forum/messages/28/32459.html?1217780528
Gary

[gundog]

Gary,
Those are the motors I ordered I planned to plumb it both ways if I ran a fan on the motor impeller do you think it would work? I may just run them in parallel.

Ed,
I planned on using 2" PVC pipe fittings and valves is that big enough? I am not sure how big the grid needs to be to get the proper air flow do you have info on that? I plan to make a 4 or 5 zone system. I routinely machine parts out of 1.25"x48x32, 1.25"x48"x28",1.25"x48"x30" in UHMW and some smaller parts .5"x6"x30" etc & full sheets of .5"x96"x48" out of HDPE. I have not designed the zones yet but I need to keep these dimensions in mind when I do.

The main reason I want to go to the vac system is I machine a lot of dovetail groves in the middle of the 96x48 sheets of HDPE and using screws doesn’t pull the sheets flat enough which then makes the dovetails inconsistent. That creates a headache when cutting the male dovetails to fit on my manual router table. I do not cut my parts through right now I leave a skin and trim them out with a laminate trimmer. I planned on continuing to do the same with the vac system. The plastic I machine is very slick so I am hoping this system will hold my parts from moving while I machine them.

If I could figure out how to post my CRV drawings I would post them so you could see what I am cutting out.

Thanks for all the info you guys have posted I have been studying it to design my system.

Mike

[Gary Campbell]

Mike...
After running these motors for about 10 minutes, the aluminum pipe between the motors got hot enough, that if you spit on it, it would sizzle. Since we may often run them for an hour or more, my mind was made up. You can make your own decision on the series setup.

If I were to set up for your cut sizes, I would make a 4 zone system that has 3 32(x) by 48(y)zones (divided the non traditional way) then I would divide the -X (front or left side)Zone in half for the 4th. I would run two 2" pvc pipes with Valterra valves to each of the large zones and one each to the smaller in front.

I would make a manifold out of 3" PVC, mount the motors in parallel near the front (to maximize vac there) and use a 3by2 wye and 45 to branch off to the zones.

If you look at the chart on the post above, you will see that you dont have to have much leakage in a zone to benefit from the parallel setup. With normal spoilboard leakage the series would show larger numbers untill you cut thru the material, but most likely would end up lower after cutting a large number of parts.
Gary

[gundog]

My Vac motors and mufflers came in so I am ready to get started. I have a couple questions before I start. I have searched and can not find my answers about the grid size for the plenum what size squares to leave and what size air channels to cut? I measured my MDF on the top and it is still 5/8" thick so I plan to resurface it one more time then cut the plenum into it. I still have two pieces of ¾” cabinet grade plywood under the MDF. I need to know what size grid to cut in my MDF.

Gary,
I like the size of the zones you recommended so I am going with exactly as you recommend. I am also going to put in some T-track. How big of a border around the zones do I need to leave? I am also wondering if I need a spoil board if I am cutting plastic and not cutting through it? It seems the plastic would seal really well with out the spoil board. Do you have to have some leakage for the vac motors? Would a perfect or near perfect seal be bad do you need some air flow?

Thanks Mike

[Gary Campbell]

Mike..
On my last plenum I left an inch for 2 reasons. First to allow a surface to adhere the spoilboard to. And second to keep vacuum slightly back from the edges of the spoilboard. Depending on how stable your material is, the smaller can be and the more vac you may have near the edge. Remember to make sure the edges are sealed and glued down well.

Plastic that you dont cut thru may actually benefit from a purpose build hold down "pallet" assuming a very thin and rigid seal to the vac source. Without that you will have chatter.

It is my understanding that the vac motors with separate cooling fans do not have a minumum air flow, in fact that is where the mfgrs rate the vacuum developed at its highest. We have run these same motors for hours like this.

A perfect or near perfect seal is what we all strive for! Let us know how you achieved it!

Gary

6839

[frank134]

PROBLEM. I got ahead of my self putting together my vac table. I bolted down the plywood and polythane that and the MDF real good. Then a friend of mine came over to show me a gun that shoot plactic nails. He uses it on his bot to hold thing down. Anyhow we shoot the plenum MDF to the plywood and I forgot the glue. I try to pull two small broads apart after nail them with the plastic nails.
The mdf broke before the nail gave. Do you think I will be alright with the MDF just nail. do you think I should plane it off and start over. 3/4" x 60" x 120" plenum table.
frank

[billp]

Frank,
Since it's already nailed together why not just go ahead and test the system with what you have? Most of us find that we keep refining the system anyway, so this way you get a chance to test the rest of your gear. Vacuum systems are always "a work in progress" and you will probably do some modifications after you test it out in a real work environment...

[frank134]

ok bill I try it out. If it work this way I guess will have a new way of doing it. If not I guess I will make a new broad.
thank maybe I sleep a little better now.

[gundog]

Gary,
I was not going to remove that much material is that neccessary to get proper air flow? I might need to re-think my plan. I am going to put T-track between the zones on the edge the T-track I chose was 3/4" wide. I planed putting the t-track in the border in the Y direction. I am thinking about attaching the t-track on the ends outside the normal table size. I am thinking of adding some hardwood blocks on the ends and cutting a slot in that for the track.

I am not sure what you mean by a "pallet".

Thanks Mike

[erik_f]

The more material you remove the better flow you will get. If you have too much space between your vacuum grid you may have problems with thin material. I cut my grid using a 1/2" ball nose and in a circular pattern. The idea was to increase flow and reduce turbulence. I'm not saying this is what you should do or that this is the best way only offering it as another idea...it is my first vacuum.

http://www.talkshopbot.com/forum/show.cgi?tpc=28&post=72202#POST72202

[Gary Campbell]

Mike...
A Pallet would be a special purpose non porous "sheet" that is sealed in a zone. It would have holes and or channels to allow vacuum only to the part or parts and not allow vacuum in the cutting area. Look at brady;s column, I think he showed something like this in one of his columns.
Gary