Suggestions? 3 Days assembling and my vac system doesn't work

[mayo@difsupply.com]

Well it seemed like a good idea.
After reading about some of the other vacuum hold down products available for big bucks, I thought I'd create one myself.

I spent 3 days cutting and assembling the PVC and drilling the table top (well, the router did that part) and I thought I'd better assemble and test one section of it just to make sure it works.

The system has 3 sections of tubing, each with 2 rows that have 12 air fittings in each row.
You can see this in the photographs.

The fittings and PVC are under the table and a piece of garden hose goes over the fitting, up through the hole(s) in the table, and is flush with the table top.

I hooked up one section as follows:
The section is U shaped with one end plugged with a PVC cap, and the other end connected to the 3.25 H.P. shop vac. Each leg of the U shape runs the 8 foot length of the table, seperated by one foot across the bottom of the U.

When I turned on the shop vac, the row that it was connected to had some suction at the table top but not enough to hold anything except maybe notebook paper or cardboard. The other side of the section had almost no suction at all.

If I connect the other 2 additional sections, I'll get even less vacuum from each fitting.
I think I may have just wasted 3 days and lots of PVC.

Would connecting the whole system from somewhere in the middle, rather than the end, provide the hold down power I'm expecting?

Should I give up on this method and use the routed channels in the table top idea? Would this work using a shop vac?

Is anyone using a shop vac and REALLY getting acceptable vacuum hold down power? If so, I'd love to hear how you did it.

Here's the pictures of my set-up below the table as well as an additional section laying on top of the table just to make things more clear.
www.difsupply.com/vacsys1.jpg
www.difsupply.com/vacsys2.jpg

[Gerald D]

Hi Mayo,

What type and size of material are you trying to hold down?

When you drop a sheet of material on to your table, does the shopvac sound as if it is starting to suck? If not, you have too many leaks, maybe:

- through the porous table surface
- around the end of the hosepipe where it penetrates the table
- through the porous material that you are trying to hold down
- along old cut marks in the table surface
- creeping under the edge of your material

Changing connection from end to middle will not improve anything in this case IMHO

[mayo@difsupply.com]

I did the initial test on a section of my table that had no cut marks, so that's not the problem.

There could be some leaks at the point where the hoses meet the table surface because I have not surfaced the table top yet, in order to make the hoses at the exact same height as the table.

What concerns me more though, is the fact that the suction is way more noticeable on the hoses which are closest to the shop vac, and not noticeable at all at the other end of the section of PVC. Regardless, even the closest ones do not have enough vacuum to hold down material. So my thoughts were, if I change the location of the shop vac connection to the middle of the length of PVC, there's less distance to the end of the section of pipe. Not knowing about vacuum technology and physics, I have no idea if this is a valid point or not.

My first test was on a piece of 3/4 inch plywood which was only about 24"x36" and it covered 6 vacuum ports. I also tested 2 pieces of MDO plywood, one of which was painted. Neither of these were held down sufficiently.

Additional information:
The PVC pipe I'm using is 1" thin wall. I have not glued any of it together yet since it was the initial test. I didn't think any air would leak from the fittings because they are all very snug.
The shop vac has the standard 2.5" hose (2.25" internal).

My table top is admittedly porous - I'm using 1/2" OSB since I will be replacing it periodically after it gets too many cut marks. I didn't think this being porous would have an effect since the hose ends were supposed to be making contact with the board. I may be making a few incorrect assumptions about all this!

I'm going to put a new filter in the shop vac today and see if anything improves. The old filter may be restricting air flow/suction if it's partially clogged with dust.

[Gerald D]

Sorry for asking the obvious:

When your material covered 6 ports, did you close off all the other ports (with plugs) too?

Do you have a dedicated shopvac only for the table hold-down, with no other free air inlets?

My first question remains: Can you hear the shopvac "taking load" when you drop the material on?

In a good vacuum system (no leaks), there is no real flow of air during operation, so the friction loss is not important, and the connection point is not important. The fact that you can notice differences from one side to the other tells me that you have a lot of moving air = leakages.

If your hose-pipes are still proud of the table, your material may be sealing only the mouth of the pipe (a very small area). A low vacuum from a shopvac needs to work over a very big area.

[beacon14]

If you are simply expecting to lay your workpiece onto the CDX table and get suction, I think you will be disappointed. I suspect you will need to create some type of gasket to seal the workpiece to the table. Even then, the CDX is probably not smooth enough to prevent significant leaks. We went through a very similar process and found that the shopvac could be made to work with large enough pieces, but as soon as any leakage is incurred (as when routing through the workpiece, (intentionally or not!) the suction is lost. You can test your suction by closing off all the ports except one. The amount of suction on the remaining port is basically what you would get from each port if you had no air leakage; once the system is closed off by the workpiece, the vaccuum pressure will equalize throughout the system.
In the end, we ended up getting a vaccuum pump (approx. $350 from Grainger), and we make a gasketed vaccuum platten using 3/4" melamine board and self-adhesive foam tape for each sized workpiece. For less than production runs, we usually try to figure a way to brad nail or screw the workpiece down in a non-critical area, it's faster than making a vaccuum platen.

[rgengrave@aol.com]

Get out the duck-tape and seal the edge.

Heard this works

[benchmark@tesco.net]

OOPS !! wrong button


Hi Mayo

I have very good results with a 1100w shop vac working my vacuum table.

There are a few items that will give you a problem , the OSB is too uneven to give a good seal and machining painted or polished materials, for some reason will not stay put as well as unfinished materials. (probable the lack of surface friction)

My vacuum table has a sealed MDF top with 32 vacuum pods, the trick is to use a 1/8” spoil board on top of this, it gives you a greater holding power than working directly on the vacuum table and saves damaging the vacuum table.

I have sent you a picture directly

[Mayo]

The idea was to have just the hose pieces pulling vacuum. This way I didn't have to create a vacuum box. The PVC pipes and fittings and hoses take the place of the box. It was similar to the vacuum pod idea except I didn't intend to make any additional vacuum channels. I thought the contact with each vacuum hose would have been sufficient.

I can now see this was not a good idea for a couple of reasons. It is not allowing me to cut through small parts (less than 6"x6"). The vacuum area of the 5/8" hose by itself is not enough.

Looks like I'll be making a vacuum box and using all this PVC for a custom garden irrigation system!

Are vacuum pumps better than shop vacs, and if so, why? How's the noise level in comparison.

[ron_cleaver]

Paul,

I'm interested in the vacuum pod idea. Can you elaborate on this? I've seen this described elsewhere on this forum, but to me there has not been enough detail to understand how to make them.

I gather you cut a bunch of regularly spaced circles in a sealed MDF sheet. What I don't understand is the plumbing needed and how to make the pods themselves.

Some people use a spoil board on their vacuum table and some don't. Under what conditions do you need a spoil board?

I've seen something that seems to be similar in a commercial product, called flip pods from Carter Products.

[davidallen]

last year I made a vacuum table and used it to cut 150 sheets of plywood for yard reindeer. it worked OK except for the small parts where I had to use tabbing to keep them down. I've since switched to a vacuum puck system (see related posts elsewhere). I like this much better. it uses a compressed air vacuum pump which is much quieter than a shop vac, pulls a much higher vacuum, and isn't as prone to leaks. I still have to use tabbing to control parts that aren't over the pucks but I still prefer them to the old table.

[sheldon@dingwallguitars.com]

Mayo,

Maximum vacuum is 14 psi. That's pretty hard to achieve and maintain. But even 5 psi adds up quickly over a large surface area. You just need to make surface area work for you. Vacuum also needs space to live, not much mind you, just enough to let the air pressure equalize and flow a bit if there are any leaks. On our jigs I use strips of 100 grit stick it abrasive. This gives the vacuum the room it needs and helps keep parts from shifting. Closed cell foam tape seals the edges.

If you have a strong enough pump with enough cfm, an mdf spoil board should disperse the air flow enough that to make your current plumbing layout work.

[benchmark@tesco.net]

Hi Ron

The vacuum table is basically 2 sheets of sealed MDF with wood spacers between them to form a box, there is no plumbing other than one vacuum connection.

The top sheet is machined with 32 square recesses 5mm deep with my shut valves in the centre which open when you place your spoil board or material on it.

I use spoil boards all the time when I machine through my material, saves replacing
the top of the table and damaging the valves.
I only work directly on the table if I am engraving. For some reason the spoil board seems to give me better holding power.

The valves I have made for me, depending on the amount I have made they are about $3 - $4 each.

I will ‘E’ mail a picture of them to you. I can also supply the Shopbot machining files as well.

The Carter pods are very expensive, especially if you cover the whole bed or hit them with a cutter.


Paul

[sheldon@dingwallguitars.com]

Paul,

Put me down for an email photo too please.

[carol]

Could you post the photos here for all to see?

[mcw]

Paul has sent the picture to me, and with his permission, I have some webspace I can put it up on. Also, Paul if you are willing to share the cutting file for your table top, I would like it. I am also interested in more information on the valves that you use, and most likely will want to order some!

[benchmark@tesco.net]

Hi Brian

Glad you like the table, it has taken a long time to get to a table that works easily.

Yes it is OK for you to post the picture on you website, much appreciated.

I am putting togther a vacuum table kit with the valves, Drawings, cutting files and some instructions.

I will keep you posted

Paul

[benchmark@tesco.net]

For all those interested in my vacuum table and would like a closer look Brian @ www.millercustomwood.com will post a picture on his website.

Thank you Brian


Paul

[benchmark@tesco.net]

For all those interested in my vacuum table and would like a closer look. Brian @ www.millercustomwood.com will kindly post a picture on his website.

Thank you Brian


Paul

[roney]

Brian, I visited your site, however I could not find the pics of the vac table. Could you please tell me where they are?
jrc

[mcw]

I havent been able to upload the picture to my ISP yet, as they are going through some upgrades, and it wont let me through. I will upload and post the address as soon as I can get through....sorry for the delay.

BM

[mcw]

Sorry it took so long, but here is the picture of Paul's vacuum table with the custom valves!

http://www.millercustomwood.com/Valve.jpg

Brian

[kodama@austin.rr.com]

Can you show and/or give more informatin about the valves.
Sincerely,
Wayne Locke

[paul]

Wayne

Brian has posted a picture on his website for me

http://www.millercustomwood.com/Valve.jpg

There is more info earlier in the thread, if you need any more help please let me know


Paul

[djhazeleger@mindspring.com]

Do you have a drawing and parts list for valve? or possibly sell the valves? I like the setup and want to build one.

[garbob]

Paul,

What kind of material are you using for spoil boards?

Your table looks neat. Good going.

[paul]

Gary

I mainly use 4mm MDF or 6mm LDF (lightweight). I try different makes as their quality varies, I just look for the most porous one.

I use the 6mm for my repetitive jobs when I use location blocks fixed to the spoil board to locate my panels.


Paul

[paul]

Dirk

I am putting together a kit for a vacuum table, it will be ready soon

[ron_cleaver]

I've been looking for some 1/8" MDF or 1/4" MDF to use as a spoil board in Paul's design. I can't find anything like it (in Northern Virginia). In fact, the only thin 4' x 8' sheet goods I can find are 1/4" hardboard and pegboard. I can't find any 1/8" sheets of anything except tileboard (looks like vinyl covered plywood) which won't work as a spoil board. I even checked for 2' x 4' and 4' x 4' sheet goods.

Does anyone know where to get 4' x 8' 1/8" MDF or 1/4" LDF?

[davidallen]

what about underlayment for flooring?

da

[benchmark@tesco.net]

Hi Shopbotters

Sorry for the delay of my vacuum kits, I have been away Holiday/Working ..... I also had to check with Ted that it was OK to let everyone know the kits are for sale through the forum.

The complete kit of 32 vacuum valves, instructions, DXF files and Shopbot cutting files is £71.00 + shipping @ current exchange rate of $1.38 = $98 + shipping.


Picture Thanks to Brian Miller @

http://www.millercustomwood.com/Valve.jpg

[Mayo]

How well does this setup handle small parts?
What is the reason for the additional holes in the MDF that do not have any valves in them? Wouldn't they defeat the purpose of only having vacuum on locations that have the valve depressed?

[ron_cleaver]

Paul,

So how would I go about ordering a kit? Do you accept credit cards, PayPal, etc? What is the shipping charge? Those who want to order by mail will also need an address.

BTW, your design is dependent on using a 1/8" MDF spoil board. I haven't been able to find any in my area yet (Northern Virginia, USA). I've checked local home centers.
So I need to find a source for the MDF before I place an order.

[williamim]

Has anyone received an answer from Paul about ordering the Vacuum Kit. The last information I received was the cost of the kit. I have not heard from him since my last e-mail requesting information about placing an order.

[williamim]

Anyone interested in Vacuum Cells check WWW. Rockler.com they are selling a U-Mach Vaccum Hold-Down kit for $39.99 part # 23530. Kit imcludes gaskets and Vaccum Cells. These are the type of vacuum cells that Paul used on his ShopBot.

[ron_cleaver]

It seems Paul disappeared from the planet. What happened to his offer to sell a vacuum hold down kit?

How many of the U-Mach kits do you need for a 4 x 8 foot table? How do you assemble it?

[rgengrave@aol.com]

I sent him 3 emails months ago and never heard a word?.

Ron V

[williamim]

I have also sent Paul several emails with no response so I purchased two of the U Mach kits only to find that the ball valve in the kits are to small for use with the ShopBot. No loss I will be able to use them elseware in the shop.

[danhamm@abccom.bc.ca]

I have found a simple way to make the valves'
I have a couple of pics, if anyone is interested
I could pass them on to Ron V, if that is acceptable to him, My web server is having problems.. the valve parts can be picked up in most plumbing wholesales, they are plastic,
the whole valve including the spring costs about
$2.00 I have put one together but don't have time to get really involved right now..

[ron_cleaver]

Dan,

I'd like to know more about those valves. I have the time to put something together, including cutting files.

Why not post the pictures here?

[dan@burningimpressions.ca]

\image Here is one pic,
The body is of PVC the ball is a superball cut in half,the spring is a piece of 1/2 door spring,

The end of the spring is made to center and insert
into the center of the rubber ball.. a
pad is drilled and the the bottom half of the pvc
is inserted through and the top put on with spring
and then glued, then make your vacuum seal or pod..

[ron_cleaver]

Here are Dan's pictures:


5293


5294

[danhamm@abccom.bc.ca]

I have gotten my web server problem somewhat sorted out, I have the pics in higher res. plus
a drawing of what my pod should look like finished
"somewhat"
www.burningimpressions.ca/podparts