Light MDF spoil board

[carlcnc]

I am using "light" MDF for spoil board.
It appears to leak horizontally between zones.
much more so than regular MDF.
I am thinking to cut a kerf within 1/16 of bottom between each zone then fill it with polyurethane caulk or maybe titebond type 3?
I was wondering if anyone has a better method?
thanks
Carl

[billp]

Carl,
The simplest way to stop this is wrapping the edges of the entire table with duct tape...

[scottbot]

Carl
I've been using the light MDF as a spoil board for over a year now with no real problems. I use two Feins for the vacuum source.

Scott

[jerry_stanek]

I like to seal the edges by coating them with shellac 2 or 3 coats seem to work out well and when you resurface you don't have to worry about the tape snagging or falling off.

[carlcnc]

Guys
thanks.
it is not leaking on the perimeter, that's sealed.
I am getting so much "crossflow" between zones that
if I am using only 1 zone I can get parts to stick in the next zone.the more area I cover in zone 1 the more flow I get thru zone 2 and even a bit in zone 3
my pump is an Air-Tech, 112cfm/29"hg.
I just finished with the kerf_and_caulk idea between zones.
I'll report my results.
thanks

[jerry_stanek]

I have seen where someone cut their spoil board into zones and sealed each edge.

[nailzscott]

I cut gasket slots between my zones in the vacuum zone board and put in gasket material from Allstar before setting my light MDF board down. I cut the slots so the gasket material barely stuck up above the vacuum zone board. I also used plastic screws from underneath to screw down the spoil board to do the final compression of the gasket. It was probably over-kill, but it works. Allstar is here:

http://www.allstaradhesives.com/gasketintro.php

[eaglesplsh]

Jay Wyant who holds the Virginia SB camp was having the same problem and solved it in a similar way. He used an 1/8 end mill to cut slots between the zones after the TRUPAN was glued down on the plenum. Then he filled them with epoxy. When you look at his table, it looks like he has dark lines outlining each zone.

I plan to do the same thing on our table in the next couple weeks. I'm not sure what type of epoxy Jay used in the slots, but I ended up buying a gallon of Bondo brand resin at Home Depot (in the paint/wall patch dept.) It was a lot cheaper than any of the epoxies I found at other suppliers. I figure it should work fine, since I'm not looking for a structural bond, just filler.

I considered the caulk but assumed that it would be hard to get it down deep into the slot. I figured that the glue wouldn't dry well in that thickness/depth.

Looking forward to hearing about your results...

Russ

[thewoodcrafter]

I did the same as Scott.
Gasket each zone.
Works great.

[chuckster]

I cut a 1/4" groove in my spoilboard to seperate all 4 zones, then glue in a 1/4" wide x 48 long strip in the groove as well as a 96" piece for the x. This way when I need to replane the spoilboard, it smoothly removes just a bit of the inlays. When using an adhesive or caulking, it tends to pull it out when replaning.

[ed_lang]

Yes Russ, you got the right stuff to pour in the cuts and it will be ready to surface the table in half an hour or less.

Use duct tape on the outside to keep the resin from leaking onto the floor. Then just peal the duct tape away.

Easy and quick.

Remember to cut all the way down to the plenum board.

[carlcnc]

My Results

My quick fix helped. I used the polyurethane construction adhesive. now when using one zone I get 16-20 hg of vacuum.
Next time I replace the spoil bd I think I will go with the indvidual piece for each zone method.
then as I lay them in I can glue them together at the edges.
Carl

[eaglesplsh]

Thanks Ed...

I'm also thinking about taking this embedded resin concept and applying it in one additional way...

I need to layout a grid of locator pins across my table. The pins will need to be removed when I'm running full sheets of material, of course. In the past, I experimented with drilling holes and placing pins in TRUPAN. The TRUPAN is really too soft to hold the pins well/acurately - the holes get enlarged from bumping parts against the pins and inserting/removing the pins with pliers. Putting removable pins in a vacuum plenum without creating air leaks adds a whole new challenge to the mix.

My plan (again I haven't tested this yet) is to pocket out over-sized holes in the TRUPAN and fill these with resin as well. Once the resin is hard, I'm going to drill and tap a hole in the center of the resin plug. Instead of using round pins, I'm going to use socket head cap screws that thread into these holes.

The resin should give me a hole that holds up to some abuse and it should keep the vacuum from escaping through the hole. Another important bonus - it won't hurt my bits when I cut into it/surface the table (I nixed using metal bushings for this reason.)

[jerry_stanek]

Russ you could pocket out and install a hardwood piece you could put an aluminum tee nut in it to screw your bolt in.

[curtiss]

I set up a two zone vac for a 48 x 48 table, I use the center zone most of the time.

I laid out a grid of 1/4 holes that hit the high spots of the plenum on 5.5 inch centers starting at 2,2... 2,7.5

I did not drill all the holes due to the metal below..

I use those holes for clamps or simply hold an item with a few 1/4 inch lag screws from below. you do have to miss the screws....

Have 1/2" Trupan over the top, screwed down at the edges that I surfaced with the vacuum on. Seems to work well so far.



48 48 vac 2 zone.pdf (http://www.talkshopbot.com/forum/messages/312/48_48_vac_2_zone-46660.pdf) (15.2 k)

[jim_vv]

Carl,

A while back I had posted on this. I used 3/4" ultra lightweight MDF and cut it into quarters. I then used silicone to seal the edges of each piece and each zone. I now have four independent zones that don't need to be masked off because of leakage through the section of the MDF.

I do a lot of V carving on pieces that are about 13" x 24" and just mask off the rest of the one open zone with shower pan liner.

Just yesterday I cut a bunch of movie set parts from 34 sheets of 3/4" AC plywood (all zones open) and held them down nicely with my two Fein vacuums.


7381

Kind Regards,

JIM

[ababian]

Jim,

I have had my shopbot for about 3 or 4 years now.I probaly don't have 200 hrs on machine. Been cutting 3/4" plywood cabinet parts. Been trying to figure out a vacumn table setup that would work for me. Sounds like you are happy with your setup, could you show me or tell me about your set up? Would very much appreciate it.

Thanks in advance.

[woodturner]

Just a thought. Couldn't you cut the spoilboard for each zone and then just edgeband it all the way around (if you have a bander, or at least the iron on stuff that is!)?

I ask because I am facing this exact task tomorrow. I bought some LDF stuff and it's 5x8 and my table is 5x10. I need a splice anyway. Why not two more joint lines separated by edgebanding?

[dlcw]

Ed,

I did exactly like you just said. I've got a PRS Alpha 96x60 divided into 4 zones. Each zone has it's own 1/2" Trupan spoil board edge banded with melamine edge banding (I use a hand iron and a J roller). This seems to have a much lower leak factor then wood veneer edge banding. Each spoil board is screwed down to the plenum. Each zone has its own 220vac vacuum pump mounted directly to the vacuum plenum. My shop is at 2500' altitude and I'm pulling 7 to 8 hg in each zone.

At some point I might add a second vacuum motor to each zone but right now it's doing the job. I would probably plumb the two zone motors so that I can run them in series or parallel, using valves, depending on the hold down requirements.

In the future, as time permits, I'm going to but a gasket seal around the edge of each zone board to help reduce any horizontal air leaks.

Don
www.diamondlakewoodworks.com (http://www.diamondlakewoodworks.com)

[jim_vv]

Allen, I sent an email to you with my phone number if you need more detail.

Here is what I did for my vacuum setup.

I plumbed my four zones with 2" PVC as shown in the ShopBot manual (slightly modified).

Each zone has a valve.

Instead of one tee in the manifold for the blower I installed two tees for my two Feins (and one more for a vacuum gauge).

I put a valve on the vacuum inlets so that I can close one in the event that I want to run only one vacuum and not suck through the unused vacuum. (I actually do most of my work with only one zone and one vacuum.)

I used the ShopBot vacuum plenum file which machines for four zones and then sealed the plenum with poly.

I then cut my 3/4" lightweight MDF into quarters and siliconed it to each quadrant of the plenum and siliconed the edges where they all meet. Afterward, I sealed the outside edges of the MDF with silicone.

After machining the table flat I occasionally have to trim the silicone between the zones off with a sharp chisel.

This setup works great for me. With all zones open and both vacuums running I can hold down a potato chip shaped piece of 3/4" plywood


One more thing......I just got rid of the Fein vacuum hoses and hard piped them to my manifold with more 2" PVC. I have had my eye on the hoses over the past few weeks because they suck themselves flat while under load and I was concerned that they would eventually crack. This may have been bad if one cracked and I lost vacuum while cutting some expensive material.

Ed,

I think that the edge banding is a good idea too.

Kind Regards,

JIM