View Full Version : what type of bleeder board to use?

Sat 11 May 2013, 07:14
Hi all,
I am in the process of building a vacuum table. I have ordered 2 light house blowers and will add two more soon. I am building a vacuum unit based on the design information of Gary Campbell / Daren LaBranche from the shopbot site. Lot of good information here.
I am planning to separate my table into six separate sections milling channels say wide and about 1 apart in both x and y directions into my existing spoil board. Here is where I have a few questions,
1: Should I separate the sections by cutting, say 5/8 deep and 1/8 wide and fill with resin to isolate the sections? I intend to resin the entire surface after I cut the groves including the edges.
2: I intend to use a bleeder board on top. I read a several things on this using different thicknesses to mdf ultralite, trupan or any other seductions. What is the better material that is stable enough not to bend?
3: Should I mill the resin off the high flats prior to glugging the bleeder down?


Sat 11 May 2013, 07:30
1) which ever that make you happy
2) no bleeder board, no bleeder board bending problem
3) IF that make you sleep better, go for it.

You will find all you answers when you have the system running.

Sat 11 May 2013, 07:35
Hi Alan,

It is my understanding the since the entire surface of the main table is sealed, the 5/8 grooves that you describe are not required. It is the bleeder board the requires the separation. The bleeder should be sized according to the table section and its edges sealed. When adhered to the smooth area around each section it becomes isolated from the others sections.

Correct me if I'm wrong.

darren salyer
Sat 11 May 2013, 08:00
I went a much simpler direction.
One 3" port through my table, under my 4x8 vacuum plenum board. When I need to hold a smaller part, I mask off the rest of the plenum board with some 1/4" UV coated plywood scraps. I've held as small as 6" square .
If I had a run of many smaller parts' I could make a plenum the size of my parts and replace the large one with it.
Fast. Easy.
The multiple zone plumbed systems do look cool though.

Sun 12 May 2013, 02:25
Mine is exactly how Darren did his. I'm too lazy to cater for every possible future variation. 1 plenum board machining, 1 hose, 1 pipe, 2 motors, some wiring. Viola, done in an afternoon. didn't even has a leaky bleeder valve to contempt with. It turn out that the vinyl carper I use for masking is an effective dust cover.

Sun 12 May 2013, 07:56
Thanks for the input thus far. I am still leaning towards a 6 section table as my work changes daily. I will separate the bleeder board sections and seal the edges as suggested.

I still would like to here the pros and cons and experiences that others had with their bleeder boards and what type bleeder board material used along with their thicknesses.

I am not afraid to try stuff, god knows <"I am a MechMate owner">, I can always mill the board off and try something else if I am not happy with the results.



darren salyer
Sun 12 May 2013, 08:01
I have a piece of 3/4" Trupan that I machined a 1/2" x 3/8" deep grid in, leaving 1" squares intact. It is installed on my table grid side down over the vac hole in the table. My work piece goes directly on this. I can feel slight air movement with my bare hand when I put my hand on the Trupan with the vacs on. I did not mill the face off the Trupan.

Sun 12 May 2013, 09:12
Hi Darren,

If I machine my exiting table as described above and add a piece of say 1/2" Trupan glued to the remaining 1"squares of the table do you think there will be sufficient holding ability? This will also act as a sacrificial table and can be replaced as required with out re-machining a new piece each time.

Excuse my ignorance I am not familiar with the Trupan product nor a vacuum table.


darren salyer
Sun 12 May 2013, 09:49
If you build to the "blackbox" plans or similar, I'd say Yes, that will work fine.
Its hard to believe the vacuum will go through a full sheet, but it was a "Holy Cow" moment for me the first time I fired it up and tried my best to shift a sheet on my machine.
2 motors will work until you get to the small stuff ( less than 200 sq. inches or so.)

darren salyer
Sun 12 May 2013, 09:51
Trupan is merely a brandname for Ultralight Medium Density Fiberboard. Any brand of Ultralight MDF should work fine, it has less density which is what makes it lighter, thereby being more porous.

Sun 12 May 2013, 17:28
Thank you, that is what I will order.

At least for the first venture.


Gerald D
Mon 13 May 2013, 00:20
Trupan makes a range of boards in different densities. Ultralight is just one of their many products.

Mon 13 May 2013, 05:28
No Trupan here, just good old stock Made in Malaysia MDF.
1 hole, 1 sheet with grids, 1 make-shift bleeder valve. Will flatten full size 1" hardwood nyatoh panels with ease.
I'll stick to vinyl floor mat + box tape masking method.
Didn't find the need to add a 3rd motor or a microprocessor control to handle the motor...
All I want is to hold jobs on the table... That's all...

Mon 13 May 2013, 16:28
Thanks, that is helpful. I am still going 6 sections. I am starting with 2 vacuum then will increase to 4. Most of what I do is hard woods. I read somewhere that some people are milling both sides before use. Is necessary?

Some suggest that they use plastic panels around the work piece and that also gives the work additional support. I have tons of 1/8" Plexiglas so that will be easy. I guess I could even shape the Plexiglas to the shape of small pieces for extra side support.

But, better get it going first, I am planning to start in about a week I will post progressive pictures.