Vacuum Problem

[Andrew Moura]

I am having a problem with the vacuum holding down sheets (mostly when doing 3/4 or 7/8 MDF doors with no backing), I have tried resurfacing the spacer and nothing changed. I also tried removing the spoil board and checking the the foam seals, in which there was a small part that had come off and was then fixed, but still not working. Just wondering if there is something else i should be looking for. Just to add, the spoil board has areas cut out of it in the middle, however they are shallow cuts and do not go through, would this effect the vacuum?

Set-up

Aluminum tabletop
3/4 MDF spoil board
3/8 MDF spacer
2 X 7.5 HP Busch DSM MM 1252V

[Gary Urlacher]

There are several factors that could cause your problem.
Your spoil board should be re-surfaced as well to be as flat as possible. Get rid of any machining marks in your spoil board.
Then start with a new spacer board that has been machined both sides.

we do not know the specs on your vaccum pumps nor do we know your feed speeds and depth of cut vs part size meaning
onion skin on small parts.

Give us the information on your pumps as well as the feed speeds you are using. Are you using 4x8 sheets or 5x10 sheets.
Everything is relevent here.

Gary

[Dale Wills]

Andrew,

Is the material you are machining covering the whole machine table? If not, it would be best to cover the remaining table as vacuum bleeding will be a problem and you will lose suction. And always remember to try and place new sheets on your table with the bow facing up. This will aid it holding to the table.

Dale

[craig huzway]

i run the spoil board through the edge bander with pvc edging.
lots of vacuum loss there too.

[mohan kommineni]

i run the spoil board through the edge bander with pvc edging.
lots of vacuum loss there too.

yes edgebanding the spoilboard has improved the vaccum effect even we are doing it on our machine

[Neville Bastian]

Hi Guys,
I have two vacuum pumps which I was hoping to use 1 for more than half the time and the second when smaller items start to move.
What I am finding is the staff are leaving the two pumps on all the time because they are paranoid about items moving.
I will try those tips suggested but a friend who has a flat bed machine says that he has a air receiver hooked up to his pump and he has very little movement issues. I thought this was only beneficial if you have a pod machine for that extra sucking power when it first goes on.
What do the users feel about this suggestion.
Have Thermwood tested this theory?

Regards

Neville

[Ryan Hochgesang]

Sometimes it helps improve vacuum flow and sheet hold down by flycutting both sides of the wasteboard/handling sheet, as well as the primary 3/4" spoilboard.

[Neville Bastian]

I thought I'd just add a update in case some looks at this topic in the future. We have a 2100 by 3600 table but the sheet size we commonly use is 1800 by 3600 which is common to my area. I should have realised that I was loosing 15% of my vacuum to the exposed area. I have painted that area plus painted the edge to reduce pressure loss. I do feel our hold down has benefited .
Regards

Neville

[Keith Neal]

As we use several sizes of material on our table I cover the "open area"with vinyl templating material"with a few corian blocks to keep it from curling.When the vacuum is on this gets sucked down as well reducing any bleed.It's easily removable plus I can fold or roll it to fit as material needs call.-Keith

[Will Williamson]

I repair any holes or cut outs with hot melt glue before re-surfacing also if I notice the edges curling up I flip the spoil board over . Also dull tools and high feed rate will cause you problems . But it sounds like your spoil board is worn out , replace it