Waste board thickness

[jason galbraith]

Hi All, we have recently changed our waste board with new sheets of LDF. It is currently at the moment 22mm (after a flycut on both sides) thick and we are getting very little suction through it. Does any one have an optimum height that the waste board should be?

[Jason Susnjara]

Hi Jason,

Is that wasteboard thickness on top of your spoilboard? If so, do you normally use such a thick wasteboard?

[Kerry Fullington]

Jason,

Hopefully the 22mm thickness is a combination of your Table Board and your Waste Board.

There have been several discussions about this and most say that LDF is not an ideal material for this application.

Jason Susjnara posted in another thread that from the factory the Table Board is a 32 lb density MDF and the Waste board is 48 lb density.

Brad McIntosh posted this to a thread in 2008 that I found really interesting.

"by Brad McIntosh » Sat, Aug 02 2008, 10:52AM

Nick,

Main Spoil Board-
Our experience here in Canada with our customers indicates that a new main spoil board should always be machined on BOTH sides. The surfaces on both sides of the sheet are somewhat "sealed" in the manufacturing process. The surfacing of both sides opens up the fibers and allows a greater flow through the material.

Waste Boards (SPACERs)-
Experience has also lead us to suggesting to our clients that they start off with a SPACER (or waste board) with an initial thickness of 3/8" (9.5-10 mm). 1/4" becomes too flimsy too fast and begins to curl up at the corners. The 3/8" material allows for a couple more "re-surfacings" before the curl effect makes them unusable.

A couple of other notes:

Periodic Re-Surfacing of the Main Spoil Board-
Since the main spoil board does not get machined into on a "regular" basis by your normal production, some of our clients have gone months without "touching up" the top of it by re-surfacing and removing 0.010" (0.254 mm) or so. What these clients also found was that they would start to have the following issues: 1. The efficiency of the hold down would decrease -and- 2. Their depths of cut would become non-uniform.

We recommend that the main spoil board be re-surfaced once a month at a minimum. This levels it out from thickness variations that can be caused by uneven thickness expansion due to humidity changes, etc. The main spoil board also acts as a filter for the fine particules/dust that is constantly being pulled into it - slowly clogging the top surface. Manipulating waste boards (SPACERs) -sliding them on and off, flipping them over, etc - also can close off the porousness of the top surface. The re-surfacing opens up the top surface and can help to rejuvenate your vacuum efficiency.

Alternating the "Face-Up" of the Waste Board (SPACER)-
Some of our clients will run X number of sheets with one side of the waste board and then flip it over and run another Y number of sheets before re-machining both sides. Although this does not reduce the amount of re-surfacing, it can extend the continuous working cycle between re-surfacing operations. Another side benefit is that curl that can develop in the waste board is minimized by the uniform machining of both sides towards the core of the sheet. This seems to work well with a waste board (SPACER) that starts off with 3/8" material."

[Jeremy Schiffer]

As per a recommendation by Josh Rayburn, we decided to try using HIGH density fiberboard ("door core" or "Rangerboard") for our spoilboard AND wasteboard. 19mm for both, for a total thickness (initially) of 38mm, or about 1 1/2".

Logic would seem to suggest that this setup wouldn't work very well for holding ANYTHING down. But we've had great success with it, so far. The best part about it is that the wasteboard pretty much stays flat under its own weight, as opposed to the 1/4" MDF that we were using, which starts to curl, and vacuum won't hold it down, which makes flycutting difficult and inaccurate, as the board tends to end up thinner around the edges because of the curl.

Using our current setup, we have been able to reduce our cut-through from .2mm to .1mm because of the increased accuracy, therefore extending the life of the wasteboard even more.

Ourse is a 4'x8' table with the 18hp Becker VTLF400 vacuum pump, and we mostly cut plywood and melamine.

The only drawback is that the extra thick wasteboard is taller than the pop-up pins, so it takes a few extra seconds to align the sheet.

[Josh Rayburn]

Glad that's working out! We do use 3/8" regular MDF for wasteboards currently, and premium MDF (Rangerboard) for the spoilboard just as a note. Glad to know it works well with a thicker wasteboard too.
jnr

[jason galbraith]

Thanks guys, we've just put on 18mm thick MDF and it is holding down superbly.