Yeah I’m about to throw the towel in on my factory wasteboard. I’m tired of skimming it. It seems like every time I need precision I find out I need to skim it again. An aluminum base with screwed MDF panels seems like such a smarter way to do this.
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If a super flat surface is your goal, I would think that cutting a .125 inch deep square the size of the work area into a piece of MDF (leaving about a .5 inch border around the edges then pour a self leveling epoxy into the .125 inch cutout. The resulting epoxy surface should be very flat and machinable.
But do you really want a super flat surface? I skim cut my MDF waste surface so it is perfectly perpendicular to the cutting tool at all points in the work area. Perfectly flat would not be near as good for the CNC.
An aluminium base with MDF panels will still need skimming from time to time, however your alu.plate will provide a much more firm base for the MDF to rest on. No much less warping will occur.
I can see skimming a wasteboard if it’s truly just a wasteboard. The wasteboard on a stock XC is both sacricial and structural. Skimming it reduces its structural integrity each time you do it. I have no problem using MDF as a wasteboard if that’s all it’s for. A strong, stable non sacricial foundation in my opinion is a better long term solution.
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You are exactly right about having a very rigid non sacrificial structural base. That is why so many people have a rigid aluminum base with t-tracks as the base plate and then mount 3/4 inch thick strips of MDF on top of it. Using strips will allow you to leave access to the t-track for hold down clamps every few inches (I have three inch wide strips with about an inch space between each). This gives the benefit of a very rigid base, very handy t-track clamping and a top waste board that can be skimmed and easily replaced.
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Granite is used for precision surface plates all the time. And you can get it with threaded inserts epoxied in place. I haven’t searched for something that would fit an X-Carve. But it might exist. The surface plates I have seen tend to be quite thick, however. You might be better served to use granite as a surface to attach the X-Carve to, keeping it quite rigid and flat, and stick to conventional materials for the waste board. Just brainstorming.
Thanks for the feedback. Before I do anything at all, I’m going to test suction cups as a hold down method, just to satisfy my own curiosity. It may be a complete bust, but if not it could eliminate the need for holes and/or t tracks. High quality suction cups are inexpensive enough to experiment with a couple of them. We’ll see.
What was your test results?
Do you have a link to the Misumi track that you used? I went to their site but could not locate it.
Thanks Bob 
At some point I’ll upgrade with a vacuum table, but I believe that your setup has the most bang for the buck.
What is the length of your track?
I haven’t done it yet.
OK, sounds good.
Whenever you have completed your testing we would be interested in how it compares to using a vacuum table.
Also, as far as materials go, what about Corian? It’s basically man made stone, but carve-able.
I would imagine this would be a very bad idea.
Tempered glass is actually under a severe amount of stress. One small nick with a bit, collet, crash the CNC Z Axis, etc., and the wasteboard would shatter into a million tiny shards of glass.
Of course, that’s what tempered glass is supposed to do. Shatter on impact. That would be very bad for a CNC wasteboard though.
On my 500mm X Carve, I had major problems keeping the waste board flat within .002 in a 4" x 8" area. What worked for me was to add support UNDER the original wasteboard, screwed flat to my table, and then screwing the whole machine down onto this “shimmed” table assembly. Very little flex or movement with changes in weather, now.
I also use sacrificial wasteboard fixture plates (1/8" thick) and skim when necessary. So far, so good.