Nomad Pro - Workholding Aluminum Perfectly Flat to Wasteboard

Every 8x8 aluminum stock I use has an imperceptible curve. How do I get it to lay perfectly flat onto the wasteboard? I want to utilize the entire 8x8 area of the stock (mostly). So I have been using double sided tape. But when I set the depth of cut, it varies wildly across the entire surface. Very noticeable when beginning my cuts and very noticeable when I try to cut the piece out at the end. Should I find a way to screw it to the wasteboard? Should I place a heavy weight on top of the stock? This is driving me absolutely bonkers, please help.

What alloy are you sourcing?

What temper is it?

What is the surface flatness tolerance of the material?

What is the purpose of the machining? What sort of parts/cutting are you trying to do?

What sort of finish do you need on the surface?

What alloy are you sourcing?
Aluminum 6061

What temper is it?
T651

What is the surface flatness tolerance of the material?
Not sure what this is or how I would find it. Purchased a quantity of 15 8x8, 1/4 inch plates about 2 years ago from Xometry.

What is the purpose of the machining? What sort of parts/cutting are you trying to do?
I’m cutting out 5 medals (3inch diameter each - 1st, 2nd, 3rd place medals, gold, silver, bronze) top left, top right, middle, bottom left, bottom right

What sort of finish do you need on the surface?
Finish does not need to be perfect, I will sand and paint afterwards. Although, the finish I’m acheiving is very smooth. IMO.

An example of my problem: To cut out (contour all the way to the bottom of the stock) varies for each medal on the same sheet. If I were to use the same total depth of cut on each of the 5 medals (.125in), some cut all the way through to the to wasteboard, some cut just to the doublesided tape, some do not even cut all the way through the stock. It’s maddening.
In the image below, I set my zero at the top of the stock, I set my total depth of cut the same as the thickness of the stock, .125in. None made it all the way through the stock in this particular instance, just the most recent one I’ve done.

What surface are you mounting this to?

If MDF, have you surfaced it?

If an alu. threaded baseplate please check how flat it is relative to the machine.

I am mounting this to the orignial mdf wasteboard that came with my Nomad Pro. I have not surfaced it.
It doesn’t APPEAR to need surfacing but that could be my own misconceptions. How would I go about surfacing this? And how likely is that the issue?

The MDF is more variable than metal, esp. if it absorbs any ambient humidity.

If it’s not flat enough for your needs, then start by surfacing it off — that should then allow a suitably flat surface to start from.

Ok I will try that. I have been thinking about doing it. What is the best method for surfacing the mdf? My largest end-mill currently is 1/8th inch. The 102 and 102z.

A #102 should be fine — (a #102z was used to surface the bed of your machine as part of the commissioning process)

Will, thank you for your quick responses and suggestions. I already have a plate on top of the waste-board in the middle of jobs. When i finish with this one, I will try resurfacing. Thanks again!

If/when you do need more stock, you could look into “mic 6”

It is a cast aluminum with purportedly no internal stress and the tolerances on it are fantastic. Certainly more expensive than your standard piece of plate but that might be offset by your time saved. (It is for me at least)

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Thank you Tyler, good advice!

Based on the project I’m guessing that you aren’t too concerned about the precise thickness other than appearance so variation in thickness isn’t really an issue. What you need/want to deal with is having it sit flat on the waste-board.

I’ve done a bunch of work with sheet brass and the issue is that it often has slight warps or curvature. I put it on a flat surface and figure out which side is up or down - in other words choose a down side that has edges up. It’s pretty easy to hold one edge against your test surface tap the other edges to see if they are lifted off of the surface - you can detected very small warps this way.

I have a surface plate but you don’t need anything that accurate, I also will use my table saw table. A stone countertop would also work.

Once you have determined the warp direction use it to your advantage such that securing the edges of the sheet works against the small amount of spring from the warping. This works well enough that I do it every time I’m working with sheet material.

Your setup doesn’t rely on edge clamping or holding of any form - it would be hard to take any warping out with just tape. I would use the screw plate for your job and just put a couple of screws thru the stock in between the medals and also use the warp to your advantage (sprung against the hold down screws)

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Hey Dave,
Thanks for the information. I have tried a quite a few things since I posted this and I’ve used all the techniques herein. Great information. It’s simple but if you’ve never done it before it may not seem obvious. Thanks again everyone for your suggestions! Big Help! I love this community!