# CNC router table flatness



## mntatonka (Sep 24, 2013)

We've got a 4x8 Pacer/AXYZ CNC router table here, with ballscrews and every other accuracy option they had available, and we've had issues with flatness across the table, even after the waste board is planed. What kind of flatness should I be expecting out of such a machine? 

I have variations of at least 0.010" in the first few inches of the waste board when moving in the Y-axis. That's way too much considering I'm trying to leave a 0.015" flange in 1/32" garolite.


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## Semipro (Mar 22, 2013)

Hello, glad you found us, it's great to have you as a member of the community, welcome to Router Forums.


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## old55 (Aug 11, 2013)

Welcome to the forum.


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## subtleaccents (Nov 5, 2011)

Not familiar with the AXYZ machine. But, what is the condition of the substrate under the waste board. Is the table base rigid or is there a possibility of the base flexing? Is there a possibility that the linears/tracks are moving as the bridge and/or gantry are moving?

No answers here, just more questions that may alert you to a solution.


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## Stick486 (Jan 4, 2013)

mntatonka said:


> We've got a 4x8 Pacer/AXYZ CNC router table here, with ballscrews and every other accuracy option they had available, and we've had issues with flatness across the table, even after the waste board is planed. What kind of flatness should I be expecting out of such a machine?
> 
> I have variations of at least 0.010" in the first few inches of the waste board when moving in the Y-axis. That's way too much considering I'm trying to leave a 0.015" flange in 1/32" garolite.


I'd look to th machine 1st ...


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## MEBCWD (Jan 14, 2012)

Welcome to the Router Forums!

Please take the time to fill out your profile. I does help answer some questions if we know what tools you have available.

It sounds like you might have movement in your spindle or the mount for the spindle. It could also be flex in the gantry if feed rates do not allow the cutter to remove waste material fast enough and put excess pressure on the system. You might try slowing your feed rate when cutting hard materials like garolite, this is a solution I have found useful. 

Also remember materials like garolite will wear down the cutting edge of bits faster than most materials and will start adding that unwanted pressure twist on the gantry and should be replaced or sharpened by a professional sharpening service .

It might also help to locate your material as close the the gantry support arms and side of the bed as possible because you should get less twisting than if your material is in the center of the bed.

I hope this at least gives you somewhere to start looking to solve your problem.

Work Safe, Have Fun, Cut Some Wood(or some garolite),


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## mntatonka (Sep 24, 2013)

I think what's going on is that my MDF wastboard isn't staying down as it's being planed. It's just held down with the vacuum pump, so there's not a lot of force holding it down when it's open for planing. The edges must not be holding down as well as the middle, so they're getting planed slightly thinner. Then, when I set it up to cut a sheet of the garolite, it's pulling down better, so those edges are slightly lower than the middle. 

I do know that there's a slight variance in the aluminum bed the MDF sits on, but it's only a few thousandths. 

It's too consistent to be the gantry flexing or any of those other problems. It's always low on the edges, and high in the middle. I even replaced all the foam gasketing on Friday thinking that was part of my problem.

Out of curiosity, how does everyone else hold and plane your wasteboard? Is it just held down with the vacuum, or do you have it screwed down or something?


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## subtleaccents (Nov 5, 2011)

What is the HP of the vacuum pump? Is it large enough to handle the amount of bleed through the waste board? How many zones are there? Does the size of the part cover enough of the zone to give the proper hold down needed to keep the part from moving?

Is there any vacuum loss in the supply lines to the table?

Again, questions just questions. That is about all we can do since we don't know your particular setup and support equipment.


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## mntatonka (Sep 24, 2013)

subtleaccents said:


> What is the HP of the vacuum pump? Is it large enough to handle the amount of bleed through the waste board? How many zones are there? Does the size of the part cover enough of the zone to give the proper hold down needed to keep the part from moving?
> 
> Is there any vacuum loss in the supply lines to the table?
> 
> Again, questions just questions. That is about all we can do since we don't know your particular setup and support equipment.


9HP busch pump, 4 zones, no (or minimal if any) vacuum loss.

The sheet of garolite covers most of the two zones I use for it, and has plenty of hold down. The parts cut out are large as well, and the cutter is only 1/8" straight flute, so it's not pulling the parts up.


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