I'm off roughly .045" mechanically. I give up

So I’ve officially lost my mind, to the point I want to light this thing on fire.

I’ve had serious issues trying to get my machine to get correct depths. I’ve done absolutely everything I know to do, and I and a buddy come by who runs a machine and CNC business is scratching his head as well. I’m off roughly .045" on the x axis. So here’s the best way I can describe the problem. I went to do a cut at .125"

Using a test block that’s exactly 2" tall, I put the spindle to barely rest on it on the furthest to the left side of my waste board (y position is irrelevant). And then slide the spindle all the way over to the right side of the waste board, I’m .04 off (using a piece of “flat” pine). I did the same thing for MDF which is obviously more true, and it ended up being .05" off. Ergo, a rough estimate of .045"… So going off the original .04 being off from right to left. I loosened the x carriage, and put the spindle in the middle. used the same 2" block and put a .02" feeler gauge on top, set the spindle on it and tightened everything down. I’m at .160 on the left, and .120 on the right. I’ve adjusted every v-wheel, both static and dynamic. I’ve checked belt tension. Everything is square. I don’t know what else to do. Does anyone have any help or suggestions, because I’ve officially hit my breaking point trying to figure this out for the last week and a half.

To eliminate possibilities, have you measured from the bottom of the gantry to the wasteboard?

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  • Level the waste board within reason relative to the X-gantry.
  • Use a large flat bit and perform a skim cut

This will ensure the Z is parallell to the waste board.

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I haven’t recently, but I will again tonight. Pending it is off, what’s the usual way to adjust?

What’s the easiest way to level the waste board? And I’m just finding it difficult to spend that much money on the 1000mm, and I have to resort to skimming the WB to get it true - which is infuriating. Or is it just me getting irritated over “the norm” in the industry?

Are you .045" off in height or X-axis(left to right)? So I you move from your reference of 0" to 10" it moves to 10.045" instead?

Have you calibrated your X-controller via the $100,101,102 codes?

Leveling the wasteboard is something that should be done to make your CNC leveled, MDF is not a perfect material and can move with humidity, however, I would recommend that you do this to the secondary wasteboard. Did you install a secondary wasteboard that you can damage if the bit goes through, where you have something to attach your hold down clamps? When it gets damaged, gouged or out of level, you can reface it again. I use the Whiteside 6210 CNC Spoilboard Surfacing Router Bit, 1/4" Shank that you can find on Amazon to perform this task. It is much faster and provides a better finish than trying to do this with a 1/4in endmill. You run a thin (probably 0.1in) pocket toolpath for the whole surface of your wasteboard.

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Level in this regard = getting the X/Y plane (WB, waste board) parallell to Z (spindle)
First order of business is to get the existing WB close, then do a skim cut.

MDF swells/contracts, it may sag in the middle due to lack of support, its a “living” thing.
Getting the surface as true as possible a skim cut is required, Xcarve or not.

I use a 3/4" flat bit, set stepover to 80% and do light cuts untill all of my surface is touched.

Before you start cutting your waste board there are some things to check. The X Carve is a great machine once properly setup. The first thing your should always verify is that the surface your machine rests on is FLAT. Notice that I used the word FLAT and not LEVEL. Your machine does not need to be LEVEL but it MUST be FLAT. The X Carve is NOT a rigid machine and will take the basic shape of the table ir rests on. If there is a deviation of 0.045" then it should be relatively easy to see with a good straight edge. A better way to check it is to use a Digital Angle Finder. Below is a link to one. There are cheaper ones available but this one reports a repeatability of 0.1 degrees. Most others are 0.2 degrees.

Digital Angle Finder on Amazon

First, lets verify that your machine is FLAT.

  1. Place the digital Angle finder on the front edge of your waste board where it is screwed down to the 2020 extrusions.

  2. Zero out the display so that it reads 0.00 degrees.

  3. Move the angle finder to the back edge of the waste board where it is screwed down to the 2020 extrusions.

  4. The display should read 0.00. If it does not then your table is not FLAT and MUST be fixed before you can truly get your machine dialed in.

  5. If it does read 0.00 then your table and machine are FLAT.

If it is not flat then you could place shims under the low corner(s). However, this is a temporary fix and will eventually lead to the center of your waste board to sag because the extrusions that support your waste board in the center will no longer be in contact with the table it is sitting on. You could remove the waste board and place supporting shims under the extrusions but in time that will probably not be sufficient either. If all you ever carve are V Carve signs then you could probably get away with it but any type of relief carving will begin to show tool marks as your waste board begins to take the shape of the table top.

A better way to fix a table top that is not flat is to add a piece of 3/4 inch laminated plywood. under your machine. Birch that has already been sanded is a good choice. Not Pine that is designed for exterior use, it is often bowed which will only add to your problems. If needed, you can shim the plywood rather than your machine as long as it doesn’t require a lot of shimming.

Next lets check to see if the Gantry is Parallel to the waste board.

  1. Move the Angle finder back to the front of the waste board and insure that it reads 0.00. If not then zero it out.

  2. Jog the gantry to the front of the machine

  3. Place the angle finder on top of the gantry and note what the readout shows. (Based on your original post, I suspect this is where you will find your error) If it does NOT read 0.00 then your gantry is NOT Parallel to your waste board. If it DOES read 0.00 then slowly move the gantry along the entire length of the Y axis. If it continues to read 0.00 throughout the length of Y axis travel then your Gantry is parallel. If it changes from 0.00 as your machine is moved from front to back then your Y axis rail height is not the same on each side meaning that they are NOT parallel. This will have to be fixed to proceed.

Fix out of parallel Y axis rails

(This works best if the belts for the Y axis rails are removed but can be done with then installed.)

  1. Cut a small block of wood that fits snugly under the front of one of your Y axis rails. Draw an Arrow pointing to the front of your machine and one pointing to the left or right. Also mark two lines, one on either side of the rail when it is under the rail so that you can insure that each rail sits on the same spot on the block

  2. With the block of wood under one rail at the front, loosen the screws where the Y axis end plate attaches to the bottom extrusions that support your waste board.

  3. Move the Gantry as far forward as possible to insure the left and right spacing is correct on the rail. The block of wood should be supporting the weight of the rail, then tighten the screws and remove the block of wood. You should use a hammer to gently tap the wood to slide it out. If it slides out too easy then it wasn’t supporting the weight of the gantry and you need to make a thicker block.

  4. Move the block of wood to the other rail at the front and repeat.

  5. Next do the same for both Y axis rails at the back of your machine. If you find that one end of either Y axis rail does NOT lower down to the level of the block of wood then you can loosen the screws that attach the top of the Y axis end plates to the rails for a little more adjustability. If that doesn’t work then your block of wood is too thin and you will need to start over with a thicker block. Just remember to keep the wood with the arrows always pointing in the same direction and that the rails are resting on the same spot on the block.

  6. Once finished repeat the steps for checking that the gantry is parallel.

At this point your X and Y axis should be running true and parallel to the waste board. The error of 0.45" should be either gone of greatly reduced. Next it’s time to consider adding a secondary waste board.

Secondary waste board Pros and Cons.

  • Pros

  • A secondary waste board should be cut to a size so that when it is surfaced there won’t be any lip around the perimeter which will affect carving on stock that is longer than the machine.

  • It is easier to replace when it gets too many cuts in it.

  • It allows you to utilize T-Tracks for work holding with small strips of waste board between the tracks.

  • Cons

  • It has to be screwed down to your original waste board

  • It will reduce the travel of your Z axis unless you add aftermarket Y axis end plates that are taller than the stoick versions.

Once you decide on a waste board configuration and have one installed it is time to prep it to insure that it is FLAT and parallel with your X and Y axis. Before you do though, be sure to check that your spindle is perpendicular, also known as trammed. Check Youtube for videos on Tramming. Once trammed, you can safely surface your waste board and your 0.045" error will be resolved.

I hope this helps. If you have any questions let me know.

Charley Thomas
Triquetra CNC


I think he is talking about the Z axis being off. Excuse the crude drawing but I think you will understand.
I hope that I understand.

You are exactly correct sir. I just edited it to reflect where I’m at with my exact numbers. Thanks for doing that, didn’t even think to try and explain it that way.

I haven’t even made it that far as far as X movement. The further I slide the spindle down the x axis from left to right, the higher the spindle sits (which is approx .045 on an average)

Thank you so much for this. As soon as I get the rest of the house squared away due to this damn hurricane, I will be doing this. I have an angle finder already so looks like I’m starting from my table again and going from there.

If you’re higher on one side than the other, surface your waste board.

Your friend runs a cnc business and not once mentioned skimming the wasteboard ?

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@SamGironda, well, to be fair, he didn’t say what kind of CNC business it was. If it is a metal machining business, using something like a Tormach, then there is no wasteboard, so there’s no bed to skim.

I had this same problem a few weeks ago. I ended up skimming the waste board first, and had a huge deviation between the front/left and back/right. I got a new skimboard from inventables, installed Y axis stiffener backers, and then shimmed my wasteboard (underneath). I couldn’t get the movement out of the Y/X axis rails and gantry needed to make everything plumb, so shimming was the the last resort. I used heavy duty foil as the shims. Result? Good enough for me!