Having trouble with Z axis after zeroing

Software Carbide Motion
1

Hello Everyone,

For the past month or so I’ve been given the opportunity to operate a Shapeoko 5 Pro.

I still have lots to learn.

The issue I’m currently having is something the previous owner didn’t encounter, so I’m thinking it’s user error on my end. I’m hoping that someone may know of what I might be doing wrong.

It happens randomly, but around 25-40% of all cuts.

After zeroing the bit to where I want to initiate cutting and running the project, and then proceeding to initiate cutting, the bit will drill exactly 0.5 inches too far into the piece immediately after starting. Sometimes starting 0.5 inches too high from where I zeroed, but mostly 0.5 below. I know it’s exactly 0.5 because I will stop the process, jog the machine, place the bit to where I originally zeroed it and the Z axis will be off by exactly that much based on the data displayed on carbide motion. The x and y are always consistent, the Z is the problem. It seems odd to be such a specific value. I wonder if there’s a coding error that pops up at random.

With zeroing - Once I’ve positioned my zero, I go to carbide motion. I select set zero, then zero all, and press done after making sure all numbers are reduced to zero. Then I go to run and start the project.

The tool bit that is used for zeroing is the exact tool used in the cut. No tool changes are made after zeroing when initiating the bit setter.

After this occurs, I jog and set the zero then start the project again. Usually there’s no issue and I can continue multiple projects without having this problem repeat. But somewhere out of the blue, seemingly at random, I will have the same issue arise.

It’s frustrating as many of the wooden pieces I work with have taken much time to put together, and then a 0.5inch deep whole is burned into it (literally as the 24000 rpm chars the wood) after the 1/32nd bit goes too far.

Hopefully someone knows what’s up. I would appreciate any help regarding this.

2

Hey Wagner, I might be able to help.

First, some questions:

  1. In JOB SETUP, What did you define for STOCK THICKNESS? How thick is the stock actually?
  2. Also in JOB SETUP, Where did you tell the software to zero; TOP or BOTTOM of the stock?
  3. When zeroing your Z, do you run the bit down to slightly trap a piece of paper laid on top of the stock?
  4. Or do you use a BitZero? If yes, do you use it to zero all three axes at once?

Let me know. Thanks

3 Likes
3

I second what Geeber posted.

When I was experiencing this problem, I think it was because of my workflow. The problem seemed to disappear after I added the Bitsetter to my 3XXL, but my workflow also changed. The new workflow is:

Initialize the machine which moves the machine to the home positions and then back to the front of the machine. I am prompted to insert a bit, which is always the same tool left in the machine from my last CNC session. I then set the zero positions using the same tool. If you are setting zero without the Bitzero, be sure to tab or hit the enter key out of each zero field on the dialog. After zeroing, I would recheck Z zero in the center of the stock (sometimes I check it twice on the nicer woods). If Z zero checks out. I load and run the job. You should be prompted to load the first tool and then the Bitsetter checks the tool height again.

When you start the job, keep your mouse pointer on the Pause button, or the emergency stop button in Carbide Motion.

Oh, before I added the Bitsetter, I would create a small test pocket cut in a scrap area of the wood so that I did not mess up my part area.

2 Likes
4

Hey Geeber, thanks for the reply.

  1. The thickness is set at 0.75inch which is exact to the piece of wood i’m using.
  2. The zero height is set for Top of the stock.
  3. When I zero, I do the paper trick.
  4. I zero the machine on the stock first to the exact placement I want it. Then as part of starting the job, the bit is measured on the bitsetter before moving over to cut the stock.
5

The problem seems to be getting worse. Today I went to cut a piece and instead of going 0.5 inches too deep, it was positioned to go 1.012 inches too deep. I saw the z-axis number before it went too far down and managed to pause and stop the project before it could ruin the piece.

What is going on…

6

We have a blog post on this sort of issue at:

https://carbide3d.com/blog/unexpected-z-axis-plunges/

If for each stage of the process you can document:

  • what you did
  • what you expected
  • what actually happened

we can look into it with you.

7

I was seeing similar behavior several months ago.
I noticed that the Z position was changing to machine coordinates and back when hitting the bitsetter. Sometimes it did not come back to the number I expected.

I started being very careful and taking pictures of the position values before and after the bitsetter so that I could document the issue and complain and it went away. I don’t know what I was doing different other than just being super careful in my process.

I have learned that I need to power cycle the machine, not just re-initialize when enabling/disabling the bitsetter. That isn’t supposed to be required but for me it was.

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