Zeroed Z height difference

[Mike1908]

Hi everyone,
I’m very new to the world of cnc and took delivery of my first machine last week. I have an issue that I’m hoping someone can shed some light on for me.
I have zeroed my machine xyz as shown in the manual but when I come to cut the test pieces I’ve done on vcarve the z seems to be a couple of mm higher than when I zeroed the machine.
Just to put it into context this is how I noticed the issue. I tried cutting a rectangle out of a sheet of 12mm mdf and I set a profile cut to cut 12mm deep yet when it had finished it was still a couple of mm from the base of the material. Thinking this was strange I tried just cutting a basic line 2mm deep into the board to see and the bit didn’t touch the material surface.
I’ve double checked the zeroing was correct on the machine so I’m presuming it’s something I’ve missed on vcarve that is causing it. This I think was confirmed when I ran a toolpath preview and it also didn’t cut the rectangle out completely. Can anyone please shed some light on where I’m going wrong as it’s driving me crazy?
Thanks in advance.

[Rcnewcomb]

Can you upload your CRV file to the forum?

How do I upload files or photos to the forum?

[garylmast]

Sounds to me you need to calibrate the steps in your controller. I have Mach3. If that's the same as yours, I can show you. If it's another one, maybe someone else can chime in.

Gary

[sharkcutup]

Sounds to me you need to calibrate the steps in your controller. I have Mach3. If that's the same as yours, I can show you. If it's another one, maybe someone else can chime in.

Gary

+1 on above

Sharkcutup

[martin54]

As Randall says providing the CRV file will be a great help, if you have set your material thickness to 12mm in Vcarve & your profile cut is 12mm then the toolpath preview should show the toolpath cutting all the way through the material :providing you have done everything correctly
If you can upload the file then someone will be able to have a look at it & make sure it is correct. If it is then the problem will almost certainly be with your control software or the machine itself

[Mike1908]

Thanks everyone! I will upload the file in the morning when I’m back in the workroom.
As I say I’m a complete newbie so I’m not quite sure what you mean by calibrating the steps in the controller.
My machine is a Yeti Smartbench if that helps any?

[mtylerfl]

Hi Mike,

After we verify your Vectric file is ok, contact Yeti Support to see if they can help get your machine calibrated if necessary (assuming you don’t have any issues with your Vectric file layout and settings).

https://www.yetitool.com/SUPPORT

[Mike1908]

Here is the CRV file for the two cuts I was trying. on the preview the line cuts, but the rectangles don't cut all the way through. On the machine the rectangles don't cut all the way through and the line doesn't cut

[Adrian]

It does cut all the way through in the preview but due to the way the preview work it doesn't look like it because you're using a v-bit and it's the very tip of the cutter that is cutting the full depth. Basically it's do with pixels but it's not really important for this scenario.

If you hover the mouse over the toolpath in the list you can see that the maximum cutting depth is 12mm.

There's nothing in the file that would explain why your cuts are all 2mm too high. Presumably you've calibrated your machine and verified it's correct by telling the machine (via your control software) to move a certain distance and then measuring it?

The other thing to check is that the bit you're using comes to an actual point. If it has a flat on the end of it then that will throw everything out as VCarve is expecting a sharp point.

Also check that your z isn't topping out at the start of the job and losing steps.

[Mike1908]

It does cut all the way through in the preview but due to the way the preview work it doesn't look like it because you're using a v-bit and it's the very tip of the cutter that is cutting the full depth. Basically it's do with pixels but it's not really important for this scenario.

If you hover the mouse over the toolpath in the list you can see that the maximum cutting depth is 12mm.

There's nothing in the file that would explain why your cuts are all 2mm too high. Presumably you've calibrated your machine and verified it's correct by telling the machine (via your control software) to move a certain distance and then measuring it?

The other thing to check is that the bit you're using comes to an actual point. If it has a flat on the end of it then that will throw everything out as VCarve is expecting a sharp point.

Also check that your z isn't topping out at the start of the job and losing steps.

Thanks for checking Adrian. The machine is calibrated and I have checked that when I return to the Z datum it is in the correct position.
The one thing on the file I was unsure of was the rapid Z settings and the Z starting point setting on the material setup. Did these look ok to you?
The bit is brand new, these cuts are the first time I’ve used it. I had previously tried cutting another rectangle with a 6mm end mill and had the same issue.
I have also contacted Yeti support and they are having a look at the file too so hopefully one way or another I can find out what’s wrong.

[Adrian]

Shouldn't be an issue with the Z settings as they are very low so no chance of topping out. I originally thought they were in inches as that's what 99% of the files I look at from the forum are set to. Nice to see a metric one for a change.

Usually the Z2 is set just above the surface with the Z1 set to clear any clamps etc. The gap above the material Z is where it goes at the start and end of the job. Nothing with the way you have them set would be causing the issue you're seeing.

Assuming you're using the correct post processor for your machine it's going to be an issue with the machine setup, controller software or the z-zero method. If it was something wrong with the VCarve file then there would be many people with the same issue. Yeti should be able to track it down for you.

How were you checking the zero? Did you set it, jog the axis around a bit and then tell the machine to go back to zero? Do you use a touch off plate for setting the zero? Is the thickness of that correct in the software?

[Mike1908]

Shouldn't be an issue with the Z settings as they are very low so no chance of topping out. I originally thought they were in inches as that's what 99% of the files I look at from the forum are set to. Nice to see a metric one for a change.

Usually the Z2 is set just above the surface with the Z1 set to clear any clamps etc. The gap above the material Z is where it goes at the start and end of the job. Nothing with the way you have them set would be causing the issue you're seeing.

Assuming you're using the correct post processor for your machine it's going to be an issue with the machine setup, controller software or the z-zero method. If it was something wrong with the VCarve file then there would be many people with the same issue. Yeti should be able to track it down for you.

How were you checking the zero? Did you set it, jog the axis around a bit and then tell the machine to go back to zero? Do you use a touch off plate for setting the zero? Is the thickness of that correct in the software?

It’s good to know everything looks ok on the vcarve side of things. The Yeti uses a plate to set the Z zero and I did that before moving around the axis then pressing go to Z. The point of the bit looked to be in the perfect place when checked, it’s only when I start the cut that the point is higher than the material surface. I realise it should do this given the Z settings I applied on the file so I presume that isn’t the cause. I suppose it could be the post processor, though the machine says .gcode files are compatible, .nc files are also compatible but I’ve not tried it on that. Hopefully Yeti come back to me with a solution.
Thanks again for your help & I’ll update on here when I find anything out in case anyone else experiences the same issue.

[Mikehell]

Are you 100% sure your material is the thickness you think it is? If you zeroed from the top of the material, and your material is just a bit thicker than you think, this will happen.

Typically, if I'm cutting shapes out, with no pockets, I zero to machine bed. I often go .02" or .01" deeper than my material to be sure it cuts through. MDF spoilboards can get unlevel pretty fast due to humidity, etc

[Mike1908]

Are you 100% sure your material is the thickness you think it is? If you zeroed from the top of the material, and your material is just a bit thicker than you think, this will happen.

Typically, if I'm cutting shapes out, with no pockets, I zero to machine bed. I often go .02" or .01" deeper than my material to be sure it cuts through. MDF spoilboards can get unlevel pretty fast due to humidity, etc

Thanks for your reply. I’ve triple checked the thickness of the board and it’s correct, also the spoilboard is a brand new piece and it’s screwed down to the machine bed.
I understand your thinking here and it makes complete sense for the cut that was going right through the material, but it doesn’t explain how the 2mm deep line completely misses the material.
Just a quick question on your suggestion of zeroing to the machine bed, I presume you can only do this if you are cutting all the way through the material?

[TReischl]

Adrian wrote above " Do you use a touch off plate for setting the zero? Is the thickness of that correct in the software?"

Pay attention. If you have that plate thickness set incorrectly it will produce exactly the issue you are seeing.