[robotek]

Hi guys,
I ran into a problem with my machine. While running a program, the machine changes its Z Axis coordinates and does not plunge into the part, instead it is rising higher between layers.
My machine is a DIY gantry router with 4th axis, 1605 ball screws, 20- series linear rails, controller is Adtech CNC4640, linear axis' are driven by 750W and 1kW servos, 4th axis is driven by 400W servo with 28:1 ratio gearbox.
Pictures show the screen of the controller while running program. Several times during program, the Z axis coordinate changes, seemingly by 5mm at a time.
The program consists of multiple tool paths created in Fusion 360, each tool path is 3d Adaptive Clearing, and is oriented in 90 degree increments of the A Axis. So, at the beginning, the machine runs the first tool path, then indexes A Axis into another position, then runs next portion, etc.
During first tool path, the Z axis changed its coordinate maybe 20 times and ended up running at 100 mm above the part. After A-axis rotated, the machine started running second portion of the program like nothing happened, happily, at the right height. Then, some time later, it shifted again, and that's when are the pictures from.
I checked the G code and there is no G commands other than G01 G02 G03 between Z axis shifts.
Any help is appreciated.
Thanks

[ger21]

I know nothing about that controller, but it looks like a bug, if it's moving somewhere other than the commanded position. Are there any tool length offsets being used?

[robotek]

I use tool length setter, the settings for it have Z axis offset, which is a height difference between the tool setter and the part origin. When i execute tool check command, the coordinates are being recorded automatically in G54.

[mactec54]

I use tool length setter, the settings for it have Z axis offset, which is a height difference between the tool setter and the part origin. When i execute tool check command, the coordinates are being recorded automatically in G54.

G54 X---- and Y----- axis is your work Offset position

Tool length is set in the G43 tool Offset page

Your Program is incorrect or your tool / work setting

The program is doing what you are telling it to do Z+ = up Z-=down so you have Z+ moves so the Z axis is going to move up.

Make sure in your drawing you have your work piece Zero to the top of the part, and the tool is set to the top of the part, then you program will have all Z- = down

[robotek]

G54 X---- and Y----- axis is your work Offset position

Tool length is set in the G43 tool Offset page

Your Program is incorrect or your tool / work setting

The program is doing what you are telling it to do Z+ = up Z-=down so you have Z+ moves so the Z axis is going to move up.

Make sure in your drawing you have your work piece Zero to the top of the part, and the tool is set to the top of the part, then you program will have all Z- = down

Thank you for your input. I really appreciate it! I’m kind of new to all this and sometimes I think I got in over my head. The only way now is forward. I checked the NC program and it has G43 commands at the beginning of every tool path, right after indexing the A Axis. This explains why the tool paths start at the right height. The puzzling thing in all this is Z-Axis “creeping” up as it progresses through the code. I ran smaller jobs on the machine and this didn’t happen then.

[robotek]

I set my part’s center point at the bottom as the origin and the attachment point to the machine. Because, when I set front corner as such, the z axis plunged right down after A-axis rotation.

[mactec54]

I set my part’s center point at the bottom as the origin and the attachment point to the machine. Because, when I set front corner as such, the z axis plunged right down after A-axis rotation.

I did not see that you where using a rotating 4th Axes.

When you are using a 4th axis it is quite normal to use the center of the part not the bottom of the part as Z zero, but it also can be the top of the part if it has a referance point to the finished part.

Your drawing and work, both must match how you want to machine it.

Most tool setters unless it is a probe are a waste of money, this too could be where part of your problem is, in the setup as well.

[robotek]

I did not see that you where using a rotating 4th Axes.

When you are using a 4th axis it is quite normal to use the center of the part not the bottom of the part as Z zero, but it also can be the top of the part if it has a referance point to the finished part.

Your drawing and work, both must match how you want to machine it.

Most tool setters unless it is a probe are a waste of money, this too could be where part of your problem is, in the setup as well.

Sorry, my last reply I just pressed a wrong button.
I actually find tool length probe very useful. Especially, when having to use multiple tools on one part.
The thing about my issue is that G code is not changing, it’s still tells the machine to go to certain height, layer after layer, but the machine is like hitting an invisible “floor” and bouncing higher.

[mactec54]

Sorry, my last reply I just pressed a wrong button.
I actually find tool length probe very useful. Especially, when having to use multiple tools on one part.
The thing about my issue is that G code is not changing, it’s still tells the machine to go to certain height, layer after layer, but the machine is like hitting an invisible “floor” and bouncing higher.

Probing is fine as I said, you said you had a Tool setter which is part of your problem if you have a tool setter, the rest of the problem is in the programing

[robotek]

Probing is fine as I said, you said you had a Tool setter which is part of your problem if you have a tool setter, the rest of the problem is in the programing

I called the tool probe a Tool Setter, my mistake. Can you suggest anything on how to identify problems in the program? Thanks

[TTalma]

It sounds like you are losing steps in the z- direction there could be a few causes:

Since it's always creeping up, I think you may be trying to drive your tool into the work to fast, causing Z to skip. Are you moving Z down in a ramp motion, or straight down? Are you using a center cutting bit? Is it a large diameter bit? is it dull? Try running the code without any stock (air cutting) and see if your Z axis is correct at the end of the cycle. If it is this is most likely the culprit. If not you need to look for something else:

- Noise on your Z axis wires, But generally this would cause loss in either direction, so sometime it would be to high, sometimes to low, so I don't think this is it
- cumulative error from back lash, You would need to do a bunch measurements to see if you have some backlash that is affected by gravity causing your axis to creep
- trying to drive your Z to fast and missing pulses, try cutting the feedrate in half and see if the issue goes away

Let us know the result of your testing and we can suggest some fixes.

edit: Also add a few pics of your machine, and it's Z axis, someone may spot something else to look at

[mactec54]

It sounds like you are losing steps in the z- direction there could be a few causes:

Since it's always creeping up, I think you may be trying to drive your tool into the work to fast, causing Z to skip. Are you moving Z down in a ramp motion, or straight down? Are you using a center cutting bit? Is it a large diameter bit? is it dull? Try running the code without any stock (air cutting) and see if your Z axis is correct at the end of the cycle. If it is this is most likely the culprit. If not you need to look for something else:

- Noise on your Z axis wires, But generally this would cause loss in either direction, so sometime it would be to high, sometimes to low, so I don't think this is it
- cumulative error from back lash, You would need to do a bunch measurements to see if you have some backlash that is affected by gravity causing your axis to creep
- trying to drive your Z to fast and missing pulses, try cutting the feedrate in half and see if the issue goes away

Let us know the result of your testing and we can suggest some fixes.

edit: Also add a few pics of your machine, and it's Z axis, someone may spot something else to look at

Anything is possible, if you look at the program though it has Z positive moves, so the Z axis is going to move up and away from the cutting surface.

[robotek]

It sounds like you are losing steps in the z- direction there could be a few causes:

Since it's always creeping up, I think you may be trying to drive your tool into the work to fast, causing Z to skip. Are you moving Z down in a ramp motion, or straight down? Are you using a center cutting bit? Is it a large diameter bit? is it dull? Try running the code without any stock (air cutting) and see if your Z axis is correct at the end of the cycle. If it is this is most likely the culprit. If not you need to look for something else:

- Noise on your Z axis wires, But generally this would cause loss in either direction, so sometime it would be to high, sometimes to low, so I don't think this is it
- cumulative error from back lash, You would need to do a bunch measurements to see if you have some backlash that is affected by gravity causing your axis to creep
- trying to drive your Z to fast and missing pulses, try cutting the feedrate in half and see if the issue goes away

Let us know the result of your testing and we can suggest some fixes.

edit: Also add a few pics of your machine, and it's Z axis, someone may spot something else to look at

Thank you. I use 750W servo on Z Axis. Strongly believe it’s not losing steps. Besides, it’s doing it while dry run.

[robotek]

I’ll try and attach some pictures tomorrow, from my computer. Phone seem to have trouble doing it.

[TTalma]

I’ll try and attach some pictures tomorrow, from my computer. Phone seem to have trouble doing it.

It's hard to know what the application is doing based on one line of code. In your image, on the right hand side, could you translate what is written above the positions?

Another way to test if it's the code, is to write a simple routine where it moves around and returns to the starting position:

(Untested code, verify it's correct for your machine before using)
G90
G00 X500 Y500 Z500
G00 Z100
G00 X100
G00 Y100
G91 F1000
G01 X-400 Y-400 Z-400

If it returns to original position, then try putting it in a loop for 100 times and see if it returns to the original position. If it does, then you probably have an issue with your file. Perhaps a tool setting or a incorrect tool offsets.

Can you run other files that don't have this problem?

[mactec54]

Thank you. I use 750W servo on Z Axis. Strongly believe it’s not losing steps. Besides, it’s doing it while dry run.

Servo's don't lose steps.

[mactec54]

It's hard to know what the application is doing based on one line of code. In your image, on the right hand side, could you translate what is written above the positions?

Another way to test if it's the code, is to write a simple routine where it moves around and returns to the starting position:

(Untested code, verify it's correct for your machine before using)
G90
G00 X500 Y500 Z500
G00 Z100
G00 X100
G00 Y100
G91 F1000
G01 X-400 Y-400 Z-400

If it returns to original position, then try putting it in a loop for 100 times and see if it returns to the original position. If it does, then you probably have an issue with your file. Perhaps a tool setting or a incorrect tool offsets.

Can you run other files that don't have this problem?

That is code that you would not want to use to check your machine

[robotek]

Servo's don't lose steps.

I know. I said that to kindly let know that losing steps is not my machine’s problem.

[robotek]

It's hard to know what the application is doing based on one line of code. In your image, on the right hand side, could you translate what is written above the positions?

Another way to test if it's the code, is to write a simple routine where it moves around and returns to the starting position:

(Untested code, verify it's correct for your machine before using)
G90
G00 X500 Y500 Z500
G00 Z100
G00 X100
G00 Y100
G91 F1000
G01 X-400 Y-400 Z-400

If it returns to original position, then try putting it in a loop for 100 times and see if it returns to the original position. If it does, then you probably have an issue with your file. Perhaps a tool setting or a incorrect tool offsets.

Can you run other files that don't have this problem?

I did something similar when tested the machine’s max speeds and stuff. It can go 20m/min and accelerate and stop almost instantaneously without any problems.

[robotek]

pictures attached