CNC skips steps along the Z axis.

[thekondrat]

Hi everyone.

I have problem with my simple 3 axis CNC with stepper motors and Fusion360.

I use simple comand 2D Pocket.

While working my CNC skips steps along the  Z axis.

The problem occurs when the milling cutter completes the operation in one pocket and begins to move to another pocket, a sharp jerk up occurs and the machine skips a step.

As a result, the first pocket has a depth of 5.7mm and the second pocket 6.0mm. 

If there are a lot of pockets in the model, then the number of skipping steps is increased. For 1 time the machine loses approximately 0.3mm (0.012 ")

Im use Mach3mill post processor.

Im trying reduce Ramp feedrate up to 300mm/min and did not notice the changes. 

Can you tell me what else can I try to change?

[daniel_lyall]

Lower the acceleration and velocity in mach3, its not a fusion error it is in mach3. 

The settings in mach3 will be letting it move faster that what it can realy do lowering them will keep the machine to a speed it can handle

What you can do in fusion is cut the lead in and lead out feed rate in half 

[thekondrat]

I'll try to do it tomorrow.
When I use another CAM program, there are no such problems.

[daniel_lyall]

It's the speed change what does it is going from 0 to 1440 and back to 0 in 5 mm it's a impossibility so haveing this at a speed that it has a higher chances of hitting will always work better.

If you made it even faster the problem will get bigger

[thekondrat]

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@daniel_lyallwrote:

It's the speed change what does it is going from 0 to 1440 and back to 0 in 5 mm it's a impossibility so haveing this at a speed that it has a higher chances of hitting will always work better.

If you made it even faster the problem will get bigger

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I do not understand, what can i do to fix it?

[daniel_lyall · Accepted solution]

Slowing down the lead in and out 

[thekondrat]

I reduced the acceleration along the Z axis from 450 to 150.
The result remained the same.
But it was slower to accelerate.

[daniel_lyall]

cut the velocity in half 

[Anonymous]

Did you ever find a fix to this issue? I have the same problem...

[thekondrat · Accepted solution]

I tightened my end mill better.
My problem was that the cutter was pulled out of the collet during operation.

[Anonymous]

I think I figured out my problem as well. It was mainly my plunge feed rates and FRO speed. It was bottoming out and would skip when trying to pull it back up.