My sizes are out

[Neale]

Sounds like your "steps per unit" calculations have gone a bit wrong. Can you recheck, or post all relevant data here so someone else can check your working?

The other way of doing it is starting with a good first guess - which you have - and then modifying the "steps per" based on the results of a calibration run. Personally, if my calculated value were out by more than a tiny amount then I reckon something's wrong - my calculation or a machine error. Slipping coupling, missing steps, or whatever. However, others take the more empirical approach. In short - keep tweaking until you get the right answer! Mach3 actually has a calibration capability built-in but don't know about your controller.

[Desertboy]

Sounds like your "steps per unit" calculations have gone a bit wrong. Can you recheck, or post all relevant data here so someone else can check your working?

The other way of doing it is starting with a good first guess - which you have - and then modifying the "steps per" based on the results of a calibration run. Personally, if my calculated value were out by more than a tiny amount then I reckon something's wrong - my calculation or a machine error. Slipping coupling, missing steps, or whatever. However, others take the more empirical approach. In short - keep tweaking until you get the right answer! Mach3 actually has a calibration capability built-in but don't know about your controller.

On the ddscv it's steps per mm

I have 8 microsteps
so 8*200/10 (1610's) for X&Y 160
320 for Z (1605)

Just double checked this is definitely what they are set to.

AM882 has fault protection it should detect missing steps and estop and I swapped all the couplings for these style, I bought the chunkier ones.



so they're rated twice the nm of the motors.

2 4nm in the bottom and 3nm on the gantry, PSU is 70v and 1kva.

Will try and cut 3 holes at 33mm, 66mm and 99mm see if the error scales perfectly I tried cutting from speed of 0.5m/min to 10m/min exactly the same results.

Carved a lot of 3d stuff on this machine and that's machining for hours not seeing issues there or sign making never noticed the size was wrong until I tried to make an adapter and it didn't fit.

Both X&Y are out by the same amount not sure about the Z.

[dazp1976]

On the ddscv it's steps per mm

I have 8 microsteps
so 8*200/10 (1610's) for X&Y 160
320 for Z (1605)

Just double checked this is definitely what they are set to.

AM882 has fault protection it should detect missing steps and estop and I swapped all the couplings for these style, I bought the chunkier ones.



so they're rated twice the nm of the motors.

2 4nm in the bottom and 3nm on the gantry, PSU is 70v and 1kva.

Will try and cut 3 holes at 33mm, 66mm and 99mm see if the error scales perfectly I tried cutting from speed of 0.5m/min to 10m/min exactly the same results.

Carved a lot of 3d stuff on this machine and that's machining for hours not seeing issues there or sign making never noticed the size was wrong until I tried to make an adapter and it didn't fit.

Both X&Y are out by the same amount not sure about the Z.

The numbers are really only to get you in the ball park. There's always a slight error on the screws.
Mine is similar on circles. I end up about 0.1mm too small so I just tweek my drawings to suit the machine. I add 0.1mm to inner circles such as do a 32mm as a 32.1mm.
Then outer edges I add 0.05mm on each end (or I can set my stock to leave 0.05mm instead).

This will give you a rough idea on methods of how to increase accuracy using Mach calibration. Or at least to check how close your machine is to see if that is the problem.
https://www.youtube.com/watch?v=XkO5tc-jSxw

[JAZZCNC]

AM882 has fault protection it should detect missing steps and estop and I swapped all the couplings for these style, I bought the chunkier ones.

AM882 doesn't detect missing steps it's got stall detection which is a different thing altogether. It also only works above 300Rpm.

Regards the wrong size parts then if the steps per is correct and you don't have slippage etc then I would be looking to the CAM and the tool offsets.
Does the controller have tool offsets.?