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Messages - Steve Stallings

61
Mach4 Toolbox / Re: When changing from mm to inch unit
« on: June 18, 2022, 10:13:54 AM »
To work in alternate inch and metric systems, you do not need to change the configuration of Mach itself.

Indeed the configuration setting only affects how the steps per unit parameter in the configuration is understood by Mach while doing the initial axis configuration.

To work in alternate measurement systems you should insert a G20 command in your-G code file to tell Mach to treat dimensions as inches, or insert a G21 command in your G-code file to tell Mach to treat dimensions as millimeters.

Mach does have a group of startup settings to select the default mode. It sounds like your default is millimeters. The startup settings are one line of G-code that is automatically run before starting any job.

62
Your code should include a G61 command for Exact Stop before the line of code that must complete before the next line starts. Then include a G64 after that move to allow resuming Constant Velocity mode if desired.

63
Mach4 General Discussion / Re: problem with g code file
« on: March 31, 2022, 03:45:11 PM »
.... and how did the Mach4 parser miss it. It should have been flagged as an error.

64
Mach4 General Discussion / Re: problem with g code file
« on: March 31, 2022, 03:30:31 PM »
The lines that appear to be intended to be labeled as N210, N220, and N230 are missing the letter "N" before the number. Adding this back makes it display.

65
It is not a good idea to push feed rate up more than 20% or so with FRO because the trajectory planning was done at the original speed. If you really want to do 100% or more speed change, code it for maximum speed and turn it down to 50% for regular run.

66
For most machine tools the best way to get higher resolution is to used a closed loop system with feedback that can measure the desired resolution and a driver that takes advantage of it.

If you want to gain more resolution from an open loop stepper using microstepping, then utilize motors with much higher torque so that the error in the angular location is not affected as much by the available torque at the microstepped locations.

For smoothness of open loop stepper systems, I usually recommend microstepping factors between 4 and 10 which do smooth things significantly without adding too much challenge to the process of generating and transmitting the step signals.

67
For stepper motors, the issue is with how much torque is available at the target location. The manufactures torque spec relates to how much torque is available just before the motor fails to hold position and jumps to the next set of winding poles. With a traditional two phase stepper motor, this happens at a shaft angle displacement equivalent to 1/2 of a full step.

If you are micro stepping you do not get the full torque if you only displace the shaft a small fraction of a full step. This is why the full enhanced resolution is not available in the real world. If your load required very low torque, then you could get closer to the ideal target location. Microstepping can offer significant advantages in some light duty instruments such as telescopes, but does not gain you much resolution for a router or milling machine.

68
The 500,000 steps applies to each axis individually. The sum of steps for all axes does not matter.

If you are approaching this limit, then decreasing the micro stepping would be my suggestion.

69
The PMDX-125 (and PMDX-126) provide a noise filter on step signals that limits the step rate to 500,000 steps per second.

At 30000 pulses per revolution and 5mm travel per revolution this filter would limit the commanded motion to 5000 mm per minute or about 196 inches per minute. Step commands issued at a faster rate would simply drop out. This is not a sharp cutoff value as this is an analog filter.

It also happens that the servo driver you are using specifies a maximum step frequency input of 500,000 steps per second at a 50% duty cycle. I would recommend that you provide some margin for the ESS and the PMDX-125 in case there is some duty cycle distortion.

It is likely that your stepper motor drivers have even lower limits on maximum step signal frequency.

Steve Stallings
www.PMDX.com

70
Mach4 General Discussion / Re: Using M2xx codes
« on: January 31, 2022, 08:11:20 PM »
The information you found is legit IF you are running MachMotion's custom profiles. The items described are not present in the standard Mach4 profiles from MachSupport.com installs.