Closed loop steppers

yes well we all got a clean slate from Zach a few days ago, so consider this your first strike :wink:

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@PhilJohnson you are correct that having one axis stop and the other not could cause a huge problem; if that is a concern though it would be trivial to use the alert output to drive a relay that could cut power to all motors if one went into alarm.

@EliasPolitis I would like to expand on your statement that the #1 criteria for selecting a stepper motor is the torque curve. For others reading this, he is not talking about the static torque specification you see listed on a motor. You also want to pay attention to the inductance of the motor as a motor that has a higher inductance will lose torque faster at higher speeds. Not all motor manufacturers publish the torque graphs, so use the inductance if it is available as a good reference for two motors of similar static torque ratings, the lower the inductance the better.

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If they don’t publish a torque curve, be skeptical.

In addition, look at the drive parameters for the published torque curve. Microstepping, drive current, etc. that all plays into the curve and you may think you have a comparible curve when in fact one is at 8X microstepping versus 16X stepping.

Honestly, before anyone even considers a closed loop motion platform. They would have to seriously assess their current gantry setup. Close looping something like the x-carve or an SO3 will amplify shortcomings of the chassis.

This is something that you should attempt after you switched to something other than belts (acme, ball screw or rack and pinion). The entire point of close looping your steppers/servos/brushless drive system is to increase the machine accuracy as a whole. The x-caves chassis is as ridged as a wet noodle in the stock out of box configuration and would need more work to make it marginally ridged. I would almost recommend building a different machine altogether before trying to make an x-carve basically not an x-carve anymore. Saves time and money.

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