Deceleration on steppers

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ramurph1
Posts: 6
Joined: Thu Mar 18, 2021 1:51 pm

Deceleration on steppers

Post by ramurph1 » Fri Mar 19, 2021 4:22 am

Just fired up my newly built machine. I don’t have my I/O wired up yet, but after jogging motors, I noticed some excess decel. I assume this is just the inertia. I held a prox switch up to simulate distance to stop by just letting off jog button when prox light came on and seen the decel would crash the prox. My question is this: Will the machine react differently when homing or is there a home speed? Or do I just need to adjust my max velocity and jerk settings? Things are looking good otherwise! I’m thinking parameters will inevitably need adjusted due to the hard stops as well. I will want the machine to stop before destroying the hard limit and associated bracket. Thanks for the help. I know it’s kind of a basic question!

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Doug
Posts: 239
Joined: Fri Feb 02, 2018 4:56 pm

Re: Deceleration on steppers

Post by Doug » Fri Mar 19, 2021 10:20 am

First, let me say that you can adjust the distance it takes to accelerate and decelerate by changing the max-acceleration an max-jerk fields on the motor configuration pages. Try increasing each of these by a factor of 10 to see how it reacts. Then, play around with it until you get feel that is comfortable. If you raise them too high, the machine will jerk and possibly stall when starting and stopping.

After you have homed the machine, the Buildbotics Controller will not allow the machine to travel outside of the soft limits that are defined on the motor configuration pages. When approaching the soft limits, it will decelerate and stop before going past the limit. This will prevent you from crashing into your end stops.

ramurph1
Posts: 6
Joined: Thu Mar 18, 2021 1:51 pm

Re: Deceleration on steppers

Post by ramurph1 » Fri Mar 19, 2021 2:28 pm

Thanks for the explanation! I will make some adjustments this evening.

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