issue with A4988,CNC sheild and grbl library

Other Hardware Motors, Mechanics, Power and CNC
1

The motor oscillates around the starting point and arround the stopping point when using the grbl library as you can see in this short clip

If I do not use the liberary, the stepper motor behaves well.

Any help will be appreciated.

Philip

2

Please post a copy of the UGS output screen that is generated while the motor is doing that.

I don't know how grbl can do that by itself. It must, I think, be getting instructions from somewhere.

3

Thanks groundFungus

I increased the acceleration, and the hesitation went away.

4

Well I did not expect that acceleration could be the problem. I will remember that. Karma and thanks for getting back with the solution.

5

groundFungus:
Well I did not expect that acceleration could be the problem. I will remember that. Karma and thanks for getting back with the solution.

You are OK
I could have stopped the reporting here, but I did not feel comfortable in case someone reading I might confuse him.

I find several issues

while it is true that pumping the acceleration up has helped(I guess overcoming the rotor inertia) the root cause of my issue was that one of the motor wires was bad quality and break. It was tricky because visual inspection shows ok.

Due to running the motor single phase, there was hesitation in the take-off and landing of the motor. The higher accelaration helped overcome this hesitation. But the root cause was a lose wire,

So now I brought the accelaration down to 50 and corrected the lose wire and things are more than perfect.

The reason I found the lose wire because the motor take off in a different direction every time I give a command to rotate possitive Y.

I searched the net and found quite few people have this issue and where able to nail it down to lose wire.

conclusion : if the motor decides to rotate in a different direction while given the same command (Say +y ) first suspicions should go to single phase operation due to lose wire or failed motor or something of that sort.

6

Really good information, thank you.

You may want to try some microstepping. Stepper motors can have problems with resonance, microstepping can mitigate that. I use at least X4. You will need to adjust the steps per mm settings.

7

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