My stepper goes faster instantly

Hello everyone.

I recently made my own CNC that currently writes with a pen and later I intend to change the pen with a laser head. The project is a very simple one, I managed to finish it and it worked ok until today. I tried to make it work faster, changed the feed rate to 4000 and everything worked ok.

Problem is that in the middle of the G-Code, the X axis instantly goes extremely fast and in collision with the machine, and over the established limits.

If I reboot the machine it works ok for several moves, and then goes fast again. The Y axis has no problem and it's settings are the same.

I have 2 NEMA17 stepper, Arduino UNO, CNC Shield, two DRV8825 drivers that I set both to 0.8V and a servo that is connected to pin 11 (limit switch +Z on the CNC shield).

Each driver have a jumper for micro stepping to 1/16.

What do you think I should check out?

Thank you.

It would seem that there is something in the gcode that is causing that. How are you generating the code?

What did you change? If you change it back, does the problem persist?

What controller board? Are you using controller firmware like grbl or marlin? Are you using a gcode sender?

Hello. I am using Universal G-Code sender and the Arduino has GRBL installed. The code is just for test, looks like this:

G00 ;RAPID MODE
G17 ;XY Plane

G90

M3 S60

G0 X50 Y0

M5

G91
G1 X0 Y50 F500


G90

G0 X0 Y0

M5

M30

This runs as it should. I hit play for a few times and after 3 or four cycles it begins to run very fast and in collision.

I will try to switch drives and see if this happens on the Y axis. Maybe this is a drive fault...

Hi,

From what feed rate to 4000?
Do you have current limit set up on your driver?
Can you please post spec/data on stepper, NEMA17 only tells us its physical properties.
What is/are your power supply(s).

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

Hello. The power supply is 12V-8A. The Nema17 is a 12V motor with 1.68A current. The DRV8825 were set to 0.84V limit.
Thing is, yesterday I got the jumpers up and back again, I played a little with the potentiometer on the DRV8825 and suddenly it began to work as expected. It's a little frustrating because I don't know what caused the problem and if it will happen again.

That will be your problem, they are not super reliable and have a relatively small contact area with the socket.
Sockets also wear out and loose their tension.

Tom... :smiley: :coffee: :australia:

Well, I didn't have jumpers and it's a kind of diy jumper :slight_smile: . I will buy new ones. Anyway, I hope this will solve the problem. Thank you.

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.