New user 3018 CNC problem

[smart51]

Hi everyone! My new Vevor 3020 desktop CNC arrived on Friday. Assembly was straight forward and the machine works when jogging from the control panel in the Candle software. I have a problem with the X axis though.

I've set the workplace zero point and sent a G code file to the machine. It starts a diagonal movement to the place it wants to start cutting but a second into the movement, the X axis jams for a second and then it continues. It will carry on and cut the programmed shape OK, just in the wrong place. As I've said, I can jog the axis without problem. The leadscrew turns freely by hand.

What potential problem could there be where it struggles with this initial diagonal movement?

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[awerby]

Is there a way to reduce the acceleration on the X axis? It sounds like it's being driven too hard and losing some steps.

[smart51]

Is there a way to reduce the acceleration on the X axis? It sounds like it's being driven too hard and losing some steps.

That sounded quite plausible, so I looked at the GRBL settings. $120 to $121 are all set to 20mm/s/s which is very slow.

I've made 5 good pieces with the machine, but more than twice as many bad starts. It seems to move about 22mm diagonally from a standing start, before buzzing loudly and moving the Y axis only for another 20mm or so, then continuing as normal. For some reason, the X axis stepper is not turning but then will again. Sending the machine in 100mm jogs in each direction is no problem at all. Then I start the job and "BZZZZZZZ", and it's all gone wrong.

[philba]

Does the "jam" happen in the same or random location? Does it happen if you do "air cutting" (run it Z up so it doesn't actually cut)? Have you adjusted the current setting of the drivers?

[smart51]

It happens in the same location and before the end mill touches the work piece. I've got around the problem by jogging the machine close to the starting point of the first cut, so it doesn't have to move much before starting.

I haven't changed any of the default settings yet.

To help pin down the problem, I tried setting the machine zero point in different places on the bed. If I set it in the middle, rather than along the far edge, it didn't jam.

[philba]

same location - probably mechanical binding. disconnect the motor on that axis and try moving by hand.

[smart51]

I think the problem is speed related. Once the speed ramps up beyond a certain point, it jams. Then as the speed ramps down, it start going again. Setting candle to jog 100mm at 1000mm/s is OK but at 2000mm/s it jams. 10mm jogs are fine because the motor doesn't get up to full speed before it slows down again. It turns freely by hand.

What speed should these machines manage when the mill is not touching the work piece?

[philba]

2000 is pretty fast for those super low end machines. I would try tightening up everything but think you may have found one of the 3018 limits. You might try decreasing acceleration.

[Hermitude]

Check that your GRBL step/microstep settings are correct for the driver and steppers that you are using. For example, if your drivers can handle 800 microsteps/mm and your grbl is configured for 1600 microsteps/mm, then a 2000mm/min input feed rate will result in an attempt to move at 4000mm/min. (And a correspondingly larger part).

I also have a 3018 clone and the little NEMA 17 steppers on it won't go that fast. I'd try 1600mm/min for rapid moves and something like 1000-1200mm/min for feed moves at most.