What do you really get for a $350 desk top engraver ?

machinedude wrote:

i was wondering if the fact that the Y axis has a lot more power than the X axis that would cause the feedback loop to work harder on the X axis and lag behind the Y axis? that would explain why it shows up on cuts when the X and Y are moving together.

adjusting the alarm set point might show this like you suggested. i just have to figure out how to make that adjustment i'm guessing that is done in the drive with communication cable they send with the kits.

 

'cause the feedback loop to work harder...' is not a meaningful statement.

Your X axis has one motor, and that motor only has to move the head.
Your Y axis has two motors, but each motor has to move half the head weight/inertia plus half the gantry.

There may be a significant difference between X and Y power/torque requirements, but that's probably due to bent or misaligned components and not a massive difference between X and Y inertia-per-motor.

Having said that, if a stepper motor-driven axis has more friction (or load) than the motor can handle, it doesn't 'lag behind'.  It will lose steps.  It may lose a couple steps every so often, or a bunch of steps and stall completely.

But it doesn't just run slower due to increased load.  Your axis motors are not a cordless drill that slows down when you stick a big bit in and overload the motor.

Yes, you need to install the tuning software, connect to the drive (drive powered on), and adjust the alarm setpoint value.  Be prepared for a horrible experience as the software is unintuitive and not well translated.

Do you have clear photos of the problem - i.e. surface finish - and a sample of the gcode used to cut when the issue appears?

what i said before was phrased as a question because i am in territory i know little about but thanks for the detailed answer to help me understand better.

i did download the software last night and had a look at the manual (PDF) and it sounds like the software is about as good as the manual

as for the lost steps i have not seen anything that shows that has happened if it is it would have to be pretty small and not obvious by eye. the only time the drive alarmed was in a stall from cutters loading up before i added the mist.At one point i even had a glass scale and DRO hooked up to see how accurate the belts were and did not see anything but that was with no loads involved.

i don't think i have any programs that are simple mostly 3D milling tool paths. I can probably do some testing this coming weekend. Anything during the week is pretty hit and miss for me since i work the night shift.

all the code i do is in fusion 360 if that helps any? i can't remember if i had smoothing in use or not that could be something to test i guess.

just opened the software and the manual tells you nothing about any of the features i was curious to see how bad it was going to be and now i know god help me

Told you it was horribleimage missing /media/kunena/emoticons/smile.png

Not sure about the "T" model, but the "Y" model drive software calls following error "Position Deviation Alarm Threshold".

 

i found a few videos but they don't cover much. But i think the alarm part should be easy enough. i think i got enough info to set that and save the new settings to the drive. seems like after the settings are saved you need to cycle the power once after that if the info i found is correct? i don't see how it would hurt anything after you exit out of the software.
i think once you change the factory setting from 4,000 to something small i will see conditions for lost steps, With the current settings if you have a condition that causes lost steps it just corrects until it gets back to where the encoder says it should be i could see that causing surface finish issues if that is in fact what is going on?

i think the first step is to get that changed and saved to the drives and do some testing to see if i get alarms or not. if i do get alarms then i need to figure out if it can be corrected in the internal drive settings or something else needs done? if all else fails i can try a 48V power supply or just get a bigger nema 23 motor if it leads back to the X axis. if that does not help then i will have to live with it as is or go back to the drawing board and make reductions.

anyways it's a way to collect more information to narrow things down so thanks for the help everyone.

The drive will attempt correct for lost steps up to the tolerance - this is a separate setting from the alarm.  If it can't correct to within the tolerance window, the drive will fault and the alarm signal will be triggered.

I think the tolerance is reasonably tight from the factory - it's just the alarm that's silly.

Regarding the power supply - increasing voltage won't provide more 'power'.  It will only permit the motor to turn higher RPM before losing steps.

On steppers, the 'power' - torque, in other words - is determined by the amps available to the motor/drive.  If your 36v supply can't manage enough amps to the drive that would result in lower torque.  Or if the drive is programmed to only use half the amps the motors are capable of handling.

You mentioned before that you adjusted the microsteps without using the software.  It's possible you accidentally set the drive max amps lower than desired via one of the dip switches.

I suggest you set the dip switches to whatever position means 'software program only' and set the max amps based on the motor, input steps/rev, and everything else via the programming software.  Note that inside the software, you won't directly set 2/4/8/10/N 'micro-steps'; rather, you'll be determining how many input pulses are required per revolution and may need to adjust LCNC's steps/unit output.

I've used similar Nema23 closed-loop steppers from Stepperonline on a medium sized plasma, and they had a remarkable amount of torque.