Um setting above 28 causes overspeed and loss of steps

[baccus61]

Hi guys,
I wore out my laser drive belts and pulleys and replaced them with new ones last week and now have a strange problem with setting the um pulses per step.
I need about 34um/step but if I go over 28 the DSP seems to run the motor way too fast and it loses steps and just squeals due to overspeed.
I have made a video of what is going on to make it a little easier to diagnose. The difference from 28 to 30 is way too large and just seems wrong or faulty
My old setup used to run at about 25um/pulse but I reduced the pulleys to get better motion and have run into this problem.
Has anyone had this go wrong with their setup?
I am running the older AW608 board with V7.52 software and I don't know what version of the firmware I have (not home right now) but I think it was about the 3rd update for that DSP.
I reduced the MaxSpeed from 30000 way down to 50 and it works but still tries to fly off the board very quickly. I have played around with a lot of the settings but without any luck. I don't really want to redo any of the motion drive stuff as I have a few hundred dollars spent on it all and don't want to waste it.
Has anyone any ideas on what I'm missing or not doing?
Any help will be good.
Richard.

Here is a link to the private video on my YouTube channel.

https://www.youtube.com/watch?v=0bU_RlI-BSo

[DonL]

I tried to view the video but it is flagged as private.

Reducing the sprocket size will have an effect on how far and how fast he axis moves, a smaller drive will make the belt move slower and cover less distance per revolution... This may have been your goal, but it may require replcing the motor with one that can handle the increased speeds required to maintain the x/y speeds you enjoyed with the larger drive. Check your motor specs.

[baccus61]

I have set the video to unlisted now. Sorry about that but I thought anyone could watch a private video if they had the link. It's now set to unlisted so you should be able to see it.
I have had a previous setup set to 43um/pulse with no problems (I'm not sure if it was with this particular setup though as it was a long time ago).
It's just that there is a huge difference between 28 to 30 pulses.
Rich.

[DonL]

Kees would be the one to ask about this one... If I had to guess I would say that by changing the pully size you have exceeded the motor's torque or microstepping ability and my need to change the motor as well or adjust the microstepping if the motor can handle it.

28 and 30 is a very high setting it seems to me... Have you tried changing the microstep on the driver? I know that when I have my X set to 16 my um/pulse is 6.5 or so and if I change the driver to 32 my um/Pulse goes to 3.25 or so
so have you tried playing with the microstep settings on the driver then recalculateing the Um/Pulse?

Just spit-balling here

[Greolt]

Richard

You have been around for a while so I am sure you have tried these things but,

The first thing that comes to my mind is, are you restarting or reseting controller after making the change?

Second is, what happens if you make the changes directly at the control panel?

EDIT, maybe you CAN'T make that change at the control panel.

[Techgraphix]

Kees would be the one to ask about this one...

He could.. but I don't have the answer to this one... I suspect that it's some kind of software interference close to the native resolution of the steppers.. As there is when you make the scangap smaller than 0.025mm..
I too think that a um/step of 28 is big.. I have mine set to 2.5um/step, although this gives you a limit of ~700mm/sec for engraving (the processor is not faster than that) But then: what would you engrave with that speed?? most of my engravings are done in the range 100-400mm/sec
I would set the microstepsetting on the stepperdriver a lot higher and reduce the um/step in the same ratio.. Your movements will be smoother overall too..
Kees

[DonL]

Kees would be the one to ask about this one...

He could.. but I don't have the answer to this one... I suspect that it's some kind of software interference close to the native resolution of the steppers.. As there is when you make the scangap smaller than 0.025mm..
I too think that a um/step of 28 is big.. I have mine set to 2.5um/step, although this gives you a limit of ~700mm/sec for engraving (the processor is not faster than that) But then: what would you engrave with that speed?? most of my engravings are done in the range 100-400mm/sec
I would set the microstepsetting on the stepperdriver a lot higher and reduce the um/step in the same ratio.. Your movements will be smoother overall too..
Kees

Agreed, I think, after viewing the video, the motor drives a pully that drives a bigger pully that drives the laser head, the motor selected was probably speced based on the torque and speed requirements, by changing the pully size, the motor is no longer in spec.

Like replacing the spocket on a motorcycle from 11 tooth to 15 tooth, You get a lot more speed on the highway but taking off from a stop sucks, A kid on a tricycle would get better acceleration... To regain the accleration you need to increase the horsepower or put the old sprocket back on.

Hopefully changing the stepperdriver DIP switches will resolve his issue....


PS
I can get .01 scangap I use for engraving small objects like Pens, and I use .04 for plaques or wood engraving, I don't use the default .1 any more since you showed me that setting
I generally engrave at 200mm/s for most jobs and 300 for larger jobs but remeber, my hobby laser is very small and right now it is just a hobby...

[baccus61]

Thanks a bunch for the replies guys.
I am using Gecko drives for the motors so I can't change the Um/pulses so I am limited to 10 pulses per step.

I know the pulses seem a bit high but I am sure ages ago with a slightly different setup I had used around 40 per pulse and had no problems but that might have also been on the older Solustan controller I was running. It's too long ago to remember.

I have had my stepper speed up to 700mm/sec and after that I lose steps and my sweet spot is 500mm/sec but going from 100mm/sec at 28um/step to 30 there is a noticeable jump in the speed of the motor like I had set it to 300 um/step. I even set my max acceleration way town to 50 (previously 30,000) and it sort of worked but the motor was still going way too fast and losing steps. It is a bit of a conundrum for me. I'm getting old too so my marbles may be scattered around a bit.

I think I will have to remove the reduction pulleys and just go straight drive by the look of it as I need to get it back up and running to do some more work.
I usually engrave at around 100 - 250 mm/sec and if engraving on paper I set to 200 - 300 with variable power settings from 15 to 40 power depending on the burn in. ( but that is rare). It's good for cutting templates from paper.

Thanks for the help, I really appreciate it this time of year. Happy New Year to you all.
Rich.

[baccus61]

Richard

The first thing that comes to my mind is, are you restarting or resetting controller after making the change?

Second is, what happens if you make the changes directly at the control panel?

EDIT, maybe you CAN'T make that change at the control panel.

I don't think it makes any difference restarting the controller and I'm pretty sure I tried that when it first started playing up but when I get home from holidays in a day or two I will give it another try. It can't hurt, can it?
I haven't tried the changes at the control panel. Might as well try that too!
Thanks for the input. Any help is welcome right now.
Rich.

[baccus61]

Well now, I've tried just about every thing I know and it just seems like it's a bug in the controller. There is just so much of a difference between going from 28um/pulse to 29um/pulse. The thing takes off at ludicrous speed and loses steps.
At 28 it's pretty subdued and drives nice and slow when set at 100mm/sec which is pretty slow.
If I go from 28 to 29 the head takes off at 10000mm/sec (just a guess) and that's still at 100mm/sec speed
You can't change the um/step on the control panel.
I tried the older 5.52 software with the same outcome.
I'm thinking of ripping out the whole computer and putting in a new one that will run 64 bit Win7 (currently on WinXP 32bit).
I have put a new pulley on it and I'm running the same drive from the motor to the input shaft so there is no reduction and effectively I have a motor with a 30 tooth pulley and the thing still want's to go at ludicrous speed. I should be able to reduce the speed no matter what the pulley sizes.

I'm lost!!!
Rich.

[Techgraphix]

Just one more question: is it in both X and Y-direction where you have this phenomena?

Kees

[baccus61]

No, just the X direction.
I have the Y axis geared down with a double reduction and it works great but I think I am missing something really simple for a fix to this. It's almost as if the settings are backwards!
I intend to have a better look at it tomorrow but now the power supply is tripping out on the RCD powering up the shed. Something is amiss somewhere and I need to have a damn good look around and check everything.

12 months ago and also 2 years ago we lost the neutral on the power pole and had all the actives go to ground on the house. We had 90 volts at 10 amps running through the house and I wondered why the wife was getting an electric shock when in the shower. Could have killed her! I lost the motherboard on my Hypertherm 1250 which cost $1900 to replace and a sundry of things were affected after that. hard to tell what was bad and what was good after.

I might even swap out the X driver with the Y driver and see if anything changes.
I might be up for a new computer too as this one is getting old after 4 years of use.
rich.

[baccus61]

I checked all the power supply today and found no problems so all is good there.
I swapped the pulleys around so I now have a -
19 tooth on the motor
36 tooth on the driven shaft
19 tooth on the x axis belt.
I got the pulses down to around.... ( I've forgotten!! bummer ) Around 15, I think.
Then tuned it in and set the distances for x and y again and now all is good.
It's finally back to square 1 and working well.
Thanks for all your input guys. It looks like you can't go over 28 um/pulse without having problems.
I am a much calmer person now.

Rich.

[DonL]

Good to hear you got it back working... Happy Ney Year Mate!