Slow jumpy feedrate

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pwolfe1011
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Joined: Fri Mar 03, 2017 3:14 am

Slow jumpy feedrate

Postby pwolfe1011 » Mon Mar 06, 2017 2:25 am

Hello everyone, new user hear learning the ropes. I recently purchased a 4w laser from JTechphotonics. Their shop is close to where I live so I had the opportunity to pick mine up in person and meet J. He was a very nice and helpful guy that showed me around his awesome shop. Anyways, I am having a feet rate problem with two different 3d printers with two different controllers on one of them. The results are fairly similar with all 3 controllers. I am hoping that I am just overlooking something that can be corrected so I may use this awesome technology. I'll list some more details with the trial and error thats been done so far.

Two of the boards are Arduino based MKS 8 bit boards. The third is a smoothieboard 32 bit clone, also by mks. On all boards I have checked the pwm signals for laser triggering. Ironically on the two 8 bit boards will fire the laser with either the M03 or M106 commands plus the S value. I have not tried this with the 32 bit. I increased my jerk and accel setting to ridiculous levels. This has helped more than anything, but I still can only get up around 900 mm per min. I increased my baud to 250000 with little to no difference over usb and the problem is identical with running on sd card. I have scoured the firmware for marlin and smoothie, trying to find anything that would cause a dwell anytime the pwm level was changed. It seemed to me that the 8 bit controller just couldn't handle that much information. I have the Pic Engrave software set to .1mm for laser width (pixel width?) which in turn breaks up all G1 command into .1mm segments with a M106 Sxx or M03 Sxx in between. This is why I concluded that it was simply to much for that card so I purchased the 32 bit with much confidence that it would solve my problem. Nope, same thing. I did however, set the 32 bit for 32 microstepping. I will try it on 16 later this week. I have been able to produce some really nice pictures engraved on some birch plywood, it just takes a really long time to do them. The outlines, if I have that option enabled, runs at the speed it should. When it starts the raster paths is when it slows down. I think i've noticed when a part of the picture being engraved has a more dense area of contrasting pixels (such as a in between shade whithin a dithered photo) the speed problem is more noticeable and erratic. If it helps, everything seems to run like butter when vector engraving.

Thank you for listening to my incoherent babbling.

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Picengravertoo
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Re: Slow jumpy feedrate

Postby Picengravertoo » Mon Mar 06, 2017 6:16 am

We have not tested a smoothie board and it's firmware.

You probably should ask your questions, or search for an answer here: https://github.com/Smoothieware/Smoothieware/issues

pwolfe1011
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Joined: Fri Mar 03, 2017 3:14 am

Re: Slow jumpy feedrate

Postby pwolfe1011 » Thu Mar 09, 2017 9:37 pm

Thanks for the reply. Just to make sure I'm not setting up the files wrong, what are some average speeds and pixel size (laser point size)? I have been using several speed and a pixel size of .1 mm

Thanks again,

Phillip

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Picengravertoo
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Re: Slow jumpy feedrate

Postby Picengravertoo » Fri Mar 10, 2017 7:35 am

.1mm is really small and with that very short incremental gcode movement surely will slow down the execution/streaming speed with any CNC controller. With an UNO & grbl, the smallest we use is between .1524mm-2032mm and the confirmed streaming feedrate we can achieve is a smooth running 5080mm/min when engraving at a 45D angle. That's when using the MultiMode grbl 1.0c firmware that is available for download on this forum's main page.

pwolfe1011
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Joined: Fri Mar 03, 2017 3:14 am

Re: Slow jumpy feedrate

Postby pwolfe1011 » Wed Mar 15, 2017 4:08 am

I thought .1 mm was kinda small. I will try a bigger size. I have had a bit of luck experimenting with smoothie's "laser module" built into their firmware. It doesn't use a on or off command. It looks for G1 and G0 commands. The smoothieboard automatically turns on the laser for the G1 move and off for the G0. I have tested up to 2500 mm/m without any stuttering. I'm not sure if this different approach has taken away my stuttering or not. This "laser module" also uses hwpwm (hardware pwm) instead of pwm. I don't know the exact differences, but on their forum they call it REAL pwm. I will attempt to set up my firmware switch with this hwpwm and go back to using a M command to trigger the laser. Hopefully I will get that to work. If i can't, I was wondering if your PicEngrave Pro has the ability to produce gcode with the G1 and G0 moves for laser on and off without an M command, but with the S value for variable power? I have the trial version, but haven't been able to tinker much. Thanks again for your help, I hope i'm not bugging anyone.

Have a good day,

Phillip

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Picengravertoo
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Re: Slow jumpy feedrate

Postby Picengravertoo » Wed Mar 15, 2017 4:59 am

Try Dithering your image in the editor and set PicLaser like this.

Capture.JPG
Capture.JPG (44.31 KiB) Viewed 4508 times


The Atkinson Algorithm works the best because it's adjustable. If you use Metric units, select it and set the Pixel Resolution based on your laser's burn line width & feedrate in Metric units. I'm not sure what comment character or the file extension the smoothie uses, so set that accordingly.

It will generate the gcode like this.

G1 X1.056 Y3.828
G1 S255
G1 X1.062 Y3.822
G1 S255
G1 X1.068 Y3.816
G1 S255
G1 X1.074 Y3.81
G1 S0
G1 X1.08 Y3.804
G1 S0
G1 X1.086 Y3.798
G1 S0
G1 X1.092 Y3.792
G1 S0
G1 X1.098 Y3.786
G1 S0
G1 X1.104 Y3.78
G1 S0
G1 X1.11 Y3.774
G1 S255
G1 X1.116 Y3.768
G1 S255
G1 X1.122 Y3.762
G1 S0
G1 X1.128 Y3.756
G1 S0
G1 X1.134 Y3.75
G1 S0
G1 X1.14 Y3.744
G1 S255
G1 X1.146 Y3.738
G1 S0
G1 X1.152 Y3.732

Or, don't Dither the image and see if variable PWM works to engrave shades. Experiment with the settings.

pwolfe1011
Posts: 4
Joined: Fri Mar 03, 2017 3:14 am

Re: Slow jumpy feedrate

Postby pwolfe1011 » Tue Mar 21, 2017 2:37 am

Update,

I have experimented some more using your recommendations. So far so good. 2500 mm/min using Pic Laser is now working. I still have not tried any faster speeds than this, but 2500 is more than enough for me. Atleast until I am able to dial things in better to get better quality at high speeds. Still have not had much time on my hands, mostly my testing has involved logo type drawings without much detail. I will try some photos soon with this new gcode setting. Thanks for the help. In the near future, I will try to get some pics up on here of my work.

Have a great day,

Phillip


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