Shaking when above 200mm/m feedrate

This topic contains 29 replies, has 3 voices, and was last updated by Profile photo of Ryan Ryan 10 months, 1 week ago.

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  • #9015
    Profile photo of Ryan
    Ryan
    Participant

    Good evening gents… SO I know few of you have lasers, but im working with piclaser, and my feedrate for that should be in the 2000-5000mm/m range, even as high as 70-100k per minute… The laser is powerful enough to draw a picture at that rate.
    However, anytime i go above around 200mm/m which is true engraving speed it shakes and lurches a LOT.

    Now i dont think its the CNC at all, i think its software… Heres why… when i do a 50 move command (the max repetier can do) it works flawlessly. and SMOOTH as heck.
    When i do a test print around all the edges just going and going, SMOOTH as heck.

    What in piclaser or any other software would cause this?

    thanks

    #9025
    Profile photo of vicious1
    vicious1
    Keymaster

    I think it is the acceleration setting in the firmware. The max stock feedrate is 197mm/s so you are basically 60x’s below that. For milling the acceleration is low so it doesn’t jerk the heavy tool around on sudden moves. The laser gcode probably has a ton of speed changes, constantly hitting the jerk and accel limits.
    A quick experiment would be set the speed to double what you have it now and run the machine at 50% feedrate.

    #9026
    Profile photo of Ryan
    Ryan
    Participant

    speed and feedrate are the same to me? im kind of a dullard when it comes to these things haha.
    am i setting changes in firmware? or just in my laser software?

    #9027
    Profile photo of vicious1
    vicious1
    Keymaster

    Sorry It is the same thing usually. In your software change the speed to double, then on your lcd or repetier turn the feedrate setting to 50%. I think that should clear it up.

    I haven’t messed with the laser too much but if you can change the travel and the burn speed to the same. For example if your software trys too move faster when it isn’t burning it will trigger the acceleration limits, but if it never changes speed it should move smoother.

    I could also be very wrong on all of this.

    I am done for the night but if you want to zip the gcode and upload it here it might help to understand what is going on. I can look at it tomorrow.

    #9028
    Profile photo of Ryan
    Ryan
    Participant

    well in printer settings in repetier i see the feedrate is set to 4800mm/m so i tried that speed knowing that when i click manual moves at that rate its smooth.
    WEll its not in the laser software, so something is telling it to jerk.
    just more info for you

    #9029
    Profile photo of Ryan
    Ryan
    Participant

    ok. ill make the changes and post results.

    #9031
    Profile photo of Ryan
    Ryan
    Participant

    Yeah, so no change… in fact i just tested laseretch (jtech software) and im running engravings at 2000mm/m there with no issues, which is fine if i could get the working in piclaser as well. Im just realizing that the speed is hitting those limits you mentioned and no change in the software will change that. its something inherent to it.
    but others have used piclaser, so i guess ill have to figure it out. or chuck it.

    #9060
    Profile photo of Ryan
    Ryan
    Participant

    anyone? karl? 🙂 jay from jtech (i emailed you earlier).

    It happens in image2gcode too, so its something to do with the way its handling images vs just laseretch software, or normal stuff.

    #9073
    Profile photo of Leo69
    Leo69
    Participant

    8 bit Laser engraving requires a much faster flow of gcode commands than vector engraving. I’m not familiar with repeater. Have you tried running the gcode directly from sdcard? How fast are your serial coms?

    #9074
    Profile photo of Ryan
    Ryan
    Participant

    leo, i havent tried running it from an sdcard.. i havent actually hooked up my LCD 🙂 which is SD as well haha… i think i tried hooking it up once but it didnt work.. maybe i didnt hook it up right

    #9075
    Profile photo of Leo69
    Leo69
    Participant

    If your laser resolution is set to .1 mm then you’ll possibly be processing 10 g1 move commands AND 10 laser power commands for every mm of travel which adds up to 20000 commands per minute at 1000mm/min feedrate. Communication must be fast and uninterrupted for this to work. I would suggest getting the sdcard working to troubleshoot further. I use marlin and found that my laser stuttered a bit after upgrading to 12864 LCD even when running from sd. I noticed my stuttering was occurring once per second, same rate as display refreshes. I studied firmware and found that the u8g library is quite the resource hog so I disabled screen refresh during laser operations to correct the problem. Unfortunately we’re really pushing the limits of what the firmware is capable of. You may consider grbl for laser engraving since its much purer and unburdened by display updates , temperature monitoring, etc…I’m in the process of switching back to mach3 myself. I enjoy coding but I’m spending more time rewriting firmware instead of getting my mpcnc dirty lately so its time to leave Marlin behind.

    #9078
    Profile photo of Ryan
    Ryan
    Participant

    Leo thanks for the info…
    Right now im actually having an issue getting my LCD working…. I try to enable the LCD in my arduino configuration.h but getting errors. failing to figure out how to get or what to do with the u8g stuff.. ill keep working on it, but if you have an easier suggestion that would be great.
    thanks

    #9081
    Profile photo of Ryan
    Ryan
    Participant

    nevermind, i got the lcd working. trying SD now

    #9082
    Profile photo of Ryan
    Ryan
    Participant

    doesnt really seem to matter if i run off of the SD card or not… same result… running GRBL instead of jtech in the software just doesnt work at all. im guessing the commands are different so id have to figure those out 🙂
    it really sucks not being able to use a huge feature for why you bought your laser in the first place 🙂

    EDIT : how would i go about disabling screen refreshes? i dont even want the LCD 🙂 but ill use it if i have to to make this work haha

    #9088
    Profile photo of Leo69
    Leo69
    Participant

    Ok so this is interesting. I think Ryan may be on to something as far as the acceleration and jerk settings go. Can you create gcode for a small image using both laseretch and image2gcode and post them here? Also post your config.h file. Now that you have lcd hooked up it’ll be much easier to play with accel and jerk settings. They can be changed through lcd interface and the new settings will be written to eeprom. Even under ideal conditions i wouldn’t expect 8bit laser engraving to perform very well at speeds over 1200mm/min or so. The hardware is capable but i doubt the firmware is.

    #9089
    Profile photo of Ryan
    Ryan
    Participant

    Leo… when i get back home in a little bit ill do that leo… However, i run 2000mm/m for laseretch and dont have any issues with jerking… Perhaps image2gcode, or piclaser is issuing many more commands than laseretch is. Or perhaps laseretch is much more efficiently using commands 🙂

    #9090
    Profile photo of Leo69
    Leo69
    Participant

    Probably a bit of both.As I understand it Laseretch only does black and white, not grayscale. That means there’s no need for constant laser power commands and it also means multiple “pixels” can be consolidated into one linear motion so I’m sure your right. If you want to do8bit grayscale then you have to accept that it’ll have to be done a bit slower. Your current 200mm ceiling should have lots of room for improvement though.

    #9093
    Profile photo of Ryan
    Ryan
    Participant

    leo,.. so i think i may know (and this is obvious now) my problem, or at least one of them.
    my image size/quality.. ive been saving them as BMPs, but not 8 bit greyscale BMPs… I never figured that part out.
    However, saving it as 256 color doesnt convert it to greyscale.. is there any native way in PAINT to do that? or do I need another 3d party product to handle that converion to greyscale.
    i think thats a large part of my problem here.

    EDIT =- so i found GIMP software, which I can convert it to grayscale, but exporting it as a BMP doesnt give me any quality options and it looks fairly high quality even at grayscale.
    So now perhaps I need to change it to 256 color in paint, what a pain in the ass.. there needs to be one program (not photoshop, i dont wanna pay for that haha) to convery from a jpgh to 8 bit grayscale :).

    BTW, i tested it with the normal grayscale higher quality and it was WAY faster, less stuttering, still a bit though.

    EDIT EDIT – so loading it in to paint, and then saving it, shows its already at a 256 grayscale. so that wont make a difference. . poo

    #9098
    Profile photo of Ryan
    Ryan
    Participant

    OK. so a few more changes.

    Set speed to 1000
    pixel rez to .25 instead of .17

    and this seems to be working great.

    However if i even go to 1200 speed there is a little stuttering, even more at 1500, etc.

    Now to try SD card with 12–/1500

    #9099
    Profile photo of Leo69
    Leo69
    Participant

    No need to convert. The software will convert a color image to 8 bit grayscale which matches the pwm capabilities of your firmware. Post gcode when you get a chance

    #9106
    Profile photo of vicious1
    vicious1
    Keymaster

    Leo, I just put this in the other thread, but, what if we drop down to 16th stepping instead of the 32. That would cut the amount of data transferred in half correct?

    #9107
    Profile photo of Ryan
    Ryan
    Participant

    ok, so it appears 1250mm/m at those settings in my last post seem stable on the SD card.

    Is that pretty standard speeds? if anyone doing pictures faster? if the answer is no, im fine with that , just curious..
    thank you

    #9112
    Profile photo of Leo69
    Leo69
    Participant

    At .25 pixel res your image quality suffers a bit The spot size on your laser should be about .16 to .17mm if using the g2 or 3 element lens. I would try those settings for best image details.

    #9115
    Profile photo of Leo69
    Leo69
    Participant

    @vicious1 setting jumpers won’t have the effect you want because the commands are generated buy the laser software. They’re going to get queued and parsed by marlin regardless of stepper settings. Each pixel in the image can potentially have a different grayscale value so each pixel has it’s own g1 move and power command assigned to it. Bryan has done good work to optimize moves with matching power values but In the end this is the nature of grayscale engraving. I think your original suggestion t look at acceleration settings is still a possible cause of ryans problem. The laser gcode is produced with a global feedrate that remainsv constant. If accel settings are too low then they could easily trip the machine up with such a fast flow of tiny movements.

    #9117
    Profile photo of Ryan
    Ryan
    Participant

    so im printing out a maryln monroe photo right now at 1000mm/m and .17 reso. its actually printing very well, its not stuttering etc. i think its working really well. ill post the pic when its done.

    now how to vent this thing. I just got a bid to run a vent hose outside, $1250. YIKES.

    #9122
    Profile photo of Ryan
    Ryan
    Participant

    so here is the photo…
    how does it look to you guys.
    knowing that its over top of some old cuts, and burns and etches, but you get the idea.

    mary

    #9137
    Profile photo of Leo69
    Leo69
    Participant

    You can try bumping the speed up 100mm at a time until you see performance issues and at that point you can try increasing firmware acceleration settings with the lcd menu to see if you can get more out of it that way.if you find the movement gets sluggish once per second , timed with xy coordinate refreshing on the display, then we can deal with that issue separately.

    #9150
    Profile photo of Ryan
    Ryan
    Participant

    IM actually ok with 1000mm/m however you can see on the edges of the image there is sometimes some bleed.. so I may need to go down to 800 or less… i dont know how many images ill be doing like this, but it would be nice 🙂
    i tried speeding it up via the LCD and it didnt allow for much speed increase before it started affecting things.

    #9153
    Profile photo of Leo69
    Leo69
    Participant

    Ok but just to clarify, I’m not talking about speeding up the Feed rate. I’m talking about playing with the acceleration setting in the firmware.Jacking up acceleration setting may let you increase the feed rate a bit more. For my feedrate I usually do grayscale at about 1000 to1200mm/min. Might be able to go faster but I’m usually watching a movie In the next room so why bother right? Maybe some other burners will chime In with their usual feed rate for grayscale engraving. The optimization that Bryan added in the later versions of image2gcode will save some time too.

    #9165
    Profile photo of Ryan
    Ryan
    Participant

    If its between 800-1200 and it requires messing with firmware that may affect other parts of the CNC, then its not worth it… 5-10 minutes on an hour job isnt that big of a deal… I think im fairly ok with where things are right now…thank you leo and ryan for your help on this

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