Probably every error in the book (mechanical)

New Home Forum LowRider Troubleshooting – LowRider Probably every error in the book (mechanical)

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  • #102675
    Hajo Piltz
    Participant

    Hi guys,

    I was hoping to get some guidance on my Generation 0 Lowrider 2. (Gen 0, because I only built it to get some experience and cut final side parts and because after the parts for the big table were delivered, I realized I’d be unable to move the table around due to the weight, so I need to decide on a new place where to put it up and a different frame underneath…)

    Anyways, these are my results and issues so far:

    1. Crown looks ok to me, given that there is some flex in the pen (I don’t own a 3D printer and forgot to order it with the other parts. So I drilled a hole in the router assembly plate and stuck a ball pen through there.)
    2. My router assembly plate is almost 5 millimeters lower on the back than it is on the front. ZY assembly is angled the same. I’ve read of the same issue in another thread here and will check for even tightening of the screws in the assembly. Surprisingly, it doesn’t seem to matter much in the result (it’s under dimension in both axis to the same degree, but angled in only one).
    3. The first part I tried out was a 100 x 100mm square in 18mm particle board. See the pictures and GCODE attached. Some things went well (e.g. I’m happy how relatively even it looks in the spoilboard) but overall I cannot be satisfied:
      1. 5 mm under dimension in both x and y. A small part of this can be attributed to the fact that the bit is slightly oversized. But that only explains 1mm of the 5mm. I have checked the steps/mm but found no significant deviation that would explain that: If I move the axis 100mm in jogging mode, I come out at 99.5mm and maybe it is 200.3 instead of 200 steps but it still doesn’t add up to my total difference… (Possibly it does not execute the arcs around two of the corners properly, which would explain it.)
      2. Skewed. I think this is natural, given that my X and Y axis are not squared up properly. Mostly that is because I have been unable to find a place to put the dual endstops on the X axis. What position do you recommend for that part? Also I realize I should completely re-assemble the whole Y axis as I think it is a parallelogram and not a square.
      3. Not parallel in the X axis dimension. I can’t understand that at all. It’s difficult to see in the pictures, but basically it looks like this: |_\
      4. Z-Steps in X axis dimension ON ONE SIDE ONLY. Don’t know what to make of this, either. I have rather pronounced (around half a millimeter) steps on the not-parallel side.

    I hope you can point me in the right direction for some of these issues. Regarding 3.a, 3.c and 3.d I suspect there might be a software issue and I have created a separate thread for that.

    Thanks for your support!

    Hajo

    #102684
    Barry
    Participant

    If the router plate isn’t flat, you’ll have errors in your cut dimensions since the endmill will be slanted.  Figure that part out first.  There was another thread today about this, which is what I think you’re talking about.  Try that fix first, and see if it helps.

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    #102699
    Jeffeb3
    Participant

    5mm is huge error though. The angle is definitely something to work on, but rest assured, you’ll get it way better than that. Your gcode looks ok to me. It’s assuming a 6mm bit, it looks like. Which is about 1/4″.

    The parallelogram and skew might be causing difficulties measuring. I.e. if you measure two parallel edges of a parallelogram, they will be closer than the length of the edge. If you start the motors with the gantry square, it should stay square, no dual endstops needed.

    As for 3c, thay could be explained by hysteresis. It might be moving to the side while travelling away and not be able to move back when travelling forward.

    But first, definitely fix the problems you can see. That angled plate is not doing you any favors.

    #102733
    Hajo Piltz
    Participant

    I ran it again, after having found a workaround for the issue I had with the arcs: The part looks much better now, but is still consistently 5% below size in X and Y direction. I haven’t gotten around to fix the Z-Axis level, yet, but since I use a tilt base as a holder for the router

    Strangely enough: If I use Motion/Axis functions directly on the LCD to move 100mm, I get 100mm and not 95. So it’s not the belt or the pulley.

     

    Is there another setting I can check to see if there is a general scaling factor or something like it? Because the GCODE looks correct for 100mm, as well. (Except I have increased the tool diameter in EstlCAM to 6.6mm, which is what I measure at the tip).

     

    Thanks!

    Hajo

    #102742
    Jamie
    Participant

    Your gcode is moving 0 to 100 in x and y, which will leave your part undersize by the diameter of the bit. Your cam software will take the tool diameter into account when cutting the outline of a part, or cutting a hole or pocket. Your gcode looks like you are “engraving” the 100 mm square with the center of the tool.

    #102776
    Hajo Piltz
    Participant

    Thanks for looking into it Jamie,

     

    it is indeed what it looks like, because we humans cannot read these G02, G03 commands easily. With arcs disabled (attached), it is a little clearer that the outer toolpath it _should_ travel is at 103.3 and -3.3 (for a 6.6mm diameter tool). So I think it is not the code…

     

    Hajo

    #102821
    Jeffeb3
    Participant

    For G2 and G3, the xy are the final position of the arc. The IJ are the center of the circle, but when proof reading, I ignore them.

    #103039
    Hajo Piltz
    Participant

    Hi Guys,

    now I know what is going on: The Marlin firmware simply ignores all GCODE lines that would send it into either negative X or negative Y.

    My origin is on the corner of the finished part, so the two sides that make up that corner are cut ON the outline of the part (rather than around it). So you were completely right @Jamie, at least in practice with this firmware.

    Not sure how others would interpret it. Has any of you tried GRBL on RAMPS? I’ve seen a thread here on it but was curious if you had ever tried it?

     

    Thanks

    Hajo

    #103040
    Ryan
    Keymaster

    That should only be true of the dual endstop firmware of mine. All others should allow negative moves. If you are using the dual you should just move your origin as you physically should not be able to move negative XY.

    #103041
    Jeffeb3
    Participant

    Hah! That will dampen your tests…

    That’s fixable with Marlin. Just turn off the soft stops (which as Ryan said, should only be on in the dual endstop version, which is so you don’t crash your switches). There is an M code to turn those off, but if you have the dual endstop version, then you probably didn’t home first, and if you did, then you shouldn’t cut so close to 0,0.

    I have used grbl, but not on the RAMPS. It works well, but Ryan doesn’t have instructions for it. There are a lot more users on Marlin than the grbl for RAMPS, and even fewer users on the 5 axis grbl/RAMPS.

    #103076
    Hajo Piltz
    Participant

    Perfect, thank you guys!

     

    I am indeed running the dual endstop firmware, but I’m not homing because I haven’t installed the switches yet. (I’m still looking for a good spot to mount them and a sound wiring solution.)

     

    I’ll stick with the proven Marlin, then, but disable the softstops (or move my origin) until I’m actually using the dual endstop capabilities. Thanks for your support!

     

    @vicious1 : I’m fairly certain G02/G03 can trick the machine into negative X and Y with softstop enabled, so there is probably a small bug in there, still.

    #103089
    Jeffeb3
    Participant

    @vicious1 : I’m fairly certain G02/G03 can trick the machine into negative X and Y with softstop enabled, so there is probably a small bug in there, still.

    Oh, that’s interesting. That explains why you were getting those funky movements. It might be worth drawing that with a pen and if that’s true, posting an issue on Marlins github.

    I think if you were to move the machine to positive 10,10 and then do G92 X0 Y0 that you can go up to -10,-10. I can’t exactly remember but I think the soft stops aren’t affected by the G92.

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