Minnesota Build – Low Rider

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This topic contains 275 replies, has 13 voices, and was last updated by  Ryan 1 year, 6 months ago.

Viewing 30 posts - 241 through 270 (of 276 total)
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  • #57053

    Anonymous

    So to do this type of pocket cut what would be the ideal bit… again using cheap 1x lumber?

    For that tool I didn’t have finishing set… better – I have no idea how to set it.

     

    #57054

    Ryan
    Keymaster

    In properties for the path set a finish of ~.5.

    Shown in the last Islands picture on this page.

    Milling Basics

     

    1 user thanked author for this post.
    #57057

    Anonymous

    So when you set a finishing allowance – what does it actually do?

    Does it do it’s normal cut and then do the finishing cut and if so how’s it any different than the primary cut.

    If  single flute bit is not good for pockets what would be a better choice?

    #57058

    Ryan
    Keymaster

    If you look at that picture you can see what it does. It cuts everything leaving the allowance there, then the final thing it does is shave off that last little part in a smooth motion under very little force leaving a more dimensionally accurate cut. All your cuts should use this.

     

    If single flute bit is not good for pockets what would be a better choice?

    A single flute is best…just not with the crazy end yours has, is is scraping out with a little point, most endmills have a flat end, the one you bought does not.

     

    You have a working machine, and some working Gcode. You should spend some time learning different materials and different endmills. You keep changing everything. Cut the same exact part or design either in the same material with different endmills, or same endmill in different materials. Don’t worry about cnc.js, or leveling, or squaring for now.

    #57064

    BT
    Participant

    The easiest way to tell what the finishing allowance does is to set up two passes in Estlcam, one with the allowance and one without.

    #57071

    Anonymous

    Ok I get how to select the finishing but I am not sure how it should be set up on tool list.

     

    #57073

    BT
    Participant

    The tool list looks OK.  It’s a bit of trial and error for the depth of cut for the finishing pass, dependent on the material, the finishing allowance, and the stepover.  Some old guy coding gives a pretty good demonstration of how to set up the finishing allowance as well as his example results in his video: https://www.youtube.com/watch?v=pLrCAeJv4KQ

    #57074

    Ryan
    Keymaster

    Just a few posts above I gave you a link to a very specific picture that clearly shows how to do this. I will directly link it this time but now I have to strongly urge you to have a look at the entire page again. There is a lot of useful information in there. Getting us to do all this for you means you are not learning to make your CAM. I am sure everyone agrees it is better for you to make the Gcode and we tell you how to correct it or will will be continually making Gcode for you.

    https://www.v1engineering.com/wp-content/uploads/2018/03/3Island.jpg

     

    #57077

    Anonymous

    Thanks guess I didn’t see how it relates to the tool list that is why I asked.  I get the feeling I should curb all of my questions.

    #57080

    Ryan
    Keymaster

    Don’t curb your questions, just try it out first. If anything goes extremely wrong you can fix the machine, you are using purple foam so it is extremely hard to make things go wrong.

    You don’t have to change anything, the tool bar allows you to change things if you need to. Until you understand why you might need or want to I suggest not changing anything.

    There is so much to learn, the more time you spend cutting the more you will understand. You keep trying to change so much at once you are going to make it confusing. Make a nice simple cut, like Jeff showed you above. Mess with one variable at a time and try it out, each cut is only a few minutes. Make a square, cut it with no finishing, then do it with .6mm finishing. See if you can tell what it does differently. you can even watch the CAM playback before hand.

     

     

    #57374

    Anonymous

    Need to cut some ABS plastic parts today – 1/4″   – What would be the ideal feedrate, etc?

    Also for plastic do I need to do trochoidal cutting?

    #57382

    Mike
    Participant

    I have only milled acrylic. For through cut of 5/16″ material I ran at about 18K RPM, something like 20mm/s in a single pass with a 1/4″ end mill. This was in Fusion, done as a 2D profile so no trochoidal. It turned out ok for what it was (a top cover for my kids side table so he doesn’t destroy the particle board top with water from glasses). To do it again, I think I would slow down the feed rate and rpm a bit. It seemed a little rough maybe due to some slight chatter.

    As for ABS, I think it is softer, maybe more melty. I wouldn’t go too slow on the feed rate with too high a bit rpm, I think that could get messy. But I’m guessing high bit rpm would be the thing to cause melting more than slow feed rate. Trochoidal might be a good option because it could give the plastic some time to cool between cuts?

    Haven’t done it, so just random thoughts not even worth 2¢.

    #57429

    Anonymous

    Well something failed –  trying to cut a sheet of ABS plastic.  Using 1/4″ upcut with trochoidal cutting enabled and the cut got 3/4 finished and the Y axis just stopped moving.    I have had prior instances where the Y would not move but after inspecting never found a binding issue or loose belts, etc.  It stopped on a turn where the Y axis would have needed to move inward to home position.   I have no clue where to troubleshoot but does not make any sense to attempt anymore real cuts.

    #57430

    Jeffeb3
    Participant

    It could be the driver overheating. Did it just stop (overheating or loose wires) or make crunchy noises (skipped steps)?

    #57432

    Anonymous

    Just stopped.

    #57433

    Jeffeb3
    Participant

    Either an overheated driver or a loose wire. You have two motors on Y, right? What setting do you have the current set to? Do you have heat sink and fan on them?

    #57441

    Anonymous

    Y is one stepper – no loose wires… I will have to check the driver. I am sure I checked the voltage.  Ramps board does not have a fan at this point – though this cut was shorter than the V1Engineering logo cut in foam a week or so agoo.  so I just don’t get it.

    #57444

    Jeffeb3
    Participant

    Well, the heat is proportional to the current. The current is proportional to the effort. So maybe it’s working harder, not longer. Plus, things might just be getting dirtier. I had something similar happen to me, and I just wired up a small 12V fan and hot glued it where it was pointing at the drivers. It’s not great looking, but I haven’t had trouble since. I also have the little heat sink that came with the drivers installed (attached with super glue).

    If it’s a drv8825, then 0.7V to ground should be about right.

    2 users thanked author for this post.
    #57456

    Barry
    Participant

    +1 for the fan.  Both my machines have fans blowing across the drivers.

    1 user thanked author for this post.
    #57458

    Anonymous

    Thanks again – will slap a fan on it and check the driver current.

    #57621

    Anonymous

    Question about dust collection on the LowRider – What success if any have you guys had?

    I designed a small collector for the Makita 701c – will test that today but am doubtful it will have much success.

    The other day when I cut the ABS absent dust collection I have ABS chip everywhere as they seem to get a static charge so they stick to anything.  Still blowing out ABS chips out of my garage so am looking to find a solution even if I have to ditch the clear 611 plate and make a new one with a dust port.

    #57706

    Anonymous

    Well, I tried the dust port 3d printed part I made for the Makita 701c  – total fail…..

    I was cutting the ABS with 1/4″ upcut and the cut failed too….. same darn Y axis issue it seems – though it did finish the cut and didn’t stop like the prior attempt….. pictures tell the story.

    I have no clue on the Y – does not bind when powered down.   belt as far as I can tell is as tight as I can get it.  I can send GCODE to move it several hundred MMs and it runs smooth….. yet during this cut something went wrong and I have no idea what to do to fix it.

    #57712

    Jeffeb3
    Participant

    That looks like skipped steps. Which is either that the current isn’t high enough, or there’s too much resistance.

    #57713

    Anonymous

    Stepper driver read out at .70 is that not where it should be ?

    #57717

    Jeffeb3
    Participant

    That’s where it should be.

    #57724

    Anonymous

    Is there a remote possibility that the cut shavings are binding up on the bearings – between bearings and pipe?  I know with the foam it got solid on the bearings and the ABS stuff is like static charged so it too is clinging to the pipes and bearings, etc.

    I switched to the new 611 plate with your dust port made sure the Y axis moves smoothly loosened the belt, etc…..

    I am cutting another part and it’s doing the same thing… so far it has not skipped so perhaps the part will come out like it should but I cannot think of anything else that would be causing this jerky movement in the Y axis.

    #57730

    Jeffeb3
    Participant

    Yeah, that’s possible. I haven’t had that myself, but anything is possible. I haven’t used abs.

    I might have my Y driver just a bit higher than 0.7V. I can’t remember now.

    #57733

    Anonymous

    I guess it will remain a mystery…… one more cut and if it fails….  the LowRider is history for me.

    #57735

    Ryan
    Keymaster

    Speed (8-12mm/s), Rapids (30 or under), how tight are the mounts (sloppy loose), how tight is the belt (doesn’t need to be a guitar)?

    More importantly did you over tighten the little idlers and they are not spinning freely? My money is on this.

    #57736

    Dui, ni shuo de dui
    Participant

    Personally, I don’t set a theoretical value for the drivers. I adjust it manually by, at the same time, turning the pot, moving the axis (prepare->move axis) and applying a bit of force to the axis with my hand to simulate a load.

    I bet my drivers are set up to more than .7amps, but it doesn’t really matter as long as you have enough cooling on them. Motors are just slightly warm so I guess in my case they are not the limiting factor (might be different on your machine if you’re using smaller motors). You can estimate how much power you draw just by hearing the noise the motors are doing while holding position. What I found gave the best results on my machine was to be able able to hear them clearly, but not to the point that it is annoying.

    The reason I find the theoretical method ineffective is that you set a theoretical value that doesn’t account for real life differences in how the axis actually can move. You just cannot have the exact same belt tension everywhere, and one axis might move a bit less freely than the other. Adjusting manually can help to take these factors into consideration.

    Just try it this way, maybe it ‘ll solve your problem.

    Also, If your bearing usually get dirty, you could add some brushes to make contact with them, so that they are getting cleaned anytime the CNC works. It should be fairly easy to do, just purchase a few toothbrushes, cut their heads and print some kind of bracket to attach them.

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