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Openbuilds 4x8 cnc

Discussion in 'CNC Mills/Routers' started by Sam Keller, Aug 14, 2020.

  1. Sam Keller

    Sam Keller Well-Known
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    I'm still getting belt slip when I push my machining too hard so I'm going to try a 40 tooth pulleys instead of the 20 tooth I'm using now. I read that more teeth = less slip.
    It makes sense, I hope it works.
    Capture+_2021-02-20-07-23-50.png
     
  2. JustinTime

    JustinTime Veteran
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    Sam, if you get slippage on the 20t you are overtaxing your hardware, and I don't mean the 20t pulley. Maybe slow down the machine? Maybe use a different belt, one more wider and less teeth per inch?
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Double the teeth, double the speed, half the torque, half the resolution
     
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  4. Sam Keller

    Sam Keller Well-Known
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    That makes sense, now I'm really curious how it will effect my machine. I have 450nm motors that I just increased from 24v to 48v so they are really strong and fast now. I'll have to play with the settings to see if I can get a good balance of speed and power for my laser and router and hopefully increase the belt holding strength.
     
  5. KramE

    KramE New
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    Just checking in to see how you're liking the build. Any changes or mods?
     
  6. Sam Keller

    Sam Keller Well-Known
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    It's been quite a while... I got tired of messingwith the belts, I was really getting a sling shot effect when cutting in the middle of the bed so I went to rack and pinion. Found some pretty cheap in Missouri and it works great. It took a while to get it lined up square and the gear mesh right but it's much better than the belts. I also changed to steel v wheels, i like them better too. I probably didn't do it the best way but that's how I do stuff...
    20220119_214604.jpg 20220119_214334.jpg 20220119_214323.jpg
     
  7. KramE

    KramE New
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    Great! Good to know, thanks!
     
  8. NickEng

    NickEng Well-Known
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    Very cool. We don't use our "sam Keller Replica" nearly enough. But we still find uses for it occasionally. What kind of speeds are you routing wood at now with the rack and pinion vs the belt before? The problem we see if we go too fast is the belt slips and "looses its place" and ruins the piece.

    We added the diode laser as you did as well, but we keep tossing the idea around of adding a plasma cutter to it. I am just not sure if and how the blackbox can handle the plasma cutter. I need to do more research, but I hope to add it to our replica machine at some point...

    Impressive Sam!
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  10. NickEng

    NickEng Well-Known
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    It may be in the video, I haven't watched yet, but what software do you use to send the gcode to machine? Is the openbuilds control software capable?

    We currently have a router and laser connected to the blackbox. Do you have to unplug the laser to get the plasma to work?

    Thanks!
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Yes, you still stream gcode using CONTROL: See docs:software:overview [OpenBuilds Documentation]

    CAM side you can use OpenBuildsCAM or Fusion360


    Grbl has only one control output, so yes, spindle, laser, plasma - all share the same "command" - you can wire up simple panel switches to enable tools though instead of unplugging things: For example:

    docs:blackbox:iot-and-laser [OpenBuilds Documentation]

    But use a switch with more positions and maybe multiple poles so you can run the Plasma trigger relay on a seperate pole from the PWM signal

    or just 3x power switches. Enable only the tool you want to use's power. It won't run if its power is off, even if it receives the signal to
     
  12. chuck english

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    Sam, Im glad to see your back at it. Helps motivate us. Did you do rack and pinion for Z axis too? And I assume you used same stepper motors that you were using with belts? Would you share the name of place in Missouri that you bought rack and pinion?
     
  13. Sam Keller

    Sam Keller Well-Known
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    I bought the r&p from Custom & Stock Gear Racks | Gear Rack Manufacturers. You have to call and order but their prices and shipping was lower than other places I've looked. I only put them on the x and y axis. I haven't really sped up my speed much but i have increased the depth of cut for fewer passes and it drives right thru with no slingshot effect. I cut 1/2" pvc in 1 pass now when it took 3-4 passes before.
     
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  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Moore Gear did make a couple of posts a long time ago but we haven't heard from them since. Their prices seemed very reasonable at the time.​
     
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  15. Sam Keller

    Sam Keller Well-Known
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    I also switched to these steel wheels and I like them alot. They roll alot smoother than the plastic ones.
    Screenshot_20220124-125457.png
     
  16. chuck english

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    Thanks for the info Sam. You must have known I was about to ask.. 8) So the racks that you ordered; were they the 1/2" , 3/4 or 1" face width . 12, 16, or 20 pitch? I assume you ordered the 12' stock. I dont see any 8'. Did you get gears from there also?
    Thanks
     
  17. Sam Keller

    Sam Keller Well-Known
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    I bought 4 of the R2020x6 ft 20 pitch 1/2" for $216 shipped 6 months ago. I bought the gears on amazon. I used m3 screws and countersunk them. I butted them together and ran the gear across the joint until it was smooth then tightened the screws. I runs smooth over the joints and screw holes. Prob not the best way to do it but it works for me.
    20220126_095151~2.jpg 20220126_095037.jpg
     
  18. NickEng

    NickEng Well-Known
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    @Sam Keller, I think we are ready to follow your upgrade to rack and pinion. We are hoping to be able to increase the speed in which we can complete jobs without (what we assume to be) belt slippage. If we try to cut wood at 1/2 the step down of the diameter of the bit, at 70-80IPM or more, we often mess up boards because the machine gets off. I would really like to increase this pretty significantly, and I think/hope the rack and pinion is the answer.

    I have called and gotten a price on the r2020 gear rack, but I am trying to make sure I am getting the correct pinion gear to match. The pinion gear must be a 20 pitch to fit that rack correct? I have had a hard time finding a 20p gear pinion. 32p and 48p are abundant. Do you have a link to what you got?

    I hope all is well!

    thanks!
     
    #198 NickEng, Mar 22, 2022
    Last edited: Mar 22, 2022
  19. Sam Keller

    Sam Keller Well-Known
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  20. NickEng

    NickEng Well-Known
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    THANKS !!!

    @Sam Keller Out of curiosity, how fast do you think you can cut wood now? I know previously you said you are pretty much maintaining about the same speed as before, but were cutting deeper. I am trying to cut 1-1/2" thick pine with whatever diameter bit would be the fastest, but I am only realistically being able to achieve about 70 IPM without worry of messing up the cut. I am stepping down about .2" with a 1/2" bit.

    I know I could probably increase my speed if I decrease my step, but I am just trying to figure out what will allow me to finish the job the fastest. I am curious as to how much you think your setup with the r&p could achieve this?

    Thanks again!
     
    #200 NickEng, Mar 22, 2022
    Last edited: Mar 23, 2022
  21. NickEng

    NickEng Well-Known
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    @Sam Keller , did you have to do any modification to connect your power supplies in series? (Isolate grounds?) or, do you just connect the + from one supply to the - of the other and connect the load to the two remaining + and - connections of the two supplies?

    Thanks!
     
  22. Sam Keller

    Sam Keller Well-Known
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    Sorry I didn't respond to your last post, I was going to do some speed tests first but got busy with orders and haven had time.

    I did not do any modifications, just connect the + from one supply to the - of the other and connect the load to the two remaining + and - connections of the two supplies.
     
  23. NickEng

    NickEng Well-Known
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    No worries!
    Thanks!
    Did you use a diode between the two supplies?

    We have made the plunge to the rack and pinion. We just got parts in and beginning to put together yesterday. We got it up and moving, but still need some tweaking.

    I wasn’t impressed initially with the ease of stalling the motors on the r and p, but I have reduced the acceleration down quite a bit and it seems to be better. I also had an issue with my blackbox, but @Peter Van Der Walt and everyone at open builds was awesome at helping me diagnose and get a replacement quick! I was very impressed with the customer service!

    Long story short: I have the dm556 drivers that I ordered before going with the blackbox. I have another project on the horizon for the blackbox and I want to be able to utilize the higher voltage capabilities of the dm556 driver now that I have gone to rack and pinion. I am hoping doubling the voltage from 24 to 48v will increase the torque of the motors.

    I think (at the moment) I have acceleration set to 250mm/sec2 for the x and y axis. This is ALOT slower than it will actually run at, but the torque seems to be so much higher!
    My max speeds are around 7500 mm/sec and I can do much higher than this too, but again I am wanting to be able to cut without missing steps more than zip around fast in transition.

    Thanks!
     
  24. Sam Keller

    Sam Keller Well-Known
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    I almost mentioned the diode... I read to put a diode on and tried it but the power supplies wouldn't work so i took it out and works fine.

    48 volts should and the dm556 drivers should fix the problem. I have the acceleration at 500 and have not stalled or gotten off track even once. I run just a little faster and a little deeper than before, I'm too chicken to try and push it on a project.
     
  25. Sam Keller

    Sam Keller Well-Known
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    Also make sure your microstepping isn't set too high. I use the 400 steps/rev. I tried higher settings and did loose steps at 1600 and above. I don't think there's any reason to go higher i was just messing around testing it. I have my acceleration set at 1000 with no problems.
     
  26. NickEng

    NickEng Well-Known
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    @Sam Keller
    ok, I have it set to 400 and now connected to 48v. Seems to be working fine. At least my rack and pinion addition. While making these changes, I increased the z axis amount of travel. I moved up to a 1040mm lead screw from openbuilds.
    I have it all up and running, and everything seemed to work fine (I think). So, I started adding limit switches that I have never added. And obviously had to run wires. Now, when I move the z axis up it sounds ok, but when I move it down it sounds awful. Seems like if it were a “strain” on the motor it would be the opposite. I have checked wiring and can’t find anything obviously wrong. Any ideas what may be causing this?

    Thanks!
     
  27. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  28. NickEng

    NickEng Well-Known
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    I will check this, but I removed the coupler from the lead screw and run the motor back and forth and it sounds fine in both directions. Wouldn’t this mean the wiring is correct?

    thanks!
     
  29. Sam Keller

    Sam Keller Well-Known
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    I would checkfor something binding like wheels too tight or three backlash nut. Can you spin the lead screw with your fingers when the motors are off?
    I kind of had the same problem, i replaced my lead screw with a lower pitch screw and block so my gantry wouldn't lower when the motors were off. I tried moving it up and down at a pretty fast speed (30 ipm/ 750 mm/min) it made a horrible noise, i don't remember if it was up or down or both. When i slowed down the noise stopped. I run the z at 16ipm/400mm/min now with no problems. I didn't look into it anymore to find why but now I'm curious. What speed are you running the z axis?
     
  30. NickEng

    NickEng Well-Known
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    Yes, I could spin it with my fingers. It is difficult to get to one side bc of the location of my limit switches though. However, I have my z axis speed set at 2000mm/min. Acceleration is set to 50. This could be the problem? I have no need to go near that fast, but I set it at that when I had the smaller z axis lead screw and it seemed to work ok. I will lower this speed way down and see what happens. What is your acceleration? What is the height of your z max travel?

    thanks!
     

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