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  1. #61
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    For me resolution wouldn't be a problem, but more of how fast these direct drives can cut through wood without stalling or loosing steps.

    If they are about 300 oz-in motors, theoretically that would produce only about 10 pounds of force with no gear reduction and a 20 tooth pulley.
    Correct me if I am wrong.

    By the way Bob (parallel__lines), are you the designer of the Momus machines?



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    Yep, I'm the designer.

    The belt drive is using a 10 tooth pulley, so you've got more torque than your are calculating. Also, the amount of force is going to depend on motor speed. Max torque is produced at very low rpm, and the curve falls off from there. So a gear reduction may not necessarily help, as the torque gained through the reduction is partially lost due to higher motor rpm. With poor design you could even end up with less force. As always, the tradeoff is speed vs. force.

    One of the most popular motor/drive packages for this machine has been the G540, a 48v power supply, and steppers that are around 381 oz.in. (From either Keling or cncrouterparts) My experience with this setup is that the limiting factor is the spindle horsepower, rather than stalling or missing steps. If you are tempted to use a more powerful router, keep in mind that with a belt drive the steppers not only need to push the cutter through the work, but they also need to hold it back. Significantly more spindle hp could get you into a potential situation of runaway climb cutting if you try to get too aggressive with the cut. I had this happen once when cutting aluminum. I forgot to re-zero my Z axis and accidentally took a 1/4" deep pass. It cut straight for about 2" before it started to go where it wanted and I managed to hit the e-stop. This was also with a much weaker Xylotex drive and 269 oz. in motors. My sense is that the Gecko would have kept it under control.

    -bob



  3. #63
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    I'm looking into buying the electrical wire now. I will have DC lines running next to AC lines. Do I need shielded cable for both, or just on the DC lines. How likely are missed steps in this machine if no shielded wire is used? Has anyone experienced this? Also, I'm looking for good sources, so if you found good inexpensive wire, let me know.

    Thanks!



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    Well I finally got my computer running (the one I'm building into the base). I got Mach 3 loaded with all the (untested) settings all set up. That was a long and painful process since I had not purchased the right connectors, etc. I also loaded the trial version of CamBam. I figure I'll give it a shot.

    I'm anxious to apply power to the G540 for the first time but the timing is just not right yet. I'm almost there. All the electronics have been sitting around collecting (saw)dust for many months. The electrons are finally starting to flow now that the pc is running. Next will be the G540 and steppers followed by the SuperPID.



  5. #65
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    Finally started playing around with my electronic setup. Did a little soldering. Laid out some wires. Powered up the SuperPID for the first time. No sparks. No smoke. So far, so good.



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    More progress on the electronics. I plan to wire up most of the features I need, get the machine running, and then cut my main switch panels (see CAD model earlier in post #52).

    Once that is all done, I'll disassemble the machine, paint it, make it look really nice, rewire everything and add all the features I have planned for, including proper cooling.

    You'll see in the photos below how there is a lot of stuff crammed inside the two electronic bays. Each bay has 2 layers. For example, the computer bay has the 12V power adapter, hard drive, a relay, and some terminal blocks on the back layer, and the motherboard makes up the front layer. I was careful to leave space between the 2 layers in each of the bays so that I can blow some air with fans. Still not 100% sure on the placement of the fans, but I have a good idea.

    Enjoy more photos...
    Pic1: Aft bay, back layer with G540 and some terminal blocks.
    Pic2: Aft bay, 48VDC power supply mounted in front of wiring.
    Pic3: Fwd bay, 12VDC power adapter for PC, SSD hard drive, a relay and some terminal blocks.
    Pic4: Both bays shown together, with motherboard shown mounted in fwd bay.
    Pic5: Lid is flipped open showing umbilical cord for SuperPID and panel current meter.
    Pic6: A closer look
    Pic7: Back side of machine showing a fused AC receptacle at the bottom. This receptacle will power the entire system, requiring only 1 wall plug in my garage. PC monitor power and VGA cable plug in above.

    I have a mini wireless keyboard maybe a little bigger than an iPhone that will be used as a hand-held control pendant as well as basic PC stuff.

    I have still not plugged this into the wall, which could explain why all the components are not black

    Attached Thumbnails Attached Thumbnails Jonathan's Build Thread-img_1018-jpg   Jonathan's Build Thread-img_1019-jpg   Jonathan's Build Thread-img_1020-jpg   Jonathan's Build Thread-img_1021-jpg  

    Jonathan's Build Thread-img_1022-jpg   Jonathan's Build Thread-img_1023-jpg   Jonathan's Build Thread-img_1024-jpg  


  7. #67
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    Plugged it in last night and flipped the switches. All components turned on as expected. Next up: Motor tuning.



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    Was able to move the stepper with the wireless keyboard last night. Also moved it around with Mach 3's manual g-code input. Motor tuning would have occurred if Gecko didn't put those tiny trimpots so deep inside the G540. My small screw driver just couldn't reach it.

    At first, nothing worked. Then I realized that I had made a crossover parallel cable instead of a straight-thru. I knew it needed to be a straight-thru, but just assumed the connections needed to be the way I had done them. The way I did it (crossover) ends up that all the wires are straight and not criss-crossing when the cable is stretched out, but I found out the hard way that this is not the definition of a straight-thru cable.

    Just so that no one else makes this mistake, pin 1 needs to connect to pin 1, pin 2 to pin 2, etc.

    Also, I am now a master at DB25 solder cup terminals



  9. #69
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    First motion!
    http://m.youtube.com/watch?v=20FtvoJ8rvQ]YouTube - Momus CNC first motion

    After I took the video, I got all the limit switches mounted. Next up: Test limit switches and set up soft limits and homing in Mach. Also will install router and get it working with SuperPID which is already wired and powers up.

    By the way, the code tested in the video was:
    G91 G17 F200 G02 x0 y0 z-3.75 i0 j-6



  10. #70
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    Looking great! Can't wait to see some chips flying.

    -Bob



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    Great Job!! The wooden left side, looks differant than the plans i have? can you show it better.
    Can you make more Video's too?
    Thanks
    Bob A
    CNC Projects



  12. #72
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    Quote Originally Posted by Bob Adams View Post
    Great Job!! The wooden left side, looks differant than the plans i have? can you show it better.
    Can you make more Video's too?
    Thanks
    Bob A
    CNC Projects
    What specifically on the left side? All I changed was the inner skin. I used 1/4" ply instead if the thicker one so that I wouldn't need to cut the notches for tool clearance.



  13. #73
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    Default First chips

    I cut my first set up chips. I made some counterbored holes at the ends of the cable arms to accept thrust bearings. I didn't have the endmill diameter necessary for use in a drill press, so I used something smaller and wrote my own g-code.

    I found that the scrap wood I have makes an excellent barrier wall to contain chips. I just stood the scrap pieces up on their ends. Any crash with the spindle would have just knocked them over, although it didn't happen. The second photo shows all the thin hair-like chips once the barrier was moved out of the way. All chips stayed inside for an easy clean up afterwards.

    At this point I'm using the machine to make the remaining pieces for itself, and then I'll take it all apart for sanding/painting/finishing before reassembling it again. I've got some collets, engraving bits and black anodized aluminum sheet on order so that I can make my switch panels for the front. That's next on the to-do list. The main switch panels are really going to make the machine look totally different. I can't wait.

    Short video here:
    "http://www.youtube.com/watch?v=20FtvoJ8rvQ&feature=share&list=UUIIaCLgcxi Ho2hRwP2Yn4Uw"]Momus CNC first motion - YouTube

    Attached Thumbnails Attached Thumbnails Jonathan's Build Thread-cnc1-jpg   Jonathan's Build Thread-cnc3-jpg  


  14. #74
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    It has become evident that I'll need a dust collection system. I'm looking into finding good airflow paths. Anyone have results to share? What has worked and what hasnt? I thought it would be neat to pull air thru the electronics bay, into the machining area, and then out. It will remove heat and clean dust at once.

    I'm only bummed about running a vacuum because what turned me onto this machine was the quiet operation.



  15. #75
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    Grrrrrr. Rapid to the left without the drill bit clearing the hole. I forgot to rezero after the tool change. The whole carriage shifted. Major setback.



  16. #76
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    Oh no! The Version 1.0 carriage comes back to haunt us. Some others had this same issue and there are a couple of things you can do. The easiest (if you didn't already build it that way) is to replace the four 1/4" studs with 5/16" grade 8 bolts and torque them down as tightly as you can. I posted a thread on here at some point showing that upgrade. That greatly increases the clamping force and seems to have taken care of the problem for most.

    There are a couple of more invasive solutions. One is to go with the new version 2.0 style carriage, which has roll pins to prevent racking. I also put a thread on here with drawings for the few parts that would need to be fabricated to install this on the old 1.x machine. Another solution is to do what Chris (OCNC) did, which is install a thin plate in the carriage that gives it diagonal shear resistance. There are also some drawings of that mod in a thread somewhere.

    -Bob



  17. #77
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    Quote Originally Posted by momus_cnc View Post
    Oh no! The Version 1.0 carriage comes back to haunt us. Some others had this same issue and there are a couple of things you can do. The easiest (if you didn't already build it that way) is to replace the four 1/4" studs with 5/16" grade 8 bolts and torque them down as tightly as you can. I posted a thread on here at some point showing that upgrade. That greatly increases the clamping force and seems to have taken care of the problem for most.

    There are a couple of more invasive solutions. One is to go with the new version 2.0 style carriage, which has roll pins to prevent racking. I also put a thread on here with drawings for the few parts that would need to be fabricated to install this on the old 1.x machine. Another solution is to do what Chris (OCNC) did, which is install a thin plate in the carriage that gives it diagonal shear resistance. There are also some drawings of that mod in a thread somewhere.

    -Bob
    Charlie Welkie probably did a better job of it than I did but a plate certainly solves the racking problem. Here's the link to his thread.

    Chris



  18. #78
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    Thanks guys. I had used the 5/16 bolts, but built mine before the other upgrades were posted.



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    Machine is apart. I'm going to get all the metal painted while I have it apart. Once it is all fixed and painted I'll put it back together and then make my switch panels and other accessories and then once I have everything I need, it will come apart one final time for painting and sanding of the wooden base.



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    Here's a picture of what the base currently looks like. I have the SuperPID LCD screen and an amp meter on the front face. Lexan protective covering hasn't been pulled off yet. All Lexan is 1/4" thick. I shouldbe able to keep the noise down prettly low with this setup.

    Attached Thumbnails Attached Thumbnails Jonathan's Build Thread-img_1065-jpg  


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