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    *Registered User* gr-cnc's Avatar
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    Default zeroing in on components

    Hi everyone, first post. Not the last.

    I'm designing a 4x6 router/plasma and I need some quick advice on motors. I want this table to be a tank and to do it right the first time - all steel tubing, gecko drivers, r/p on x and y, 2.2kw spindle, etc. I'll be plasma cutting about 20% of the time. I'd also like to mill aluminum block from time to time without worry. Large wood panels like doors and tabletops too.

    Everyone says motors and electronics should be the last thing to buy, and I do trust that advice. I only want to know if I'm on the right track so soon because I'm having some 1/4" steel plate laser cut for another project and if I can at least make a decision on the motor, all the 1/4" steel parts will be free. (I can fit my parts in-between the client's parts)

    All that said, if someone can take a look at the attached image and tell me which motor they would choose, that will help a lot. Based on what I've learned here so far and what I'd like to do with the machine, the green line looks the best.

    Also, gantry + z axis + spindle will weigh about 100 lbs.

    If this is a terrible way to ask the question, sorry. There are so many choices though...

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    Default Re: zeroing in on components

    If your budget is for the KL series just get the pre-made NEMA 34 package from Kelinginc and go from there. Make sure your power can handle the loads. Good luck. But I wouldn't call a machine running Gecko controls or steppers a "tank."



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    *Registered User* gr-cnc's Avatar
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    Default Re: zeroing in on components

    Oh, I was under the impression that Gecko controllers were some of the best. And I also thought KL motors were good. If I have to spend an extra $500+ for better motors and drivers, I will.

    What would you suggest?



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    Community Moderator ger21's Avatar
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    Default Re: zeroing in on components

    I'd probably go with the KL34H280-45-8A, running at 72V.
    I'd use either the Gecko G214V or Leadshine EM806 drives.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    *Registered User* gr-cnc's Avatar
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    Default Re: zeroing in on components

    Thanks, Ger21. The "lower inductance is better" concept seems to be much more nuanced than I thought and that I have a lot more reading to do. I ruled out wiring these at higher voltage because the torque curve doesn't appear to be that much better but inductance jumps from 2.2 in parallel to 8.8 in series.

    In any case it sounds like nema 34 is the way to go and I'll draw the parts to fit.



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    Community Moderator ger21's Avatar
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    Default Re: zeroing in on components

    You always want to wire them parallel, never series.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default

    Router built for power
    Plasma built for acceleration

    Plasma moving components normally light weight for acceleration.... Cutting force is zero.... Just mass of components shunted about.

    Router moving components normally heavy .... Cutting force is that of the tool and mass of components being shunted about.

    .... It depends what you want to cut with plasma (material and thickness) and what you are going to plasma cut it with (amperage)...... High amperage + thin = high federate.

    Plasma is very abrasive and messy, the plasma cut material is cut by the air and plasma arc ejecting the kerf material.... And it tends to get airborne.... It gets everywhere and is hardened material so makes great grinding paste.

    Two tables would be better or a means to adapt the machine to different operations would be key.

    Router requires a nice level bed with a spoil board.... Plasma normally has sacrificial slatted bed that is only level the day you put it together ..... Then it has gouges and lumps all over it from every time the plasma cutter traverses over a slat whilst cutting.

    What drive mechanism are you intending to use?



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    *Registered User* gr-cnc's Avatar
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    Default Re: zeroing in on components

    Two machines would be nice, but I don't have the room. Since I work full-time from home and my margins are fairly high, I really don't mind spending a day or two cleaning and converting the machine from one mode to the other. The water pan would be drained and swapped for a spoil board. I know I'd have to re-face the top every time, but that's not a big deal. I only make about two things per month, sometimes it takes three months to make one. Precision isn't even that much of a concern to me most of the time, but if I do need it, I have it.

    I'll probably never plasma cut anything thicker than .125 and 90% of what I do cut (with hand torch) is .065 bronze, cor-ten, and sometimes SS. I have a powermax xp45. Recommended speed for that gauge I think is around 120ipm. I don't mind cutting more slowly at a lower amp; none of what I do is production work - all one-off.

    Drive system will be rack and pinion from Fineline Automation on both x and y geared down 3:1 and z will either be pre-made assy. from ebay or home-brew double ball screw using a beefy IKO linear slide block I bought at an industrial auction. I haven't thought that one through quite yet.

    I'm still considering a Saturn 4x4 to save me a month-long build, but I really want at least 4x5 so when I cut 4x10 sheets, I'll only have to slide the sheet down and index it once to cut the other half. My design is a 4x6 only because the gear racks are already 6' and it will only be an extra $100 in steel for one more foot I would probably someday wish I had.

    Also, my son wants to be a robotics engineer, so I think it will be a fun and valuable project to do with him. He really enjoyed building a 3d printer with me.



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    Default Re: zeroing in on components

    What the cut charts don't tell you is that for plasma acceleration is king! The laws of physics will see significant slowdowns when cutting which will cause a whole host of cutting problems and only some can be corrected if you have Corner lock/Velocity Anti Dive. If you have a 100 lb gantry those features won't solve your problems. Expensive high performance servos may get you over the line. Robert has nailed it! The design parameters for routing and plasma are totally different. Best to just pick one and design for that.

    Rod Webster
    www.vehiclemods.net.au


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    Community Moderator ger21's Avatar
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    Default Re: zeroing in on components

    The design parameters for routing and plasma are totally different.
    Not exactly. The difference is that you can get away with less performance from a router than you can for a plasma. A router will run better with faster accel as well. But it's usually a lot more expensive to make a router that accelerates fast enough, because you are moving a lot more weight.

    And what you may find with those rack and pinion drives, is that they can't handle really high acceleration when you are moving a lot of weight, as you'll exceed the spring loading pressure and the pinion will jump out of the rack.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  11. #11
    *Registered User* gr-cnc's Avatar
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    Default Re: zeroing in on components

    I guess something's gotta give, which would probably be router performance because I am a metalworker by trade. From what I've read here it seems one can have an awesome plasma / terrible router, or an awesome router / decent plasma. I'll make the gantry lighter perhaps using all aluminum and go from there. What I do know is it's going to be stout. I tend to over-engineer everything because I don't know what the hell I'm doing most of the time.

    What's the disadvantage to having no spring load between the pinion and rack? It can't jump if it can't move, right? Maybe I should have mentioned that I'm only using the gear rack and gears/pulleys from FL, not the spring-load drive system. I'll be integrating all that stuff into the side plates. I'd be happy to share a cad rendering of my concept if anyone is interested. Several people here claim that solid mount is ideal with r/p anyway and people only use the assembled drive system for convenience.



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    Community Moderator ger21's Avatar
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    Default Re: zeroing in on components

    What's the disadvantage to having no spring load between the pinion and rack?
    You need to mount the rack perfectly straight along it's entire length, at the exact height needed to properly mesh with the pinion.
    Without spring loading it, you'll possibly have some backlash, depending on the interface between the pinion and rack.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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