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Thread: Official start to CNC plasma table build

  1. #1

    Default Official start to CNC plasma table build

    Well, after what seems like an eternity I'm finally starting to acquire components for my CNC plasma table build project, to mate up with my Everlast PP60S and my Lincoln PowerMig 200 welder (for most any welding that will be part of the process). I've spent a LOT of time researching this and that to determine whether I'd go for a complete turn-key solution (like PlasmaCAM), more of a kit type solution, a complete DIY type solution or a hybrid of DIY and kit. Obviously one of the key factors has been cost but not at the expense of performance and capabilities. That said, I've decided pretty much the direction I'll be going is part kit type and part DIY/custom parts. I've also been acquiring parts to build up my compressed air distribution system (air lines, filters and regulators, etc).

    I've decided to go with a CNC CRP6060 Hardware Only CNC Router Kit (http://www.cncrouterparts.com/crpxxx...kit-p-140.html) to build a 5-ft x 5-ft CNC table. I'll use most of this kit with the exception of filling in the middle of what normally is a support area for a router spoil board with aluminum extrusions. Instead I'm going to use the end piece extrusions and design and build a sub-frame for plasma cutting, as their original design with aluminum supports spread evenly across the length wouldn't work well in a plasma process. I decided on the 5x5 size as it will fit well in my work area for now and should I need to expand its length in the future it shouldn't be too much expense or trouble doing so.

    For motors, I decided to go with servo motors instead of steppers. I recently discovered Teknic has a somewhat new servo motor product that incorporates the servo drive and motor in a common package that several people have demonstrated on YouTube and others have commented about on other forums and exclaimed how pleased they are with them. I was seriously thinking of going with these until I searched more for servo motors, and found some of Teknic's industrial grade servo motors on eBay along with some older but very capable servo drive modules available at prices I couldn't pass up so I wound up buying 4 Teknic M-3422 motors and 5 Teknic SSt-1500-UCX servo drive modules. These have already arrived at my home.

    For motion control I've been pretty well decided I'd go with an Ethernet SmoothStepper (ESS) but hadn't finalized what breakout board (BOB) I'd use with it until I read through the BOB Vendors page on Warp9TD.com and looked into a fairly new one called MachBob2 (MB2). After comparing this to PMDX-126 and a few from CNC4PC.com I decided on the MB2. These parts are on their way to my home as I write this. My next purchases will be a large linear unregulated 73V DC power supply for powering the servo motors and another smaller regulated 5V, 12V and 24V power supply for the motion control electronics to operate.

    Hopefully I'll get some time soon to start installing the Windows OS on my CNC control computer and getting Mach4 installed so I can start be ready to start testing the motion control components. One thing that will slow me down some will be building the cables that connect the servo motors to the servo drives and the cables from the ESS/MB2 to the servo drive inputs. Once these are done and the testing proves out this part of the system I'll get to build cables for the home/limit switches to go onto the table and gantry. Lots of fun in store for the next several weeks/months.

  2. #2

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    OK, here's the latest on my project.

    I did decide on the ESS and MB2 and both have arrived at my home. I will say I'm pretty impressed with the design and build quality of both. The MB2, which you can find out more here (http://www.cncroom.com/index.php?mai...09&language=en) if anyone is so inclined, is advertised as "an Industrial environment BOB, featuring: 6 Axis Line driver; I/O that utilizes all 3 ports of the ESS; OSSD safety output; Status LEDs for all signals; Requires a single 24V power supply". The options it has built in are going to work well with the Teknic servo motors and servo drives I've selected as the MB2 can be used with single-ended and differential encoders as well as digital and analog servo motors. It also provides the ESS with 5V so there's no need to run this power separately to the ESS.

    Also during this time I created a scale drawing in Visio of the steel NEMA enclosure that I plan to buy for containing all motion control electronics (power supplies, ESS/MB2 and servo drives) so I could determine if everything could and would fit while still allowing room to get my hands inside to wire up everything. It will be a little tight but not bad, even with all 5 servo drive modules.

    I also spent some time determining what cables and types to use. The Teknic servo drive manual recommended Belden 9935 (shielded, 24 gauge, 10-conductor) and 8618 (shielded, 16 gauge, 3-conductor) cables for encoder/signaling and motor power, respectively. From past experience I know Belden to be good quality cable but can be, and in this case is, somewhat pricey. For example, I got a quote from an online vendor for building 4 cables which came to $518.00 for the build. I was a little taken aback until I priced out the cable and concluded this was actually a pretty fair price, but higher than I wanted to deal with none the less.

    That said, I decided to see if I could use shielded Cat 5e network cables for the encoder/signaling cables and determined it was doable but would be more complicated and take more time to implement than using the recommended cables. Then recently I lucked out and found an eBay seller listing Belden 9935 as New Old Stock (NOS) for close to half the price I had found elsewhere. I jumped on that and bought enough to build all the encoder/signaling cables I'd possibly need, even if I get to implement a rotary axis later on. Also during this time I found a suggestion on a website to search for "Belden equivalent" cables and found a cable from General Cable (under Carol branding) that had the exact same specs as Belden 8618, again for about half the cost of Belden. So now, I'll be able to build all the cables for connecting the servo drives to the servo motors for about half the cost of the quote above, and without sacrificing any quality. This go around, my time and patience paid off nicely.

    Now that the cabling issues are resolved I'll get started with selecting and buying the Molex connectors and crimp pins for terminating them and also get the bulk 73V power supply and the smaller 5V/24V and even smaller 12V power supplies ordered. I also need to get the Windows OS installed on the computer I have for CNC control operations and get Mach4 and the plugins for ESS loaded. Once all this is done I hope to be able to see some servo motor action that indicates the motion control system is functional. That will be a BIG step to success in getting the CNC table up and running.

    Well, that's all for now. I'll update this again when I have more to report.

  3. #3
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    Sounds like it's coming right along. What are you shooting for as your max feedrate? I'm a big fan of servos over steppers for most things. I also want to try those ClearPath servos in a upcoming SCARA project. With the supplied software, it looks like it makes tuning the servos a breeze.
    Long arc, short arc, heliarc and in-the-dark!

  4. #4

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    At the present time I haven't determined what max feed rate I'd like to end up with, but with these servo motors, and even using 3:1 belt drive rack and pinions for all axis, I think this system should easily be capable of 1000 IPM - not that any of what I plan to cut would require that kind of speed though. According to specs for these Teknic motors, the ones I bought have a max RPM rating of 5K RPM. On another website (https://www.reddit.com/r/CNC/comment...s_from_teknic/) someone built a 4ft x 4ft CNC Router Parts CNC table and replaced the original NEMA 34 stepper motors and drives with Teknic ClearPath servo motors and he was very pleased, saying it was much smoother, stronger and faster. Even with the max RPM of the ClearPath motors generally being in the 1000-1500 RPM range he was able to get 1000 IPM from his initial setup, but did slow them down for better cut quality and precision. I would also agree, from what I've read, the motor tuning is really easy using the Teknic software and produces good results. I know I'm really looking forward to seeing these motors and the table in general in action.

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