Another G0704 Conversion


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Thread: Another G0704 Conversion

  1. #1
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    Default Another G0704 Conversion

    Ok, yes, this is another CNC conversion thread for a G0704. This project is a little different than others in that my goal was to combine my love of electronics and building things with my love of 4 wheeling. In the end, the machine tools I build now to populate my shop will let me fabricate a rock crawling monster buggy just for the fun of it and to say I made it.

    I plan that this small mill will allow me to build a Plasma Table, a CNC Tubing Cutter and lots of buggy parts.

    The highlights of this build are:
    Standard G0704 from Grizley, (Actually I had the G0759 which is the G0704 with DRO installed)
    Clearpath SD servo's from Teknic
    Pokeys 57CNC controller.
    Several interface cards built by me to eliminate all ground noise and wiring issues.
    KBMM125 spindle motor controller.
    Mach 4 running on a Intel NUC with a 24 inch touch screen.

    I started the project in December of 2016 doing research on all the parts and software required. I tried to steer clear of the lowest cost Chinese parts as much as possible because I have lots of experience with their difficulties with quality. I selected parts with the idea that at some point I would upgrade to another mill with more rigidity and a larger work envelope so to that ends the servo's selection went way over on the beefy side. Also I wanted everything to be connectorized so I could take it all apart and move it easily to another place or even a different application.

    Here is a photo of the almost finished project. Following posts will provide more details.



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    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-09-13-15-12-00-jpg  
    Last edited by maxspongebob; 09-17-2017 at 03:05 PM.


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    Default Re: Another G0704 Conversion

    The first step in the design was to select a set of ball screws and motor mounts. Like so many before me, I thought that I wanted to keep the hand wheels on each axis so I could still use the system as a manual mill. Also like most others who make this choice I find that I will probably never use the system manually again. It is just too easy to write G Code to do the same thing but better than I cold by hand. Anyhow, I selected the conversion kit from CNCConversionKit.com. I selected the NEMA 34 motor mounts and double ball nuts for each axis. I think this was a good choice. My backlash on X and Y is less than .002".

    There are several things about this kit that I would do differently if I could.

    1. The ball screws have been turned down at the end to accommodate a coupler to mate with the motor shaft. The shaft diameter where the coupler mounts is only 8mm in diameter. Also there was no key or flat milled into the shaft. With my NEMA 34 servo's the provided couplers almost immediately spun on the screw shaft. No amount of tightening the set screw on the coupler would keep it from slipping. To remedy this, I had to replace the flexible couplers with Spider couplers that clamp onto the shaft instead of using a set screw. This solved the problem, but I am still only able to set the maximum allowed torque of the servo's to 50%. On my next build the screw shaft diameter will be as large as possible, and definitely no less than 12mm.

    2. Optimally the axis screws need to be setup so that there are opposing ball bearings at the end of the screw to zero out the backlash. This kit, although there is a bearing at each end, they are not setup so that you can adjust the runout of the shaft to zero the backlash. I had to remake the mount for the Z and Y so I could add an additional bearing.

    3. The finish of the parts is not the best. Most of the parts I put into the mill and removed a few thousandths to clean them up.



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    Default Re: Another G0704 Conversion

    There were 2 things about this upgrade that made the installation of the ball screws difficult. Keeping the hand wheels so that you can still use the mill manually was the first one, and using double ball screw nuts to get zero backlash was another.
    Double nuts required a lot more modification than other kits require. Since the nut is longer I had to remove a lot more cast material. I had to carve out the underside of the base at the front so the Y nut could travel to the maximum forward position.


    Boring a 1" hole in 2.5" of cast iron is no simple task when all you have is a drill press and hand tools. However I did find the best tool to do this. Here it is. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 The end result came out alright.


    Next came the modifications to the saddle to accommodate the X axis ball screw and nut. I used an angle grinder to remove the minimum amount of material.


    This worked but I found that after trying to reinstall the table, there was interference between the screw, the nut, and the underside of the table. This required me to trim down the flange on the nut as much as possible and I also had to grind a lot of material from the bottom the the table.



    With the modifications to the mill complete, I was able to assemble it back together with the new parts.


    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-05-02-11-15-00-jpg   Another G0704 Conversion-2017-05-02-11-26-05-jpg   Another G0704 Conversion-2017-05-02-11-26-35-jpg   Another G0704 Conversion-2017-04-12-17-56-25-jpg  

    Another G0704 Conversion-2017-04-12-16-17-34-jpg   Another G0704 Conversion-2017-05-03-15-05-40-jpg   Another G0704 Conversion-2017-05-03-00-11-34-jpg   Another G0704 Conversion-2017-05-03-15-05-47-jpg  



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    Default Re: Another G0704 Conversion

    Limit switches came next. Like most, I wanted to drill the least number of holes in the casting as possible so I was able to come up with some brackets that mounted to existing holes.

    X limit switch.

    Y limit switch

    and Z



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    Default Re: Another G0704 Conversion

    Now the fun part. Electronics. Like I said at the beginning, I wanted the entire system to be pluggable and to be immune from poor grounding and electrical noise problems. Although most of the controllers on the market operate at 3.3 or 5 volts, It is never a good idea to run those single ended signals over long cables with other high voltage wires. So, I developed interface PCB cards that sit between the controller and the devices that it connects to. This could have been done using breakout boards with screw terminals, but I think this is a better solution. Also, I have incorporated the E-Stop functions into the hardware. There is no way that you can press the switch and have the high voltage stay on to the motors. The system is built for 4 axis's and I was able to squeeze everything into a 16" x 24" x 10" case. Finally almost every signal that goes to or comes from the mill has a corresponding LED indicator so you can see what is happening.



    Last edited by maxspongebob; 09-17-2017 at 06:56 PM.


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    Default Re: Another G0704 Conversion

    Here is the control box with all the interface circuitry. Originally I also had a NUC computer installed in the box but it was more convenient to move it out to the table next to the mill. At the left mounted to DIN rails is all the AC switching and patching. 110 Volt AC comes in through the yellow cable and goes directly to a circuit breaker. Then the AC is switched on the front panel with a master on/off switch. Then back to the DIN mounted E-Stop disconnect and finally distributed to internal devices. All the other devices that don't run off AC are powered via a 12 volt DC supply. All the interface cards and switch gear is 12 volt except for the servo's and spindle which have their own power supply.

    Control box front panel.



    Sideways view of Control box.


    The Pokeys 57CNC controller has an interface card for each of its major functions. These cards perform all the voltage conversion and have diagnostic LED's for virtually every signal so you can see what is going on. I designed and fabricated each of these cards.

    This is the Servo interface card which does the power distribution for the 2 servo's and takes the 5 volt step and direction signals and sends them, isolated, to the servo's as 12 volt signals. Also it fuses and distributes the 75 volt DC power to the servo's.


    This is the E-Stop and home/limit switch interface. All the E-Stop button's go through it and it in turn will activate the main disconnect if there is an E-Stop sensed.


    This is the probe and encoder adapter. The encoder circuitry is connected to the spindle encoder to sense RPM. It powers the spindle encoder which in my case is only using the index signal. There are 2 probing signals, one that is ON and the other is NC. Both of these are buffered through a micro-controller to debounce the probe and to sense if there is a probing error. A probe error signal is generated if the probe is active for more that 200 miliseconds. The Pokeys uses this signal as "stop motion" signal to keep the probe from crashing into anything.


    Finally there is an interface for the console switches and auxillary outputs. The aux outputs are each driven 12 volt DC up to one amp each. Each circuit has flyback protection to drive relays. I am using just one of these outputs to control the coolant solenoid.


    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-10-15-01-51-29-jpg   Another G0704 Conversion-2017-08-11-09-48-44-jpg   Another G0704 Conversion-2017-10-15-01-50-56-jpg   Another G0704 Conversion-2017-10-15-01-50-48-jpg  

    Another G0704 Conversion-2017-10-15-01-50-40-jpg   Another G0704 Conversion-2017-10-15-01-50-20-jpg  
    Last edited by maxspongebob; 10-17-2017 at 11:50 PM.


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    Default Re: Another G0704 Conversion

    I have setup a MQL system based loosely on the fogbuster type design. The major difference is that I can control the pressure to the air and lubricant independently. The system works well however it is going to take a bit more adjustment to get the flow rates correct.


    Nozzle design #2


    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-10-16-15-59-45-jpg   Another G0704 Conversion-2017-10-15-01-52-49-jpg  


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    Default Re: Another G0704 Conversion

    For the moment I am using all the stock mechanical drive parts for the spindle. However I have a belt drive kit on order. I noticed that the motor gets quite hot to the touch when under load for a long period of time. So I decided to mount a fan to the top of it and run it off a temperature sensing switch. You can see the fan at the top. It is an AC 120mm pancake fan. The thermostat switch is indie the red case strapped to the motor. When the temp of the motor hits 40 degrees C the fan comes on. Works great.

    Both the fan shroud and the red thermostat sensor case are 3D printed ABS plastic.



    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-10-16-16-04-47-jpg  


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    Default Re: Another G0704 Conversion

    Nice work on this conversion. Keep the updates coming. If you find that mounting your Fog Buster tank much lower than the nozzle causes the coolant to drain back to the tank quickly during tool changes, etc., add a $10 Parker A4VC4-MG check valve (available on Amazon) to the liquid line to keep it from flowing back to the tank too quickly. This will keep your coolant close to the nozzle for quick response when cutting starts. Otherwise you'll end up cutting for a few seconds while the coolant flows back to the nozzle every time. Nice job on the Fog Buster BTW. One of the cleanest DIY units I've seen.



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    Default Re: Another G0704 Conversion

    Thanks. I am using Mach 4 and have modified the M6 macro to turn on the mist at the same time the spindle turns on after a tool change. This gives me a few seconds for the bubbles to come out of the line. I like the check valve idea though.



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    Default Re: Another G0704 Conversion

    Yeah, great job on the conversion so far. Looks like you've put a lot of time (and money) into it so far. I think since you've gone thru the trouble of putting double ballnuts on and clearpath servos, you may be disappointed in the performance of the motor couplers. Those spring types are exactly that, a spring, and can be a source of significant backlash under cutting forces. Before you close everything up for the last time, you may want to look into oldham style couplings. You can get them cheap on amazon and may save you frustration down the road.

    Looking forward to more updates.



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    Default Re: Another G0704 Conversion

    Yes, those couplers are BAD. I found that out early but didn't have any photos of the new couplers. I got a set of spyder couplers from McMaster Carr that clamp onto the servo and screw shaft. I They are much larger and are zero backlash with the hardest plastic insert.


    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-coupler-jpg  


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    Default Re: Another G0704 Conversion

    glad to hear that's been addressed!



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    Default Re: Another G0704 Conversion

    Well, it has been a while since any updates to the mill. I have just completed an upgrade to a belt drive system. Here are the details:

    This is a collection of parts, some purchased, and some home built. I liked the Benchtop Precision spindle and pulleys and speed sensor ring but wanted a more sturdy motor mount than was was in their kit. I have to say that the parts that Scott Makes and BP are super high quality and work very well. The fit and finish are fabulous. I am still using the stock motor and except for one major problem, it has been working. Here are a couple photos. You can see the motor mount are much like the Hoss rails and top plate but they only use the 2 rear mount holes on the top of the head so they are not as long.







    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-12-01-10-49-42-jpg   Another G0704 Conversion-2017-12-01-10-49-48-jpg  


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    Default Re: Another G0704 Conversion

    I finally took some photos of the couplers that I used. Here they are.
    Z Axis
    X Axis

    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-12-01-10-59-29-jpg   Another G0704 Conversion-2017-12-01-10-59-47-jpg  


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    Default Re: Another G0704 Conversion

    I wanted to show a few photos of the table I that built for the mill. Mine is probably not a new concept, but I have not seen it done before.

    In designing a stand for the mill, I wanted to incorporate the strength and rigidity of a steel frame and the ability to use a flood/mist coolant system. I have not yet built into the stand the flood coolant, but the system is working well containing chips and a good bit of other swarf.

    I designed the table around a set of 3 removable trays. You can see them in the photos below. The trays slide under the stand so that all the cuttings can drop into them. When they get full, you can simply pull the tray and dump it. Between the trays is a deflector that keeps the chips from falling between the trays and onto the floor.

    Removable Tray:

    Slides for trays:

    Chip deflector between trays:


    When I build a flood system, I will replace the plastic trays with metal one's the same size. The flood trays will have a hole in the center for the coolant to drain into much like a kitchen sink.

    Attached Thumbnails Attached Thumbnails Another G0704 Conversion-2017-12-01-10-50-37-jpg   Another G0704 Conversion-2017-12-01-11-49-15-jpg   Another G0704 Conversion-2017-12-01-11-48-09-jpg  


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    Default Re: Another G0704 Conversion

    I have been having some problems with the spindle motor upgrade. With the new bearings and pulleys, the thing is blowing fuses. Here is the thread.

    http://www.cnczone.com/forums/bencht...e-spindle.html



  18. #18

    Default Re: Another G0704 Conversion

    Nice work. I'm in the midst of an enclosure build myself. I'm strictly a mist coolant guy, but those chip trays are a great idea. I'll have to look at how to incorporate that into my design.



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    Default Re: Another G0704 Conversion

    Quote Originally Posted by ChrisAttebery View Post
    Nice work. I'm in the midst of an enclosure build myself. I'm strictly a mist coolant guy, but those chip trays are a great idea. I'll have to look at how to incorporate that into my design.

    The trays do work really well. Mine are plastic and I got them at Lowes. I haven't had any problem with oil on the plastic, but if I was doing it again, I would get steel one's from the start.
    Here is one for example. Mortar Mud Pan | bedrocksupplies.com



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    Default Re: Another G0704 Conversion

    If you switch to flood the outer ones will fill up with coolant pretty quick, maybe consider replacing the outer two with trays that divert everything to the middle one. My swarf drawer has a similar design that drains back into the coolant tank. It took a couple attempts to contain my sprinkler system but works very well now.

    I made my tops out of scrap, the base is an L so the lip overhangs into the base, they just lift off. It's easier to access the never ending build.
    Another G0704 Conversion-mill-enclosure-jpg



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