I'm converting G0704 to CNC

timl1641

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This will be my build thread.

My background is 40+ years working with, on and applying all manner of CNC machines.

this build is a post semi retirement project.


I'll be using Mach4 and the PoKeys57cnc board, ball screws and mounts from Automation Inc., steppers from Longs. all items have arrived. actual build will begin in a few weeks after I finish a contracted production manufacturing project.
 
Following your thread. You may consult the thread below; G0704 CNC conversion by @macardoso. His work is exemplary.

Bruce


 
Looking forward to see your build. And welcome to the Hobby-Machinist community !
 
Following your thread. You may consult the thread below; G0704 CNC conversion by @macardoso. His work is exemplary.
Bruce
I got started reading through the @macardoso thread. It seems all the attachments in post #10 are now missing. There were 21 of them.
It may be intentional. Maybe they became superseded further into the thread, I don't know. It leaves one curious..
 
thanks for the replies. this forum has been invaluable selecting materials. I 3d printed my limit switch mounts. I'll post pics and when all is said and done, I'll make models available to all. I do all my modeling with Solidworks (( I do have a licensed copy, 2021 used for my business). I plan on using 2 switches per axis while combining the homing on switch. The x axis ids a bolt on while the rest will required some m5 holes drilled and tapped. I also have a full 3d model of the machine.
 
I got started reading through the @macardoso thread. It seems all the attachments in post #10 are now missing. There were 21 of them.
It may be intentional. Maybe they became superseded further into the thread, I don't know. It leaves one curious..
Unfortunately HM had a server crash a few years ago and those pictures got deleted. I lost the originals and couldn't replace the broken links. There were just a few pictures that showed the machining setup for the belt drive portion of my spindle build. Specifically truing the quill spline to accept my conversion.
 
Welcome to HM!

The G0704 is an excellent platform for a CNC conversion and makes for a great benchtop machine for machining small to medium sized components. It is not the most rigid nor the largest machine out there, but outperforms most "hobby" class machines.

My build thread admittedly gets a bit intense, don't feel like this is what is necessary to make a CNC conversion work. It was focused on the industrial controls side of a high end AC servo motion control system and glosses over the basic conversion (I had done a stepper conversion about 6 years prior to this thread). If there is anything on the mechanical conversion end that I can share with you, please let me know.

Similarly, I working in industrial automation and do electrical and controls design all day long. Happy to help with that end of things if needed.

Couple of takeaways I can share based on things that worked well for me and some that didn't:
  1. When you start with the conversion, take some time to improve the fit of the ways and gibs. This could be as involved as hand scraping for better bearing on the ways, but at a minimum make sure the gibs are touching in the proper places and have a good snug fit. Do not assume that they are good from the factory. Mine are not and remain an item to be reworked. This, more than anything else, plays into the rigidity and cut quality that this machine can handle. If well fit, the machine will perform like a machine twice its size
  2. Spend a bit extra to get ballscrews with acceptable lead error and good preload from the factory. I highly recommend ground double nut ballscrews. There are some people on here who have experience getting screws directly from asian manufacturers which far surpass the quality of the screws commonly available on Amazon and eBay. In manual machining, the operator can effectively take out backlash by hand during the cutting operation, however in CNC, this backlash creates positional uncertainty that ends up being your general purpose limit of accuracy. Yes, you can program especially with this in mind, and yes software backlash compensation exists, but neither really solve the issue well. I bought Roton brand ballscrews and have spent a lot of time repacking the nuts with bigger balls to reduce backlash. You do not want to have to do this.
  3. If using steppers, design your control with the highest motor drive voltage possible. If your motor drive accepts 12-72VDC, use a 60-70VDC power supply. I'll skip the physics behind this, but this will give you better motor acceleration performance and top speed given the same motor used with a lower power supply voltage.
  4. In my personal experience with this mill as a CNC, it is most optimal to use 1/4" tools for steel, and 3/8" tools for aluminum and plastics. Yes you can use larger, but there is no gain from doing so as you'll need to seriously back off on the aggressiveness of the cut. As such, the 2250 rpm stock spindle is too slow for modern tooling. I highly recommend looking to upgrade this to a belt drive configuration in the 5000-8000 rpm range. In fact, a dual speed range of 0-3000 rpm and 0-8000 rpm would be ideal to give you the option for higher torque drilling and tapping. I ended up with a single speed 0-5000 rpm belt drive and it serves most of my needs very well. I no longer have a functioning quill, which has not been any issue at all with the Z axis controlled by the CNC.
  5. Compared to when I started my CNC conversion, there are many options for motion control hardware and software available to you. I recommend doing a comparison of the options before selecting one. I use Mach 4 / Ethernet Smoothstepper and have been very happy with it. Easy to set up, very flexible and customizable, and quite reliable. Acorn CNC is another popular option. I would try to stick to a platform with good support, ongoing development, and an engaged community.
  6. The Tormach TTS platform of tooling is an amazing addition to your CNC kit. Having all your tools preset in holders is a massive quality of life improvement and is far superior to touch plate style tool setters. The upfront cost hurts a little bit but you can expand over time.
  7. Take it easy on how much tooling you buy out of the gate. A good 4" machine vise, parallels, and clamping kit (3/8-16 studs) is about all you need to get started. I recommend going middle of the road on a vise. Glacern makes some great vises. I went super cheap and got a $100 vise from Shars (they don't offer this low budget option any more and their higher end vises are much better). My vise was bowed like a banana and made machining accurate parts quite difficult.
  8. Plan your controls cabinet out well ahead of time. Make sure to follow proper electrical codes, use circuit protection, size your wires appropriately, and use wire duct to keep things looking neat and organized. AutomationDirect is your friend for good quality controls hardware at a decent price. Ask questions here and we will certainly give you a hand if we can.

Have fun - excited to follow along on your project.

EDIT: Wrote this without fully reading your first post. Mach 4 and PoKeys57 will be a great combination. The automation technologies ballscrews will be miles better than what I bought!
 
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Looking forward to your project!
I ended up with a G0619 mill that I have the crazy idea of converting to CNC as well!
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Several years ago, there was a Grizzly to CNC build on the web called 5bears. I bet the wayback machine can find it in its entirety.

Yep, found the old site archived. Good info, should you care to pursue it.

 
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