G0678 CNC Conversion Thread

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ScotY
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Re: G0678 CNC Conversion Thread

Post by ScotY »

Nicely done...everything looks awesome! Sure wish I had room for a bigger mill! Curious to know what kind of couplers you’re using and also where you got that cast? motor mount.
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Re: G0678 CNC Conversion Thread

Post by Dave_C »

Nicely done...everything looks awesome! Sure wish I had room for a bigger mill! Curious to know what kind of couplers you’re using and also where you got that cast? motor mount.
The cast motor mount is from Automation4less.com. It isn't cheap, around $100.00 with freight but it is sooooo easy to make an inline mount system using this bracket.

The couplers are suremotion couplers from Automation Direct. I ordered a series (size) 30 at first and then I changed it out to a 40 size. The 30 just didn't grip enough of the shafts and left a gap in the middle. The 40 fits perfectly for a NEMA 34 motor. These are not cheap either. Each end piece is about $20.00 and the spider is $10.00 and comes in three different hardness ranges. I chose the hardest one as my servos produce 15 NM (2,000 oz in+) at max torque.

But why buy cheap parts at this point of the game? I've learned over the years that you get what you pay for! Buy right, pay once and forget about it.

Dave C.
Grizzly G0678 Mill ,CNC conversion with Acorn. G4004G Lathe, Mach 3 conversion to Acorn.
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Re: G0678 CNC Conversion Thread

Post by ScotY »

Thanks, Dave! I have no problem spending money :shock: but do try to cheap out when I can. :lol: Industrial electronics is where I still get sticker shock.

I asked about the brackets because I may need something like that in the future...good to know. I was most curious to know how your couplers are working out. They look like spider type and the ones I have were not so good.
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Re: G0678 CNC Conversion Thread

Post by Dave_C »

I was most curious to know how your couplers are working out. They look like spider type and the ones I have were not so good.
Couplers can be a weak link in the CNC drive train if undersized! That is exact why changed out the 30 size coupler for a 40. The 40 is rated for 15 nm so I'm comfortable with it. The suremotion coiuplers are quality couplers so I think anyone who uses them will find them satisfactory.

They are spider type, the series 30 is only a two leg per side and the series 40 is a three leg per side.

Time will tell I suppose,

Dave C.
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Re: G0678 CNC Conversion Thread

Post by ScotY »

Have you had time yet to measure backlash? What is the spider made from?
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Re: G0678 CNC Conversion Thread

Post by Dave_C »

Nope, have not had time to measure backlash. However, the spider is a very tight fit and is not made like what you'd get on a motor coupling for a pump for example. These spider come in three hardness ranges and I choose the highest one for stiffness. (98A durometer). They are designed for Motion control thus the name "Sure Motion" couplers.

Look Here: https://www.automationdirect.com/adc/Sh ... C-JS40-98A

Once I get this mill all together I'll start measuring things like backlash, screw comp and so on.

Dave C.
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Re: G0678 CNC Conversion Thread

Post by Dave_C »

Progress Report:

I know before I even start to post this it is going to draw some criticism! That's OK because this is just a temporary way to operate the Spindle so I can move on to the Spindle Encoder.

The backlash is .025" and I can overcome that by putting a little pressure on the downfeed handle if I need to.

The first picture is the back of the plate and yes, I made a machine mark with the end mill but it is what it is. :oops:
0211181055.jpg
The second picture is the front.
0211181055a.jpg
The third is with the servo mounted. Now I need the pulleys and a belt and then I can tune the motor.
0211181110a.jpg
This will let me use the Mill to make more complex parts when I get around to doing the permanent solution. I'm actually rethinking how to get more Z and I may put a ball screw under the knee and a servo underneath the stand and drive the screw from below. That would solve the 4" of Z that I have now.

We will see!

Dave C.
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Re: G0678 CNC Conversion Thread

Post by Reedfirst »

Wow!

Very nice work!

One of the things I want to investigate with Acorn but haven't had the time yet is;

I'd like to see if it is possible to use the 4th axis on the Acorn controller to drive the knee for tool height offsets only.


I'm a cnc newbie so my terminology might be incorrect but what I am imagining is, if I set my part "0" with one of the tools in tool library and further into my program another tool is commanded by the G code and there isn't enough Z clearance for that particular tool the 4th axis (the knee in our case) would automatically adjust for that tools height offset and continue with the program.
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Re: G0678 CNC Conversion Thread

Post by Dave_C »

Progress Report:

I started doing the fine tuning on the Motor turns per inch. I was pretty close just from the calcs, something like .0015" in 12". So I did the calcs, tested again and now I have a good track from center table for at least 6" + and - minus in X and that's as far as I can measure for now.

I have a nephew who runs 10 Centroid CNC machines and has access to a laser screw calibrator. I'm hoping I can get him to come do my screw compensation for me.

I'll work on Y tomorrow.

To answer the question of backlash on the spider coupling, there is NONE! I used a DTI against a 123 block fastened to the table. I did a jog of .001" each way and the needle moves .001" and then right back to .000"

I also got the Y axis belt cover made, no big deal but I'll post a pic on the next go around.

I ran into the jog sticking issue, touch screen is clean, so I have no idea why it did that. It did it when set to cont mode. Fortunately I was in slow jog!

Dave C.
Grizzly G0678 Mill ,CNC conversion with Acorn. G4004G Lathe, Mach 3 conversion to Acorn.
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Re: G0678 CNC Conversion Thread

Post by ScotY »

Thanks for that, Dave. I’m hoping I can try some of those couplings out but they may not fit in the available space. I have a weird combo of shaft sizes...3/8” on the motor and 5/16” on the ballscrew. Only have a hair over 1” OD available before I have clearance issues.
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