Converting an AMAT25LV

[Lloyd Barnes]

As per the title, the plan is to convert an AMAT25LV. It seems a well trodden path so am hoping with the info available and some nudging back on track where required from you guys all should be well. I do have some questions at the bottom so would really appreciate your comments;
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For info, I'll be machining aluminium perhaps 80% of the time, with occasional steel parts thrown in. Mostly car components for various petrolhead projects. I can always do some of the serious hogging out on the Bridgeport if it becomes a better option.
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Things I've done/bought so far....
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Electronics
• NEMA23 4nm motors for X & Y axis
• NEMA34 8nm motor for Z axis (I plan to add power drawbar etc and had read that a bigger motor would be a good idea for the Z axis
• Digital steppers, 5.6A for NEMA23 and 7.2A for NEMA34
• CP0-10V 4 axis breakout board. Only planning on using 3 Axis initially but wanted to leave option for 4th if it ever became desirable
• 48v power supply for drivers/motors
• 24v power supply for breakout board
• I've added an additional 4 relays and seperate 5v power supply to control box for future upgrades
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At this stage I've pretty much finished up the machine control box. (you'll note from the pics that even if I cant afford a Tormach, I can at least have a fancy Tormach inspired logo? lol)
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The current thing I'm working on is an enclosure. I want a really solid stand (I had the RF30 on a flimsy stand and it rattled like a good un). The plan is that whatever I make will also be bolted to wall/floor. I also want something enclosed to keep the chips down. I've pretty much made the base and am starting to fiddle with the tray and enclosure next.
The mill should arrive in a couple of weeks. I went with Amadeal as the price seemed fair and also they had an R8 version in stock. All of my Bridgeport tooling is R8 and whilst I'd want at some point to dedicate tooling to the CNC mill, seems to make sense to keep options open.
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I do have some questions. Mostly thoughts I've got based around what I've read others doing;
1. I've read that bracing the Z column helps rigidity a lot. It sounds like common sense but has anyone tried it and able to comment or advise on what works best. I've put a box section upright on the rear of the base to give me something to brace to (or could go to wall if necessary)
2. Is it worth upgrading the spindle bearings to angular contact (see next question)
3. Is it worth increasing the spindle RPM? Playing with a feed/speed programme 4,000rpm seems a useful speed to aim for when I'm machining aluminium?
4. If so is it simply a case of swapping out pulleys or will the motor struggle? It's sold with a 1kw brushless DC motor.
5. I was planning initially to run mist coolant although I'll build the enclosure with flood in mind. I understand that chip evacuation is my primary goal with lubrication a second and cooling a third priority. I'll read through other posts but any major objections to mist?
6. I'm a little baffled by the pro's and cons of mechanical limit v proximity sensors? I have some limit switches but if its the right way to go, then happy to ditch them and switch to proximity, or am I getting this back to front and I need both??
7. Can anyone confirm how I should work out the amp setting for the drivers (am I being thick again?!)

Appreciate any thoughts

[Clive S]

Welcome to the forum Lloyd. My comments would be up the volts on the drives if you can 68V is a good number with AM882 or EM806 drives and it definitely needs to be higher on the nema34.

I take it you are using ball screws.

I have done the conversion on the WM18 and used 23s with belt reduction all round and it runs fine.

Good luck with the build

[Lloyd Barnes]

Thanks Clive

I'm using drivers from CNC4YOU.

5.6A, 50V CWD556 for the 23's
7.2A, 80VDC or 60VAC CWD872 for the 34.

I guess that means my best bet would be to keep the 48v supply for the 23's and add a 68V for the NEMA34 then?

[Clive S]

Thanks Clive

I'm using drivers from CNC4YOU.

5.6A, 50V CWD556 for the 23's
7.2A, 80VDC or 60VAC CWD872 for the 34.

I guess that means my best bet would be to keep the 48v supply for the 23's and add a 68V for the NEMA34 then?

That's the problem that has been highlighted many times on the forum with buying kits.

Personally I would change the drives and built a toroidal transformer type PS.

[Lloyd Barnes]

That's the problem that has been highlighted many times on the forum with buying kits.

Personally I would change the drives and built a toroidal transformer type PS.

No kits here Clive, I prefer to choose parts/screw things up myself

[John S]

Go for 2:1 reduction on the head and you won't need gas struts etc.

[Lloyd Barnes]

Thanks for the heads up on this. Have spoken with the motor supplier and done some further research.
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Can I check my understanding. As I understand it (be gentle I'm, still learning this stuff!) running the driver for the NEMA34 at 48v is going to generate a much lower torque. Rather than the 8.7nm its capable of, it's probably going to be running somewhere closer to 4.5-5nm. Speed however shouldn't change? Is that right?
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Assuming I'm getting this right, then my options are to belt drive the motor to the ballscrew 2:1 thereby doubling the torque if halving the speed, or up the voltage to the 34 to something closer to the 80v the driver is capable of handling. Rather than rip apart everything I've done, I could add another PSU running 68V and hook that into the NEMA34 driver. As a bonus it would free up some load on the 48V PSU if I ever wanted to add a 4th axis.
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I added the 34 to cope with the added weight of a future power drawbar, but you guys are running the Z axis on 2:1 geared belt with NEMA23? Are you saying the you need closer to 8nm to happily run the Z even without additional weight on it
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Just trying to understand the problem and my options going forward. Have to say there is a tonne of information out there, some of it conflicting. Reading through various sites I've seen people converting the G0704 with 4nm NEMA23 direct driven to the Z.

[Lloyd Barnes]

Made some progress on the enclosure this weekend. Quite a lot yet to do but with luck I'm hoping to get it in primer and enamelled next weekend.
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Have set it up for flood coolant for the future. There's also box section at the rear to bolt the Z column to. If nothing else should be able to hold everything pretty rigid.
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Mill arrives next Saturday so hoping to make a start taking that apart soon.

[Lloyd Barnes]

I'm using the Oldham style couplings from CNC4YOU on my build. On the NEMA23 they clamp around the shaft with no other locating method (the NEMA34 motor has a woodruff key in the shaft, so I'll cut a corresponding slot in the coupler).
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What's everyone's experience using these? Do they slip at all or is there not a problem. There is a flat on the NEMA23 motor shafts, so I can drill and tap the couplers and add a grub screw locking onto the flat if its worthwhile?
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Appreciate any advise

[John S]

Yes Grubb screw as eell