[rs4race]

Thanks deuce. My boards are currently down with bad batteries, but they are tons of fun.

Thread milling and 3d milling are on my list. I just have to find something to cut out first, and an excuse to buy a thread mill. After the chamfer I thought to myself. Precision debur everything!

So last night I got the mill to change speed within mach! So very cool, but I imagine I have a ways to go. I hooked up the mx3660 in parallel with the stock pot on the mill's face plate. This seems to drop the voltage from 8v to 5v. Im going to try disconnecting the pot and see what happens there. I could only get the rpms to change a few hundred. I will check I get 0-100% duty on pwm and I'm guessing if thats the case I will need to adjust the trim pots on the motor driver.

I'm just doing this out of curiosity for the time being. I am planning an AC motor upgrade, but stuck on the HP rating. Grizzly's specs say 1hp, the motor has a 1000w sticker on the side, but I've stalled out on much lesser cuts. My guess is thats a peak rating, and not sure how to compare it to an AC motor that has a continuous rating.

[lcvette]

1.5 - 2 HP 56 frame AC inverter duty motor is about optimal for this mill. You can go larger but the price for motors and drives jumps a ton past the 1.5hp mark. Check out dirtdiggerand cncshopmill on YouTube, they have some good examples of that size motor being put to the test and what they are capable of handling. I think much beyond what they are cutting and you will have increased machine flexing on heavy cuts that will render the extra power a bit wasted.

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[rs4race]

Yeah I have a few 56c motors here at work, and they just look waaaaaaaaay too big for the mill. I'm looking at metric motors as they can be packaged smaller than the 56 frame motors and still pack a good amount of power.
The options Im looking at are:
71 frame
3/4 hp 3600 rpm and just 15 lbs
80 frame
1 hp 3600 rpm and 21 lbs
1 1/2 hp 3600 rpm 27 lbs

My thoughts as far as power go are the stock motor might be 1hp peak, and probably much less continuous where these motors are rated continuous, so even the 3/4 hp motor will be an upgrade. I'm not sure the price difference for vfd's but for the motors its about $40 more for the 1 1/2 vs the 3/4 (not a big deal). I was more concerned with the extra weight effecting feeds and possibly tilting the head out of tram.

I guess I'm just trying to find something that is most compatible with the machine, and an actual upgrade over the stock motor.

[lcvette]

If the head can tilt out of tram, there are other issues that will need to be addressed for any motor to work well. Hence why all of these linear rail conversions are popping up.

I don't have experience with the metric motors, do they perform identically to their 56c counterpart? I would go at least 1.5hp and I have heard that a 1700-1800rpm motor is a better performer for low end grunt without the need for pulley reduction which makes velt drives nice and simple and with a VFD you can still spin it to 6000+ rpm.

A 56 frame is a big motor to fit, but I have seen the results and would say they by far have been the most impressive I've seen to date. I know my 2.2k BLDC doesn't come close to comparing with an AC Motor and I have about 3 times what it would have cost to go AC and VFD from the start because I too was concerned about weight.

Turns out power was the issue and not weight.

I have a big air cylinder, big 2.2kw motor, 6" rotary table and a few other odds and ends and the 560oz in moved it but the jacked up dovetails would cause stalling. I went to a 1200ozin closed loop stepper tightened up the ways which improved surface finishes but is still a far cry from what I'd consider good, and the new vl stepper doesn't even notice any weight. It powers right along without changing so much as a hint of strain. Rapids are plenty fast at 450ipm which I turned down to 250 because that's alot of mass running that fast and 250 is quite fine on such a small mill. The biggest improvement was the acceleration with the new motor.. Where before I had to slowly get the head moving or it would stall, now it zips right up to rapid with accel set to 100 (570 wasn't reliable at anything over 15).

So I wouldn't worry about weight if you have a good size stepper, I'd prefer to have enough power. Besides, you will spend more time cutting than rapiding. If you can muscle through material with twice the speed and depth of cut. Your machining times will be lower the the other way around even if you could rapid at 1000ipm.

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[Fastest1]

I thought the stock motors were 750 watt? I run the Weiss 1100 watt since my stocker burnt up.


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[lcvette]

I have heard the Weiss is a good alternative, hat driver do you use? And what is the rpm range on that motor and with what gearing/pulley ratio?

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[Fastest1]

The motor itself runs 5156-5160rpm WFO at the motor and 5700 max at the spindle with the present gearing. I am running a KB125 IIRC.

[rs4race]

The motor itself runs 5156-5160rpm WFO at the motor and 5700 max at the spindle with the present gearing. I am running a KB125 IIRC.

How much did you pay for the weiss motor? The only place I found online was aliexpress and they want about $360 shipped.

[rs4race]

I found a 1hp 71 frame motor. I imagine this will do pretty well I think it may be a drop in as well but didn't measure the stock motor yet. Now I'm double thinking it and looking at that 1.5hp motor. The problem is I can't find any cuts that are typical of my use that the 1hp wont cover. It looks like my typical cuts are around 1/4hp and .5 cu ipm MRR. With the 1 hp torque curve I adjust cuts (in hsmadvisor) to .75 hp and 1.5 MRR.

I mean its obvious that 1.5hp can remove more material I just need to find the application. What kind of cuts are you guys doing that requires 1.5hp?

[Fastest1]

I don't remember how much I paid. It sure wasn't 300.


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[rs4race]

Ok. So I think I have found my motor upgrade. I'm looking at a 71C 3ph AC motor 1hp. The 1hp is continuous, and by my calculations it should have 2.1 Peak HP.

I based this off of the following:
NEMA Type C typical performance data,
Breakdown torque @ 75% synchronous speed.

Motor manufacture performance data,
Breakdown torque/Nominal torque (Tb/Tn) = 2.8
HP= N*T/5252

Peak = Nominal * Tb/Tn *75%
2.1 HP = 1 HP * 2.8 * .75

What does the peak HP number mean? Nothing really, but since a lot of the motors that come on equipment like the g0704 are peak rated I needed something to compare it to. This motor is also nearly identical to the PCNC 770 motor. I believe this is about as matched up to the G0704 as possible. It is a bit larger overall, but because its an aluminum frame it should be about the same weight. I estimate the stock motor at 8kg (through solid parts modeling) , and 71c at 8kg (7kg actual). That's what I'm thinking right now, unless I'm just way off with my sizing.