[SScnc]

This was my Saturday project. My motor has alway run a bit hot but I recently had to replace my motor control board in my Grizzly G8689 X2 and my motor now runs fine but was getting even hotter. With the new board my rpm's went up to 4900 too so I'm happy about that part.

So since I run programs for hours and some times all day and all night, I decided to take care of this problem once and for all.

The pics pretty much tell it all, I made a "water jacket" that slips onto the motor. I turned the motor to true it up and clean it then turn rings with grooves for O-rings on the inside. The outer case is 4" exhaust pipe.

The coolant runs into the bottom, fills and circulates around the motor then discharges from the top and into the Loc-Line and finally out the nozzle onto the endmill and part.

Needles to say I was thrilled when on my first test there were no leaks !

So I'm going to run a program that will take about 6 hours to complete and see how it does. I expect it will keep it cool and all will be fine.

I finally did get my tapered roller bearings adjusted properly and I'm very happy with them, the head get to about 110* and stays there on long programs, I don't think that's too bad.

Here's the pics...

[SlowRiderr]

Great work!

[TXFred]

That's a good looking rig.

I'm wondering why your motor gets so hot. Even after several hours of milling, mine is cool to the touch. When you had it apart, did you see anything that might be causing it to overheat?

[port_huon]

I agree with fred, it looks good but you seem to be treating a symptom rather than addressing the cause i.e. why the motor is overheating in the first place.
The fact that you've had to replace your motor controller should be an indication of an underlying problem.

Still, it looks really cool! (no pun intended)

[SScnc]

I thought all these motors get hot after running full speed for hours, I'm surprised to hear Fred's stays cool ! I've seen others use different types of fans on their motors.

My original controller had a fair amount of hours on it, every now and then it was acting as if the switch was being turned off then back on just as the rpm's started to drop. I will diagnose and repair it later.

The armature and wiring on the armature (that's visible) all look perfect and I have checked the heatsink on the controller at times and it's never hot so I don't know why the motor runs hotter than some of yours.

[The Aspirator]

That's so cool!!! I might have to try that. I've got the same machine and my motor gets really warm, but not too hot to touch. Then again, it's not CNC yet, that's actually what I'm making this evening, the stepper mounts.

I think I'm having the same problem as you, sometimes the spindle will just shut off. It's as if there's an overload circuit, cause it seems to happen when I'm cutting too hard (although sometimes just whenever it feels like it). What circuit board did you replace it with?? This problem is really really annoying, and I think it'll be horrible when CNC'ed cause the spindle might turn off and the steppers might keep moving.

Also, I would LOVE to see what you're machining for 6 hours straight!

[The Aspirator]

Also what are the tapered needle roller bearings you're referring to? Did you upgrade the spindle bearings or something?

[LongRat]

Aspirator - there IS an overload circuit on the X2 motor controller. I had the same problem as you, I could even trip out the motor by rubbing the rotating spindle with my hand. Turned out that one of the current-sensing power resistors on the controller had snapped a leg, causing the current limit to be cut in half. Check your board - the linked PDF explains the issue - http://www.modelbrasscannon.com/ServiceManual.pdf.
Hoss pointed this out to me and it saved me a lot of time and money.

[SScnc]

Also what are the tapered needle roller bearings you're referring to? Did you upgrade the spindle bearings or something?

Yes, I did change from the original ball bearings (which had gotten noisy and also generating allot of heat after I changed to belt drive) to rollers. You can see about it in THIS thread. It took some time for me to get the preload adjusted so the spindle will spin easily and also quietly and with out too much heat. But they're great now.

I replaced the control board with another identical board Grizzly sent me under warranty. The power resistors were the first thing I checked on the original board and they were ok. I think it's one or both of the MOSFETS's (?).

Some of the things I machine that may take 6 hrs or more are emblems and medallions which often require very small endmills like .03 or .0469 ones and DOC of .02 and feed rates of only 1.2 IPM. I don't know how else to do it without a 30,000 RPM spindle.

[The Aspirator]

Thanks both of you. I of course e-mailed hoss last night and he sent me those same links, you guys are great! I'll go check those resistors right now, sounds like a very likely culprit.

[SCzEngrgGroup]

Thanks both of you. I of course e-mailed hoss last night and he sent me those same links, you guys are great! I'll go check those resistors right now, sounds like a very likely culprit.

A motor controller that shuts down prematurely is almost certainly in need of having it's current limit adjusted. These things are often VERY poorly adjusted as the come from the factory. Blown FETs will result in no speed control at all - it'll be either full on, full off, or stuck at one speed.

Regards,
Ray L.

[SScnc]

A motor controller that shuts down prematurely is almost certainly in need of having it's current limit adjusted. These things are often VERY poorly adjusted as the come from the factory. Blown FETs will result in no speed control at all - it'll be either full on, full off, or stuck at one speed.

Regards,
Ray L.

That makes sense Ray. I'm going to check the current setting on the original board. What's your opinion/experience on the motor heat ?

[SCzEngrgGroup]

That makes sense Ray. I'm going to check the current setting on the original board. What's your opinion/experience on the motor heat ?

The motor *will* get hot with extended use, but it should not get *too* hot. Motors are designed to handle a fair amount of heat, and "hard" milling for long periods will get the motor too hot to comfortably touch, but should not get it hot enough to do any damage. Most motors are designed to operate somewhere in the 70-85C (160-185F) range with no damage. If it's getting hotter than that, then something is very wrong with either the motor or the controller. High heat means too much current. You can buy a cheap IR pyrometer from Harbor Freight for about $20, and see what the actual temperature is. But a good rule of thumb is if you can put your finger on it for even a couple of seconds, you're OK.

Regards,
Ray L.

[SScnc]

Okay good, I expect any electric motor to get warm or hot after extended use. Mine was as you describe "put your finger on it for even a couple of seconds". And a couple of seconds was about all comfortably. Since I have the water jacket on it now I'm going to measure the air temp blowing out the top just to see.

Thanks Ray

[forrest39]

If nothing else, this may be an effective way to reheat coffee!

Seriously though, It looks Great!

-4ist

[SScnc]

If nothing else, this may be an effective way to reheat coffee!

Seriously though, It looks Great!

-4ist

LOL, That's a good idea ! I drink ALLOT of coffee !

Thanks.


I didn't have time to run a long program yesterday so it's running one that will take about 5 hrs, 45 minutes right now. So we'll see how it does, so far nice and cool and just slightly warm air out the top.

Steve

[The Aspirator]

A motor controller that shuts down prematurely is almost certainly in need of having it's current limit adjusted. These things are often VERY poorly adjusted as the come from the factory. Blown FETs will result in no speed control at all - it'll be either full on, full off, or stuck at one speed.

Regards,
Ray L.

That did it! I first checked the big white ceramic resistors for broken legs, they were fine. I checked 'em with my multimeter all over, and wiggled then with the spindle turning, they were perfect. Then through some quick trial and error I adjusted the VR1 pot (has rubber cement on it so you don't adjust it, haha) from the factory value of 17.9k (measured with power off, otherwise the spindle turns on when you measure!) two turns counter-clockwise for a value of 20k. Now I can't stop the drill chuck with my hand anymore, the belt just slips. It's perfect, completely fixed my problem!