[hoss2006]

I know this is irrelevant to CNC's machines, but can anyone tell me how to zero the x and y dials on the G0704? I can't move them, and I don't see any kind of a set screw holding them. There is nothing in the Owners Manual about it.

Mine rotate pretty easily by hand to adjust, I'm looking at one right now.
Maybe your handle is too tight and they are jammed.
There's only about .010 air gap between the dial and the inside of the handle that
tightens against the leadscrew.
maybe add a washer in yours.
Hoss

[mrcodewiz]

Can anyone tell me if this sounds right?

I hooked up an ammeter and measured the amp draw.

In Neutral with the speed control turned up maybe 1/4 to 1/2 max I was reading about 1.5 amps - so that is without the load of the spindle bearings.

In low at 1000 RPM I measured about 3.1 to 3.2 amps.

In High at 1000 RPM I measured between 3.5 and 3.6 amps. If I grab the spindle, I can make it climb to 3.8 or 3.9 but thats about it.

Very early on I saw it jump as high as 4.5, 6.5, and 8 but I have no idea why. It was within the first few minutes of running my test and I couldn't reproduce it. Would a poor connection cause it to read high? Doesn't seem like it. This is also with no load - later this week I will try to make some cuts starting out light and see what the draw is like. I will also hook up the treadmill motor again and see what that reads.

[mrcodewiz]

Here is something odd I just noticed. If I crank it up in high gear it will hit 3K RPM. With no load, it draws about 3.5 amps. If I grab the spindle, I can make the draw jump to 8 amps. When I release, it may drop down to 3.5 but several times it either didnt drop or it dropped down to like 6.5 and stayed there with no load. Not sure what that means.

[chipslinger69]

Have you tested the output voltage of the controller?

[mrcodewiz]

Have you tested the output voltage of the controller?

It seems OK. 0 to 90.9 volts.

[arizonavideo]

Bal-tec has a substantial discount per unit if I order over 500 (it goes from $.26 ea to $.18 ea). I considered ordering enough to do a few sets, but even with me buying extra and selling at group buy rates it would come out to be about $42 shipped a set for 2 axis. It does save you about $10, but it's still not cheap. If the Z nut takes about 70 balls then it would come out to be about $50 for all axis shipped.

I don't want to order a large amount and then not be able to sell them. Knowing my luck I'd order them and then that place on eBay will get them back in stock @ $12 per 100. So that kinda kills the idea of a group buy discount. If I decide to order any I'll probably get some extra and might sell a few, but no promises.

Someone earlier said to get stainless steel balls and that is not what you want. You want chrome steel,that is what comes in the ballscrew. They cost less too.

[mrcodewiz]

So this morning I pulled the quill out of the head in order to test the amp draw without the spindle or spindle bearings being factored in but with the rest of the drive train intact. That means all the geas as well as the quill sleeve and bearings.

For a little more background, it was colder this morning than it was when I ran my test yesterday. It had been in the 40s all day yesterday and dropped to the 20s last night and was maybe 30 this morning. I mention that because that quill sleeve seems much harder to turn when its cold.

I turned it on in high gear to about 350 RPM and it was already at 3.8 to 4 Amps. Turning it up past 400 RPM made it climb to 7 or 8 Amps. This is with no load and not even a spindle.

I can't imagine that the speed controller would have any effect on the draw would it? It is just pushing voltage to the motor. So it either has something to do with the friction in the drive train (maybe those bearings) or this motor is also no good.

[Thomasn]

I'm on motor number 2 and it's not looking good. It gets pretty hot during break-in. I don't have a thermo, but it's hotter than you want to leave your hand on for more than a few seconds. I'm guessing it's about 150deg. I stopped the break-in procedure after about 30sec at 2000rpm the motor started making noise and spitting plastic shavings out of the top. I have since made some light cuts in AL below 1500rpm and it seems to run fine, so I'm just going to keep the speed low and hope it holds out till I can get the CNC conv finished and then run it like it was SUPPOSED to made to run. She'll either go or blow and I've got 10mo left on the warranty.

[photomankc]

That seems really excessive for the RPM. That definitely seems like the motor is straining a lot for no cutting load. How hard is the spindle to turn in neutral? On my PM25 I can spin it several rotations by hand in neutral.

[mrcodewiz]

Well, with the quill out I can spin the spindle and it keeps spinning. Inside the quill sleeve, I have to turn it by hand and I can not spin it hard enough to make it spin by itself. It is definitely harder to turn than the spindle on my X2 but not that much (that's real quantitative i know).

[mrcodewiz]

Also curious - what does the max RPM trim pot do? I haven't touched the pots on the KBMM but I would assume that the max pot would raise or lower the max RPM being put out by the controller. I confirmed that mine is putting out 90.9 Volts at max but 3000 RPM seems high?

[photomankc]

Mines a PM25 but the controller seems to be the same between them but the motors and RPM they develop may be different. The MAX RPM trim adjusts just what you think it does. But, it has an effect on MIN RPM too so you have to kind of adjust both back and forth a bit to get what you want from both. The controller is pulse width modulation as far as I understand it so it's varying the duty cycle of the motor inputs not really the linear voltage. At least that was how I understood the KBM controllers to work. It would not surprise me if a cheap digital multimeter read the full 90V a little before the motor actually saw the full drive out of the controller.

[mrcodewiz]

Ah yeah, I guess that makes sense. Is it possible that the controller could someone cause the excessive amp draw or do you think that is unlikely?

[Maglin]

Have you checked your controllers SCR and Diode temps? If they are sky rocking within minutes of turn on that could be part of it. It also sounds like your spindle might be a little to tight or maybe you have a bad gear in the head. But being able to make it jump to 6+ amps and stay their with no load is strange.

Since you have the treadmill motor and speed control might try just the controller on your current motor and see if it will repeat the same issues under the same conditions. Definitely sounds like you are getting closer to the problem now.

Edit: Just saw you used your stock speed control with your treadmill motor. Also something just hit me. Are you able to pull your brushes? Might be a good idea to see what shape they are in and if they are making full contact. If not or if they are bouncing around that could explain the higher draw. Less contact would require more current. Current is Flow and Voltage is Pressure when it comes to power (in easy terms). ::deleted:: I now more current is required for the same amount of force with less voltage than with more voltage. And now I'm at a loss until I get some sleep.

[Maglin]

Hoss,
Quick question on the CNC conversion. Is it possible to use a lathe to thread the ballnut mounts? Looks like it wouldn't be to difficult to use. Would also shave almost $70 off of the cost to cnc it. Those large taps are expensive and probably would never be used after the conversion.

[mrcodewiz]

I haven't used the stock controller since motor #2. I will have to plug it in and see what happens with this motor. It will just be a pain since I removed the HP resistor from the OEM board and soldered it to a quick connect so I could plug it into the KBMM board. Maybe I will just solder a couple leads to it temporarily. I will also pull the brushes and inspect them. I may also see what sort of draw the treadmill motor has although I haven't finished the gear setup I want to use for that so that probably won't tell me much. This isn't what I want to be doing.

Just planning ahead, are these the correct bearings? I don't think it's a gear - it seems just as tight in neutral as it does in gear. I think its these bearings. Heck, maybe those tight bearings have been at least a part of my problem since the beginning.


http://www.vxb.com/page/bearings/PROD/Kit8891

http://www.vxb.com/page/bearings/PROD/Kit9569

[photomankc]

My dad always used the analogy of water. Voltage is the PSI and current is the flow rate. I can move a ton of water in a huge pipe at next to no pressure and I can move the same amount in a small pipe with much higher pressure. Voltage is how many electrons are all piled up wanting to move somewhere. Current is the torrent of electrons in motion. Greatly over simplified but might help to visualize it.

Generally, and simply, the load determines the current not the driver. The driver has an amount of current it can safely supply but if you hook up a motor that can suck down twice that then it will till the components of the driver smoke out. Now a driver can over-amp things by hitting it with higher voltage which will then move more electrons faster through the load, but that's not the case here.

[photomankc]

Is it possible to use a lathe to thread the ballnut mounts? Looks like it wouldn't be to difficult to use. Would also shave almost $70 off of the cost to cnc it. Those large taps are expensive and probably would never be used after the conversion.

Absolutely. I did that on both the X/Y and the Z. A tap would be faster though. I used a carbide insert bar from Shars. Worked great. I'll see if I can dig up the link at home.

[Maglin]

Opps I pretty much messed it up. TY photomankc. I'm going to fix it.

mrcodewiz do you have a G0704 or a BF20 or PM20/25? Your second bearing is huge and not for a G0704. If you had to use a hammer to get it installed into the head you could have distorted the race (unlikely but possible) which would of course cause some issues.

Edit: Also that Nachi Bearing 45x85x19 isn't an AC bearing and it could be bound up with angular loads. I'm willing to bet it could be the root cause of the problem. Did your first motor go out shortly after you replaced the bearings?

[mrcodewiz]

Opps I pretty much messed it up. TY photomankc. I'm going to fix it.

mrcodewiz do you have a G0704 or a BF20 or PM20/25? Your second bearing is huge and not for a G0704. If you had to use a hammer to get it installed into the head you could have distorted the race (unlikely but possible) which would of course cause some issues.

I have a G0704. I am not talking about the spindle bearings but the bearings that the quill sleeve rides in. It is pretty big. I have never touched those bearings - I only replaced the spindle bearings which are extremely smooth and free now. There was no change to the amp draw with the spindle in or out.