[mattbesquare]

Having a serious issue with my RF45 conversion. I am using this 1800 oz/in stepper and yet cannot lift the z axis faster than 5 in/min without it locking up on me. turned the accell down to 1, and still at anything more it locks up and makes an obnoxious noise.

Running it through a gecko 302V @72v and 6 amps.

Am I running too much voltage for the given current? Should I drop the voltage to the stepper? Any ideas? Thanks! X and Y work great up to 50+in/min but that Z is having issues. Even with a 17:60 pulley ratio! See numbers below...

                z axis	
                microstep multiplier       	10
		Stepper Resolution	        200
		motor pulley	                17
		axis pulley	                        60
		Drive Ratio	                        0.283333333
		Ball Screw Pitch 	                0.1180855
		Steps per Rev:	                2000
		Steps for 1 ball screw Rev	7058.823529
		Steps Per Inch	                59777.22523

Help?

[Crevice Reamer]

Hi Matt.

I have a few questions for you:

1. How do you have the motor wired? Parallel or series?

2. What kernal speed do you have Mach3 set at and what is your computer speed?

3. 1800 oz.= 112.5 LB. 112.5 LB x 8TPI= 900 pounds of lifting force if the motor is geared 1:1. The head cannot weigh 900 pounds, so 1:1 gearing should lift it easily. Why are you gearing this big slow stepper motor at 3.5 to one? Are you REALLY expecting to be lifting 3,150 pounds of mill head?

CR.

[mattbesquare]

Hi Matt.

I have a few questions for you:

1. How do you have the motor wired? Parallel or series?

2. What kernal speed do you have Mach3 set at and what is your computer speed?

3. 1800 oz.= 112.5 LB. 112.5 LB x 8TPI= 900 pounds of lifting force if the motor is geared 1:1. The head cannot weigh 900 pounds, so 1:1 gearing should lift it easily. Why are you gearing this big slow stepper motor at 3.5 to one? Are you REALLY expecting to be lifting 3,150 pounds of mill head?

CR.

No, I was too lazy to do the math and over purchased assuming this would be enough to get the job done even if it was underutilized-if that was the case I would get a cheaper one and use this stepper for something cooler like my giant moon shrinking laser beam lifting mechanism. But really, I just "bought the big one" because I thought it would easily do the job at hand and be ready for future upgrades or other uses.

It was wired in bipolar (parallel), and last night I went over all wiring again and rewired it in bipolar (serial) to see if it would make a difference. I read several conflicting sources but the majority of them said series would give me more low end torque. Since I shouldn't be stressing this motor at all in the rpm department, I figured the torque wouldn't hurt.

Kernel speed in mach is the recommended speed. The motor is making the noise (loud buzzing) and the spindle doesn't lift. looks like the stepper is trying to keep momentum to get to the next step alignment of the rotor but is not making it.


My confusion, as you stated before, is that such an overpowered stepper is having so many issues. I lifted that spindle by hand for a couple of months and it took a fair amount of work, too much maybe. But it looks like I can't disassemble the head without taking the whole thing apart because I do not have a cherry picker to lift the head out of position. (so the spindle, motor, and anything else heavy enough would have to be removed so I could lift the parts by hand).

I am unsure of the feasibility of the above plan of removing things by hand so am greasing, oiling, and waving a chicken leg over every bearing I have access too for the z axis. gibs are loose, oil is dripping off the thing...and I want to make sure I am not missing something obvious in the wiring of this overkill motor that is keeping it from manhandling my spindle...Does that make sense?

[Crevice Reamer]

What's the "recommended" speed? Do you mean 25K? How fast is the computer?

CR.

[mattbesquare]

25k, the computer is a 1.7ghz running xp that is completely void of any single service or application not related to mach3. I have been building computers for speed and tweaking OS's since I was in high school (a long time ago).

I went over to the shop and increased the kernel speed to the next 3 higher settings. same results for the stepper...

[Crevice Reamer]

How tight are your gibs set? Have you tried loosening them? Are you using grease on the Z ways or oil?

CR.

[mattbesquare]

gibs loose, screw is almost an inch out, ways are oiled. have moved from top to bottom, using synthetic 80wt gear oil atm..havent ordered my vectra yet. still a layer of oil on ways after head moves over...

[Crevice Reamer]

Can you turn the ballscrew by hand--At least to LOWER the head, or is it unmovable by hand?

CR.

[mattbesquare]

Can you turn the ballscrew by hand--At least to LOWER the head, or is it unmovable by hand?

CR.

yep, I can. Also at 5 in/min it is working just fine, I havent seen a skipped step yet. I am trying to optimize my gcode for the gimp Z while I figure this out. What a headache. Ill post pictures of how things look at the moment.

I am thinking the there is either something wrong with the motor, the bearings the ball screw is spinning on are shot, I should cut voltage and increase current, I wired something wrong, or a combination. I rechecked wiring last night, and cut out the connector so the stepper is going right to the gecko. The connecting wires are stranded 18 gauge so thicker than they need to be..... I am lost.

I have a 2:1 transformer and my power supply is in two independent channels. If I drop one side to 36 volts through the transformer, I should have somewhere between 15 and 20 amps right? but then my geckos wont push more than 7....and still stuck... Ill go remove the resistor to see if another amp will do it maybe also some damping capacitors? I wouldn't know where to put them.


Removing the resitor wont overload my 203v's right? Since they will just operate at the max switched amount and no more?

Are Kelings steppers user serviceable? I was kind of hoping he would have responded to this thread also.

[mattbesquare]

Do you think over tension (radial force acting on my stepper armature) from my belt could cause the armature to gap and the motor to lose strength? I was thinking of an adapter that was a direct connect to my steppers and served as an radial loading member between the belt and the pinion gear, this would try to ensure the steppers were only working on their intended axis...

The blocks you see are my new belt tensioners/belt guides. I was having problems with belts slipping off and the z axis skipping teeth. I spend so much fricken money at SDP for belts to only find out exact sizes I needed aren't stocked, I had some ball bearings laying around and I built the dual point tension blocks you see. I could loosen the Z axis a bit for sure, first thing in the morning.

I have been having this problem for a while, but it was occasional. now it is almost constant.








This is my X axis:




I will scrape and clean the ways on my Z tomorrow, then elongate the slot for the tensioner to take some out.

for tonight.... bed. Thanks CR, I really appreciate the extra voice of reason.

[Crevice Reamer]

Rewire the motor to parallel. Your Voltage is just exactly what it needs to be. You don't want to run the motor at any higher Amperage than the 4.1A it's rated for.

OK. It's moving at 5 IPM, just not faster. If you can turn the ball screw by hand, it's not binding. It's possible there may be a "stiction" problem, (especially if you smoothed out the ways and eliminated the oil grooves) but I think your MAIN problem is the gearing you have imposed onto this poor motor.

Steppers are not like servos. Servos run at high RPM and need to be geared down for torque. Steppers LOSE torque when geared down like this, because it makes the motor stall at much lower screw RPM. Get some same-sized pulleys that will fit within your belt envelope and run that thing 1:1.

CR.

[Crevice Reamer]

Another thing. That setup should run at least 25 IPM as-is. I was trying to figure out what happened to the other 20 IPM. I believe it is your belt tensioner set up. Those look like bindomatics to me. I think the tensioners are causing so much friction that the motor can't cope. ALL of your steppers should be running 1:1 with NOTHING between the pulleys and just slot adjustments for belt tension.

CR.

[mattbesquare]

Another thing. That setup should run at least 25 IPM as-is. I was trying to figure out what happened to the other 20 IPM. I believe it is your belt tensioner set up. Those look like bindomatics to me. I think the tensioners are causing so much friction that the motor can't cope. ALL of your steppers should be running 1:1 with NOTHING between the pulleys and just slot adjustments for belt tension.

CR.

Ok, great point on the torque and gearing. The tensioner's have ball bearings in them for the main contact point. The side tabs that keep everything on track are rounded on the inside.

I went with gearing because I didn't know which ball screws I would end up with (buying used on ebay) and wanted to still get accuracy. But now I am seeing the light. I will re-gear the Z so it can do what it does best.

And that Z axis is not easy to move by hand, I just think its internals are crap-another user took his apart and found broken ball bearings inside....with greasing and oiling I finally "broke it in" to its smoothest before the motors were applied. I will lower the current to the Z axis, because I completely missed the 4.4 amp limit (stupid me).

When everything is rearranged I will let you know and maybe help someone else down the road who does the same thing.

Always thankful.

[mattbesquare]

Another thing. That setup should run at least 25 IPM as-is. I was trying to figure out what happened to the other 20 IPM. I believe it is your belt tensioner set up. Those look like bindomatics to me. I think the tensioners are causing so much friction that the motor can't cope. ALL of your steppers should be running 1:1 with NOTHING between the pulleys and just slot adjustments for belt tension.

CR.

My X axis works great, X and Y are smooth with fabulous IPM's and the backlash is in the hundred thousands.. but My Z belt is tighter than it should be, I do realize that now. I just included an image of the x because I was proud of the tensioners and everything is finally working great on those two axis.

[mattbesquare]

The axis was over extended and by trying to compensate for the weight I pulled the stepper out of its comfort zone just as you predicted.

Switching to Parallel gave me another 5 IPM's, back to 10. And I have gears on the way to make it 1 to 1.

Hey CR, where can I learn the equations to "run the numbers"? Every time the stepper question comes up, people tell you to run the numbers but not which ones nor the operations to apply. Is there a place you might recommend?

[Crevice Reamer]

That's good news Matt! I'm glad to see it is starting to work out for you.

Start here. Mariss is the Master:

https://www.geckodrive.com/upload/St...cs%20Guide.pdf

CR.