Need Help!- Motor missing steps then reversing ???

[SScnc]

My Z stepper has started missing steps when going up and then it actually hums and reverses !

It reverses in a "slow motion" manner while the motor hums. I put my arm on the head of the X2 while jogging up and it does it every time. I do have to put pressure on it though. I completely loosened the gibs and it made no difference.

I then switched cables with the Y and the Z behaved the exact same so it's not a particular driver. I'm using Keling 4030's and 36v PS.

I really need some help with this, I'm trying to mill the second half of a mold and have already ruined one block of aluminum because the Z didn't lift up.

Any ideas on what is causing this ?

Thanks,

Steve

[SScnc]

Here's another bit of information, I put the hand wheels back on and it only takes a small amount of finger pressure on the hand wheels to quickly stall the motors on all axis.

I have the DIP switches on the Keling drivers set to max amperage.

I'm wondering if my PS is going bad ???

Have any of you had similar problems or have any suggestions ?

[Mariss Freimanis]

That is a typical symptom when one of the motor's two windings has lost connection to the drive. Check motor continuity at the drive with an Ohmmeter.

Mariss

[SScnc]

Originally Posted by Mariss Freimanis That is a typical symptom when one of the motor's two windings has lost connection to the drive. Check motor continuity at the drive with an Ohmmeter. Mariss

Hey Mariss,

I did as you say and all three steppers have the same reading on each set of coils, ~500 ohms. And I checked voltage at the PS and it's right at 36 volts.

It seems as the steppers aren't getting enough amps, I'll check that tomorrow morning.

This setup was working perfectly then this suddenly started.

[Fixittt]

Originally Posted by SScnc Hey Mariss, I did as you say and all three steppers have the same reading on each set of coils, ~500 ohms. And I checked voltage at the PS and it's right at 36 volts. It seems as the steppers aren't getting enough amps, I'll check that tomorrow morning. This setup was working perfectly then this suddenly started.

I has a somewhat similar issue but with my rotary axis. check your motor tuning, is any one axis tuned alot higher then the others? if the slightest bit of pressure causes the motors to stall then are they spinning at a high RPM to move the axis? Steppers loose torque the faster they spin. Try lowering your motor tuning. cut it in half and see if it still does it. As for loosening the gibs, you dont want them to loose because you increase the chance of the axis`s able to bind.

[HackMax]

Originally Posted by SScnc Here's another bit of information, I put the hand wheels back on and it only takes a small amount of finger pressure on the hand wheels to quickly stall the motors on all axis. I have the DIP switches on the Keling drivers set to max amperage. I'm wondering if my PS is going bad ??? Have any of you had similar problems or have any suggestions ?

If all axes are stalling and it just recently started occurring then the problem wouldn't be in settings anywhere, I wouldn't imagine. You have to trace it to what is common with all the axes and IMO that would be the power supply.

Rick

[Khalid]

Basically, what I understand is the heavy weight of your Z-axis.. your motors have no holding torque to move it up.. You can do 6 things IMHO:

1- Check out all motor wiring and power supply, check wether power supply output voltage and current are the same what is recommended ..

2- Install a counter weight system at z-axis like i did in following thread
Diy- Build Router In 10 Days

3- Decrease the acceleration and Velocity values in your CAM and Controller software

4- Decrease the weight of z-axis assembly

5-Upgrade to Higher torque steppers/servos..

6- last but not least, grease the linear rails and check wether any dust is accumulated in lead screw...May be Mechanical problem!!!

Best of luck
Regards
Khalid

[SScnc]

Originally Posted by Fixittt I has a somewhat similar issue but with my rotary axis. check your motor tuning, is any one axis tuned alot higher then the others? if the slightest bit of pressure causes the motors to stall then are they spinning at a high RPM to move the axis? Steppers loose torque the faster they spin. Try lowering your motor tuning. cut it in half and see if it still does it. As for loosening the gibs, you dont want them to loose because you increase the chance of the axis`s able to bind.

Thanks Fixittt, I reduced the velocity on all axis and that did increase the torque considerably. I had changed those settings a while back to increase speed but it was a small amount and didn't seem to cause any trouble until recently.

I did realize last night that at the time my X2 screwed up the mold I was milling I had engaged Feed Rate Override in Mach3 to 300%. The feed rate I had entered in the program was only 2 so Mach3 bumped it up to 6 which was still slow. But that's when things really went bad.

I still need to check the amperage output from the PS. And I only loosened the gib just while I was checking it. I have reset them properly now and I recently dismantled the column and sanded and polished the ways and the gib strip and they are very well lubricated. The gib strip and the ways were pretty awful, especially the dovetail on the head, it was very wavy and now it's flat and shiny.

So anyway, reducing velocity in motor tuning seems to have solved this problem. THANK YOU ! I guess I have to choose between reliable operation and speed so I'm just running the steppers slower now, I just finished the main milling of the new mold part and made the DOC .1000 instead of .0400 and set the F/R in the program to 5 IPM and did NOT touch the FRO in Mach3 this time.

HackMax and Khalid, Thank you both too, I feel I will have to upgrade to a higher torque stepper at least for the Z and I still think my Keling PS isn't putting out enough amps, maybe a switching PS isn't as good a choice in this application as a transformer based one is. (???)

At least it's working now and is able to produce parts without mangling them because the Z wasn't lifting when it was being told to.

Thanks again for all the great replies,

Steve

[Fixittt]

Steve speed without reliability is useless. Glad it worked. I had one of my machines cranked way up trying to decrease the machining time. but after having to machine the same thing 4 or 5 times, I realized that it would have taken less time to lower the speeds and do it right the first time.

Fun stuff!!!!!!

[HackMax]

Originally Posted by SScnc HackMax and Khalid, Thank you both too, I feel I will have to upgrade to a higher torque stepper at least for the Z and I still think my Keling PS isn't putting out enough amps, maybe a switching PS isn't as good a choice in this application as a transformer based one is. (???)

What is the size of the z stepper you have now? As a matter of fact what are all your stepper sizes out of curiosity? My X3 I just converted has tons of torque on the 425oz steppers on x and y and the z I haven't really determined yet. I need to grip the wheel quite firmly and that is when the axis is rapiding (which is probably when the motor is weakest.) I remember reading something somewhere about the switching power supplies not being the best choice for certain applications and it swayed my opinion on using one even though it was the cheaper route. I purchased a 39v 10A power supply from Antec on eBay.

The problem with your setup has one key clue that I can see with the info you have given and that is it worked fine before and now it doesn't. That tells me something out of the norm has happened to cause your problem. If you made no settings changes or tweaks and all three axes are weak when they used to be strong then something else has changed. It also tells me your power supply was probably adequate before your problem. Did you notice any large amount of heat generated from it at anytime? Maybe you were over-driving it and its starting to give out?

Rick

[SScnc]

Hi Rick,

This is the stepper-driver-PS setup I've got...

http://www.kelinginc.net/ThreeXCNCPackage2.html

I had made a slight change in velocity in motor tuning and then done the FRO (feed rate override) while running a program when this started. I won't repeat everything I made in a previous post but I have noticed some heat from my driver/PS enclosure as seen here...

http://www.cnczone.com/forums/showpo...50&postcount=1

I didn't try to deliberately stall any of the steppers before all this started but I really expected there to be more torque from this setup. I would like for my system to run fast and reliably. That being said, I'm still impressed at how you can design something in software and then have such an inexpensive machine make it so well.

I don't mind upgrading to get more torque, I just don't know if it's best (expense wise) to go with higher torque steppers or a different type of PS or if both are required.

To sum up what I would like my machine to do is to go faster (10 to 15 IPM) even if I have to have less DOC, reliably.

[HackMax]

I was looking at those package deals but the more powerful route and just decided to put my own together based on their larger 425oz and 640oz steppers. I didn't want the power supply they offered and the transformer type was about $30 higher than Antecs so I just bought their motors seperately and also got the bigger 6050 drivers. They handle more voltage and amperage but you lose out on microstepping options since you only get 1/2 and 1/8. Fine for my needs though I hope.

Now back to your issue... if you were happy with your system before the problem then there is probably no need to upgrade it's probably not your problem. I would just get a transformer type power supply and see if that is the problem. This type of power supply is very simple and not much can go wrong with it. As long as you don't draw more than the rated current you shouldn't have any power issues. You could always use a backup PS anyway. I think I found the article I read about the switching power supplies and it said that they were a bit noisy for pulse width modulated circuits. Not your problem.

Rick

Edit: I just looked at your other post. For some reason I was under the impression your system was working fine at one time but you mentioned that you were having z problems right from the start in the other post. Now that could be a setting problem since the package deal should be adequate for your mill since it was designed for it. I was going to get those steppers before I was talked out of it. I'm still using my acme screws that came with the mill so it was recommended I go the 425s for sure. Glad I listened I can't wait to start cutting parts.

If your cutting parts at .1 inch at 5 ipm now I think that is quite good. The only thing I've made with mine so far is the z axis motor mounting plate and supports. I cut these at 5ipm and .080 DOC and didn't try for more. I just wanted to get the feel for the machine.