[ontariocnc]

Hey Guys, I am working on getting an older Techno Isel CNC machine up and running. It seems that I have one bad motor. The motor is smooth when I rotate it by hand but under power it clunks as if it has a dead spot. It jumps forward about .200” each revolution.
Does anyone happen to have a spare motor they can sell me? I called Techno but they want 400 for a new one plus shipping and being a teacher with almost no budget this is an issue.
Does anyone happen to have a spare motor they might be able to sell me.

PN 0242-02-008
Model Number E242
Make – techno Isel
Blue and silver label
Cheers


Rodney

[Al_The_Man]

It may not be the motor, if that is the part number of the motor, it looks like a Electrocraft DC brushed, if so try the motor on a automotive battery and see if it runs smoothly in both directions.
Al.

[Montabelli]

look into kellingcnc I have one of their motors in use and it seems to work fine, I have started using the encoders availble from automation direct, they work well and seem seald fairly well against dust. thy also have ball bearing mounts.

also check your brushes and give it a sniff test see if it's burnt.

[Al_The_Man]

MotionTek are in Canada, they should have an equivalent, did you try the 12v test?
Brushed DC Servo motor Encoder driver Gecko G320 Viper 95 CNC KITS Canada USA Australia
Al.

[ontariocnc]

You were right, hooked up a 12v supply today and the motor runs smooth as silk.

When I got the machine 2 wires, small black and a small red were disconnected from the pins. I picked up some new pins crimped and reinstalled them. Not sure if it is the root cause of my issue but it is the same motor that I am now having trouble with. The encoder seems to be the issue but I am not certain if it can be removed. It seems to be press fit on the shaft.
Does anyone know how to take this off such that I do not damage the glass scale?

[Montabelli]

Techno has used a couple different encoders, all can be removed. remove the black plastic cap. look over the encoder and see if the glass/ plastic plate is damaged, or full of dust. if it is cracked the encoder is toast, if it is just dusty blow it out gently with dry air, and try again. if you are convinced the encoder is the problem ther will be one of two size set screws in the hub that mounts the wheel to the shaft. there is probably a little pull out tray on one side of the encoder at the bass pull this out then release the set screw and un bolt the encoder and see if yiour can remopve it with out totally destroying it, I haven't yet. once the encoder is off carefully install a new one. consult your wioreing on the techno literature and on the replacement encoder. make sure they are wired correctly. yu need a 1000 line differential encoder with 5v you should have a a' b b' i i' =5 v and 0v or gnd.

[ontariocnc]

I got it off, there is a small chip in the glass on one part of the encoder. I would suspect this is the root cause of my failure mode.

[Al_The_Man]

I got it off, there is a small chip in the glass on one part of the encoder. I would suspect this is the root cause of my failure mode.

That was a standard encoder fitted to Electrocraft from Renco, they are owned by Heidenhain now and have trimmed the line down quite a bit, so you may have to go with a sub, although there are many other through hole encoder suppliers.
The chip may be the problem although glass discs do not get chipped normally, you could try powering the encoder and test for voltage from common to each of the A,/A & B,/B outputs.
Al.

[ontariocnc]

My electrical or electronic experience is limited. Is the wiring the same on the like encoders. On my current one I have about seven wires coming out of it. Is this typical or will I need to change the wiring based on my configuration.

[Al_The_Man]

Normally on these encoders there is 8 conductors, +5v, Common, A,/A, B, /B, Z, /Z.
Al.

[ontariocnc]

I have been playing around with the encoder trying to get it going without having to buy a new one. I put it all back together and must have done something wrong. When I plugged it back in the machine took off like a rocket and slammed into the end stop. I remove the motor and it runs wide open in the direction of my choice but will not stop. I suspect that I have further damaged the encoder or possibly I have not installed it correctly. I took it apart today and can see nothing that looks wrong. Anyone have any idea what might be going on? I would hazard a guess that it is not reading the encoder.

[Montabelli]

yep classic toasted encoder runaway, now you gotta get a new one.

[Al_The_Man]

Motor run away is usually either a fault of a tach or the encoder, and AFAIK this motor never had a tach fitted?
So there is a good chance you have a defective encoder, you can check it with a meter to some degree, you need to supply 5v and remove the motor power and turning by hand measure each of the outputs from common and see if all transition from 0v to just below 5v, the marker will only be 1 pulse/rev.
Al.

[joejared]

I have been playing around with the encoder trying to get it going without having to buy a new one. I put it all back together and must have done something wrong. When I plugged it back in the machine took off like a rocket and slammed into the end stop. I remove the motor and it runs wide open in the direction of my choice but will not stop. I suspect that I have further damaged the encoder or possibly I have not installed it correctly. I took it apart today and can see nothing that looks wrong. Anyone have any idea what might be going on? I would hazard a guess that it is not reading the encoder.

There are 2 problems, actually. First, excesserror is not being used on the LM628/629 chipset, which is why the machine runs away. In my own software, I typically set ExcessError to the equivalent of 1 inch, so that if the difference between theoretical position and actual position is greater, automatic shutdown occurs. The second failure is either a reverse polarity tach wiring, or failed encoder. In my own software, current position is always visible in interactive mode. I believe Techno's software works identically in this area, or at minimum, has a monitor mode.

[chris_techno]

Were you getting full runaway before you took a look at the encoder? You'll get full power runaway typically when there's NO encoder information being sent through to the software.

The software believes it's stuck/binding/pushing through material so it'll continuously apply more power until the encoder reports something.

[Al_The_Man]

The software believes it's stuck/binding/pushing through material so it'll continuously apply more power until the encoder reports something.

Although a decent controller will detect a pre-programmed following error value and stop at some point, otherwise motor burnout may occur?.
This means the controller has lost control!
Al.

[chris_techno]

Additionally the encoder connector (on the more recent encoders) is keyed and there's a DB15 on the outside end. Generally speaking it's unlikely that your reconnected it backward but, as someone else stated, we have gone through several generations of encoders.

Is yours directly wired to the encoder? Or is there a small black connector going into the encoder?

[chris_techno]

Although a decent controller will detect a pre-programmed following error value and stop at some point, otherwise motor burnout may occur?.
This means the controller has lost control!
Al.

Yes, it would mean that the controller has lost control, as it's blind to the real world situation. Our amplifiers on most units will not burn out the motor but regardless it will always run into the limit switch at the end of the gantry and shut down the system before it would ever get to that point. The moment that circuit is broken power is cut.

It's the alternate purpose of the limit switches in addition to the obvious normal operational usage.

I qualified "most" as our older units may burn a motor possibly. It's not possible for me to generalize for all of the styles we've designed over the life of the company.

Also recommended that during further troubleshooting you keep a hand free for the emergency stop if it tries to run away. The (modern) limit switches are durable but smashing them over and over will cause them to break eventually.

[Dave's_Not_Here]

Rodney,

Good luck with getting a replacement encoder. I had one go to pieces a while back and was told there were no replacement encoders and that I had to buy a completely new motor.... $900 later I was back in business.

At some point, I will most likely retro fit mine with all new motors from a different manufacturer, which are not as costly and use laser etched metal encoders.

Good luck!

[Montabelli]

automation direct has a light duty encoder that will work just fine, it has an 8mm hollow shaft, I just chuck up a piece of 5/16 alu rod, drill out the center on the lathe to .25" and use it as a bushing with some locktight or superglue and solder on a new 15pin plug. they come with a 2 meter cable, $96. plus freight. they have a spring mount, base, and ball bearing mount, I have had far fewer encoder problems since I started using them.

There are plenty of sources for small dc servos out there too.