4896 Plus Servo - Axis Problem

[Dave's_Not_Here]

I have my 4896 Plus Servo machine running on Build 420Q.

I am in the middle of a large engraving job for a corporate client. I had a portion of the job completed last night and powered down.

I came out this morning to complete the project. When I tried to set the Origin point for my long axis, (X) in my case, using the arrow keys on my keypad, the gantry bolted like a scalded cat and wanted to slam into the limit switch.

All other axis work fine.

I have done everything, from rebooting, resetting circuit breakers, blowing out the computer, resetting cable connections, etc... everything but reinstalling the 420Q. I have three calls into Techno and waiting for return calls.

Any Ideas why only one axis is acting this way and what might be causing it?

I really need to get this job out ASAP.

Dave

[Montabelli]

you have a toasted encoder. with the power on the amps disabled try and push the x axis if the encoder seems to read normally, something else might be at fault. but in my experience it's an encoder.

[Dave's_Not_Here]

you have a toasted encoder. with the power on the amps disabled try and push the x axis if the encoder seems to read normally, something else might be at fault. but in my experience it's an encoder.

Yup, got a call from Bob at Techno and he had me do the same test... no joy... toasted encoder.

That makes two encoders on two servos in less than 9 months... the last one while powered down for the night!

This is getting old... not to mention expensive.

Thanks for the input,

Dave

[Dave's_Not_Here]

... so, given the frequency of Techno Servo failures on my machine, what specifically do I need to look for in replacement DC Servos?

In other words, what is important to ensure that a replacement (eBay) DC Servo works with the AMPs in the Techno controller and processes the g-code programs accurately? Are the cable connections "industry standard" or do manufacturers make specific connectors to force you to use their servos?

I am ignorant regarding what needs to be considered between the Techno Interface, Servos and Controller... and what would constitute a "direct replacement."

I figure I might as well start to stock pile some replacement servos as funds allow... since I feel this is going to be a frequently recurring nightmare.

D

[Montabelli]

I think the three big enemies of the encoders are shock, heat and dust. I think the dust generally gets most of them. get one with a spring mount, which has its own bearings, and seal it in its case very well. automation direct has some in stock that have an 8mm hollow shaft or 8mm shaft, you can bush the hollow or couple the shaft encoders, coupling the shaft encoders will make it difficult to fit in the enclosure on the back of the motor, but a soup can and hose clamp can make an adequate housing, make sure of your wiring and perhaps build your own connection system to link to the techno wiring and it should work well. you need a differential type 5v 1000 line the light duty ones are $86.00

[Pplug]

I would check the all capacitors in the controller box and on the cards just to make sure they are OK. They are in just about everything, and you never know if they could be the culprit!

[Dave's_Not_Here]

I would check the all capacitors in the controller box and on the cards just to make sure they are OK. They are in just about everything, and you never know if they could be the culprit!

Since I am electronic challenged, just how do I go about checking the capacitors and where are they on the board?

D

[Dave's_Not_Here]

Techno did not have any new or refurbished X - Y Axis Servos in stock. I was told that I could use a Z Axis Servo and that the controller would automatically disable the Brake on this servo. So, it should be here tomorrow and we will see. Hopefully things get better and not worse.

I would really like to replace all the servos with another brand that uses laser etched metal encoder discs... and typically cost a lot less.

D

[Al_The_Man]

I would be inclined to add a small electrolytic cap at the encoder end across the +5 & Common.
Just in case it is a spike occurring over the long cable run.
It would not hurt in any case, 50µf would be ample.
Good quality glass etched encoders should be enough on that type of machine, you can clean the glass disc with de-natured alcoholic if they are dirty, but if it takes off without stopping I swould suspect the encoder electronics.
Al.

[Dave's_Not_Here]

I would be inclined to add a small electrolytic cap at the encoder end across the +5 & Common.
Just in case it is a spike occurring over the long cable run.
It would not hurt in any case, 50µf would be ample.
Good quality glass etched encoders should be enough on that type of machine, you can clean the glass disc with de-natured alcoholic if they are dirty, but if it takes off without stopping I swould suspect the encoder electronics.
Al.

Al,

All the electrical references are over my head.

When you say "if it takes off without stopping (which it does) I would suspect the encoder electronics", What electronics are you referring to? On the controller board? The encoder circuit board? It would be nice to just replace the encoder circuit board, assuming Techno would sell me one, which I seriously doubt, as they paint a really bad picture of trying to replace an encoder on your own... which scares the novice like me, into a new motor.

D

[Al_The_Man]

By encoder electronics I meant the encoder itself.
Usually replacing an encoder is not that complicated, especially on DC brushed servo's, if on AC or Brushless DC is another story.
I am guessing they are through hole encoders? these fit over a rear motor shaft, as opposed to the type connected by a coupler.
There are a few manufacturers of these, at most, it may require some soldering, but you should be able to get that done locally if not up to it yourself.
They are ordered by hole dia. and encoder count.
Al.

[Pplug]

I had a shattered encoder that did just that on my z axis when I first purchased my machine about three years ago. It would go all the way up until it hit the stop and I got an m3 error. Techno sold me a replacement for $180 that I was able to bolt on very easily.

As go my previous post, the capacitors are the little cylindrical shaped objects that look like a can that has been shrink-wrapped around the sides. If the tops are swollen/bulging or you can see corrosion on them from leaking, they are the root of the problem and will keep frying other electronics . Ive made a bit of money from swapping out defective caps over the years!