Mike's 6-Axis Articulated Robot

[macardoso]

Can you use a motor with a double shaft front and back and put the original encoder back end on it? Get a motor same specs and just replace that part leaving all the feedback servo encoders in place?

Yeah, that'd work, but finding an electrically identical motor would likely be nearly impossible unless it were from the exact same series that this one was made from. I think I could substitute a non-DENSO motor made by Panasonic at the same timeframe, because I doubt Panasonic retooled their motor winding line to make special motors for DENSO. But I don't think I could take a 50W Allen Bradley motor and get the original control to run it.

Slim chance, but maybe the original servo amplifier in the control box is dumb enough to not even care... hrmmmm.

 

[macardoso]

I should also mention that before I bought this unit, the DENSO tech warned me as to the age of the unit and the fact that few of this model were sold in the USA. Likely most went to asian markets. This seems to be the case as most spare and aftermarket parts are being sold in China, rather than the normal US places like Radwell.

I knew what I was getting into at least.

 

[strantor]

So my thought is this. The original control is more or less ready to run (especially since I own the teach pendant). I'm missing these components (items in bold are things I'll need regardless):

• Controller Power Cable
• Robot Motor Cable
• Teach pendant Cable
• Robot Batteries
• Control Batteries

You're leaving a few things out aren't you? The important things you can't build yourself or get off ebay? Like... a unicorn floppy diskette, an obsolete unicorn panasonic motor that was custom order to begin with, motor data, a way to integrate anything but the Panasonic motor, any means connecting to the thing to make changes in the proprietary software, etc ( I thought there was more but lack the time/energy to go back and look).

It's your project and I'll stay tuned no matter which direction you go but I just feel like I'm watching someone buy and invest in tooling for one of those mill/lathe combo machines that I know they're going to outgrow in 6 months and wish they had just bought the lathe and the mill to begin with, rather than waste time and money on something else, just to end up buying the proper machines anyway in the end.

 

[Cadillac STS]

Yeah, that'd work, but finding an electrically identical motor would likely be nearly impossible unless it were from the exact same series that this one was made from. I think I could substitute a non-DENSO motor made by Panasonic at the same timeframe, because I doubt Panasonic retooled their motor winding line to make special motors for DENSO. But I don't think I could take a 50W Allen Bradley motor and get the original control to run it.

Slim chance, but maybe the original servo amplifier in the control box is dumb enough to not even care... hrmmmm.

I would disagree with the idea that it would be difficult to find a replacement motor. Find the voltage and rough size specs and there should be many choices. Get one with the rear shaft to connect your sensors to and it should work.

 

[macardoso]

I would disagree with the idea that it would be difficult to find a replacement motor. Find the voltage and rough size specs and there should be many choices. Get one with the rear shaft to connect your sensors to and it should work.

You might be right, but I do think it is a bit more complicated than that. Motor mechanical dimensions, power rating, and voltage matter greatly, but there are many other electrical and mechanical parameters which vary from motor to motor based on winding design that affect performance. These are:

• Torque Constant
• Rated Torque
• Peak Torque
• Inertia
• Poles Per Revolution
• Winding Resistance
• Winding Inductance
• Inductive Time Constant
• Rated Speed
• Maximum Speed
• Continuous Current
• Peak Current
• Damping Coefficient
• Voltage Constant
• Overload Limit
• Max Acceleration

All of these parameters are factoring into the Space Vector Pulse Width Modulation (SVPWM) algorithm that controls the motor. If they differ from the original motor by any significant amount then the control of the motor will suffer with symptoms of poor torque, excessive motor heating, or instability with the manufacturer programed servo gains.

If all else fails, I might have to try just what you are suggesting.

As an aside, this is the reason it is so difficult to mix and match servos between manufacturers. Usually these parameters are not publically available and often times servo drives only allow you to pick from a list of motors they tested the drive with and don't actually permit entry of custom values.

 

[macardoso]

You're leaving a few things out aren't you? The important things you can't build yourself or get off ebay? Like... a unicorn floppy diskette, an obsolete unicorn panasonic motor that was custom order to begin with, motor data, a way to integrate anything but the Panasonic motor, any means connecting to the thing to make changes in the proprietary software, etc ( I thought there was more but lack the time/energy to go back and look).

It's your project and I'll stay tuned no matter which direction you go but I just feel like I'm watching someone buy and invest in tooling for one of those mill/lathe combo machines that I know they're going to outgrow in 6 months and wish they had just bought the lathe and the mill to begin with, rather than waste time and money on something else, just to end up buying the proper machines anyway in the end.

Oh I'm painfully aware of what I'm getting myself into. For me, this project is very much about just having fun learning and reverse engineering the old robot. I don't care quite so much about the long term use of the unit - although I do want it to work eventually. To buy a ready to run unit, even needing a LOT of work would have run in the $3-5k range and then I'd be just as limited by proprietary software.

I'll pull the gloves off and go for some more drastic approaches if I can't do the low hanging fruit.

I already have the PLC and servo drives which I am researching in parallel so we will see where this goes, even I don't know yet

A lot will depend on how much info I can squeeze from DENSO and Panasonic.

 

[strantor]

I would disagree with the idea that it would be difficult to find a replacement motor. Find the voltage and rough size specs and there should be many choices. Get one with the rear shaft to connect your sensors to and it should work.

If you're not aware, an AC servo motor is a totally different animal than an AC induction motor. If we were talking about a lathe spindle motor then sure, just go get one with the same voltage and rpm, good to go.

Here's an analogy: the motors (I think) you're probably thinking of (lathe/mill motors) are like a 5hp Briggs engine on a tiller. That engine goes out, you can put another Briggs or you can put a predator or just about any engine will work. These servo motors are more like the engine in a modern automobile, with control modules that speak Chevy, and a very specific model of Chevy. You can't just drop in a Ford engine or even a different model of Chevy engine and go. With a bunch of painstaking work involving programming, you could force it to work, but it is much better to just get the right engine. And the engine in this case is like a one out of an imported Lotus. They don't have piles of them laying around at the local scrap yard.

 

[Cadillac STS]

Would something like this be close enough, maybe swap out the magnet inside or a bigger part of the motor?

Denso 410622-0631 Axis Robot Servo Motor MSM5AZQ6Q | eBay

Find many great new & used options and get the best deals for Denso 410622-0631 Axis Robot Servo Motor MSM5AZQ6Q at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[matthewsx]

Magnet building project?

 

[strantor]

Would something like this be close enough, maybe swap out the magnet inside or a bigger part of the motor?

Denso 410622-0631 Axis Robot Servo Motor MSM5AZQ6Q | eBay

Find many great new & used options and get the best deals for Denso 410622-0631 Axis Robot Servo Motor MSM5AZQ6Q at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Yeah, actually. I think all the critical aspects of that motor you found are the same as what he needs. The 2nd half of the part number is different but that's probably to do with the encoder and any other custom options. I bet the rotor out of the eBay motor can replace the damaged rotor no problem.