VFD, Motor or Mechanical ?

[wdd0422]

Hi everybody, looking for some advice here. We have a Toshiba molding machine with a rotary platen. Its kind of a prototype machine, there's only one more in the states from what I'm told. We have had some problems with it, we keep getting errors on the screen for The following;


ROT: Speed Error
ROT: Over Torque
Rotary servo speed error occurs


They are intermittent. The servo drive, encoder cable and motor have been replaced, service has been here for 5 days and can't figure it out. They are telling me the next step is to replace the motor that they just replaced in October of last year. Its a $8k motor but more importantly we need the machine to run. Nameplate FLA is 9.1. I separated the motor from the gearbox and had them rotate it in both directions and it was pulling 1/2 an amp steady. Reconnected the motor to the gearbox and rotated in both directions and the inrush was about 8.5 and it ran at about 5 amps steady. Reconnected it to the Platen and rotated it in both directions the inrush was about 12 and it ran at about 7.5 amps steady. These numbers seem fine to me and I feel changing the motor is not going to help.


The machine ran all weekend and shut down occasionally for the above mentioned errors but it has a smaller mold it. The heavier mold is going back in today and this is the one that we cant run because it errors out too frequently.


If anyone has any advice or recommendations on how to proceed with troubleshooting I would greatly appreciate it as we are getting to the point where we are going to be causing problems for our customer if we don't get this sorted out. I am going to attach a screen shot of the errors and Motor nameplate date.


Thanks to all
Bill

 

[Steve Bailey]

It seems to me that simply connecting to the gearbox produces an unusually high load. You're at more than fifty percent of full load current just to turn the gearbox.

Is there additional loading when you start running product? Drawing 82 percent of full load current when not running product sounds suspicious.

 

[drbitboy]

Smaller mold runs at 80% of the amp rating as a test and has rare trips; heavier mold has frequent trips?

Both KT and empirical analysis would seem to suggest either the load (gearbox + heavy mold) is the problem with the current motor capacity, or vice versa.


I'm with @SteveB about the gearbox.

 

[saultgeorge]

Hi, I would try turning the gearbox by hand and then the platen by hand and then the gearbox and platen coupled. Something is binding or has a brake that is not releasing.

 

[wdd0422]

Thanks for the replies everyone, I did suggest to them that since this is a prototype machine is it possible that the motor and gearbox are undersized. The GB seams fine when turned by hand but I did find when I had everything uncoupled that the GB was dry or nearly dry however filling it did not change anything when I rechecked the amperage. The platen could be the problem, it might be all gunked up in the gearing.Its not making noise at all. Its probably the next logical step though. I haven't insisted they do that yet because one, they probably aren't going to have the parts and they keep telling me they don't know anything about it. Also since the GB pulls higher amps uncoupled and it only runs a couple amps higher with the platen coupled I have held off because pulling the platen is defiantly going to be a lot more downtime that we cant afford right now especially if we have to wait for parts.



Thanks again everyone for the help