Indexing table master-slave vfd

[low_on_the_pole]

Greetings,
We have an osa-lator 90 degree indexing table in a robotic mig and spot welding cell that has been taking teeth out of the gears on the motors and main bull gear. It has two-3/4 hp euro-drive motors situated 180 degrees from each other on main bull gear. Motors have brakes on them and forward-reversing contactors.
The fixtures on table are probaly well over 1.5 times rated capacity. Old platform ran out went from welding rocker panels to
door sub-assemblys. Enginering failed to look at new fixture weight.
My supervisors boss came to me and said he has the fix. Told me to order 2 accell and decell current limiting relays for motors. I said ok right away monday morning.
My thought was to order A/B powerflex drives in a master slave combination. To expensive. Could I get away with just one drive if sized big enough for both motors? Really the cost saving isn't that much but unable to locate accell and decell relays.

 

[leitmotif]

has been taking teeth out of the gears on the motors and main bull gear.
The fixtures on table are probaly well over 1.5 times rated capacity.
It has two-3/4 hp euro-drive motors situated 180 degrees from each other on main bull gear. Motors have brakes on them and forward-reversing contactors.
The fixtures on table are probaly well over 1.5 times rated capacity.
Enginering failed to look at new fixture weight. QUOTE]

OK so you have overloaded by a factor of 1.5 or more.
It appears to me that you do not need electrical controls
BUT
you neeed a larger gearbox that will be able to handle the increased load.
OR you need to look at lubrication of your gearbox.
OR you need to reduce the load

Dan Bentler

 

[OkiePC]

Yes, you can run two motors with one drive. RTM for the drive you have selected. Usually they recommend individual overload relays between drive and motors, since you will set the drive full load amps high enough to fry one motor if the other one is disconnected.

Are the motors being started at full voltage?

If so, then putting a softer accel rate (by installing a VFD or two) will help with acceleration.

Deceleration can be accomplished too with a VFD, but having brake motors means you will need to ramp down to a slower speed before the brake is engaged. This could add more time and materials to the project depending on how you are controlling the table position currently.

What kind of control and feedback are you using to position the table now?

 

[low_on_the_pole]

The accell and decell are built into the table through their arrangement of cam followers. Thats why I was thinking of installing vfd, sounds like 2 would be better. The only control are proxes for sensing position once proxes are made cam followers take up tthe decell. And there is no feed back such as encoders. Their is talk of larger gearboxes. If i install 2 vfd what would be the best protocol between vfds?