Synchronizing 2 asynchron motor

Products from the molding machine are dropped on to conveyer and the motion is synchronized by two gear now. This can damage the molding machine if a foreign object go into the the molding machine. Molding machine will not stop because the motor can not detect any "torque-increase" due to large torque at the conveyer.

We plan to seperate the molding machine motor from the conveyer motor and need synchronizing both asynchron motors. 1 or 1/2 Hp for the molding machine and 5 Hp for the conveyer (Now a 5Hp motor drive both the molding machine and the conveyer).

Anybody can help?

Darius
[email protected]

It sounds as if you want to index the conveyor every cycle. That is, just run the conveyor briefly once each time the moulding machine closes up. You can do this via a variable speed drive which supports indexing (this gives you ramp up and ramp down), or just closing and opening a contactor (which can be harder on the contactor and motor).

Isn't this what the system is *already* doing though? I'm assuming the motor on the injection moulding machine (IMM) just runs to open or close the machine (via a cam drive) and stops when the machine is closed up. If it is, then you are just looking at duplicating the existing control hardware (in a smaller size) for the new motor.

Something that sounds a bit odd though is that the IMM needs a 1/2 or 1 HP motor, while the conveyor needs a 5 HP motor. Unless you have a very long cooling conveyor with a small IMM, then either I do not understand your description or there is some information missing.

What I have seen people more commonly do is to not try to coordinate the IMM with the cooling conveyor. They just run the conveyor continuously very slowly and adjust the conveyor speed to be a bit faster than the machine (so subsequent parts don't get dropped on previous ones). If the machine is running all the time (which it should be), then there is no difference between indexing and continuous running. If the IMM stops, then you have some empty gaps on the conveyor (as it keeps running), but that doesn't normally make any difference.

Thank you for your information. It is not injection molding, but pulp molding machine. We have 300m conveyer for drying the products.

The machine is not index but run continuously. The conveyer has hundreds of trays and the products must be put exactly on the middle of the tray continuously.

For details of the process, you may see http://www.emeryinternational.com/videos/54video.html
Any other suggestion?

Hello,

If the forming machine and the tray conveyer are not synchronized every time, not only will the products drop out the tray, but the machine will also clash the tray.

Especially when at startup, either the machine or the conveyer must run first to find the safe position for not having collisions, then both the machine and conveyer may run synchronously together.

I see that I had an incorrect impression of your process. It sounds as if what you want is similar to an electronic gearing application. Electronic gearing is using electronic controls to coordinate two or more motors in a manner as to give the effect of being joined by a shaft and gearbox. I would suggest talking to someone in your area who sells motion control (servo systems) about your application. Electronic gearing is a feature built into many drives, as this is a common requirement.

I would bite the bullet here and use servo motors. If you can time the servos to your machine with a digital IO line or an encoder signal you are much better off. With servos you can torque limit, but more useful is fatal following error which can detect a jam and kill your motor rather quickly if something goes wrong. This all depends on the failure mode of what breaks and what you have for gearing, etc, but with a servo you definitely have more control.

~Ken

Have you heard of Contrex/Fenner? They make synchronizing controls that will work with any variable speed drives that have an analog input. Their controls are pre-programmed for the application, you just setup the parameters. I used them years ago and they work well.

http://www.contrexinc.com/

Bill

Michael,

Correct. What I need is electronic gearing, but instead of servo motor, I plan to use asynchron motor, which is cheaper. I cannot find anybody in my area that supplies this system. Maybe they have the products but they do not really understand the ability of the products. Do you have any idea which inverter from Schneider, Siemens, Omron, Toshiba or Mitshubishi provides this function?

Darius

I will contact contrexinc. My only worry is the technical support at our region.

May be asynchron motor at the conveyer and servo at the molding machine is a good idea.

Any other solution?

A vector drive with electronic gearing might be able to do this. I don't want to recommend a particular brand though. Hitachi has a vector drive with electronic gearing. I would suspect that all of the companies you have named have something equivalent. I would suggest that you pick out a couple of your favourite vendors and take this up with their applications people.

I haven't tried anything like this with a vector drive. I also don't know the details of the characteristics of the load. I don't know therefore if you would get good enough control from a vector drive for this.

That function is available from many VFD suppliers. Yaskawa and Siemens come to my mind. The feature is often named "electronic line shaft" because it is used to synchronize two machines. For Yaskawa drives (G5 and F7 at least), a firmware change is required.