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Will this DC motor control work?

Greetings All, I have been trying all sorts of designs out in my head for controlling wire feed speed. The goal is to have a push-pull wire feed system in a small MIG welder. The pulling wheels should try to spin just a little faster than the push wheels to keep the wire taught. I'm thinking about 5% difference but with a slip clutch on the pull wheel. The slip clutch will be adjusted so that it slips before the wheel slips on the wire. I have built and tested the clutch and it works well. My latest plan is to use wheels spinning at identical speeds with the pulling wheels being 5% larger in diameter. To keep the wheels spinning the same a tach would be driven by the idler push wheel and the output used to control the pull driver wheel. By using the push idler wheel as the speed reference even if the push drive wheel slips on the wire the idler wheel should not slip. I think I've got the mechanical part figured out. However, does this sound like a good plan electronically? Thanks, Eric R Snow

Reply to
Eric R Snow
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Belt or gear drive both wheels from a single motor. Forget the electronics - not needed if you do that.

Ed

Reply to
ehsjr

Hi, Eric. It sounds like you want one motor to pull the wire off the spool, and another to push the wire into the feed.

Of course, the slip clutch is a good idea to keep tension on the wire. But, instead of trying to coordinate the speeds of the two motors directly, how about having a caternary loop between the two motors, a dancer arm between riding on the loop to evaluate slack, and a microswitch attached to the dancer arm to turn the despooling motor on and off? If you put a small nylon pulley on the dancer arm, the dancer arm pulley can ride easily on the wire.

I've seen this type of control method for material feeding done well in many applications.

Good luck Chris

Reply to
Chris

Greetings Chris and ED, Thanks for the replies. Unfortunately neither suggestion will work. This is because the wire spool and push wheels are inside the welder. The wire is fed into a 10' long cable. The cable carries the wire, the welding current, and the shielding gas. The cable terminates in a handle, called the "GUN", which holds the trigger and from which the welding wire exits. The pull wheels will be mounted in a modified handle. This type of setup is common in some larger MIG welders. But no push-pull setups are available for my small MIG welder. This is why the electronics seem to be the best way to go. ERS

Reply to
Eric R Snow

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