Looking for ideas: Tension controll on roll of film

I am making a ghetto roll laminator. I have an apache pouch laminator that i made a set of 4 arms for, which hold 2x 12mm shafts that 2 rolls of laminating film are sitting on. The rolls have 1" core, and i am thinking of using linear motion bushings as roll inserts: Uxcell a12102600ux0463 LMF12LUU 12mm x 21mm x 57mm Bushings (already have in hand). I'll have to build up the bushings OD to match roller ID. What i am looking for are suggestions to add tension control to tension the film as laminator pulls it in. A ghetto way of doing it would be 2 shaft collars on each shaft with a spring between one shaft collar and one of the bushings. The problem i have with this approach is that tension would be controlled by position of the shaft collar next to the spring; which would be hard to fine tune. I am looking for ideas on making some sort of mechanism that lets me essentially turn a knob/nut or a screw that adjust tension and keeps its position.

Any ideas would be appreciated.

pcm81 said:

...A ghetto way of doing it would be 2 shaft collars on each shaft with a spring between one shaft collar and one of the bushings. The problem i have with this approach is that tension would be controlled by position of the shaft collar next to the spring; which would be hard to fine tune. I am looking for ideas on making some sort of mechanism that lets me essentially turn a knob/nut or a screw that adjust tension and keeps its position.

Click to expand...

Thread one end of the shaft and one collar. Then just turn the collar to adjust.

guest said:

Thread one end of the shaft and one collar. Then just turn the collar to adjust.

Click to expand...

I'll try, but not sure i can thread it. It's a linear motion shaft, so probably case hardened steel... i don’t have a lathe or power threader. Not sure if elbow grease alone can cut it.
Do they make something like clamp on threads or similar?

You may have problems cutting a case hardened shaft with a die.

You could make a 2 piece collar- imagine a 1" bolt with a 12mm hole through the center. Cross drill it for a 10-32, slide it in place and lock with a set screw. A nut threaded on the OD would push against the spring. Stick a 12mm fender washer between the nut and the spring if needed.

I have used hystersis brakes for tension control and they're very accurate and adjustable.

Stuart

guest said:

You may have problems cutting a case hardened shaft with a die.

You could make a 2 piece collar- imagine a 1" bolt with a 12mm hole through the center. Cross drill it for a 10-32, slide it in place and lock with a set screw. A nut threaded on the OD would push against the spring. Stick a 12mm fender washer between the nut and the spring if needed.

Click to expand...

That is kind of what i am looking for, but instead of making it, would rather spend $20 and buy it. If such a thing is a standard part, any idea what it would be called?

pcm81 said:

That is kind of what i am looking for, but instead of making it, would rather spend $20 and buy it. If such a thing is a standard part, any idea what it would be called?

Click to expand...

I think you'll be re-purposing something that was meant for a different application.

You might be able to find a suitable threaded bushing as a starting point.

Threaded Template Bushings – Countersunk Type (TTB) | Carr Lane

Bushings and Inserts - Lee Valley Tools

Bellevue washers work well for providing tension on a shaft.
Another way is to add a pivot arm that presses on a brake pad or band. The force can be adjusted by positioning a weight closer or further out.

I have done that with a permanent magnet DC motor connected to a pinch roller with electronics to effectively govern the speed to zero. By building in a torque limit in the electronics, the drag will be constant regardless of speed.

Bill

9100 said:

I have done that with a permanent magnet DC motor connected to a pinch roller with electronics to effectively govern the speed to zero. By building in a torque limit in the electronics, the drag will be constant regardless of speed.

Bill

Click to expand...

That is the "proper" way. I am looking for "easy and cheap" way for this ghetto set-up. Going with shaft collar + spring for now. When i can fine a threaded pipe in pipe or hollow bolt described above i can add that between spring and collar.