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Manual tube bending speed control

MikRIn

Plastic
Joined
May 11, 2021
I have a manual tube bending operation at my shop. We have extreme inconsistencies in the material alone, (Hast X) as far as the tube wall thickness and material hardness. Unfortunately this program is set to be removed from the OEM program and only be an overhauled item in the next 2 yrs, which means we cannot spend big money on a customized machine.

So my problem is, we want to be able to bend these parts a little more consistently. Each operator produces a slightly different bend which causes great issues at the next operation.

The fact that it is a manual operation, based on the principles of rotary draw, how can I control the speed of the bend? We have a long handle that wraps the tube around a die, then we hold it for a few seconds and release. Speed of the bend and pressure are the critical components to the quality and precision of the bend. (Adding a picture. Cannot show picture of actual fixture or part due to government regulations and company policy)

Tube Bend.jpg

I have thought of a flow control valve on a rotary actuator, but not 100% knowing what I am looking at.

Any help on this would be great.
 

gary-sc

Aluminum
Joined
Aug 20, 2010
Location
Santa Cruz, CA USA
Maybe something similar to the handle on a manual cold saw that has a spring in it to limit the amount of force, which I think should correlate the the speed of bend?

Big problem is the inconstancy of material, we see changes all the time on orders from the same supplier. A fixed limiting device won't compensate for material variations, that all comes down to the skill level of the operator as does speed of bend,
 

Strostkovy

Stainless
Joined
Oct 29, 2017
For sheet metal and plate I have found that the speed of the bend doesn't matter at all, as long as you can stop at the same position every time. On cheap manual tools the pressure you apply against the stop often has a significant effect on the position the dies stop at.

EDIT: I have seen dwell time matter when there is a lack of rigidity, such as bending thick aluminum plate using urethane die film
 

johfoster

Cast Iron
Joined
Dec 15, 2016
I don't understand the diagram you added at all, and if I did maybe I would have different thoughts on it. More important to me is the consistency of the pull through. One employee can pull the bend straight through all the way vs. another needs to stop halfway and reposition their grip or something. In my experience material consistency is the problem in all repeat bending jobs. It doesn't even have to be a big difference to throw out the window whatever you used for the last run. I would think you could dial in the process with 1-3 scrap bends at the beginning of each new batch of material.
 








 
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