Gripper force calculation

Hello - I'm want to build a small ball gripper system to create a quick-connect torque transfer (maximum 1Nm at this point, so very small). I'm leaning towards using a ball gripper type as I believe it's easier than a finger type to build and will be strong enough for my application.

I'm trying to figure out how to calculate what size taper (diameter and angle) I should take and what pulling force will be required to create the torque coupling without slipping.

Have no idea where to start from - as most ATC build I see here start from a known taper and then probably reverse engineer the pulling force needed to keep things from slipping. I'm trying the opposite route of knowing the torque I want to transmit without slipping and how small I can do the coupling. Ideally I'd be able to use standard steel without hardening so I can manufacture it myself?

Thanks for any pointers and insights.

I have similar stuff for an proxxon mf70 why dont buy it Look at usovo in germany and no i have no link with them ;)-

Hi - thanks for your link. I found Usovo all right. However they are designed for Proxxon / Dremel tools.

My application is slightly different, I'm trying to couple a stepper motor so I can control different (slow-moving) tools like 3D print-extruders. As such I'm looking for much smaller footprint, which I thought possible due to the much reduced torque.

Gripper and 3d print i dont get the context Even i use both ...

Let me add some context - this will hopfully unlock imagination :)

Currently all 3D printers use one nozzle (with one polymer, but also one nozzle size). There are several designs out there with dual extruders, but they all have issues - not least because one way or another you either have the second nozzle at the exact same height (and wiping over the shape being printed) or you need a quite complex mechanism to tilt / retract the nozzle precisely out of the way (all having to be both precise and accurate).

My idea was could we not leverage the technology we use in CNC mills, as in exchangeable tools and apply that to 3D printers: simply have several direct extruders / nozzles available to the machine in a parking position and the system would pick one, connect the stepper drive to the extruder mechanism (to save weight and complexity: one stepper motor on the carriage, connecting to the all extruders through the quick-connect).

While you would have to manage or accept more switching time, and how to keep the extruder warm / not oozing separately, the big advantage would be limitless possibilities of colors / polymers, but also speed: large nozzle for inside and fine nozzle for details / outside...

Before all this is possible though, I just hoped somebody could help me design the quick-connect to both locate and transmit the steps from the stepper in a small package...

Looking forward to your suggestions!

Context helps. Why build a gripper at all? How about a 1/4 hex screw driver bit and a magnetic socket. The stepper might have to turn up to 60 degrees to line up, but that shouldn't be too hard. Is a bit of backlash a problem in an extruder?

Thanks Vegipete - I think we could compensate for a little backlash indeed. In between moves the extruder often executes a 'retract' move, briefly turning opposite of the driving direction to back off the extrusion. But having just played with an extruder where I introduced a little bit of backlash it seems to work.

A separate reason I thought of a couple was to be able to use the coupling as a positional reference point - I need to get my head around how I can ensure the extruder head is located properly and repeatably every time. Right now I think about magnets and two conical locating pins... More testing to do :)