Help needed with an unusual stepper motor coupling

Community General Discussions
1

 

Hello all.

I'm completely new to your world and am building a kind of robot that's a bit out of your usual line - this robot makes vodka!

Seriously, I'm an experienced amateur distiller in New Zealand - where home distilling is perfectly legal.  I build my own stills as well as use them.

My latest project is to build a completely electronically controlled vodka still of the kind available to major distilleries ( at huge cost ) on a hobbyist budget.

I can handle the electronics on an arduino, the welding in my shed and have worked out how to sidestep the expense of multiple accurate temperature & pressure sensors.

But I just can't find a simple coupling to join a stepper motor to a needle valve and I'm hoping that someone here is clever enough to work out a practical, durable, sensibly sized & inexpensive solution.  Some custom machining is almost certain to needed at the valve end of the coupling and that's fine.

The problem is that the gap between the end of the stepper motor drive shaft & the top end of the valve stem is not constant:

as the stepper motor turns the valve stem to open the valve, the top of the valve stem rises towards the stepper motor and visa versa.  So the gap is constantly changing as the motor adjusts the valve.

The axial travel that I need to accomodate is at least 2mm and perhaps as much as 5mm.  I will not know until we start determining the valve travel needed by experimentation.

I know it can be done because there's a commercially available unit - at insane cost and using inappropriate valves for my application.  But the picture shows exactly what I want to do.

Any brilliant ideas to help me would be hugely appreciated.

 

stepper_valve-1.jpg

 

 

 

2

Other way arround?

Maybe it’s an idea to mount your stepper so it can move freely up and down, but not turn arround?

Here a picture that I’ve seen earlier before. It came accros my mind when I was reading your question. Here you see a motor used to close a water valve. The metal plate is attached to the motor housing but NOT to the wood.

rb35_waterkraan.jpg

(Picture from picbasic.nl)

 

 

3

Idea

Sounds like you need some type of telescoping coupling, maybe something with splines that will slide in and out of a larger one. You could also just use a dremel tool to cut verticle slots in the sides of the coupling nut and then insert something like a roll pin to turn the actual valve. That would give you the vertical travel you need but would be easy to take apart for repairs or adjustment.

 

Just my $.02, your milage may vary.

4

Idea 2.0

Hadn’t seen your picture originally, You should be able to spring mount your motor mount or use slides to mount your motor so it had some travel. Here’s another thought, if you used a screw drive linear actuator type arrangement, the coupling nut would move up and down the same amount as the valve stem if you used a screw with the same thread as the valve.

5

Something like the hex axles

Something like the hex axles that comes with the tamiya track and wheel set.

 

Maybe you can fabricate something with an hex key and a bit holder piece?