Mcwire drive screw to motor connection

Hi all. I am in my final stages of building my mcwire based printer! As of now, I do not have the stepper motors connected to the leadscrews on the stages. I can't seem to find a good connection for them. On the mcwire site, the suggested connection is made using aquarium tubing. I went out and got some but I can't for the life of me use it to attach the motor to the drive system. It simply does not have enough friction to keep things from slipping. I want to know how others connected the motor to the shafts.

Did anyone use a D shaft set-screw type connector instead of relying on tubing?

As of now, I am epoxying the tubing onto the motor shaft and leadscrew, but this is not good, because I will be taking apart the stages often to align them and perform maintenance and whatnot. I'd like something that can be undone and refastened with ease (not involving glue!).

Thanks.

You are probably using too large a tubing. Go for a smaller one, dip it into boiling water for a short while to make it more flexible, and make sure you have at least 10mm on the motor shaft and the screw thread.

You can also try a cable tie pulled very tight over the tubing. If this doesnt work, take a length of 1.5 square mm copper wire (from mains twin with earth cable), wrap it round the tube+shaft twice then use some pliers to twist the ends together tightly.

Good luck!

There's some very good reasons to use a flexible coupler like the aquarium tubing. If you use a connector that doesn't flex, you'll put a great deal of extra stress on the bearings and motor.

I used fuel line tubing from the auto shop. It worked OK except for the Z stage, where it didn't grip well enough to hold the Z stage up. So I clamped it on both ends with a twist of bailing wire. Works fine, and it's still flexible enough to compensate for off-center or out-of-line mounted motors, slightly bent leadscrews, etc.

I suspect that a bit of bailing wire would fix your problem. That's true of most problems of course, but in this case I suspect it's a pretty good solution. You could use small hose clamps on the aquarium tubing instead if you wanted something more "official" looking.

Most hardware stores sell bailing wire as "tie wire" now, as it's used to tie rebar together in concrete construction.

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I'm building it with Baling Wire

The tubing comes in 4mm 5mm 6mm ~ 10mm sizes in the UK available from B&Q

I have used the 10mm and 6mm together before now to connect 6mm steppers to 10mm trapezoidal drive shaft.

To maintain a grip on the shafts just use a tie wrap over the plastic tubeing.

[en.wikipedia.org]

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Thanks for the responses. I'll try out the fuel line + bailing wire approach. I was also worried that I'd have to make the motor shaft dead center on the leadscrew, but with the tubing I feel a bit better about the relaxed constraints.

Today I bought some 1/4" fuel line and some hose clamps. I fastened them to the motor and lead-screw and it seems to be a really good connection. Thanks for the suggestion guys!

Thank you, reading your post gives me warm fuzzy feelings...

I do remember one reason NOT to attach it too firmly though. If the motor is driven beyond the endstops, the hose should be able to pull off, providing a harmless failure mode. If it is attached too firmly, you'd end up damaging something else - bending the motor mount, crushing the MDF/acrylic, ripping the trapped nut off, etc.

So either be really careful and don't make that class of mistake, or loosen the clamp a bit.

edit: spelling corrections

Edited 1 time(s). Last edit at 01/30/2010 09:53AM by jgilmore.

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I'm building it with Baling Wire