SO3 Z-axis spring alternative

discussion of design changes / improvements / suggestions
WillAdams
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SO3 Z-axis spring alternative

Post by WillAdams » Fri Sep 18, 2015 10:39 am

Turns out they make stepper motors w/ integrated brakes:

http://www.automation4less.com/servobrake.htm
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AnonymousPerson
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Re: SO3 Z-axis spring alternative

Post by AnonymousPerson » Fri Sep 18, 2015 12:50 pm

US $195 each. Ouch. ;)
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twforeman
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Re: SO3 Z-axis spring alternative

Post by twforeman » Fri Sep 18, 2015 1:03 pm

Interesting. That's not actually a motor, it's just a brake unit you bolt onto the front of the motor. And you have to energize it separately so you'd need some control circuitry.
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WillAdams
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Re: SO3 Z-axis spring alternative

Post by WillAdams » Fri Sep 18, 2015 1:23 pm

OIC.

Well, that explains why it wasn't standard on the SO3.
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veng1
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Re: SO3 Z-axis spring alternative

Post by veng1 » Fri Sep 18, 2015 4:29 pm

When I looked at these I couldn't see what they would improve at any price. As Tim said, the brake requires power and if the power fails, the spindle still drops into the work.

So far, nobody has had a suggestion that works well when the power fails and improves on the current spring.

CastIrony
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Re: SO3 Z-axis spring alternative

Post by CastIrony » Fri Sep 18, 2015 4:53 pm

Does anyone have specs on the current spring, so we could find one that will still fit but be slightly stronger?
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edwardrford
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Re: SO3 Z-axis spring alternative

Post by edwardrford » Fri Sep 18, 2015 4:56 pm

All

I'm working on this - somewhere along the line there was a disconnect between the springs that I originally speced for the machine and the springs that are being delivered.

I'll have some definitive information to share by Monday afternoon and will report back here.

-Edward
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cvoinescu
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Re: SO3 Z-axis spring alternative

Post by cvoinescu » Fri Sep 18, 2015 4:57 pm

Aren't the brakes normally-applied? So that if the power fails, they clamp on, like the ones they use for elevators?
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veng1
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Re: SO3 Z-axis spring alternative

Post by veng1 » Fri Sep 18, 2015 5:22 pm

Not the ones I could find. I had the same thought when wondering about both a heavier spindle and increasing speed. They may exist or maybe we need to design our own.

I have been doodling a spring clamp held open by a solenoid but seems either complicated, increases the distance the spindle is away from the V-wheels or wears the belt.

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Re: SO3 Z-axis spring alternative

Post by cvoinescu » Fri Sep 18, 2015 6:12 pm

I'd go with a belt-driven screw with a healthy lead, rather than fuss with brakes. Tr 8 x 8 (P2) seems ideal: it's inexpensive, and it has 8 mm of travel per turn, which is only five times slower than belt drive with the stock pulleys. Except it's not, because it has five times the mechanical advantage, so you can keep almost the same acceleration (almost, because rotor inertia stays the same). Tr 10 x 12 (P3) is even better (12 mm lead), but costs double and there may not be room for the larger nut.
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