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Worm/Crossed Helical Gear Binding

Worm/Crossed Helical Gear Binding

Worm/Crossed Helical Gear Binding

Hi Folks, I have designed a small DC motor driven actuator that simply arcs a lever back and forth over a 10 mm arc. The system consists of a 1 start worm, and a 28 tooth helical gear. This lever has physical stops at both ends of travel. On occasion when the lever hits one of the stops, I experience bind between the gears and the system locks up. I need this system to actuate rather quickly, so cannot slow it down.

Is there any advice that anyone has to prevent a bind condition in a system like this? Would a 2 or 3 start worm prevent this?

RE: Worm/Crossed Helical Gear Binding

What is the lead angle of the worm? Too low and the gearset is self-locking. You should still be able to drive it with the motor though. Maybe there is a locked-in load (preload) when banged against the stop.

RE: Worm/Crossed Helical Gear Binding

So several questions.
Quality level
Correct contact pattern.
Mounting precision quality
Lube type.
Would a worm gear been better than a
Helical gear.

RE: Worm/Crossed Helical Gear Binding

Thank you both for your interest. Currently it is a prototype so quality is not so good. Contact ratio is 2.0. Geometry is from a very expensive software tool. I would not expect this to be so sensitive.
The intention however is to produce this by injection molding, so will live with a cross helical gear arrangement.

My concern is not about backdrive.

It seems to me the binding only occurs when I have inertia. The system gains speed, hits a wall, and gets stuck. When the system is already against the wall and full power is applied, it does not get stuck.

So I am looking to understand what I can do to reduce or eliminate this, knowing I cannot slow the system down.. is there some theory I should apply to the design to balance inertia? Or is there some design rule for building a system like this?

Thanks again!

RE: Worm/Crossed Helical Gear Binding

Well contact ratio is good but that is not the same as contact pattern.
What is the gear material?

It doesn't matter if it is an expensive software. If the quality of workman ship is poor.
If the gear set has poor contact pattern.
(Profile of teeth having at least 80% contact on the profiles and is central.
The correct back lash is also critical.
Not enough and it will bind.
The shock or jolt of impact is not good for gears. Might want to rethink the design.
Some type of spring to absorb the shock.
If this is a propriety design.
Then you may need to hire a pro.
Get an NDA. To protect your design.

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