Electric actuator with multi-start Acme screw
Electric actuator with multi-start Acme screw
(OP)
I am working on an electric actuation standard for my company (we make gate valves). I have found a lot of info on the web about Acme power screws, which are what we use in our actuators, but there's one thing I can't seem to find: a discussion about the availability/practicality of using multi-start screws. I am aware of the mathematical relationship between lead, torque, speed, etc, but I wonder whether it makes sense to recommend anything more than, say, a two-start screw. Even though a three- or four-start screw might make sense theoretically, I wonder if such screws are readily available at a decent cost, or if there are other reasons to avoid specifying them. Any insights? Thanks.





RE: Electric actuator with multi-start Acme screw
RE: Electric actuator with multi-start Acme screw
Mike Halloran
Pembroke Pines, FL, USA
RE: Electric actuator with multi-start Acme screw
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If we learn from our mistakes I'm getting a great education!
RE: Electric actuator with multi-start Acme screw
RE: Electric actuator with multi-start Acme screw
RE: Electric actuator with multi-start Acme screw
dlee83,
it might be interesting for you to have a look at how a world-wide European company solves this problem, several electronically controlled versions and options available.
http://www.auma.com/cms/auma/en/
RE: Electric actuator with multi-start Acme screw
0.079 >= X
X = Lead/(PI * Mean Thread Diameter): this is the tangent thread helix angle
Lead: for example if you have a 3 lead thread and a 1/4 Pitch the lead = 0.75"
PI = 3.14...
MTD: (Nominal Thread O.D. - 1/2 Pitch) : 2.5" diameter thread with a 1/4 pitch would be 2.375"
so for our above example (0.75/PI*2.375) = .100 so this thread would not be self locking
The coef. of friction of 0.079 is the conservative portion (the value came from a motor manufacture) since when calculating the stem torque we typically use a value of 0.2
Ref: "Mechanical Engineering Design" 2nd Edition PP295-299
RE: Electric actuator with multi-start Acme screw