Lead Screw - Jam Condition
Lead Screw - Jam Condition
(OP)
I have a 1/4 x 16 Acme thread (1/16" lead) .... if an acme nut on this rod hits a stop, the nut will jam and lock against the stop.
I have a 1/4 X 1" Lead Screw (1" lead) ... if a leadscrew nut on this rod hits a stop, the nut does not jam or lock against the stop.
My question is, what is the minimum lead/angle/pitch that will not easily jam or lock up?
Short of experimentation and a lot of prototyping, I am hoping someone here can make a general statement on the subject or perhaps state a rule of thumb.
Thanks,
Glenn





RE: Lead Screw - Jam Condition
Have a look at this link and towards the end there is a graph relating to self locking and friction coefficient, lead screw angle.
http://www-mdp.eng.cam.ac.uk/web/library/enginfo/t...
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: Lead Screw - Jam Condition
Cheers
Greg Locock
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RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
Just to clarify the application a little... on the motorized lead screw shaft is a fixed collar/stop. The lead screw nut is permitted to travel axially until it hits the collar/stop at which point it stalls the motor. I don't want the lead screw nut to be able to jam against the stop/collar and I'm sure this will require a high helix. Self holding and backdriving the system are not concerns.
Thanks,
-Glenn
RE: Lead Screw - Jam Condition
"The lead screw nut is permitted to travel axially until it hits the collar/stop at which point it stalls the motor."
"I don't want the lead screw nut to be able to jam against the stop/collar and I'm sure this will require a high helix."
I don't think the helix angle does diddly in this case - if you don't want the lead screw nut to jam on the stop collar, then
A) remove the stop collar, or
2) don't keep turning the screw when the nut approaches the stop, or
iii) put a torque-limiting clutch between the motor and the shaft, or
7) use a ball screw shaft/nut combo., with an overrunning or freewheeling capability.
RE: Lead Screw - Jam Condition
The 1/4" x 1" lead screw I have here is of such a high pitch that there is no way that the nut would jam (and lock) up against the collar. I need to find the lower pitch limit for a non-jamming condition.
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
The leadscrew is a mild steel.
The nut is acetal.
Thanks,
Glenn
RE: Lead Screw - Jam Condition
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
RE: Lead Screw - Jam Condition
RE: Lead Screw - Jam Condition
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
There is also usually a significant difference between static and dynamic frictions. Static (breakaway) friction coefficients are usually much higher than dynamic (sliding) friction coefficients.
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
Some other 1/4 leads I can choose from include .333", .500", and 1.00" leads. I know the 1.00" lead will not jam. I have some .333" lead on the way to test next. I might have that as soon as today.
Thanks,
Glenn
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lead Screw - Jam Condition
Thanks for all the input.
-Glenn
RE: Lead Screw - Jam Condition
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.