Gearing down a motor for linear motion?

What is the pitch of the screw it’s turning?

That link you gave shows one with a 3/8”-24 thread. Take the 8000 RPM, pass it through the 9.5:1 box, and you’ll get a hair over 842 RPM.

8000 / 9.5 = 842.105…

Turning a nut in a 24 thread-per-inch (like a 3/8”-24) screw will get you 1” per 24 revolutions.

That particular model will move at just over 35”/minute

842 / 24 = 35.087

That’s ~891mm/min, which is ~14.8mm/second.

35.087” * 25.4mm/” = 891.2098mm per minute

891.2098 / 60 = 14.853… mm per second

Using the 19:1 instead of the 9.5:1 will halve the output RPM to ~421 RPM and halve all the speeds, but still be far faster than you want.

As for what gear ratio, that really depends on the pitch of the screw and the RPM of the drive motor.

And lastly, suppliers…. I don’t think there are any off the shelf that slow. If you want something at 0.1mm/second, you’re wanting something REALLY slow, probably a custom job. I can say that the higher the weight limit, the slower they will go; they mostly use the same motor, but the higher weight-limit ones trade speed for force. Still, the slowest I’ve seen so far is 0.16”(~4mm)/second for one with a 1500-pound max and a 52:1 gearbox. With the same pitch screw and motor RPM, you would need a gear ratio closer to 2000:1…. or a 40:1 feeding a 50:1 (40*50=2000) if you wanted to keep size manageable.

What you need is a stepper motor which is kind of the same, but adds controls that regulate it’s speed and travel better than a simple linear motor…. though at increased cost. At the very least, you need more than simple “on/off” unless you are going to go the custom route that will likely involve a two-stage gearbox.

Or, since the current gearing is still resulting in a movement of about 14 times too fast…

Can you not add a 1:14 gear to be added in line to the one you have?

@whitenoise That depends on the construction of the actuator, but odds are that that would be a custom job as it’s not quite so simple to find a gearbox of the desired ratio, and it’s even harder to make one, assuming it’s even possible. If it’s like this , you’re out of luck, but if it’s like this then you may be able to do something. There really is no changing the “gearing” of a ball screw; any changes in gearing have to happen “upstream”.

That said, it’s possible to rig it up on the output end with a lever arm arrangement that would reduce speed by a factor of 14… but that would also reduce the stroke to 1/14th of it’s original value. Depending on how much travel you need, it may or may not be feasible to go that route.