Hi - I ordered a generic linear actuator set from amazon (here) and it comes with an 8mm leadthread that has a 2mm pitch. When I used this calculator (1:1 gear ratio, 1/4 step), it says 400 steps per mm.After testing this out, I found it to be inflated, and did some back and forth testing and came to the conclusion that 325 was a much closer estimate (which would be a 2.4615mm pitch). I'm certain it's 2mm from crest to crest, so I'm really not sure where the accuracy is being lost.I'm not 100% sure that 325 is giving me a perfect mm per rev, just much closer - I would like to get perfect accuracy but I was hoping a calculation would do that for me...is it common for these things to be off?
Ahhh - good idea :}I'll do that in an hour or so and report back, sorry for being incomplete...I'm new to calibrating these things.
Did you read any of the feedback on Amazon to see how inaccurate this product is?
Your measurements seem to be correct, but you did not report measuring the stepper motor rotation to see if you can get 1 complete rotation using the 1/4 step mode.Paul
i see they have a brass threaded nut assembly on the threaded rod. Just for fun, Press the nut hard toward one end and measure the distance from the nut to the end of the rod. Now, press the nut the other way and measure the distance. A good fit will show a very small difference in length. A proper nut would be a two piece nut on the shaft. one tightened against the other in order to remove the slop in the nut threads. The faces of the nuts would be sanded or shaved down until almost all of the sloppy movement disappears and the two nuts are jammed together tightly. Your assembly, from the picture does not do this. Also, the threaded rod and the nut must have grease or oil for lubrication.Paul
The play is only a problem when starting a back and forth movement. It may be a problem when initially starting a movement. When the nut is actually driving something with some resistance to moving, the thrust bearings at the ends of the threaded rod may allow movement that is a problem. Except for ball screws, all of your bearings will allow movement.Paul
Some lead screws have multiple "starts". That affects the turns per inch. See this page.
I didn't pick up how to check to see if there were multiple starts
Just look at the end of the lead screw.https://www.quora.com/What-is-the-difference-between-a-single-start-thread-and-multi-start-threads
If you indeed do have an inch lead screw, you cannot do metric properly. Just as the lead screw in my ENCO lathe is inch and I cannot do metric threads. But my other lathe at the plant does have a metric lead screw and will easily do metric threads. Which do you want your machine to do? Metric or inch? Get a lead screw to match.Paul