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Cheap screws + DC motors + encoder?

PostPosted: Wed Jan 29, 2014 6:19 pm
by tommythorn
Inspired by the "cheap printer" and "New build log" threads, I had another thought: Did I understand correctly that the expensive screws are mostly because we can't run the steppers fast enough to make it useful otherwise? Well, DC motors can be had in a much larger variety of speeds and while DC motor + encoder by themselves aren't much cheaper, the savings in screws might be enough to matter. In fact I wonder if the screw itself is reduction enough that we don't need any further gearing.

Re: Cheap screws + DC motors + encoder?

PostPosted: Wed Jan 29, 2014 6:29 pm
by Nicholas Seward
You want expensive screws for two reasons. 1) They are rated for straightness 2) speed.

To me speed is not much of an issue.

I don't know if it would save you much money in the end but it could be a much faster, smoother machine. The prices for fast travel and standard travel on this page are all about the same. http://www.mcmaster.com/#acme-precision-lead-screws/=qgpsrr The nuts are what get you. I am pretty sure we could print our own nuts and load them to reduce backlash.

Re: Cheap screws + DC motors + encoder?

PostPosted: Thu Jan 30, 2014 8:06 am
by cdsteinkuehler
Nicholas Seward wrote:The nuts are what get you. I am pretty sure we could print our own nuts and load them to reduce backlash.


Just make your own: http://bbs.homeshopmachinist.net/thread ... e-easy-way

Re: Cheap screws + DC motors + encoder?

PostPosted: Thu Jan 30, 2014 2:55 pm
by Nicholas Seward
I have the CNC router and the 3D printers. Now, I have to convince my wife that I need a lathe. :D

Re: Cheap screws + DC motors + encoder?

PostPosted: Thu Jan 30, 2014 5:06 pm
by see3d
Nicholas Seward wrote:I have the CNC router and the 3D printers. Now, I have to convince my wife that I need a lathe. :D


I looked at the thread carefully. My conclusion is that this would be a very good nut for LISA.

I don't think you need a lathe at all. You could do this with a disk sander.

Set up a wooden jig with the lead screw able to rotate between two bearings with the molded nut in between. Align it to the disk and clamp a stop in the right place for the diameter you want to end up with. Then slowly rotate the screw and move the fixture into the disk sander until it is against the stop and perfectly round. You could put a thin brass shim against the stop that you remove for the final touch up finish or to adjust the final dimension a hair.

Once you have the setup, you could make a bunch of nuts.

Re: Cheap screws + DC motors + encoder?

PostPosted: Sat Feb 08, 2014 3:00 am
by phonx
Hi seed3d;

Could you sketch out idea - a picture will explain better


Thank

Phonx