Re: [CAD_CAM_EDM_DRO] Re: What the hobby CNC industries need!

Thanks I have begun converting my machine to roller ball leadscrews to take out the backlash error.  Where did you begin with software? And I am going to use a coamputer that has no parralel port have you had success with usb to par converters?


George Reynolds
greynolds@...
St Matthew School
Computer Department

--- On Thu, 3/5/09, Jon Elson <elson@...> wrote:


From: Jon Elson <elson@...>
Subject: Re: [CAD_CAM_EDM_DRO] Re: What the hobby CNC industries need!
To: CAD_CAM_EDM_DRO@yahoogroups.com
Date: Thursday, March 5, 2009, 3:23 AM






universeartman wrote:
> I agree also I have been reading however this is the only forum for this topic I am currently on. I think I get the 400 vs the 200 in oz but do not get the servo vs stepper. I am in the process of upgrading a machine for my use in Art projects and have been going very slow so as not to make any mistakes. Possibly what would really help is a list of the most common mistakes the hobby cnc people make.
>
Oh, my! This last sentence, ALONE, could take a book to answer! Maybe
the biggest fallacy that many beginners have is thinking that software
backlash compensation can let them use a machine with massively worn
Acme screws and nuts and suddenly turn out perfect parts. A worn screw
means the motor is controlling the table position with a loose linkage,
and the table is free to bounce around over the distance of the backlash.

A second common mistake is thinking you can bore a hole in a solid bar
and couple a motor to a leadscrew. There is always misalignment, and
this can put enormous radial forces on the bearings, causing all sorts
of problems. Toothed-belt drive is often the easiest way to do this,
but there are also a variety of couplings that will do the job.

Some people try to convert manual machines with rack and pinion quill
feeds to CNC. The racks have cyclical (gear tooth) errors as well as a
LOT of backlash.

And, of course, there are people who try to use insanely small motors to
drive large machines, or occasionally massive motors on small machines.
You can actually make some worst-case calculations of cutter forces, and
design your motor/drive/ leadscrew accordingly.

Jon


















[Non-text portions of this message have been removed]