Sure, but all you have to do is limit your working area to avoid the center
pivot. Step size is smaller near the pivot and larger away from it, but with
a nice linear microsteppng controller and some drive reduction (see the
pictures) neither extreme should be a problem. The calculations required to
convert x,y into polar are not terribly difficult, and the cost of the unit
goes WAY down because only a couple of components need to be precision.
Next objection? <GRIN>
Now back to those nuts... Did you measure the slop before and after
tightening? And did the friction increase?
---
James Newton, massmind.org Knowledge Archiver
james@... 1-619-652-0593 fax:1-208-279-8767
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Message: 10
Date: Wed, 16 Jun 2004 11:02:26 -0000
From: "ballendo" <
ballendo@...>
Subject: Re: Turcite nuts, was: bit cleaning while drilling PCBsf
James,
Didn't see the link yet, but usually you trade one source of error
for another. The probnlem with rotary-used-linear machines is that as
the distance from the pivot changes so does the mech.
advantage, "step" size, etc. And trying to make a linear move near
one of the pivots requires a nearly instantaneous change in direction
and requires acceleration far in excess of what most inexpensive
drives can achieve...
There's more, but these are the bigge's
Ballendo
In Homebrew_PCBs, "James Newtons Massmind" wrote:
>As far as "error components" goes, has anyone looked at reducing the
>number of joints required as a means of reducing error? And
interesting idea is that of using only two joints in a radial system
rather than the 4 or more required in a linear system.
> http://www.massmind.org/techref/idea/lccam.htm scroll down
> http://freeandeasy.sourceforge.net/ at the end of the paragraph
about
> "prototype XY table"
> http://freeandeasy.sourceforge.net/rotary.php
>
> Roller-skate bearings top and bottom on the main shaft were sloppy
(as
> expected) but when they are pressed towards each other, the
compression
> takes all the slop out and the result is very good. It reminded me
of what
> you were doing, but I don't think it is really the same.
>