Re: how important is backlash in a simple home setup ??

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dhiren Shah" <dshah@s...>
wrote:

> Software can compensate for your backlash. It will add or subtract

number of

> steps equivalent to your error in mm every time it changes

direction.

>
> The error could be different in each of the axis.
>
> Engraving is usually tough if you have backlash problem. Imagine

engraving a

> number like 8 or a character like g. Both X and Y are changing many

times in

> engraving just one character.
>
> Dhiren Shah, Dir., Operations
> Solustan, Inc.
> 165 Chestnut St., #200, Needham, MA 02492
> PH: 781-449-7666 FAX: 781-449-7759
> WWW.SOLUSTAN.COM
> WWW.LINKMOTION.COM
>
>

The problem with using backlash compensation is that in some
controllers it negates the CV (constant velocity) setting which gives
you smooth performance on curves. As you stated, backlash varies
from one axis to another and worst, from one location on an axis to
another, meaning that the number will not be the same over the length
of an axis. That then requires a "mapping" setting (and a lot of
work) to make the backlash a lookup number depending on where you are
on the leadscrew.

If you want to do detailed work like small plaques and precison
engravings then build a precision machine with minimal backlash. On
a router you can see very small errors in detailed cuts since in most
circumstances you need to take multiple passes and any error will
show up as ridges around the parameter of the cut. You can get
around that by making a finsh cut at full depth around the parameter
but you need to plan that in your CAM part of the equation.

On a small machine as you are describing I would suggest that
anything more than .002 in backlash is excessive for doing precision
work and numbers lower than that should be your goal since the
overall accuracy of you machine is the product of all factors not
just backlash.