Re: [CAD_CAM_EDM_DRO] Re: Belt vs. Direct Drive

Tony Jeffree wrote:

> (snip) There shouldn't be any extra backlash if you use the stepped
> "timing
>
>belt" style of pulleys/belts(snip)
>

The real answer to this question has always been the same and its is
based off of *other* information.

What are you building ? What Accuracys and Resolutions must you maintain
? How much money do you have, and how much time do you want to spend
getting it right the first time? THAT is what you need to base your
desicion on.

To really get direct drive right, you need to do "the math" the very
first time so that it works as you intend. In actuality, not all of this
can do that including myself, and even some of the OEM builders ONLY
find out what is *Right* after making numerous prototype machines and
then using the best of the best results for the final product. Even
then, sometimes cost overruns screw that all up anyhow, but in any event
on a one shot build, If you did your math wrong, you may have to replace
a lot of components to get it work right.

This all ties in with how much money you have in the budget because in
the above case, you likely would be purchasing components new to Spec.
because the "hit and miss" surplus parts you usually find for cheap will
not always fit into that "mathmatical" device you designed.

However, with Belt drive, again, depending on what YOU are building, you
can take a hodgepodge bunch of stuff and "make" it work. If you
miscalculate something or simply "must find a way" to make that 1" lead
leadscrew work for you for at least a while, A simple belt and pulley
change and an increase in driver resolution just might help you get by.
The "swap" of those components is chump change compared to a
miscalculation on a motor or leadscrew that you bought new to spec.
So, even though there are strong feelings on both sides of the issue, It
makes a BIG difference with exactly what you are trying to do and how
much time, patience and money you have to make it work correctly. There
is no right or wrong way.

In all honesty, I have yet to see a Router or Engraver suffer because of
backlash lost in belt. If by chance I did, I'm likely to find the wrong
belt, wrong pulleys, or wrong concepts applied. Mills may be a bit
different, yet I've seen plenty of in tolerance work done on belt driven
converted mills......

In almost all machines, especially the homebrews....... Just put a dial
indicator somewhere and "Lean" on the machine. Often times there is a
lot more "Flex" in the framework, that most would agree that any
introduction of backlash in the belt is frivilous.

Of course the above is my opinion, and I am well aware of the
differences, gains, losses etc of both methods. It only comes down to
what one NEEDS.
Dont forget too, sometimes belt = quiter, direct = noisier. ( I said
sometimes !)

C