Re: suggestions for router lead

Graham,

I have used 1/2 or 3/8 diameter, 10tpi, 2 start for machines of this
type. Using a 297/298 type bipolar chopper driver and a 34vDC power
supply, the top speed is about 100IPM. Using 1/2 stepping drivers,
the resolution is .0005, which is adequate for most tasks, and until
fairly recently was the single most common resolution for cnc systems.

The steppers were in the 150 oz./in. range: I have used both size 23
and 34 motors with this setup and gotten similar results. The spindle
tool was a woodworking laminate trimmer.

The nuts were Turcite, which is a brand of acetal plastic.

I have used both Ball Screws and Actuators, and Kerk, as suppliers
with good success. IME, the Kerk nut design is better; but the BSA
nut is more "available" on short notice. I have described how to
make "do-it-yourself" anti-backlash nuts in messages in the archive
of this group.

Hope this helps,

Ballendo

P.S. Your message suggests that you may be considering the axis which
moves the table to be a Y axis, when it is properly called the X axis
in a bridge design as you have described. Several internet websites
continue to mislabel machine axes, with resulting confusion for
everyone.

P.P.S. One such site is the super-tech site, which may be of interest
as their minirobo design may be similar to what you have in mind.
Have a look, but beware of their axis labeling<G>

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler <eexgs@n...>"
<eexgs@n...> wrote:

> I am trying to design a small CNC router based around a Dremel or
> similar. I have decided upon a fixed bridge design with Y axis on
> the bed and X,Z on the bridge. I thought that this would give me a
> nice stiff machine and maximise the force available from the Y
> stepper.
>
> Anyway, I'm looking into leadscrews. I am considering acme screws
> with Delrin nuts but am having a hard time deciding on the lead I
> should go for. Obviously more lead gives greater speed but
> resolution suffers.
>
> I want a reasonable swift machine that will do some basic pcb
> milling, ply part cutting and mould making. The design is based on
> an A4 paper sized bed and is designed to be sturdy as I intend to

use

> quite a lot of 1/2" ali in the construction. Steppers a 200 step
> bipolars.
>
> Cheers,
>
> Graham Stabler
> Nottingham, England.