wrote:
On Thu, 29 Jan 2015 16:17:36 -0600, "Terry Coombs"
wrote:

David Billington wrote:
On 29/01/15 18:18, Terry Coombs wrote:
Tim Wescott wrote:
On Wed, 28 Jan 2015 22:58:41 -0600, Terry Coombs wrote:

Got any stepper motors for cheep? I think nema 34's will work ,
I want to power the X axis and maybe the Y on my benchtop mill .
I have (or have components to build) controllers and power
supplies , can fabricate mounts and the rest in house . I
actually had an 18v HF drill motor all but mounted , using a PWM
controller and a 13.5 volt supply . At the speeds I need it
didn't have enough torque - though I may revisit that setup now
that I can cut gears . And speaking of cutting gears , how
about cutting pulleys for cogged belts
, anybody got experience doing that that they'd like to share ?
Having worked with stepper motors in space- and power-constrained
devices, I am highly prejudiced against them. That doesn't mean
they won't work -- it just means that I've had bad experiences. I
much prefer a servo motor driven by a feedback loop (at least,
when
I get to design the controller).

Check with Herbach & Rademan (http://www.herbach.com) for motors.
They may not have what you want, but they have lots of stuff in
that sort of size.

For pulleys and belts and whatnot, check Stock Drive products.
They aren't a surplus place, but they have fair to middlin'
prices on
fair to middlin' stuff, and they'll have the same thing next
year. I've had good success tossing together mechanisms using
their parts.
Thanks , I'll check that supplier for motors . As far as gears
and pulleys , I'm equipped to make those , from casting the blank
in aluminum or brass to final machining . I have lots more time
than money ... and a big pile of casting stock .

Do you heat treat the aluminium at all as my limited experience with
as cast items is it is soft and gummy and not nice to machine. A
mate that worked as a designer at a company the made a number of
products with aluminium castings said they always heat treated
them, not for strength reasons, but for machinability as the
surface finish achieved was much better and some other benefits.

My experience has been that extruded stock makes gummy castings .
Material that was originally cast usually machines just fine . My
usual practice is to dunk the casting in water as soon as it comes
out of the mold , this both helps machineability and helps get
residual molding sand off the piece . Letting a casting stand for a
few days also helps , as I understand it aluminum gets some temper
from just aging .
It really all depends on what your smelting stock is. What alloy are
you casting? If you start with 6061, you will get a machineable,
weldable casting. If you start with 3000 series aluminum, you will get
bubblegum.
6061 age hardens.

So does A356 - as do most aluminum alloys to some degree . That
soft/stretchiness of the 3000 series is one of the attributes desired for
stamping and other cold forming ops isn't it ?

--
Snag