[chbot] Stepper Motor Checking

[Simon Knopp]

I stopped reading the first link when I saw "...torque is usually measured
in ounces per inch". A whole page about measuring torque prefaced by an
incorrect definition. Oops.

Simon.


On Thu, Jul 7, 2011 at 11:43 AM, Mark Beckett <m.beckett at amuri.net> wrote:

> Since there is a dgree of interest around steppers
> I found this while searching for something else.
>
> http://www.romanblack.com/stepper.htm
>
> I'm sure the members could improve on the glue it down approach.
> Also he is measuring the hold torque, which will be different to the
> rotating torque.
>
>
> For Robin
> He has a very interesting section on one wire
> http://www.romanblack.com/blacknet/blacknet.htm
>
> For those folowing the CNC he has this
> http://www.romanblack.com/cnc_good.htm
>
> Mark
>
>
> On 4/07/11 16:43, HARTLEY, ROBIN (ROBIN) wrote:
> > Hi,
> > I've looked at the trim routers and initially disregarded them as they
> are 1/4 chuck, rather than 1/8, and a lot heavier than a dermal.
> >
> > After destroying 2 home made spindles, 1 after 10 hours work cutting ali
> which I think was an air flow issue&  the next after 20 minutes because it
> was a cheap armature, I may well look at the trim routers again.
> >
> > The extra weight puts higher demands on the Z axis, which in my case is
> where I found out all about some uni-polar steppers not liking bi-polar
> drive with PWM.
> >
> > Due to my design I'm a bit limited on space&  I got another stepper but
> it has the same problem.
> >
> > There was a comment in this thread about speed control, here's my
> experience.
> > Most of these home made machines are routers rather than mills&  so cut
> with a very fine feed so you only need enough speed rather than managing a
> speed feed relationship of a mill where it produces chips.
> >
> > My approach is to do a test piece run and adjust the depth of cut to keep
> chatter under control, almost impossible with a plastic cased dermal.
> > I then ramp the speed up until I here the spindle start to load
> significantly, I can hear the speed drop, then set my G code to run up to
> about 50% of that feed rate.
> >
> >
> > With a home made spindle, which is basically a cheap dermal knock off
>  removed from it's case and ali blocks for bearing mounts, I can cut 2mm
> deep at about 150mm/minute feed.
> >
> > The secret to cutting ali is to keep it flooded with coolant. In my case
> I use lots of CRC. I basically stand there with a spray can&  keep the grove
> full of CRC.
> >
> >
> > For any one building a machine alignment of the feed screws is the
> biggest issue. What worked for me is to mount a bearing on the lead screw on
> the opposite end from the motor&  clamp the lead screw against for/aft
> movement and at the motor end I use a piece of rubber fuel line as a
> coupler. The modern reinforced fuel injection line has a lot of reinforcing
> that prevents twist.
> > For lead screws I use 8mm threaded rod, 1.25mm per turn,&  for the nuts I
> use a piece of plastic chopping board.
> >
> >
> >
> >
> >
> >
> > Regards,
> > Robin
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: chchrobotics-bounces at lists.linuxnut.co.nz [mailto:
> chchrobotics-bounces at lists.linuxnut.co.nz] On Behalf Of Chris Hellyar
> > Sent: Saturday, 2 July 2011 11:03 a.m.
> > To: Christchurch Robotics
> > Subject: Re: [chbot] building CNC router - was Free stepper motors
> >
> > 'Urro...
> >
> > Given a dremel new is $120-150 ish...
> >
> > Trim routers like these:
> >
> >
> http://www.powertoolshop.co.nz/product_info.php/cPath/20_96/products_id/20
> >
> > For $119 with a full alloy body are a better bet.
> >
> > As I see it, it's cylindrical so it's easier to mount, no speed control
> > inbuilt so you can use a closed loop speed control on it for better
> > cutting in soft stuff.  It'll also have higher rotor inertia and a
> > better quality chuck.
> >
> > There are a few on the market.  When I last looked there were a few
> > options on the shelf at Bunnings/Mitre10 that looked good.
> >
> > I was specifically thinking dremel replacements for wood/plastic/alloy
> > cutting.  If you're looking for dedicated spindle ebay is probably your
> > friend..
> >
> > And, having said all that, my next project is going to be swinging a
> > water cooled VFD spindle.  I am sooooo over the noise of brushed
> routers!!!
> >
> > Cheers, Me.
> >
> > On 02/07/11 10:17, Volker Kuhlmann wrote:
> >> On Sat 02 Jul 2011 02:06:20 NZST +1200, Chris Hellyar wrote:
> >>
> >>> There are some very reasonably priced options rather than sticking with
> >>> a dremel.
> >> Can you elaborate?
> >> And are these options for a dremel replacement or a CNC spindle?
> >>
> >> Thanks,
> >>
> >> Volker
> >>
> >
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