[chbot] Stepper Motor Checking
Mark Beckett
m.beckett at amuri.net
Thu Jul 7 04:12:33 BST 2011
Simon
If the authors terms spelling or otherwise offends or confuses you, then
simply move on.
If you are so keen on Foot pounds of torque then divide by 192.
The actual method of checking is correct, which is what the article was
about.
The reason I presented it to the group, was it was a relatively easy
means to check an otherwise unknown stepper motor.
/While the academic amongst the group argue over the correctness of the
written theory, the more practical will have done any checks and moved on./
Mark
On 7/07/11 14:26, Simon Knopp wrote:
> Your quoted excerpt makes my point: torque is measured in *ounce
> inches*, not ounces per inch. Torque = force x distance, not force /
> distance.
>
> Ounce(force) per inch would be a valid unit for stiffness, not for
> torque.
>
> Simon.
>
>
> On Thu, Jul 7, 2011 at 2:12 PM, Simon Chester <simonches at gmail.com
> <mailto:simonches at gmail.com>> wrote:
>
> It's not incorrect: http://en.wikipedia.org/wiki/Torque#Units
>
> In British unit, "pound-force-feet" (lbf x ft),
> "foot-pounds-force", "inch-pounds-force", "ounce-force-inches"
> (oz x in) are used, and other non-SI units of torque includes
> "metre-kilograms-force". For all these units, the word "force"
> is often left out, for example abbreviating "pound-force-foot"
> to simply "pound-foot" (in this case, it would be implicit
> that the "pound" is pound-force and not pound-mass).
>
>
> On Thu, Jul 7, 2011 at 12:07 PM, Simon Knopp
> <shrunken.apple.head at gmail.com
> <mailto:shrunken.apple.head at gmail.com>> wrote:
>
> 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 <mailto: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>
> [mailto: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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