[chbot] Stepper Motor Checking

Thu Jul 7 03:12:27 BST 2011

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>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> 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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