[chbot] Stepper Motor Checking

[Mark Beckett]

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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