Re: 8541 package questions - PMDX-340
- The new offering that Ron mentioned is the PMDX-340.
It is a more full featured and robust driver package
at a more affordable price, but I must caution that
it is not quite plug and play with Sherline supplied
motors. The Sherline setup runs the motors as unipolar
and the PMDX-340 uses bipolar mode. To use it with
the Sherline motors you will need to remove the 5
pin DIN connectors and attach the wires to the PMDX
supplied plugs with the motors connected as half
winding bipolar motors.
If you choose to supply your own motors, then you
can select Nema 23 motors rated at up to 3 amperes
and these are available from many sources at good
Among the additional features gained by using the
PMDX-340 are a switched outlet to control the spindle
and inputs for home/limit switches and a probe input.
--- In SherlineCNC@yahoogroups.com, Ron Ginger <ronginger@...> wrote:
> I strongly agree with getting the Sherline mechanical package. I made my
> own motor mounts before Sherline offered them, but when they came out I
> bought them. They are a fine, neat, well engineered offering.
> I also strongly agree to NOT get the Sherline stepper control. it was a
> poor design, very slow, very weak, when it was new 10 years or more ago.
> It is now hopelessly out of date. The motors they offer are much weaker
> than most guys use.
> There is a new offering from PMDX.com of a single box with all the
> electronics in it. It has a power plug, a parallel port and screw
> terminals for the motors. Its about as easy to hook up as it could be.
> It will run either Mach or Linux equally well.
> ron ginger
- Thanks Jeff. So would I better off then with the smaller motor. The endgame here for me is to cut molds for highly detailed organic pieces that will be plastic injected. Much like what you see in 32mm wargamming pieces.
From: Jeffrey Birt <birt_j@...>
Sent: Monday, July 1, 2013 3:32 PM
Subject: RE: [SherlineCNC] Re: 8541 package questions - PMDX-340
With the 20TPI screws on the Sherline larger motor are a detriment. You
already have a large amount of torque developed due to the mechanical
reduction. What you want are motors with low inductance and low inertia (low
rotating mass). We package 166 oz-in motor with our Taig and Sherline kits.
If you search for Soigeneris on YouTube you'll find some videos of a Taig
doing 250 IPM with my 'tiny' motors.
Matching the motor/driver/power supply is the key to getting the most out of
the motors and your machine. Bigger is not better.
From: SherlineCNC@yahoogroups.com [mailto:SherlineCNC@yahoogroups.com] On
Behalf Of bruce_e_layne
Sent: Monday, July 01, 2013 5:17 PM
Subject: [SherlineCNC] Re: 8541 package questions - PMDX-340
--- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ,
Hamilton Elliott <hamilton@...> wrote:
>I'd generally agree that bigger and more powerful isn't always better, much
> Keling steppers KL23H284-35-4B which are too big
> and I believe makes them slower and more likely to do damage if
> accidents happen... Bigger is not always better!
as that contradicts the basic programming of my Y chromosome.
I put larger motors on my 25" X 49" CNC router because the specified NEMA 23
motors seemed a bit anemic. I haven't installed the end limit switches yet,
so I set the maximum current in the stepper motor controllers to a lower
value, and they still have plenty of torque at low speeds. If your only
concern with larger motors is too much torque, you should be able to reduce
the torque by reducing the current, which is done with DIP switch or rotary
switch settings or possibly potentiometers on modern stepper drivers.
The 5mm/turn ball screws on my CNC router provide a lot of mechanical
advantage. A crash in X or Y would be ugly, but I was genuinely concerned
that a +Z crash would damage the top of the Z stage. I doubt it'd break the
1/4-20 machine screws, even in shear, but the top plate was deforming upward
at an unhealthy angle and the tapped holes in the aluminum plates were
I went a bit larger on the NEMA 23 stepper motors on my Sherline 4000 CNC
ready lathe than Sherline specified, but I didn't go crazy. I didn't want a
big heavy stepper motor cantilevered out on the end of the cross slide where
it might contribute to accelerated wear in the saddle or rails.
>I used double shaft motors on my CNC router so I could turn the axes by hand
> If you think that you will want to use the mill by turning
> the handles then you need to get the double ended shafts.
> I put the handwheels on for a short time and then removed
> them because of vibration and with the larger motors they
> were too hard to turn comfortably.
when the stepper drives were powered down, but I used large diameter knobs
rather than the more traditional handles. I didn't want the spinning handles
protruding where they could catch on stray objects, and the knobs are
radially symmetric so they don't tend to cause harmonic problems that can
momentarily stall a stepper motor at certain speeds. Those lost steps can be
very frustrating (ruined parts) and very difficult to diagnose.
I decided against double shaft motors on my Sherline 4000 CNC mini lathe.
For the times I'd use it as a manual lathe, I'll probably jog it via
LinuxCNC or type G code into the MDI interface rather than cranking handles.
Most of my manual lathe work will be done on a larger lathe. I also wanted
the smallest and neatest integration for that CNC mini lathe and I didn't
want knobs hanging out at the ends of the axes. I was going for the CNC look
and feel, and not the CNC conversion look and feel, not that there's
anything wrong with that.
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