Cole,
I've built my own setup using EMC to drive minimill - works great - many
thanks to all the people involved with the development of EMC!!
Here what I did:
Built a simple power supply - 10A @35V Transformer + Bridge rectifier +
2 x 22000 uF capacitors - no problems (see
http://pminmo.com/simpleps.htm)
Built my own stepper motor driver cards using the L297 / L298 running as
a bipolar half stepped drive (check out st.com for the datasheet this
gives a circuit linking the L297 and L298) - no problems
Built an optoisolator card - had some problems here since EMC pulses are
very short in the end I used 6N137 optos and the information here
http://www.freescale.com/files/microcontrollers/doc/app_note/AN2342.pdf
to build a 12 channel output only card i.e. step and direction for
channels A, B, C, X, Y, Z. The card so built works really well - make
sure you have truly isolated power supplies for the CNC and PC side.
Purchased some low cost stepper motors (make sure you get the wiring
diagram) and connected the X and Y directly to the table axes. For the
Z axis I found a ball screw on eBay attached it to the mill by means of
a purposed made plate with thrust bearings. The Z motor drives the ball
screws by means of a 9mm timing belt. Try and drive your axes directly
as this reduce backlash and since the steppers produce high torque at
low revs so using belts and pulleys to increase torque is counter
productive as the stepper must rev higher to get the required traverse
speed - Initially I drove the X and Y axes using 2:1 reduction - this
has now been junked and for direct drive via Oldham couplings.
Sat down and fiddled with Linux(dark world of pain for me) and EMC
(confusing initially but loads of help via this forum - it starts to
make a lot more sense when you finally see a motor turn!!) and finally
got the system going. It been running for around six months now and,
touch wood, has operated faultlessly.
The above development took me around 18 months in between the wife,
babies, shopping, decorating ...
Hope this is of some use.
Regards
Andy
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Colin
Sent: 08 January 2007 13:49
To: emc-users@lists.sourceforge.net
Subject: [Emc-users] Parport stepper setup
Hello,
I have been investigating using EMC2 and some stepper motors to a small
milling machine. I have a cloudy area of understanding around driving
the stepper motors. As usual I am trying to do it on the cheap :-) and
hence would like to develop my own stepper driver. I am hoping someone
can provide some direction so that I don't fall off any cliffs.
So far I believe there is two ways to generate an amplified stepper
signal (half, full etc).
Method 1
Using the parport config to send a step signal and a direction signal
for each axis. Run these signals into a stepper driver chip which is
configured for the stepper phase that I require. This method should
leave a few extra pins on my parallel port to play with later.
Method 2
Use the functionality of the stepgen module to perform the required
stepper phase for each axis. Amplify each signal into the motor. This
method will use up more parallel port pins depending on the amount of
coils in the stepper that I purchase, I may even need another port if 5
phases is required.
Are both methods possible? Which method is the most common or gives the
best result?
I also intend to opto isolate the signals coming from the parallel port
to protect my motherboard, is there any unforeseen problems doing this?
Cole
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