Messages

1

General Mach Discussion / Re: Very odd rapids stepper motor stalling problem

« on: May 19, 2013, 06:42:40 PM »

I too was having issues with weird stalling on rapids in Gcode. Worked great with jogs.

A few months back i started seeing the issue, after I upgraded past 2.48 to 3.043.022

Well, it came back today on a critical "one shot one kill MIL job I have to get out tonight. Thank god I did a dry run with a laser edge finder (the job is a bear - trying to line up stuff on an already machined box)

I heard it stall on a diagonal. Always the same line. Rest of the code ran great.

After putzing around with this and that in 3.043.066 today (saw it back months ago thought .066 fixed it - wrong it turns out)

Went back to 2.48; did a full uninstall - reinstall, (restored my back ups of the macros sub dir and my xml from that version - thank god I'm anal about backing up stuff and keeping old cfg's)

No issue.

It's only on code rapids, where the x and y are at different speeds. Only happens with certain rapids; when it does it's fairly consistent - it always stalls at the same place, same ammount - the stall leaves the axis at the same wrong machine coord. In this case it was 220mil off. Every time.

If it were some marginal thing with hardware, pulsing, etc... it'd be more random. Nope. If you changed a pulse rate, pulse width, etc... it'd change but repeated runs would then lose the same distance.

Something went amiss in the version 3 build. It could be PC/OS environ specific. Maybe there was something in Arts original code that was a bit fragile, dependent on some compiler, machine config, chipset, etc... dunno.

But I'm sticking with 2.48. It works.  I ran 2.48 for quite a few years, hundreds of jobs with it never had an issue.

2

General Mach Discussion / Re: MAXNC CL10 "qaudrature" and MACH3

« on: March 09, 2013, 11:01:46 AM »

There's a great read here at this link:
http://www.stepperworld.com/pgTutorials.htm

Note in both the unipolar and bipolar links where he states

"In a basic "Wave Drive" clockwise sequence, winding 1 is de-activated and winding 2 activated to advance to
the next phase. The rotor is guided in this manner from one winding to the next, producing a continuous cycle.
Note that if two adjacent windings  are activated, the rotor is attracted mid-way between the two windings.
The following table describes 3 useful stepping sequences and their relative merits.  The polarity of terminals is
indicated with +/-.  After the last step in each sequence the sequence repeats.  Stepping backwards through the
sequence reverses the direction of the motor.  Note that these sequences are identical to those for a Unipolar
Stepper Motor.

As you can see on the top scope (the one that shows the xy plot) the waveforms maintain a constant phase angle during a stop. Please note that the scope is showing the input to the gates of the drive MOSFETs. If you look at the schematic on the yahoo maxnc site - I have a copy of it on my site here:

http://home.comcast.net/~ajawam5/max/Cirquit_diagram-Maxnc15CL-Controller.pdf

that otto simply made his software on the PC output a quad signal on two pins to the  PIC microcontrollers. So instead of having to generate the drive signal for the FETS/Darlington transistors (depends on the model MAXNC Controller) from a step and direction signal, he used the MAXNC PC software to generate the quad signal... simplifying the logic required in the maxnc controller/drive. This also allowed him a bit more latitude on being able to alter the drive timing characteristics on the PC side of things.

The old DOS MAXNC disk had a dos program called TIMESET that wrote parameters to a file to control the timing based on the PC's characteristics

This is from an email Art sent me long ago:

"Yes, when you select the CL option, which is quadrature outputs, the pin
settings you use are ignored and set as per factory specs for the CL pins.


Usually, in CL mode the user sets pin 17 as the enable output. Then it is
low until you press reset to enable the controller
at which point it goes high, this suffices to reset the CL.


The Enable pin shoudl work for that.. Also, in CL mode , the Input#1 is
normall used as a hold for position signal to
keep the CL from overruning in speed. I believe pin 10 as below is used. If
pin 10 goes active (Active high) then output stops till the Max determines
its OK for further movement. This makes the CL a semi-closed loop system.
(Hence the CL designation..) Make sure then that pin 10 is set to Input #1
and is set "High active". Setting Pin17 to Enable#1, and setting it "high
Active" as well makes the CL reset when MAch3 does. Also youll notice pin 16
below is the real enable, so you need to set Enable #2 signal to pin 16 and
set it low active" to allow movement when in CL mode.

Here are the MaxCL pinouts..

1............... M3 OUTPUT (LOW=ON, PULSE FOR PWM)
2............... A AXIS (quadrature)
3............... A AXIS (quadrature)
4............... Y AXIS (quadrature)
5............... Y AXIS (quadrature)
6................X AXIS (quadrature)
7............... X AXIS (quadrature)
8............... Z AXIS (quadrature)
9............... Z AXIS (quadrature)
10.............. INPUT, MOVE ENABLE (LOW=NORMAL OPERATION, HIGH=STOP, SEE
NOTE)
11.............. INACTIVE
12.............. INPUT, HOME SWITCH (NORMAL OPERATION LOW)
13.............. INPUT, G61 SWITCH SENSOR
14.............. M8 OUTPUT (LOW=ON)
15.............. NONE
16.............. OUTPUT, DISABLE POWER TO MOTORS (LOW=NORMAL, HIGH=DISABLE)
17.............. OUTPUT, RESET CONTROLLER (LOW=RESET, HIGH=NORMAL)
18.............. ALL SIGNALS GROUND
19 TO 25 ....... NONE
"


One of the best sites on steppers I've found is at U of Iowa:
http://homepage.cs.uiowa.edu/~jones/step/

3

General Mach Discussion / Re: MAXNC CL10 "qaudrature" and MACH3

« on: March 08, 2013, 07:14:33 PM »

Quadrature means that the windings are driven with a waveform (usually square or sine) that are 90d shifted with relation to each other. Mathematically, it can be stated as a sin and cosine function (sin(x) and cos(x)) :
http://en.wikipedia.org/wiki/File:Sine_cosine_one_period.svg

Say you have 2 pins, A and B as shown in the illustration; the signal on Pin A is the red wave; Pin B blue

So B  would be, say  90 degree shifted ahead of A for clockwise rotation, and 90 degrees behind A for counterclockwise.

Here's vid of mach 3 driving a MAXNC drive on my bench:
http://ajawam5.home.comcast.net/max/DSCN1107.avi

Note how the phase (the scope with the "scrambled egg" pattern) displays the phase of the two signals.

another great image:
https://engineering.purdue.edu/ece477/Webs/S11-Grp03/imgs/encoder_direction.png

From EDN:
http://www.edn.com/design/integrated-circuit-design/4363949/Decode-a-quadrature-encoder-in-software


This is how rotary encoders work (like the volume control on newer radios that spin forever). Not to be confused with resolvers (a whole different beast). We'd use a simple circuit to derive direction and magnitude; as the EDN article states it's now typically done in software using GPIO ports on a micro-controller (I think Arduino even has a sample for this)

Step and directions simply means that one pin is used for the direction (say High for CW, Low for CCW) and the other pin simply "steps"  the amount of rotation. Some controllers allow "micro stepping" which means that the motor will move a fraction of the rated full step rotation.

This is the series I used on my mill, driven by an arduino (it has an allegro driver IC built in )

http://www.anaheimautomation.com/products/stepper/stepper-integrated-item.php?sID=49&pt=i&tID=132&cID=50

My mill page:
http://home.comcast.net/~ajawam3/swarf/mill_mods.html

The vids show it stepping and micro-stepping...

4

General Mach Discussion / Re: Run from here returns to 0,0,0 sometimes- MAYBE SOLVED

« on: December 30, 2012, 09:56:13 PM »

I think I figured out what's up..

Recall I do a full stop. So the spindle stops.

I noticed when I do a Run From Here, it asks to do the prep move and TURN On the SPINDLE (BTW thanks Brian for fixing it to move to safe z FIRST - Awesome!!!).

So I hit OK....

IF I hit the CYCLE START before the DWELL is finished, it does the 0,0,0 move then moves back to where it should be.

I'm wondering how many people have given Run From Here a bad rap because of this?

I Just tested hitting CYCLE START before the DWELL completed, everytime it did the 0,0,0 move.

So far, everytime I wait for DWELL to stop, it performs flawlessly. I'll see how it goes and if I'm just crazy by about now...

5

General Mach Discussion / Run from here returns to 0,0,0 sometimes

« on: December 30, 2012, 08:18:37 PM »

Occasionally Run from Here will return to 0,0,0 (not in the code, just moves to the origin; the DRO shows it; the Code Window holds on the line it's supposed to be going to) then return to the line selected, then continue on.

Doing a feed hold, then full stop.
Rewind to beginning
using go to line number to select the line
hitting run from here
then letting it go to the Preparation Positioning

I've done this exact sequence about 50 times, and about 10 times it returned to zero; the other times it ran as expected.

I've been running hundreds of jobs with previous versions over 10 years; this only happens with the latest stable version; R3.043.066 I installed today.

Was using 1.84 for years; the past year or so running 2.48. I recall versions previous to 1.84 doing this.

Any idea what I'm doing wrong? Or is this a known issue?

6

General Mach Discussion / IMACH P5, acceleration, MACH Version

« on: March 03, 2011, 02:53:09 PM »

Just got the VistaCNC P5 pendant and noticed stalls when reversing directions in C or S mode ... seems the acceleration was a bit low - anyone else seen this issue?

The P5 manual rec's 2.63 or higher which is what I'm using. Any benefit using MPGs like the P5 with newer MACH versions?

Any settings i should be aware of? My machine has run well with CNC jobs for the past 8 years... using Gecko 201's, std parallel port, 74ACT buffers as per Mariss.

Also - any issues with higher accelerations on typical MAXNC BSA antibacklash nuts?  My MAX is oversized, Mitch way back when made me a 22" x, 20" Y and 22" Z so it's a bit more mass than a standard 15...

Also have issues with the P5 losing comm with MACH 3, just stops working. unplugging and replugin the USB seems to get it going again.