Re: EMC & Linux

> -----Original Message-----
> From: Dan Falck <dfalck@...>
>
> Tim,
>
> I have been running EMC this week on a Sherline mill. I haven't made any
> parts yet, but have been running the table to get a feel for it. On G02,
> G03, cirular interpolation- I have been using I and J format with no
> problem so far. Maxnc uses I's and J's, so I'm use to it now.

What I noticed was not that EMC wouldn't process the I & J format, but that
it seemed as if I had more errors than if I used the R format. Except for
very simple stuff I use Vector 7.0 to generate my g-code and what I found
was when I generated both styles off the same part there were far fewer
lines that errored with the R format. This could be an indication that
Vector's g-code algorithms are a little lacking when it comes to the I & J
style, but I never had a problem with it in DeskNC.

Despite having used the I & J format in the past I will admit that I really
don't understand it. It is my understanding that the X & Y values indicate
the destination position, but can you clue me in on what the I and J are
indicating?

> I found out that if you set the Acceleration too low, you get some odd
> behavior. The move that is just ending slides to a stop slowly after the
> next move starts. The ramping was working pretty good for my setup and I
> kept running it lower and lower just to try it out. At
> Acceleration set to
> .05 it does this lazy motion thing. At .15 it looks ok. When I cut parts
> I will check it for sure.

I haven't tried going to settings that low, but it is good to know what type
of behavior to expect if you get it too low. Currently I have the
acceleration set to 0.8 and that seems to be working well. I am not sure
what the symptom would be for having it set too high, but it seems as if it
would be hard on the drive train (cogged belts in my case) to have the motor
try to hit top speed in too short a time.

> What kind of problem did you have with the XZ motion with the lathe? Did
> you set up a G18 (XZ plane) before trying to make a curve? I haven't tried
> it myself yet. I will try it tommorrow.

Actually I had no problems running any code in lathe mode. Here is the few
lines I tried to run. It has small enough move you should have no problems
if you want to give it a try. It isn't anything special. It just turns a
shaft down to a number of steps with roughing passes and then has a finish
pass to complete it.

N10 F20
N11 G40
N12 G00 X3.559 Y-1.118
N13 G01 X3.559 Y-1.068
N14 X1.113 Y-1.068
N15 G02 X1.039 Y-1.118 R0.079
N16 G01 X1.095 Y-1.174
N17 G00 X3.559 Y-1.174
N18 G01 X3.559 Y-1.068
N19 X3.559 Y-1.018
N20 X1.118 Y-1.018
N21 X1.118 Y-1.039
N22 G02 X1.113 Y-1.068 R0.079
N23 G01 X1.168 Y-1.124
N24 G00 X3.559 Y-1.124
N25 G01 X3.559 Y-1.018
N26 X3.559 Y-0.968
N27 X1.118 Y-0.968
N28 X1.118 Y-1.000
N29 X1.118 Y-1.018
N30 X1.174 Y-1.074
N31 G00 X3.559 Y-1.074
N32 G01 X3.559 Y-0.968
N33 X3.559 Y-0.918
N34 X1.118 Y-0.918
N35 X1.118 Y-0.968
N36 X1.174 Y-1.024
N37 G00 X3.559 Y-1.024
N38 G01 X3.559 Y-0.918
N39 X3.559 Y-0.868
N40 X2.039 Y-0.868
N41 X1.118 Y-0.868
N42 X1.118 Y-0.918
N43 X1.174 Y-0.974
N44 G00 X3.559 Y-0.974
N45 G01 X3.559 Y-0.868
N46 X3.559 Y-0.818
N47 X2.113 Y-0.818
N48 G02 X2.039 Y-0.868 R0.079
N49 G01 X2.095 Y-0.924
N50 G00 X3.559 Y-0.924
N51 G01 X3.559 Y-0.818
N52 X3.559 Y-0.768
N53 X2.118 Y-0.768
N54 X2.118 Y-0.789
N55 G02 X2.113 Y-0.818 R0.079
N56 G01 X2.168 Y-0.874
N57 G00 X3.559 Y-0.874
N58 G01 X3.559 Y-0.768
N59 X3.559 Y-0.718
N60 X2.118 Y-0.718
N61 X2.118 Y-0.750
N62 X2.118 Y-0.768
N63 X2.174 Y-0.824
N64 G00 X3.559 Y-0.824
N65 G01 X3.559 Y-0.718
N66 X3.559 Y-0.668
N67 X2.118 Y-0.668
N68 X2.118 Y-0.718
N69 X2.174 Y-0.774
N70 G00 X3.559 Y-0.774
N71 G01 X3.559 Y-0.668
N72 X3.559 Y-0.618
N73 X2.118 Y-0.618
N74 X2.118 Y-0.668
N75 X2.174 Y-0.724
N76 G00 X2.174 Y-0.928
N77 X2.039 Y-0.928
N78 G01 X2.039 Y-0.868
N79 X1.118 Y-0.868
N80 X1.174 Y-0.924
N81 G00 X1.174 Y-1.118
N82 X3.559 Y-1.118
N83 G01 X3.519 Y-1.039
N84 G00 X3.519 Y-0.539
N85 G01 X3.401 Y-0.539
N86 X2.039 Y-0.539
N87 X2.039 Y-0.750
N88 G02 X2.000 Y-0.789 R0.039
N89 G01 X1.039 Y-0.789
N90 X1.039 Y-1.000
N91 G02 X1.000 Y-1.039 R0.039
N92 G01 X0.055 Y-1.039
N93 X0.111 Y-1.095
N94 G00 X3.519 Y-1.095
N95 X3.519 Y-1.039
N96 M2

> I really do like this program so far. The fact that it is rewrote
> constantly and the source is out there is kind of reassuring. I
> am looking forward to being able to use it for the lathe and gang the

spindle to the

> compound using encoders. I don't have servos yet, but someday I will bite
> the bullet and get them.

I agree on the program. I like what it has to offer a lot. I want to get a
better handle on how to use the cutter comp and I would like to find a way
to know what line it is that is failing on a program, but all in all it is a
far superior program to the DOS / Windows based items I have been using.

I'm also with you on the servos. I have started talking with Jon Elson and
will be taking a look at building up his design. You may want to take a look
at it.

Tim
[Denver, CO]