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Messages - kf2qd

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General Mach Discussion / Re: Using Mach3 with Reprap extruder
« on: May 03, 2010, 10:02:37 PM »
Feedrates work a bit different in a normal CNC operation. - if there is no axis move then NOTHING will run. Your G01 F1500 will do nothing as there is no axis move. You will get the same results from the following move with F3000 as you would without the G1 F1500 line. the only way you can have any "motion" would be to treat the extruder as a "spindle" and set its speed and motion using the S1500 M3 command and the add an S3000 to another move. then to stop the extruder you would use M5. The other problem with your idea is that you would have to have a, Say a C-Axis tied to the extruder but it programming it would be a challenge as coordinated moves all axis start and finish at the same time.

General Mach Discussion / Re: Using Mach3 with Reprap extruder
« on: May 03, 2010, 12:16:34 PM »
What is it your are trying to do? Are you trying to control the Reprap with Mach3 or are you trying to make parts for the Reprap? From the research I have done into the Reprap you will be running a 3 axis machine with an extruder to lay down the material. 3 axis are X Y & Z. Does the extruder need a speed contol or on/off control? is the extruder the 4th axis? Might it be setup as the spindle axis and use speed commands to control extrusion rate?

If you want answers you need to describe your problem a bit more fully so those reading your post know what you are doing. otherwise we are apt to give you that answers we think you are asking for instead of answers that would be of some use to you. Not meaning to harsh, but we can't see what you are working with or imagining and thus it is hard to give good answers.

I started out in the machine shop many years ago running a LeBlond Tape Turn Regal. The GE 550T control handled errors in arcs by completing the arc and then moving to the end point. A few times i manually programmed and arc wrong and tried to make a fillet and then move through the part parallel to the spindle. Or radius the outside corner and turn the OD in 1 G02 move.

I will have to look into converting my VB code in my CAD program to produce incremental IJ.

In my experience it was some of the older controls that used incemental IJ, but the machines I have run all used IJ mode as set by G90 or G91.

And yet another reply... (is there a way I can edit a previous reply? I haven't seen it tif there is.)

I am working in Inches & Inches / minute, Were you thinking mm & mm/min?


Decided to take a look at the program those earlier code segments came from and it loads and looks fine today. Don't know what is different, loaded and ran other programs this morning and they were fine.

Have to see what happens tomorrow...


I am cutting some 1/2 thick countertop material, some kind of plastic. Some scrap I have that works nice for testing. I am using a 1/8 endmill and I could go faster, but choose not to so I lessen my chance of tool breakage. I was working on a project yesterday that gave me errors, and recoded it today witht the same tools,( a Visual Basic app I am working on in ProgeCAD) in the same sequence and had no problems whatsoever. Is there an Odd/Even date randomizer in the arc routines? Or maybe I am holding my mouth wrong. Having written some programs for PC and PLC I have had those things show up that only seem to happen during the right phase of the moon or some other obscure outside occurence.

I have a copy of Mach on 2 machines, both older Dell Optiplex 260's @ 1.8GHz, with the one tied to the Seig XE CNC not connected to the network. So far, when one does something strange the other does the same thing.


Here's the actual code to the point where the error occurs.

G92 X0 Y0
M6 T1
S2000 M3

G0 X0.1250 Y1.9622
G1 Z-.1 F3
G1 X0.3388 Y2.0681
G2 X0.4554 Y2.1763 I0.4992 J2.0121
G3 X0.5444 Y2.2738 I0.4077 J2.3092
G2 X0.6253 Y2.3301 I0.6103 J2.2654
G2 X0.7749 Y2.4246 I0.7759 J2.2573
G2 X0.8486 Y2.4818 I0.9086 J2.3283
G2 X0.9249 Y2.5227 I0.9063 J2.4658
G2 X1.0291 Y2.5469 I1.0096 J2.3945
G2 X1.1100 Y2.5793 I1.0863 J2.5213
G1 X1.3539 Y2.4535
G0 Z.1

G0 X1.1682 Y1.9091
G1 Z-.1 F3
G3 X0.1250 Y1.9622 I0.5713 J0.4561
G0 Z.1

I can get this code to choke if I oload only the last 'paragraph' of code.

It is the start of a Rose. I have a version of it that does work, just that 0,0 is in a different position. I am working on a nameplate for the Principals door here and at one point it does the same thing. And those arcs all start at nice 90 degree positions.

Mach is Version R3.042.029


Mach is configured Absolute positioning, Absolute Arcs. I find it much easier to think in absolute, and the G-Code is much easier to read.

Lots of arc segments with much smaller radius, this is an arc with 1.5"+ radius

the code fragment that these numbers came from looked like this -
G92 X0 Y0 Z1
M6 T1
S2000 M3

section of code...
G0 X.1

G0 X1.1682 Y1.9091
G1 Z-.1
G2 x0.125 Y1.9622 I.5713 J.2651
other code.

I pulled these numbers from my CAD program and transcribed some numbers wrong in my first message, the stuff after the equal sign was correct. Like i say - the radius error is out there in the 100,000 ths place and I don't have a lot of influence on it.

At first I thought it was improperly drawn entities in my CAD program, but the only way to get it any more accurate is to go more decimal places as at 4 decimal places it is as accurate as can be had.

Will post the first part of the code tomorrow from work. The machine is in my classroom at the school where i work.

I keep getting the error - Radius to end of arc differs from raduius to start line ...

Using absolute I & J

When I go back in and check the difference it comes to less than 0.00001 (1/100,000) error, and is awfully hard to get rid of.

For instance -

startpoin to center radius -
X 1.1682 - I .5713 = .5969, squared = 0.35628961
Y 1,9091 - I.5713 = 1.453, squared =  2.111209
added together = 2.467499
square root = 1.570827365

End point to center radius -
X0.125 - I .5713 = -0.4463, squared = 0.199,183,69
Y1.9622 - I 0.4561 = 1.5061, squared = 2.268,337,21
added together = 2.467,520,9
square root = 1.570,834,46

Difference =
1.570,827,365 - 1.570,834,46 = -0.000,007,095,0

Add 0.0001 to any of the dimensions and the radius grows too much.

Any clues as to how to minimize this problem so Mach3 can tolerate this insignificant bit of error?

I am doing some "artsy" stuff that has many arc segments but have to deal with this only 2 or 3 times in a program.


I have been working on a simple CAM application that works in side ProgeCAD or AutoCAD. It is written in VBA and lets you pick a line or an arc and create the CNC code. By picking sequential entities and clicking the appropriate button it creates teh CNC code which you can then save to a file and run. Right now I am working on it in ProgeCAD Professional and I am planning to get it working under AutoCAD after I get a couple more features working. It is one step above manual - you just have a few buttons to click and the code it created 1 entity at a time. you can also enter lines manually for G & M codes and Z axis moves - It is primarily 2D at teh present, but I plan to do more as I develop it further.

I would like to get some feedback from others, so please post if this interrests you.


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