Configuring extruder steps per mm

Recently Emt mentioned that for ease of reading g code that I set my skeinforge feedrate and flowrate to the same number. I had originally configured my extruder's firmware to be .1131 steps per mm, as per a formula I found on the wiki and numerous posts by other users. That would allow the Reprap host software's default 3000mm/min to be a good starting point for extrusion speed. But I switched to Skeinforge and setting feedrate and flowrate to the same value means that the steps per mm on my FW will need to be modified. I have had limited success so far. I have been printing 100mm lines as per emt's suggestions but every time I get a setting to where I think it is correct it always seems to not be good enough. I wanted to create a test gcode file that would allow me to compare different steps per mm settings all in one print. So I thought I would be able to just increase the extruded amount while keeping the distance the same. I have been going back and forth between .55 .6 and .65 steps per mm. Each is a 5% increase from the last. I figured I could keep the steps/mm set at .55 and just add 5% to the extruded amount. Is that right?

; .55 Steps per mm
G1 X100 Y0 Z0.18 F1500 E100
G1 X100 Y10 Z0.18 F1500

; would 'emulate' .6 Steps per mm
G1 X0 Y10 Z0.18 F1500 E205
G1 X0 Y20 Z0.18 F1500

; would 'emulate' .65 Steps per mm
G1 X100 Y20 Z0.18 F1500 E315
G1 X100 Y30 Z0.18 F1500

Edited 1 time(s). Last edit at 08/24/2010 07:56AM by steveo290.

Hi

A test file is an excellent idea.

Isn't a 5% increase on .55 steps .5775 steps per mm

You have no E value on the second line of your programme

You must have an E value on every line that is extruding.

So assuming start at X0 Y0 & E0 which you can set with G92
No need to repeat F value on every line as it stay set until altered by a different F value

G1 X0 Y0 F1500 ; send X & Y to zero without extruding.
G92 E0 ; zero E register
G1 Y0 X10. E10. ; first 10mm move
G1 Y10. X10. E20. ; another 10 mm of extrusion for the 10mm Y move
G1 Y10. X0 E30. ; another 10mm for the X move
G1 Y0 X0 E40. ; another 10mm for the Y move

5% more extrusion on the above programme would be:-

G1 X0 Y0 F1500
G92 E0
G1 Y0 X10. E10.5
G1 Y10. X10. E21.
G1 Y10. X0 E31.5
G1 Y0 X0 E42.

---

Regards

Ian

Ian, yes 5% increase on the step per mm would be .5775. I was adding 5% of 1.00 to the steps per mm, not 5% of the current steps per mm (.55). But adding 5% to the current steps per mm is a better idea I think.

I purposely didn't have extrusion on the y moves, just to separate lines easier. It might be better for the test tho if I have it continuously extruding. Like a raft almost.

My g code generated by SF has a F variable on every line just about and my electronics (5D) seem to only want to extrude if there is a F variable in the line of code. I need to do some more testing though to determine the minimal amount of arguments needed per line of input.

Last night I didnt get a chance to test this but tonight I should be able to. I will update with results. Perhaps the test file I make will help the next person.

EDIT: I looked through your code and I think we are on different pages as to what I am trying to do. I want to try and determine the optimal steps per mm for my extruder but with out having to change the steps per mm for every test. So I want to print a series of parallel lines, not in a square, with each one 'simulating' a 5% increase in steps per mm. Like a laser printer configuration test page, where a series of alignment patches are printed and you pick the best looking one. This way I can compare the lines to each other and determine which one is just right, not to much or too little. Did that convey my idea better?

Edited 1 time(s). Last edit at 08/24/2010 02:17PM by steveo290.

Hi

Ok, I now see what you mean. End of a long day when I sent my earlier message....

You can do incremental with the Firmware.
Makes your programme easier.

Start at X0 Y0

G1 X0 Y0 F1500
G91 ; incremental
G1 X100 E100
G1 X-100 Y10
G1 X100 E105 ; E 5% greater each line
G1 X-100 Y10
G1 X100 E110
G1 X-100 Y10
and so on as many line as you want
then

G90 ; set back to absolute
G1 X0 Y0 ; sends extruder back to zero

---

Regards

Ian

Ok thats understandable emt. Last night I spent my time rewiring my heating element and thermistor. Did a few tests but only the last few lines actually extruded anything. The filament was 'leaking' out the hot end pretty rapidly during the heating ceremony. So I am thinking there could be something wrong with my thermistor. Still reads at 190 and the thermistor is right against the barrel, just past the heating wires at the tip. Same place it was the last few times where it worked perfectly.