First movement before extruding

Hey there,

I like Slic3r very much but there is one thing I want to change and I wanna know wheather this is possible:

When I print a part sliced by Cura, the first movement (after heating is done) is a linear movement to the point on the platform, where the printer starts extruding (for example "G1 X50 Y40 Z0.2"). This movement is done by all three axis simultaniously.

But when I print a part sleced with Slic3r, the first movement is "G1 Z0.2" and then "G1 X50 Y40". This first sets the nozzle on the bed and then moves it to the starting point.

Is it possible to change this behavior of the first movement in Slic3r to behave like Cura? (Maybe in the start gcode section but therefore i would need variables for the coordinates of the starting point)

I want to do this, because it minimizes the hazard of crashing my nozzle into the clamps which hold the glass plate at the four corners.


Thanks for your help

Try copying cura's start gcode to slic3r.

You can specify by start gcode any movements, extrudes, retracts you want. You can move the head to a nozzle cleaning brush and go around in circles before moving to begin your print.

If you combine the commands you get combined movement so
G1 X50 Y50
G1 Z50

Will move x and y simultaneously, then when complete move z.

Whereas
G1 X50 Y50 Z50

Will move all three axes at the same time. Don't forget to specify speed in mm/min using an F parameter also, otherwise your machine moves at the last specified speed which might be quite slow.

My preferred start sequence is heat build plate, preheat extruder to 130, home, move to bed centre, do a G30 to set Z level (or autolevel/calibrate etc..), then raise the print head/lower the build plate (depends on the printer) by around 60-70mm, then heat extruder, then extrude 30mm of filament (which I grab and pull away as the nozzle descends), then print. Positioning the nozzle at bed centre makes most sense whilst heating as this is most likely to be closest to wherever a print might start.

This ensures no ooze/strings, and the first layer begins immediately without having to build up pressure. So in theory you could dispense with a skirt (or print just one loop to visually verify the nozzle to bed gap for the first layer before leaving the machine to get on with it).

Edited 3 time(s). Last edit at 04/11/2017 09:30AM by DjDemonD.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

First of all thanks for your answer.

I know a bit about gcodes but this movement I am referring to is the first line of gcode of the actual print code (after the start gcode).
I was just wondering if there are variables for the coordinates of the point where extruding begins so I would be able to move there already in my start gcode which would make the first two lines of the print gcode redundant if you understand what I mean.

I am not sure if I understand what you mean with

Quote

Positioning the nozzle at bed centre makes most sense whilst heating as this is most likely to be closest to wherever a print might start.

This ensures no ooze/strings, and the first layer begins immediately without having to build up pressure. So in theory you could dispense with a skirt

Does it make a difference where to heat my nozzle in whatever matter?
If I would heat my nozzle for example at X0 Y0 Z15
And then (as heating is finished) do a "G1 X50 Y40 Z0.2 E10" right before the print, I would have built up pressure in my bowden, I could start printing right away (maybe with one loop of skirt) and the 10mm string would have been deposited outside of the building area.
In this scenario I wouldn't have to grab into my printer and this would be the way I want to go (even if it might take 10 seconds longer), but therefore I need these variables (because print does not always start at X50 Y40)

All I meant was that since I hate ooze, I let my hotend heat up positioned 70mm above the bed centre, then I used to clip any ooze before printing started, but this often meant poor flow for the first 50mm of the first layer whilst pressure built up, so now the purge runs when the extruder is heated I pull away the excess, so I get no ooze and more or less instant start on the first layer.

Since the head is over bed centre for any given print it's never going to be too far away from the starting point.

I should say I'm using a delta and a corexy (with belt driven z axis) so z moves are practically the same speed as x and y moves, if I had leadscrews I'd start on one side of the bedat a much lower z height.

I don't think there is a variable you can call for [start position] in slic3r but it would possibly be quite useful.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions