Extrude in tpre#

CanDo415

Hi. I need to retract 30mm and extract 30mm of filament while toolchanging. Retracting works fine with G1 E-30 in the tpost.g
Extracting with tpre0.g:
G1 U34
G1 E30
gives the error massage:
T0
Error: Attempting to extrude with no tool selected.

How can I fix this?

Ntrack

The way I'm dealing with that is by defining a false axis (A in my case) with same parameters as E axis . Instead of retracting with G1 E30 you'll use G1 A30. That way you can have extruder movement without a tool selected.
You will also have to create a homeA.g file to home it - just need to have G92 A0 in it.

CanDo415

Problem. I use 2 extruders in line. 1st moves the heavy filamentspool, the 2nd is the direct drive. 3rd is my U-axis to select the color...
1st and 2nd are mixed 50/50

Ntrack

Create the false axis using the two extruder drivers if using the same parameters on both (steps/mm) or two false axis ( A & B) and move them with G1 A30 B30

sebkritikel

@Ntrack said in Extrude in tpre#:

The way I'm dealing with that is by defining a false axis (A in my case) with same parameters as E axis . Instead of retracting with G1 E30 you'll use G1 A30. That way you can have extruder movement without a tool selected.
You will also have to create a homeA.g file to home it - just need to have G92 A0 in it.

That is a super interesting way of extruding without selecting a tool - nice!

Ntrack

Probably you can do it without a homeA.g file by hiding the false axis using the P parameter in M584. then you'd have to unhide it each time you need to extrude without a tool using something like :

M584 P6 ;show the false axis
g92 A0 ; home the false axis
g1 a30 ; move the extruder
M584 p5 ;hide the false axis

CanDo415

this works even worse than before.
tpre0.g:
G1 U34 F500
G1 A+14 B+14 F3600
G1 A+1 B+1 F300

it extracts fine. than it retracts.

Ntrack

@CanDo415 yes , my bad. You need to move in relative position with g91.
G1 U34 F500
G91 ;relative pos
G1 A+14 B+14 F3600
G1 A+1 B+1 F300
G90 ; absolute position

CanDo415

THANKS. now it works fine.

dc42

@CanDo415 said in Extrude in tpre#:

How can I fix this?

Don't extrude in tpre. The tool has not been selected until tpre has completed and its temperatures have not been set, in fact it may be completely cold. If you need to extrude, do it in tpost instead.

Most multi-extrusion systems don't need tpre files at all, only tfree and tpost files.

CanDo415

@dc42
Can You explain When the tpost, tpre and tfree exactly will be executed!?

dc42

A tool change happens when you execute a Tn command and the new tool number n is not the current tool, or you execute M109 either with a Tn parameter (where n is not the current tool) or when no tool is loaded. The tool change sequence is:

If no tool is active, skip to step 4.
Run tfree for the current tool. On a tool changer, this is where you park the current tool.
Deselect the current tool. This removes its offsets from the motion calculations, and sets its heaters to their standby temperatures.
If the command was T-1 then there is no new tool and we're done.
Run tpre for the new tool. On a tool changer, this is typically where you pick up the new tool.
Activate the new tool. This means that its offsets will be added to future movement commands, and its heater temperatures are set to their active values.
Run tpost for the new tool. Typically in here you use M116 to wait to its heaters to reach the set temperatures, and then do any wiping or priming that is needed.

HTH David

CanDo415

Thanks. The timing helps a lot on my 7-Filament system. now it works without the dutyness of A and B