Thing-O-Matic: Manual Wipe and Splodge

The first step of a good print requires nailing the extrusion to the build platform. The Skeinforge Splodge plugin seems to thicken the first part of each filament on the first layer, which is not helpful. So I turned that off and added a few lines to start.gcode that do a much better job.

I also disabled the Wipe plugin, because you really can’t wipe the nozzle after the first few layers without having some part of the Z stage clobber the object. Rather than enable Wipe for just the first layer, I put a manual wipe in start.gcode, too.

The relevant sections look like this; they fit after the homing sequence at the end of the file:

(--- manual wipe ---)
G0 X54 Y-57.0 Z15	(move above wipe start)
G0 Z8   			(down to wipe level)
M6 T0				(wait for temperature settling)
M101				(Extruder on, forward)
G4 P4000			(take up slack, get pressure)
M103				(Extruder off)
G4 P4000			(Wait for filament to stop oozing)
G0 Y-40				(wipe nozzle)
(--- manual splodge)
G0 X-50 Y-55		(to front left corner)
G1 Z0.50			(just over surface)
M108 R2.0			(set stepper extruder speed)
M101				(start extruder)
G4 P2000			(build up a turd)

Depending on a myriad imponderable factors, the manual wipe sequence flips off either a huge tangle or a tiny strand. That’s why I used a 4 second delay: it’s long enough to leave the extruder pressure in a consistent state no matter how it starts.

The manual splodge location depends on your platform layout; I’m thinking of putting it entirely outside the build area. It must be somewhere near the front left corner, because Skeinforge starts each new layer from that direction. Two seconds of extrusion at 2 rev/min forms a blob with a generous contact patch, although the nozzle must plow through the side on its way out.

Note that I leave the extruder running at the end of start.gcode, which means that it’s printing all the way to the outline. That won’t interfere with any part of the object, because (by definition) the first layer of the object lies entirely within the outline.

The Outline plugin puts a single filament around the entire object, allowing me to measure the actual nozzle height and extrusion width on the first layer. More on that later.

The final result looks like this:

Manual Splodge with Companion Cube
Manual Splodge with Companion Cube

Notice that the splodge turd isn’t firmly glued to the platform, but the thread leading to the outline sticks like it was glued and the outline comes out perfectly formed. That’s the whole idea in a nutshell: paste the thread down from a stationary nozzle, then start moving with the turd acting as an anchor.

Trying to start pasting the filament with the nozzle moving doesn’t work well, as witness the left edge of the outline around these test pieces:

ABS coating on aluminum build plate
ABS coating on aluminum build plate

Admittedly, that was with a DC extruder, but the same principle applies to stepper extruders.

4 thoughts on “Thing-O-Matic: Manual Wipe and Splodge

    1. We printed out a set of four, ranging from tiny to huge (well, sorta) and they’re insufferably cute…

        1. The very ones!

          (So we were together in meatspace in Tarrytown? Egad! My apologies for not recognizing you!)

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