RepRapPro Fisher – 4

I figured it out why the shortage of filament extrusion last night finally.
The right amount of force against filament at the geared shaft and idler bearing requires to provide good retraction. Extruding filament after specified length of filament retraction, i.e. 3.5 mm in this case, demands stronger force due to the pressure and friction in Bowden tube.

When the extruder can’t push filament, the geared shaft grinds stuck filament and it ruins entire printing.

cDSC_0026

In Fisher’s extruder drive, the squeezing force on filament is regulated by spring loaded lever. As I set the bolt length between lever and bolt head to 18 mm, filament starvation began to disappear.

Another important one is that melting temperature of filament affects extruding force.
Lower temperature needs stronger squeezing force at the extruder drive.

Failed Robot
cDSC_0158

No retraction, 215C
cDSC_0015

Retraction 2 mm, 210C (lower half), 205C (upper half)
cDSC_0017

Retraction torture test, retraction 3.5 mm, 215C
cDSC_0012

cDSC_0024

Retraction torture test, 205C

cDSC_0027

About janpenguin

Email: janpenguin [at] riseup [dot] net Every content on the blog is made by Free and Open Source Software in GNU/Linux.
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