getting a blob at the start of each thread??

New thread created as it is a different issue.

In response to my stating I get a blob at the start of each new extruded thread in this forum thread brnrd asked:-

>What did you set your retract and restart to?
>I guess with the new firmware setting for SF 40
>you should have it set to 1 and 0, respectively.
>If your restart is larger than 0, then you will probably
>get a blob.

My retract distance is set to 2.0 mm and restart extra distance set to 0.0 mm. My retraction speed is set to 10 mm/s

Cheers

I have my retraction speed set to 300 mm/s (18000 mm/min) which is the default setting in the reprap host. With PLA, I don't get blobs most of the time and with ABS, I haven't seen blobs so far.

The one thing that fixed retract/restart in my case was blowing air at the PTFE insulation for cooling. I have an Adrian Geared extruder in the standard X mount and I think there's not enough ventilation in this configuration to prevent too much of the feed from getting soft. This problem is worse for PLA than ABS since it has a lower Tg. I wrote about this in another thread. Without the additional cooling, retract doesn't stop the ooze. Maybe your problem is related.

Also, 2 mm might be too much retract. Nophead recommends 1 mm to start with.

Edited 1 time(s). Last edit at 03/13/2011 12:12PM by brnrd.

Gosh - 300mm/s!! is that with sf40 so that is 30mm of feedstock a second!!

??

AgeingHippy Wrote:
-------------------------------------------------------
> Gosh - 300mm/s!! is that with sf40 so that is 30mm
> of feedstock a second!!
>
> ??

He said he was using the reprap host, which uses the extruded filament speed rather than the feedstock speed. I use 2 mm and 30 mm/s for my sf40 settings. You want to use as fast a retraction as your extruder stepper can handle without skipping steps. I print with PLA at 175 C and with those settings have no issues with blobbing.

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Oops. Sorry, I haven't changed my firmware settings yet. NewPerfection is right, that's the speed in terms of extruded filament that I'm using with Skeinforge 040. So your retraction speed is about right.