Custom purge-line calculations  

RE: Custom purge-line calculations

Posted by: @sembazuru

This is particularly targeted to @bobstro because I use your primeline code from your MuppetLabs page, but anyone can chime in.

I've finally gotten various diameter nozzles, specifically 0.2, 0.4, 0.6, and 0.8. I'm working on creating printer profiles for the different size nozzles (I'll also be pouring over your MuppetLabs page section on dependencies), and want to calculate new purge lines for the different nozzles. What formulas do you use to calculate the extrusion mm for the 3 sections of the purge line? Do you think there is a formulaic (is parametric a better word here) way of doing it based on the configured nozzle diameter instead of using a different value across the 4 different nozzle sizes that I have? (Easier to maintain if the custom start gcode for the 4 printer profiles are the same instead of subtly different.)

I'm using the same gcode for all nozzle sizes, and it hasn't resulted in any problems. As CNC Kitchen noted in a video recently, smaller nozzles can produce wider extrusions (to a point), so the results don't even look as different as I'd expected.

My selection of feed rates was pretty simple: I liked having a few transitions to verify the flow. After comparing a few defaults from various slicers, I start thick with a stationary blob to trap any nozzle ooze, then a thick segment to get flow going, a thin segment to verify the transition is clean, and a middle width segment to wrap it up to be close to actual print rates. The wipe at the end gets rid of any string. I do set Linear Advance to 0 at the start of the prime line to eliminate extruder clicking.

That's really it. I have finally disabled skirts as they're a bit redundant at this point.

RE: Custom purge-line calculations

Edit: I did calculate the feed rate - distance divided by the amount extruded over the move. That's what's identified in the "intro line @ 0.XX" comments. Just a bit of pencil and paper math and visual confirmation of what looked good.