Solving for skeinforge flow rate
by DaveD, published
Volumetric 5D may make this obsolete.. Also, the "work in progress" note from Thingiverse is no joke! It's very much a work in progress. In particular, it's better at lower thread widths than higher ones - you'll probably need to add a bit to the flow rate as widths get higher.
Just a simple program that I was goofing with to find the correct flow rate of a skeinforge profile given some other set of parameters. Most params have min, max and increment values. The program is simply a set of nested loops that iterate through these values - from min to max, adding the increment each time.
Since this solves for a range of flow rates, you may have problems if you give it too narrow of a range for flow rates. If you're looking for a very specific flow rate, use values like "1.9" min and "2.1" max instead of setting both to "2.0".
Mostly obvious stuff if you've messed with skeinforge before except:
Gear diameter: this is the diameter of your filament drive gear. Preset to the default of my MK5 gear
Gear Swell Mod: this internally modifies the gear diameter to make up for small inconsistancies in how various bits perform and are measured. Basically, this is a "plus a bit" modifier: if profiles come out blobby, tweak this up a little; if they come out too thin, tweak it down a little
Flow Fudge Factor: I have to enter 1.0 into the flow rate to get 2.0 RPMs on the extruder.. I got tired of doing this math so I added flow fudge factor and set it to 0.5. This doesn't change the volume calculations - it just modifies the flow rate on the table. If you have a MK4/MK5 extruder with a DC motor, start this at 127.5 to get the PWM value to use
(thread area) and (thread width) columns. Just numbers that I like to know but skeinforge doesn't care about
- (unfudged flow) column. This is the actual, calculated flow rate before the flow fudge factor gets applied
Good thread width values probably depend a lot on your nozzle. For my 0.35mm big head, values under ~0.20mm don't make sense and values over 0.75mm don't come out nice. For a 0.5mm MBI nozzle, values like 0.5 to 1.25 probably work well.
If you're messing with profiles a lot, thread area is a good one to keep track of. Mostly, the same feed rate/flow rate combination that works well with one thread area value will work well with any other profile that has the same thread area. (edit: see, for example, the screen shot lines for .25mm/2.8 and .35mm/1.714; both have the same feed & flow rates and the same thread areas..)
The code (included in the zip) is a bit of a mess. Work in progress. Yeah, it's C# so Windows only. Easy enough to port to some hethan language, though. (edit: also confirmed to work on Mono!)
V2: added Infill Solidity and Support Flow Rate RPM to the new profile form; assorted cleanup; column sorting on the table view
V2.1: retargeted to .NET 2.0, made infill solidity & support rpm optional (just leave them blank to not set those in the profile)
V3: slightly better calculation of thread volume; should support creating profiles that repg can add now, too
For Ultimaker machines: set "Gear diameter" to 7.85 and "Flow fudge factor" to 26.5 - that's working quite well for me.
- Unzip exe to some directory
- Nuke exe and prefs.xml
- Run exe
- Enter lots of random numbers
- Click Go button
- No results? Enter different random numbers & try again
To clone an existing skeinforge profile and add generated values:
- Click on one result line
- Click Profile... button
- Change "profiles dir" value to where existing profiles live
-- Skeinforge button resets profiles dir to where skeinforge puts profiles
-- ... button brings up standard windows-dir browser
- Change "clone from" value to chose profile to clone from
- Give the new profile a name
- Click Clone it button
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