Extruder push measurement. by MKSA

Last crawled date: 3 years ago

In technology, nothing like measurements to be able to qualify a design. Yet, so far I only see expressions like "Wow !, Greatest, Fantastic, The best" and all kind of similar salesman's talk.
Let's consider the extruder, what is important is its ability to push the filament down the hot end. To measure it, is in fact easy just measure the pull :).
As seen on the picture, Just take a short piece of filament, thread it in the extruder, make a loop on the other side, secure it with scotch tape, attach it to a small scale hanging from the frame top, (try to keep the scale vertical, in line with the extruder, use bracket, bar if required).
Videotape while you run the extruder motor till the filament starts to slip or the stepper loose steps. Reviewing the video, you will be able to see when you reach the max, when it starts to grind etc.
If you notice the filament slips while the motor keeps going, your hobbed gear is the limit. You can block the motor detach the top of the scale and pull till the filament slips to measure its capacity. If not enough, adjust or replace. My hobbed gear plus idler hold more than 40N so you can see here it is the motor the limit.
How much force is required from your extruder depends on may things, filament type, T°, nozzle diam etc...
You can guesstimate it by reducing the motor current till it starts to loose steps then measure the force as explained here. Set the current let's say 50% higher as safety margin. If you can't,your set up is at the limit.
In my printer, for PLA at 200°, about 10 - 15N is enough.
Yes the motor has to pull the wire from the spool and push it but unless you use poor filament guide an intricate path, spool etc ...( I see a lot of them!!!!) , it is not a lot. You can measure it :) Note the head movement pulls the filament too. This can affect print quality BTW.
PS: The stl file is there because of thinkverse, not used.
Plenty more things to write about but. anyone knowledgeable can fill in the blanks or comment :)