An Idea for Better Filament Fabrication: Compensate in Software!

Hello!

I am trying to build a filament extruder – the one that produces rolls of filament from pellets by smelting them and extruding through a nozzle.

I know that some filaments you can buy online that even are made on factories with quality control and stuff (yeah, right) can be pretty inconsistent in thickness. So here's my idea: while the filament is extruded on "factory" it's precise thickness should be measured and stored into a file that is shipped with that exact roll of filament! Then, when you use it, you feed this file to the firmware and firmware would then know the filament thickness precise deviation at every say 5mm and would adjust the extrusion rate accordingly. One can even fancy a bowden tube length variable into this calculation.

The only thing factory need to make sure of is that thickness will not exceed maximum allowed thickness and not clog your hotend. Point is that if your filament is THAT inconsistent – do something with it, probably other than compensating in software.

How do we store this information on a roll of filament? Answer is - we don't! We attach a QR or RFID marker onto the roll that has only a link to a file that is stored in the cloud. When you install a fresh roll you tap\scan the marker with your phone to get the file and put that roll-info file onto the SD card. Printer then would detect a change in that file's hashsum/header and assume you've installed a fresh roll and set current used filament length to 0.

For multiple rolls printers would just store multiple roll-info file hashsums/headers along with the used filament value in EEPROM or other storage.

It is not hard to implement it on the filament-production side, however I have no idea how to implement it in Repetier or RepRapFirmware.

If this gets implemented this would lower the entry barrier into filament fabrication and every makerspace, every reprap owner can have a filament extruder. Those things aren't expensive, they aren't hard to build, they just produce filament that normally is a tad under tolerances that are considered "high quality". RepRap answer to that would be "just compensate in software!", isn't it so?

Let me know what you think.

Edited 1 time(s). Last edit at 03/15/2016 02:41PM by toxuin.

There is already a compensation routine in Marlin that takes the readings from a sensor.

Saving the data from one roll in a file and then use that file is not going to work because you have no idea what is left on the roll. As soon as you have removed a part you must store that info somewhere and then (re)set that info in combination with the file. Therefor a "live" sensor is a better idea imho

My Repetier-based machine shows a "printed filament" length statistics that is stored in EEPROM I guess. Same way it could store precise used up length of current roll in EEPROM. We deterimine the "current roll" by a file on sd card - either it's header or it's checksum. Switching between the rolls is as easy as swapping (renaming?) a file on SD.

I haven't seen any accessible filament width sensors. Some only measure that you haven't run out of filament and some require a laser sensor that ain't so easy to obtain (neither it is cheap). By accessible I mean that one can either buy for <= 20$ shipped or build at home with basic tools (no multi-layered boards and BGA components!)

Header for a roll-info file would have a UUID, a mesurement interval (resolution of measurements on production), total filament length and data start offset. Next, every 4 bytes it would store a measurement reading as a floating point number. Current filament thickness would be then calculated by reading a float from an offset from data start based on current used up length and roll measurement resolution.

Quote
toxuin
I haven't seen any accessible filament width sensors. Some only measure that you haven't run out of filament and some require a laser sensor that ain't so easy to obtain (neither it is cheap). By accessible I mean that one can either buy for <= 20$ shipped or build at home with basic tools (no multi-layered boards and BGA components!)

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Edited 1 time(s). Last edit at 03/16/2016 02:40PM by Frans@France.

Interesting idea.

But how are you going to measure the filament diameter when you manufacture it? And why wouldn't you just put that sensor on the 3D printer to measure the filament diameter there?