Hey everyone, I am new here I hope I am posting this in the right sub-forum.

My rig is a Reprap Prusa clone, using an Arduino 2560 Mega + RAMPS board, an Repetier Host as my software to control the printer.

I'm trying to print a very thick paste. I've built a custom extruder using the extruder motor of a Reprap that was turned into a linear actuator, that depresses a syringe. At the moment I am using a 1ml syringe whose tapered tip has been cut off, because my paste is very viscous. If the tip is on, it does not extrude.

What I want is a 1:1 extrusion rate to X-Y rate, so if the linear actuator depresses the syringe by 1cm, I want a 1cm extrudate on the plate.

I tried to increase the extrusion multiplier from the default of 100% all the way up to 500%, but it is still not enough. I estimate that I may need extrusion multipliers in the 1000's of %. For example I tried to print a 20cm long line, and for this the extruder should move the linear actuator by 20cm, but it only did so by ~1cm. Repetier Host does not appear to allow the user to increase the extrusion multiplier beyond 500%.

My two questions are:
1. How do I increase the extrusion multiplier beyond 500%?
2. How do I reduce the ratio at which the extruder moves in the X-Y plane, in proportion to the extrusion rate? What I mean is that there must be some ratio between how much the extruder motor turns for a standard 1.75mm filament with a 0.4mm nozzle, to print a line of a given length on the plate. What is this ratio called and how do I play around with it?

Thanks for any input/advice.

Try looking at the problem a different way, you have more than one knob you can adjust.

Set your nozzle size to something like your actual one.
Then play with print speeds, flow rate, layer width and extrusion multiple. All of these can be tweaked separately on CURA, on S3D, you only get speeds, layer width and extrusion multiple. Not sure about other slicers.
The slicer that you are using will dictate what knobs you get to twiddle. You will have to fiddle around and find the settings that will give you what you want.

DLC

Edited 1 time(s). Last edit at 09/09/2020 05:45PM by dlc60.

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

You could also raise the steps/mm of the extruder motor

Edited 1 time(s). Last edit at 09/09/2020 07:10PM by Ohmarinus.

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http://www.marinusdebeer.nl/

Quote
Ohmarinus
You could also raise the steps/mm of the extruder motor

Good point. He is trying to get the same flow as movement as well, which will require some other knobs - your dodge would also work on his X/Y steps/mm as well. There are a lot of knobs and it sounds like an interesting project to experiment with.

DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

OK thanks everyone, I will try your advice and report my results May be a few days until I report back...