Filament material characterisation

Hi I’m working on a project trying to characterise what makes an ideal filament material for FDM. I’m trying to figure out what the key physical properties are, for instance; thermal conductivity, glass transition temp, viscosity at glass transition temp, ductility etc.

Does have any ideas on this? what physical properties are the most important, ? Any other info on potential materials would be interesting too! Thanks

Ask a metallurgist what the best type of metal is to work with, or a carpenter what the best wood is to build something. They're going to tell you they can't answer that question without knowing what you're building. There is no "ideal" as ideal for one print may be the opposite for another.

That makes sense but surely there is a set of material characteristics that determine how well material will work in FDM or wether it is impossible to use in FDM? I'm trying to come with a set of criteria that could be used to benchmark potential materials against to asses their suitability.

Ability to bridge, adhesion between printed layers, bonding to print bed while hot and easy release while cold, low-warp when cooling down, good retraction qualities, not too fluid but still very soft and easily extruded so that there is no oozing while moving...

This is all in simple terms. I can talk about viscosity, conductivity, transition temps etc, but I think those are things that cause qualities. The above qualities is what an average user will see when he/she is printing.

Extrusion temp is ideal around 200~220ºc as half of all hotends are made with a PEEK isolator and/or PTFE liner. But depending on what you are making of course. If you want better heat-resistant material you need a material that extrudes well above 220ºc and this is usually printed with an 'all metal' hotend, but these hotends usually have problems printing with PLA as it has a low hardness when it gets warmed up just a fraction (around 60º it gets very soft already) and stainless steel has higher friction coefficient than PTFE.

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Yeah those are exactly the sort of things I was thinking about. I'm quite interested in the physical properties behind those qualities. The investigation I'm working on is probably more in depth then what the average user would need to know!

Make magazine did this characterisation this year. It's worth searching for.

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