More temperature resistant PLA options

[geoff-t 0]

I spin cast low melt metals like pewter and use low temperature vulcanising silicon for moulds. This involves heating to 90C with the mould under pressure so standard PLA will soften and distort too much in the process. As I don't have a heated bed ABS isn't an option at the moment so I was wondering if anyone could recommend something likely to resist the heat and pressure of my process. I'm in the UK.

So far we have had success with sand casting directly from prints but this is limited by complexity of shapes, we've also done some lost wax style burnout of PLA with reasonable results but it's a lot of effort and a bit prone to less than perfect results.

 

[IRobertI 520]

Maybe PLA 90 from Orbi-tech could work?

 

[gr5 2,194]

Fascinating. I envy you and your molten metals!

FYI many people print ABS without a heated bed. There are 2 issues - shrinking, and shrinking. The first issue is that it's harder to get things to stick to the bed (due to shrinking). Some people have solved this with "ABS GLUE" (google it) and printing on glass. Also adding a brim helps and printing as hollow as possible helps (infill pulls at the sides lifting the corners off the build plate).

The second issue is shrinking - if you print something like an inverted cone - something with overhangs - even very mild overhangs, the shrinking effect which pulls in on the sides of the part as you print - now it rotates the edge and mostly lifts the edges of the part until the print head hits these edges and either damages the part or knocks it off the print bed. Even a mere 45 degree outward angle is a major major problem with ABS. Pretty much unprintable without heated chamber.

But if you are printing things with vertical sides (like typical mechanical parts) (rounded corners on top are not a problem - it's outward leaning sides). And if you are printing smaller objects (under 2 inches across) then you might be fine with ABS. With ABS glue and 1/4" (thick!) glass plate you might even be able to use the full 8 inches of bed space.

 

[geoff-t 0]

Thank you IRobertl, that seems to have the required properties, a supply in the UK would be ideal but not a great hardship to buy from Germany if it works.

Thanks gr5 for the abs tips, I'm mostly doing jewellery sized objects without overhangs so that too may be worth a try.

 

[geoff-t 0]

A bit delayed but I've had a go now, the PLA 90 worked perfectly for making a mould but I have found it very difficult to get such good printing results as standard PLA. As I'm generally making jewellery type objects this is a bit of an issue. However I can see the potential for some less exacting requirements.

Within the same mould I also placed some standard PLA patterns depending on shape and fill density there were mixed results ranging from severely crushed and distorted through to acceptable. I'm going to have another go try and keep the temperature and pressure lower for longer and use nothing but solid patterns. I'll try and take some photos next time.

anyone mystified by the process can read more here

http://en.wikipedia.org/wiki/Spin_casting