When printing with basic budget PLA, what are the consequences of having it slightly over temperature. For example 5-10 deg above the recommended temperature for the brand, or significantly over temperature such as 50 deg?
How will this be seen on the print, and what are the inherent risks - if any - to the printer?
Presuming that the print is allowed to complete, and there are no other external factors that might effect either the printer or the print.
If it is only a little higher, the properties of the plastic may not be ideal and it may reduce part quality. For example, it may be less viscous and drool out the nozzle faster over empty spaces, causing stringing and bridges may sag more than they would at a lower temperature. There may be some benefits though. For instance, layer adhesion might be better.
If it is a lot higher, the plastic could burn instead of melting. If it burns inside the nozzle, it may clog the nozzle. It may also smoke and/or emit toxic fumes. (Although the burning fumes are much worse for other plastics like ABS and nylon.)
Assuming you are not exceeding a safe temperature for your hotend, including a limit of around 245-260 °C if it's PFTE-lined and a limit around 300-330 if the block is aluminum, there are no significant risks to the print quality, printer, or user unless you get to extreme temperatures. PLA prints great up to 270 °C and in fact this is the sort of temperature you need to print at high speeds without a very long melt zone. Somewhere around 320-350 it will start to smoke. I've had this happen when purging PET (which I print at 350) with PLA and forgetting to drop the temperature first, but nothing bad comes of it.
If PLA sits in the hot zone at excessive temperature (especially over 240 or so) for an extended time, it will crystallize and become brittle, but the damaged material is easily purged as part of the purge line or skirt for the next print.
