There are things (tower shapes with bridges) for this in Thingiverse, search calibration and pla. The problem is to get the printer to print different parts at different temperatures, so as far as I can see you have to import their g-code and run it, i.e. no stl and slicing. I run at 210°C and 65 °C bed.

I’m no expert (only just started with mine).

STL files are not printer files – they need to be processed by the slicer program to be converted to code for the printer, to organise exactly the order of operations understandable by the machine. The slicer program will contain the temperatures, not the STL, which is basically an engineering drawing from a CAD program. Not all slicer programs are alike.

Small items will likely give different results to very large items. I cannot see that printing directly on, or close, to the bed is going to be quite the same as printing as much as 300mm (or more on some larger machines) from the bed. Layer-to-layer adhesion may be different, by virtue of this.

Adhesion to the bed seems a particular issue (it is for me, so far). As I see it, once the first layers are placed in position, heat transfer between the bed and print will change. Contraction can affect the adhesion properties. I like the idea of a cold plate, but they don’t mostly have heated plates for no good reason? As I see it, once printed on a heated bed, they need it to stay the same temperature to avoid the plate and workpiece parting company.

Enclosed printers will undoubtedly operated more consistently than open frame machines – especially if situated in less than ideal situations.

Comparing machines by net ‘influencers’ and often by good ‘neutral’ reviews may well be flawed by choice of parameters due to lack of truly exhaustive testing under different conditions.

Comparing ‘stringing’ between machines is one area that I have found to be questionable. My results, compared to those reported by others are different. I suspect my filament suits my machine and the particular slicer/machine settings.

The standard ‘benchy’ can even give variable results, and each machine likely needs tweaks (to settings) to optimise that little task on that machine. Mine did.

My conclusion is that whatever item, for a test, that may be chosen might work for one model and one PLA supply, but not aross multiple machines and variable filaments. But I wouldn’t bank on it.

It take a wee bit longer to print but look at this:

http://www.3dbenchy.com/

It has bridges, holes, bosses, overhangs, compound curves etc. and there's a downloadable sheet with all the dimensions on so you can compare your results to what they should be.

The compound overhang at the bow is a good test for curling up layers. The text underneath shows how good your first layer is and if your z-height is too low. The text at the stern is a good test for small nozzles and fine layer heights but will barely appear at 0.2mm layers with a 0.4mm nozzle.

Another advantage is that there are online guides to different print issues that use Benchy as the example making comparison easy.

Neil

I also found agreement within a couple of degrees between the bed and hotend thermistors and a temporarily attached type-K thermocouple. However on two different machines I have had the hotend thermistor spontaneously change calibration by more than 20C. Enough that on one the filament would not extrude and just ground up the filament with the extruder gear(s), on the other PETG was overheated enough that it produced prints with a burning smell that were very brittle.

The sensors were both the type that are I think still glass encapsulated Pt100, but in metal cartridges Neither had  been damaged by grub screws and just had to be replaced. 

Andrew.

Edited By Andrew Entwistle on 07/05/2020 13:42:20