Actuator foot weakness - stage Y-axis actuator broke :(

[Pelle]

@r.w.bowman

If you figure out a nice test, let us know

Will do! Some small actuator foot similar to leg_test.stl would be nice to have. And then a way to fixate it and measure how much force it can withstand (twisting included). Some fun experiments during summer ahead!

[Pelle]

aahaa, that is interesting. I guess the ester approach is how my silk PLA was made then. Thanks for the links!

[ebob]

I’m following up on this to see if anyone got anywhere with a PLA test foot.

I’m currently trying to specify the PLA requirements for building quite a large number of units, and so am quite keen to get this right! My initial thought was to go for a Sunlu LightGold, which is a PLA Silk, but the comments about knowing just what is in the silk and the vagueness of manufacturers’ descriptions of their ingredients is making me nervous.

So any models I can use as tests, maybe involving some gentle destructive testing, to put some ‘strength’ numbers on various brands / colours etc, would be great.

If not, I’m happy to do the cad for a test model, but I could do with some inspiration for its design (my skills, such as they are, lie elsewhere). The need to consider twisting is particularly interesting.

Thanks!

[Pelle]

Hi ebob,
no, unfortunately I have not found time to put together a actuator test foot.
As you say, it would be quite useful to have for before investing in PLA for a large number of units.
I will try to design one at some point (hopefully by the end of the year), and I will share my results in this post.

[ebob]

Hi @Pelle that would be interesting to see.

I has some thoughts on a test design, in the thread over here:

PLA material metrics on characteristics

There have been a couple of threads* touching on the behaviour of PLA, and seeing how central the material is to the system, I was thinking it might be useful to have some way of testing how good a particular one is. Obviously we have the leg test stl, but that’s more of a binary go/no go. It would be nice to have something which lets you get a number out of it so you know just how good or bad one is. (And numbers are always nice). *The particular threads that got me thinking are: So someth…

If I get time soon I’ll see if I can design it, and will likewise report back.

[r.w.bowman]

There’s one test print in the repo, which is one of the legs of the microscope. That includes a few flexures, so it’s a reasonable part to test. As others have said, “silk” PLA seems to be quite variable, and the only silk spools I’ve used have been rubbish so I’ve tended to avoid it.

I guess you could try the leg test print, and if it is twisting that’s the problem, you could manually try that, and see if it breaks in the same place?

I have sometimes done test prints by loading up the main body in a slicer (Cura/PrusaSlicer/Slic3r), then just cropping out the bit I’m interested in - in your case, perhaps you could crop out one of the actuators? I’d include the whole bottom of the leg, i.e. all the way in to the static part around the objective - that way you could assemble and drive the actuator, and see if it fails in the same way.

[ebob]

Thanks, I’ll give that a go, and try to calibrate the test jig/model I’ve created against that.

As well as Silk PLA, I’m also looking at PETG which, from looking through old forum posts here, doesn’t seem to suffer performance-wise, but people may not be so familiar with when it comes to dialling-in their printers.