Printing tiny things

jens55

I am attempting to print a Luer Lock adapter. A syringe needle usually has a Luer Lock connector on the side that screws into the syringe It is quite small with a wall thickness of only 4 lines printed with a 0.2 mm nozzle and a 0.1 mm layer height. The area that fails is about 5mm in diameter.
I tried reducing the print speed down to 40 mm/sec figuring that things are just getting too hot. I also attempted to print 4 of the adapters at once in order for the layer time to increase. I am obviously doing something wrong ... but what? The part is printed in PETG. Should I go even slower? How much cooling air should I try? Is it even possible to print features this small?
This is what I am getting ... even if I print only one part at a time, the failure is always around the same height on the model.

A secondary issue I have is how to avoid the typical PETG stringing which becomes a serious problem when one is trying to print something that has a 1 or 2 mm hole in the center.

LuerLock4.jpg

mrehorstdmd

I'd print something that small using ABS. Even if your printer isn't made for ABS, it should work fine because the parts are small. ABS is less stringy than PETG, so it's a bit easier to control the extruder to get good prints.

jens55

@mrehorstdmd, thanks, I will give that a try. Would you stay with a 0.2 mm nozzle or would you go with a 0.4 mm nozzle ?

dc42

@jens55 in what way does the print fail?

You could try printing at a slower speed, at lower hot end temperature, and perhaps with a little print fan cooling. The central 1mm or 2mm hole is never going to be accurate, so accept that it will come out smaller and you will need to drill it out.

jens55

@dc42,thanks! I had PLA handy so I tried printing in that. I went waaaay down in print temperature to 185C when the calibrated optimum temperature for that filament was 215C. Much to my surprise, despite the ridiculously low printing temperature, the part printed (and with excellent inter-layer adhesion to boot)
I now have a printable base model and I can try different materials, different nozzle sizes and different printing parameters.
It's amazing how one can tweak for the best print for a given material but those settings are only useful for an average print and any number of factors can screw with the settings required. (Vooodooo anyoe?)

BTW, for the PLA print I went down to 30 mm/sec and 100% fan. I increased the size of the passage way to 2 mm and that printed perfect. The only fly in the ointment is ever so tiny whisks of filament in the center passage. They are barely visible but the adapter would be used to force grease into linear bearings and I don't want to risk screwing things up with an errand tiny piece of plastic.

I will try PETG and ABS tomorrow to see what can be done with those materials given what I have learned today.

Thanks @mrehorstdmd and @dc42 !

alankilian

@jens55 I love it when people keep experimenting and do things "the wrong way" as a test and it works!

Thanks for the update.

o_lampe

@jens55 Like we discussed in the other thread: some things are better done with resin printers.
Alternatively CNC a mould and use 2k resin.

Bad thing about resin prints: I have to re-adjust the fudge-factor we are used to use in designs for FDM printers.

If you like, send me the .stl file and I give it a try with ABS-like resin.

jens55

@o_lampe, thanks for the offer. I agree 100% that a resin printer with a strong resin would make short work of the issue. I have an old Elegoo Mars sitting on my desk but it has only seen work in the capacity of 'decoration'. Part of that is lack of strength of the standard resin, cost of 'strong' resin (although in this case material use is minimal), pain-in-the-ass factor of post processing and cleaning up the left-over resin in the vat and on the model etc etc. Lastly, needing to use a different slicer and totally different procedures doesn't make much sense for one tiny part over a period of a year or longer. It wouldn't be an issue if I printed with resin on a frequent basis but I don't.

o_lampe

@jens55 said in Printing tiny things:

Lastly, needing to use a different slicer and totally different procedures doesn't make much sense for one tiny part over a period of a year or longer.

Actually it's a good practice session, to be prepared when you need to use resin/moulding etc.
Otherwise, I agree with all above.Although with a well planned workflow, cleaning is no big issue. I leave the resin in the VAT for weeks, just cover the printer with an extra paper bag.
The ABS-like resin isn't too expensive. In fact it is much easier to clean than water-washable. With two-stage cleaning and an IPA-recycling tank, the overall cost gets even lower.

o_lampe

[OT] Just found a nice upgrade kit for the Elegoo Mars. It's "only" 2k resolution, but the Mono LCD improves workspeed by factor 3-4 and enhances livetime.

jens55

@o_lampe, interesting but ,and this is totally off topic, I was unable to figure out how to upgrade the firmware on the Mars and the instructions for the kit specifically call for upgrading. Current firmware is for type C board and apparently will not work on type a or b board that I have. I might try to tackle it in the future ...