Not unexpected, but is it predictable ?

[Michael GilliganParticipant @michaelgilligan61133]

I did a little test with the Bambu Lab P1S this morning

Drew a simple tube in FreeCAD

O.D. = 23.2mm

I.D. =22.2mm

Length = 10mm

printed it [0.4mm nozzle, PLA filament] with a suitable 5mm ‘Brim’ for adhesion to the plate, and everything worked fine except, of course, for those diameters.

 

A rough check with the Mitutoyo Caliper gave

O.D. = 23.44mm

I.D. = 22.14mm

Surface finish is not bad at all, but clearly an “allowance” will need to be made to home-in on target dimensions.

Is this predictable [in the sense of being calculable] or just a matter of inspired guesswork ?

MichaelG.

.

[Tony Pratt 1Participant @tonypratt1]

Hi Michael,

I also have a P1S, I’m sure there is a calibration setting on these machines but I’ve never used it but may be worth investigating also a calibration cube for fine tuning dimensions? I have printed only PLA atm , door shut, 31% humidity and sizes are say +/- .02 so I’m lucky.

You should be able to get much closer to target dimensions without guessing, I just Googled ‘bambu lab p1s dimensional accuracy’ and there is shall we say an abundance of information that you can trawl though, I’m finding this with 3D printing , there is perhaps too much information, some of it conflicting.

Good luck, and let us know how you get on!

PS that is quite a thin walled tube, try a solid cube

Tony

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Tony

I will get round to ‘calibrating’ it sometime … This morning’s little test was rather whimsical: just exploring the behaviour when the specified wall thickness was somewhere close to the nozzle diameter.

MichaelG.

[Julie AnnParticipant @julieann]

When I bought my first 3D printer I did a lot of experiments with 25mm cubes. I reached the conclusion that PLA consistently shrank by around 0.5% from nominal.

I recently bought a new 3D printer and have just printed some fixtures, in PLA, to hold the rear hubs caps on my engines for painting. The part was printed with a 0.4mm nozzle, no scaling adjustment or brim, 0.2mm layer height and standard infill. This is the fixture:

Starting with the largest OD and working in to the ID I get the following results:

Design   Measured  % Error

3.625″     3.611″      -0.38

2.75″       2.745″      -0.18

2.1875″    2.177″     -0.48

2.0625″    2.061″     -0.07

These figures indicate that the PLA does shrink but by slightly less than my previous printer. There is 12 years between printer design, so I would hope that things have moved on in that time.

In the results above the ID variation is likely due to shrinkage. It seems odd that the OD is oversize. It might well be due to the thin wall section of 1mm. Looking at the actual measurements the difference is 1.3mm, ie, around three times 0.4mm. The printer cannot print a half width line. Try a design with a wall thickness of 1.2mm and see what the measurements are.

Julie

[Julie Ann]

On Julie Ann Said:

[…] Try a design with a wall thickness of 1.2mm and see what the measurements are.

Julie

Good suggestion, Julie

… I will try that this afternoon, and report back

MichaelG.

.

P.S. __ am I being dim ? … I did have a bad night’s sleep

23.2 minus 22.2 was intended to produce 0.5mm wall thickness

[Julie AnnParticipant @julieann]

Michael: It’s not you, it’s me being dim. My only excuse is that I have blonde hair!

Julie

[Michael GilliganParticipant @michaelgilligan61133]

🙂

[BazyleParticipant @bazyle]

Consider designing in relation to how it is made. While it is sensible to help it out with lines that are multiples of the nozzle dia also think about what happens in extruding the goo out of the hole – it spreads out. So then maybe multiples of hole dia are not so good, Think about how you would design the slicer software to cope. It might be interesting to make a test simple straight wall of different thinknesses.

Meanwhile you have first the accuracy of the mechanical movement to calibrate first, then the shrinkage which will be different in x,y, and z and also affected by geometry eg edges and middle of the test cube because of the orientation of the filament laying.

I was lucky, my first ever print, a changewheel, was withing a couple of thou and fitted its shaft perfectly.

[Michael GilliganParticipant @michaelgilligan61133]

Oh dear … now we have an interesting puzzle:

Following Julie’s admirable suggestion, I decreased the ‘Pocket’ [i.e. the bore of my tube] from 22.2mm to 20.8mm … to give a nominal 1.2mm wall thickness

The print was a disaster; so I printed another, with almost identical result.

I then changed the ‘Pocket’ diameter back to 22.2mm and printed another thin-wall version.

In chronological order, we have A, B, C, D

A and D are of quite acceptable quality

B and C are utterly useless.

.

The FreeCAD file was saved and exported with the same name[s] at each step

The Slicer was “happy” at every stage, and the Bambu reported “print success” for each run.

.

It looks like a resonance/chatter problem to me … but your considered opinions and wild guesses are welcome.

MichaelG.

..

Note: any apparent size discrepancy within the pairs is an artefact of using a wide-angle lens … they are actually quite well-matched.

.

[Michael GilliganParticipant @michaelgilligan61133]

I have just let the printer start its self-calibration routine.

… meanwhile I shall have strong black Coffee !

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[Michael GilliganParticipant @michaelgilligan61133]

Well … It looks like something must have “settled” for want of a better term.

Following that calibration-run I have just started what will be a set of tubes … all will be 23.2mm O.D. but the bores will run from 22.0 upwards in 0.2mm increments.

The first one looks excellent !

MichaelG.

[Julie AnnParticipant @julieann]

Out of curiosity I ran a test piece, in PLA, while having supper. Design parameters were OD of 23.2mm, ID of 20.8mm and height of 10mm. This is part that appeared, no brim used:

Measurements are:

OD = 23.05mm

ID = 20.80mm

Height = 9.97mm

Julie

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for sharing that, Julie

I will be back later

MichaelG.

[Author]

Posts