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.

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[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.

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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.

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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.

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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.

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[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.

[Alan Wood 4Participant @alanwood4]

Hi Michael, might not be totally useful to you but there is a good resouce on Simplify3D with many helpful articles.

https://www.simplify3d.com/resources/articles/

In particular there is one about thin wall printing.  This is important for the aeromodelling fraternity and current slicers use Arachne coding for this to allow printing wall widths less than the nozzle diameter.

Soarkraft has explained a bit more on this in one of his videos

Both these links are now somewhat dated but still relevant

 

 

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Alan … that looks interesting

It will probably be tomorrow before I am back here; I appear to have done something silly in FreeCAD 🙁

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

< phew >

I shall probably never know what that was all about, but we’re back in business now … and I have just successfully printed the thick-wall tube.

It may not be quite as clean as Julie’s example, but everything seems to be fine.

I think I will save each version with a novel file-name before continuing with my ‘experiment’

… Housekeeping lesson learned !

MichaelG.

 

 

[Alan Wood 4]

On Alan Wood 4 Said:

Hi Michael, might not be totally useful to you but […]

 

 

Thanks again, Alan …. very interesting links, and definitely worth re-visiting

MichaelG.

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Edit: __ Reading this one would have saved me some early embarrassment:

https://www.simplify3d.com/resources/articles/rafts-skirts-and-brims/

[Gerard O’TooleParticipant @gerardotoole60348]

Michael, not sure if you mentioned what slicer you are using. In Cura, there is a separate setting to compensate for small internal hole sizes. Apparently, as the PLA layer settles it swells slightly resulting in slightly larger outside measurements, but slightly smaller inside hole measurements. Where the internal measurement is critical, I have found a setting for ‘hole compensation’ of 0.1 to 0.2mm right for my printer, an old Ender 3.

Yes, saving each new version from FreeCad with a version number is definitely recommended. At least until you have a nice accurate, quality print, then delete  the surplus files .

 

[Michael GilliganParticipant @michaelgilligan61133]

At the moment, Gerard, I am still exploring the low foothills and am simply letting Bambu Studio do its stuff  … I have a lot to learn !

MichaelG.

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Ref. __ https://bambulab.com/en-gb/download/studio

 

[Julie AnnParticipant @julieann]

Out of idle curiosity this morning I printed a ring with a 0.4mm wall thickness while watering the fruit bushes; OD was 23.2mm, ID was 22.4mm. I was impressed that my printer had no problems and printed a perfect ring with no brim. Wall thickness measures around 0.41mm as best I can tell.

For years I used Cura with my Ultimaker2 printer. Having recently moved to a Prusa printer I am now using the PrusaSlicer software. Consequently I am on a bit of a learning curve again. I’d never heard of Arachne, but deep down in the PrusaSlicer expert options there is an Arachne perimeter option. It seems to be on by default and can’t be turned off unless I fiddle with some other options.

Julie

[Dick HParticipant @dickh]

Not sure if this is a non sequitur. Google Thingiverse and Lathe Spacer. I made a set of these for my little Proxxon, 3 jaw lathe chuck for gripping small parts. If nothing else this discussion shows that 3D printing can give parts of a reproducible size, perhaps not accurate but precise. There are various designs and for an odd ball part you can 3D print a holder (as long as the part doesn´t get too hot).

[eefweeninkParticipant @eefweenink]

Looking at the object (cylinder shape, thin wall) consider using “Vase Mode” when printing.
– Set the printwidth to the wall-thickness. Maybe you have to do a few testruns to get the correct measurements.
NB: A nozzle of 0.4mm can easily do a wall-thickness of 1.2 mm (depending on the shape of the nozzle sometimes even a bit more. I trust it can at least do 2.5x the nozzle diameter).

This will give you a very nice print result. better then a nozzle what has to do 2-3 turns.
PS: This is also the cause “of the thickness-issue”
Your wall should be 1 mm. Then nozzle is 0.4mm. So it does 2 loops and some kind of infill.
Or it does 3 loops (and you end up with about 1.2mm).

regards, Eef

[Michael GilliganParticipant @michaelgilligan61133]

Not happy at all with my [lack of] progress today … I has intended to complete print the full set of my samples, and have so far had:

• network connection problems
• a firmware update
• another of those raggedy mis-prints
• an adhesion failure

… Grrr!!

I have just let the printer go through its calibration routine again, and am hoping for a little more success before the day is out.

MichaelG.

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Edit: make that two adhesion failures !

I missed this one whilst I was typing the above 🙁

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[Michael GilliganParticipant @michaelgilligan61133]

This may turn-out to be embarrassing, but if I fix it I will be very happy anyway !

I think I now know why I got the adhesion failures …

MichaelG.

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