Shrunken Prints - Settings Issue?

Hi Guys,
I'm printing a very basic part. It's just a tube to be used as a standoff. OD 0.25" x ID 0.14" x Height 0.19". The height comes out fine but the OD and ID are both undersized.

The actual printed part measures OD 0.23" and ID 0.12". Is this part just too small for the machine to print properly or am i getting some shrinking during the print? Printing in PLA at 205 degC. I have not adjusted the cooling settings from the Ormerod standard profiles.

Thanks,
Jordan

Have you done the calibration set up with the single wall test that Ian had a thread on. I've had problems printing gears to fit the stepper motor shafts so played around with the extruder multiplier even after setting calibration. Worth measuring filament as I have one labelled as 1.75 and is actually 1.7 so in moving 100mm you don't actually have the same volume of plastic to extrude

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Regards

Chris H

I don't know if it is contributing to the shrinkage, but unless you are using very old firmware then 205C is too high. Try 195C first layer and 190C remaining layers.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi Jordan another potential problem is that if you're just printing one these, the part won't necessarily have time to harden- when I've done parts lime these I've printed 5 or more at a time with reasonable spacing to let the top layer on each part cool before the head gets back and applies more hot filament.

As dc42 points out 205is probably too high a temp which would exacerbate the problem above. As well as calibrating your feed as described by Chris, you can tell slicer to print with a defined width (equal to or greater than .5 mm), then make sure your walls are a multiple of that width, then print half that multiple of perimeters without infill (I'm on a kindle and can't do the head sums at the moment but will give more detail later if you're interested)

Ray

Hi Guys,
I just tried printing at 195C/190C and I did find that my filament is closer to 1.70mm so I changed this but alas, no improvement. My parts are still undersized.

@Ray I am printing 3 of these on each trial. I'll try 5 and spacing them out.

Sounds like I need to run through the calibration steps to find the extrusion multiplier. Will do this and let you guys know what I come up with.

Thanks!
Jordan

JordanD85: What firmware version are you using? Pre December 13th 2013 (I can't remember the version number) had the wrong steps per mm.

Ian
RepRapPro tech support

Hi Ian,
I'm using the 057a version. I think that's still the most recent version.

I've not yet had a chance today to try the calibration that Ray and Chris suggested. But in the meantime, could this be a cooling issue? Should my fans be running continuously throughout the print?

Has anyone experimented with slightly scaling parts up in size before slicing? I know that in large process extrusion molding for plastics (and injection molding for some plastics) the tooling must be purposefully scaled larger to allow for shrinking during cooling. Not sure if this applies to printing.

Thanks,
Jordan

My Z-gear had a lot of play so decided to print a new one but faced the same problem as topic starter mentioned.

Ended up with printing two calibrationrings and checked their dimensions. The following settings are acceptable for me

Filament measured is really 1.75 mm
Set the nozzle width to 0.6 mm and filament to 2.00 mm. Parts are oversized 1%
First layer height set to 0.25mm, no extra filament on the first layer

Bigger nozzle size forces the moves towards the inside, bigger filament diameter compensates the calculated filament feed rate
Dimensions are 0.2 mm below spec (measured 10mm inside, 20 mm inside/outsdie and 30mm ottside, both rings fit perfect in each other.
I would like a small adjustment in oversizing but it only accepts integer values in % but it's fine with me as it is now.

Hope it's helpfull

NB (I am using the latest firmware)

Good luck

I should think that the same shrinkage issue would be present in printed parts as in moulded parts. After doing the calibration and wall test, I suggest printing a test piece and using the scaling function in Slic3r to adjust when you have a tight tolerance to meet.

Dave
(#106)