Dimensions off on final part

3

I'm experiencing an issue with my Makerbot Replicator 2X (2000+ hours printing). The dimensions of my final part are smaller than what is initially modeled. My parts have been coming out roughly 0.3mm smaller than what is initially modeled. Is this a common issue or does this sound more like I may have a hardware issue?

I've confirmed that all my belts are tensioned properly and lubricated correctly. I haven't seen a calibration step that would correct for this issue short of manually scaling my parts to correct for the offset. The offset appears to only occur in the XY axis, never seems to happen in Z though

Example: In the part modeled I had the width designed to be 35 mm (face to face, parallel walls). It doesn't seem to matter what size of part I have the final dimensions always seem to be off by about the same amount.

35mm width modeled

Diesel

Posted 2017-01-06T19:24:53.300

Reputation: 1 745

Hi Diesel. Can you please include a photo? – StarWind0 – 2017-01-06T21:19:36.063

Is this a consistent 0.3mm, or does it increase with part size? – Sean Houlihane – 2017-01-06T21:27:13.593

It seems to be fairly consistent offset. (I'll be able to add an image on Monday) – Diesel – 2017-01-07T01:42:32.163

1Are you using a filament which shrinks more upon cooling than the software is configured to compensate for? – Davo – 2017-01-11T14:24:24.380

I think so? Only because the z-axis dimensions are usually pretty spot on (variance largely due to roughness), and the amount of shrinkage stays constant regardless of the size of part. If it were a thermal contraction issue I would expect it to shrink more the larger the part is? (That's half statement half question) – Diesel – 2017-01-16T14:22:16.147

Answers

1

Yup that is what happens. It is simply the plastic cooling and shrinking. It will happen on just about any printer. 0.3mm on a what 40mm part. That is 99.3% on target.

There are some great blog links about it, and here is a Stack overflow where I talk about it more in detail.

The only mitigations I can think of is 1) use a hear chamber. 2) use a SLA 3d printer.

I wouldn't worry about it. Just make sure your designs have good tolerances.

StarWind0

Posted 2017-01-06T19:24:53.300

Reputation: 2 913

Great info! I hadn't thought about the internal dimensions shrinking due to expansion. But, it seems that I'm experiencing the opposite effect. My outer dimensions are smaller than what is modeled. 35mm becomes 34.7. Would this still be a result of the same thermal expansion do you think? – Diesel – 2017-01-18T01:06:51.567

Yup. Things will Shrink when cooled. You will see Expansion only at the first level (IE elephant foot) but that has to do with over extrusion. Circles will always shrink as well. – StarWind0 – 2017-01-20T19:29:59.210