Interlocking Parts

Ive been calibrating my printer and have it printing with a pretty good quality.
Im now looking for accuracy: for the part to match the model within .05mm or less.
Ive done the whole interlocking blocks and decrease perimeter extrusion width but it hasnt worked too well.

What else is done to calibrate this aspect of printers? Any special tricks?

Thanks for all the help,
-Nick

... for high accuracies/precision you have to calibrate your XYZ-positioning with other means than measuring printed objects -- better insert a sharpie and draw some squares ... or measure the translation of every axis against a precise measure.

Then you have to fine calibrate your extrusion width and height ... especially when squeezing the filament, as common.

I don't think, you'll achieve better repeatable printing accuracies than 0.1mm, even if your positioning acuracy will be 0.01mm ... simply because of the inaccurate (around +/- 0.05mm) XY-dimension of the extruded filament ...

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Viktor
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If you're trying to print interlocking parts it isn't usually precision that matters, it's repeatability if you end up scaling it all down or up by 5 or 10% it'll all still interlock.
Not interlocking is usually a function of poor repeatability, not calibrating the extrusion width, or having a model with no tolerance.
Even if you precisely machine them an 8mm rod is not a slip fit into an 8mm hole, you need some tolerance usually in the 0.02 mm range, with extruded plastic I'd go with a lot more than that.

Edited 1 time(s). Last edit at 01/24/2013 12:10PM by Polygonhell.

I think that a tolerance of 0.05 mm is asking too much from FDM. When I print parts that interlock, I give allowances of up to 0.5 mm.

Why do you need that level of accuracy? I know when I want very accurate holes for example, I find it much easier to drill/ream out the hole to exact specs than I do trying to calibrate my printer more than it already is. Getting 0.05mm in all directions is going to be very tricky.

I have a project in my engineering class where we design and print a mousetrap vehicle. The class has a Dimension FDM printer but I would like to use my own. So really I just want to get the most accurate parts possible. If I must drill holes and account for tolerance that's fine, I just thought Ive heard of people printing a part that perfectly matches the model.

-Nick

VDX wrote: I don't think, you'll achieve better repeatable printing accuracies than 0.1mm, even if your positioning acuracy will be 0.01mm ... simply because of the inaccurate (around +/- 0.05mm) XY-dimension of the extruded filament ...

That is an interesting and illuminating statement. I hadn't considered the filament's inherent diameter variance as a source of issues in this way, but it's patently clear now, since extrusion rates are based on an assumed filament diameter, not actual.

thank you.