Accuracy of printed parts

[matthiash 0]

Hello,

I really enjoy printing with my new Ultimaker.

Nevertheless I know observed several times that the scale of printed parts is not accurate.

I m printing parts for a mechanical prototype, which should be mass produced out of aluminum next year.

In the cad drawing the part has a size of 50 mm x 149 mm. When I imported the stl into cura the measures were still the same.

Nevertheless the printed part had measures of 49 mm x 142 mm.

I searched on cura for settings to maybe solve the problem but I couldn't.

For me it sounds like a problem with the gcode, but I have no idea how to handle it.

Did anyone observe the same problem?

Would very much appreciate your help.

Cheers,

Matthias

 

[illuminarti 18]

UM1 or UM2? Anything non-standard about it?

You might see differences of a mm or less on X-Y dimensions due to shrinkage, etc. But 149 v 142 is way off from what you should expect. It seems like the steps-per-mm calibration is probably wrong in your firmware.

 

[matthiash 0]

It is a UM1 standard, I m using it since last week, everything is standard.

How can I adjust the steps-per-mm calibration in the firmware?

Can the shrinkage be reduced by using a heat plate?

 

[illuminarti 18]

No, heated plate might help if the shrinkage is causing the print to warp or crack - but that's usually only the case with ABS. It's just a fact of life that plastic shrinks slightly, and there's nothing you can do about it. Injection molding has similar challenges.

Do you have an Ulticontroller? If so, look in Control -> Motion for the steps per mm settings, and report them back.

If not, there's a gcode that shows the settings, but I'm not sure - maybe M503, but I'm not sure if that supported in UM1 standard firmware. Try sending that to the printer using Cura, Pronterface, or whatever you connect with.

 

[IRobertI 521]

I think Pronterface spits those values (along with other config values) out as soon as you connect to the printer.

 

[matengi 0]

Do the differences change after rotating the part 90°? The shrinkage is extremely unbalanced, 0.5% vs. 3.5%.

 

[gr5 2,331]

In the cad drawing the part has a size of 50 mm x 149 mm. When I imported the stl into cura the measures were still the same.

Nevertheless the printed part had measures of 49 mm x 142 mm.

 

WTF? That's a typo, right? Seriously? If it really printed 7mm short then something is very very wrong.

With heat off place a ruler on your bed. Move the test head to a postiion over the ruler and then move the test head 50mm. It should move 50mm. Not 48.

Pronterface is a very useful tool for messing around - moving an axis 10mm at a time or whatever and for examining and changing the steps/mm values.

 

[gr5 2,331]

If that was a typo then I have totally different advice...