Accuracy of our printing parts

[chris 0]

Hi community,

i´d like to talk about an interesting theme. The accuracy of our printing parts.

Something for your information. I´am an engineering in development and design and

design products, for example pumps for the gas analytic market.

I bought the ultimaker 6 weeks ago, because I´am planing to print prototypes of my designs by myself.

Then check the parts for assembly, before I order an injection mould for thousens of euros. So far so good.

Now I got the big problem, that the printed parts are not accuracy enough to assemble them safety. I need

an accuracy about 0,1mm. I think that is not a tall order.

I started to print easy parts, to research the accuracy. For example an rectangle 30x30x5. When the printer is finish,

the part is about 29,5x29,3x5. The z-axis is very accuracy. Thats enough. But what about the x- and y axis. For my

need it´s very bad. When I scale the part to for exmple 30,5x30,7x5 it fitts perfectly. But sorry, that´s not the plan, to scale every object before priting.

Lets start a discussion, how accuracy your parts be. Maybe print rectangles, too, and tell me about this.

Another thing that I hope for, are tips and tricks too increase the accuracy. I´am a little bit frustrated, sorry.

Thanks to all Chris

[joergen 2]

I can Totally understand where you are coming from, and since you worked with injection molding and thermoplastics before, you know that plastic shrinks more or less, and that the extrusion needs to be perfectly calibrated...

the good part is, if you print PLA, you get all the material out that you drop in, at least you don't have to deal with shrinkage. the bad part is that you need to meticulously calibrate/measure your filament, and test different slicers for accuracy.

the UM itself will be spot on, 100mm are really 100mm.

how the slicers treat the extrusion width, and how they calculate the outside dimensions based on that extrusion width is another story, some might calculate the tool path as 100mm (easy to see in the gcode if you print a rectangle), ignoring how much extra material the extrusion is contributing, some might take that already into consideration, but it definitely falls into that range of 0.5mm error, which would be constant across various sized objects.

hopefully daid can give his 2 cents, since he knows the most about cure.

[alaris2 1]

you shouldn't hope for better than 0.5mm accuracy really with UM. Like Joergen says, it is theoretically capable but I have yet to print anything that was better than holes = 0.5mm too small and pegs = 0.1mm too large.

some slicers like netfabb (costs money) or k'slicer (free) can be tuned to give quite accurate parts by automatically shrinking and enlarging holes and edges - but if your filament varies in diameter at any point you can expect errors to creep in.

most people adjust the design to take this into account..

[chris 0]

I can Totally understand where you are coming from, and since you worked with injection molding and thermoplastics before, you know that plastic shrinks more or less, and that the extrusion needs to be perfectly calibrated...

yes thats right, but thats the problem of moulding company :lol:

the good part is, if you print PLA, you get all the material out that you drop in, at least you don't have to deal with shrinkage. the bad part is that you need to meticulously calibrate/measure your filament, and test different slicers for accuracy.

 

the PLA from Faberdashery is very good quality and high precise. I´am using it in white, most of the time. I tried different slicers. I got a Nettfab license but i´am not happy with it. At the moment it´s to hard for me to understand all settings, to get good results with Netfabb. But I think that is just because i am new in the business . I do all my prints with Cura. It gave me good results (except the bad accuracy) and makes me happy.

the UM itself will be spot on, 100mm are really 100mm.

how the slicers treat the extrusion width, and how they calculate the outside dimensions based on that extrusion width is another story, some might calculate the tool path as 100mm (easy to see in the gcode if you print a rectangle), ignoring how much extra material the extrusion is contributing, some might take that already into consideration, but it definitely falls into that range of 0.5mm error, which would be constant across various sized objects.

hopefully daid can give his 2 cents, since he knows the most about cure.

tomorrow I plan to measure the accuracy of the traveling distance of the x and y axis. I can´t believe its fully accurat. For me 0,1 would be enough.

When you are right, and the software caused the problems, why does nobody work on it, or do they .

: Please tell me something about the problem, if you got an idea.

The other thing I would really like to know. Is there nobody else you got the problems. What about printing things from Thingiverse. When everyone has the same problem, everybody needs to drill the holes after printing, cause a 3mm hole is max. 2,5mm.

Thanks too all.

[joergen 2]

The other thing I would really like to know. Is there nobody else you got the problems. What about printing things from Thingiverse. When everyone has the same problem, everybody needs to drill the holes after printing, cause a 3mm hole is max. 2,5mm.

holes are a known issue, where the polygon optimization in the slicer and in the firmware, combined with buffer underruns tend to fill in holes more than they should, and the slicer needs to take active steps to render holes the proper size. yes, i've been drilling my holes ever since, and I only saw perfect holes once, an earlier release of slic3r had it perfect, but the code got yanked, and is back in the que of things to be implemented.

[joergen 2]

I can´t believe its fully accurat. For me 0,1 would be enough.

I am sure you have read up on thermal expansion of plastics, since you are a specialist in this field.

0.1mm from a €1200 machine is asking a lot. and you can't always get what you want to™

[hlabs 0]

Yes, Ihave the same problem, and I'm trying to figure out where it comes from.

To the people saying it comes from the inaccuracy of the filament, I tend to think that this inaccuracy would be multiples order of magnitude lower than what we have AND not repetitive.

What we have is a very repetitive problem, so that's nothing we can't fix in the slicer.

Now, I wonder how to tackle that because it is not a constant problem accross the sizes of test elements I have printed so far. I came accross this problem while printing cylinders, but they are not good to investigate this since the slicer has to transform them in polyhedron anyway...

I'll try to investigate more