Geometric Accuracy


#1

I have read all accuracy topics posted here and couldn’t find full answer for :
How to evaluate the XYZ performance and how to fix issues.
I have very distorted parts (oval shape).
I’m planing of printing a cube at few platform locations.
Can the issue be 3D (meaning that the accuracy changes at different Z positions) ?
Peopoly - any official instructions ?


#2

http://wiki.peopoly.net/doku.php?id=moai-checkup
follow the instructions here to evaluate the performance


#3

Thanks for the link but the instruction are not the case (all is set as instructed)

My concern is more related to the following topics:


Basic Accuracy


#4

At the link below:
http://www.zamisel.com/SSpostavka2.html
you can find explanation about Laser-scanning image field distortion.
The distortion looks just like 120mm Square Test Pattern
Here are the important issues:

  1. The arrangement of the mirrors leads to a certain distortion of the image field. The distortion arises from the fact that the distance between mirror 1 and the image field depends on the size of the scan angles of mirror 1 and mirror 2. A larger scan angle leads to a longer distance.
  2. The distance in the image field is not proportional to the scan angle.

ZAMISEL d.o.o. offers a software solution package of programs that eliminate the image field distortion effect. More information is available in the file rectification.pdfwhich is available on request by email.

Source: SCANLAB’s PC Interface Board RTC3 Manual. SCANLAB produces scan heads for the galvanometer scanners.

Peopoly -
Some of us (the users) really need accuracy.
Please do your best to solve it (I suggest you contact them ,or similar ,since your struggle takes too long)


#5

Geometric accuracy - round 2

XY calibration:
I have printed 2 cube (one in the center of build plate and the other in the right front)

Cube is 24X24X24 mm
After two rounds of - Printing , measuring ,changing X-SIZE and Y-SIZE in setups
I have achieved:
Center cube - X/Y/Z below 0.1 mm error
Corner cube - X/Z below 0.1 mm error , Y +1 mm error

Can this kind of error enable mechanism and mechanical assembly print ?

Error mapping
I have print a grid on half the build plate (the right half) as shown below:

I measure each square (which are about 13X13 mm) just after cleaning but not curing
(I have done it very gently with caliper under microscope)
I put error results in % per each square for X and for Y

Results:
X error – below 0.7 [%] all around (great ! ! )
Y error [%] :


As can be seen the center (Y) is perfect but get to be very distort as you move off center.
What is the criteria for acceptable error ?
I assume below 0.5 [%] is the target for mechanical parts printing.
Peopoly are working on a correction.
Is it machine specific or general ?
Can a general solution be good enough ?

Print verification:
After realizing how distort is the print I run sanity check by printing male cylinders and female cylinders (0.2 mm gap) which should rotate freely.


The parts were printed one beside the other at the center of build plate and close to its right end.
Results:
The one on the center perform OK
The one on the right-end was too oval to rotate freely.

Notes:
My setup:
Resin - Peopoly white
Machine works fine
Leveling is perfect
PDMS VAT


#6

Hi! This is a known issue with laser galvo systems. It can be corrected with a F-tetha lens but then the price for the printer would go up by quite a bit…

The dissortion problem was adressed with the 1.16 update and to my knowledge Peopoly is trying to adress this issue even further.


#7

we are taking software approach to this as optical solution is too expensive for a printer at this level. The next version of Asura is slated to have this feature and we are working to get it out as soon as we could. The fix would not be perfect but should reduce some of the distortions we have and we plan to continue to fix it. The Asura will create the adjusted gcode for printing.


#8

we are taking software approach to this as optical solution is too expensive for a printer at this level. The next version of Asura is slated to have this feature and we are working to get it out as soon as we could. The fix would not be perfect but should reduce some of the distortions we have and we plan to continue to fix it. The Asura will create the adjusted gcode for printing.


#9

Use the Asura 2 Beta with integrated calibration.

X was great all over before and seems the same now.

Side distortion in Y direction (X center Y at right edge) was reduce from ~4.6 to 0.75 %.
Great result ! ! !

Corner distortion in Y direction was reduce from ~5.0 to 1.5 % ,Not perfect but in the right direction.

Well Done Peopoly ,Keep going


#10

good to hear about the feedback. We are still working on improving it so stay tuned


#11

Where is the calibration STL shown in the Asura user manual?


#12

It’s an option that’s now part of the built in slicing, you can select the distortion correction from the calibration menu when you hit the export button.


#13

Not on my export menu. I’ve got v2.0 installed. I still have to load the STL before doing the export.