IEEE Robotics & Automation Magazine - June 2022 - 39

then suggests that the layers might be not increasing due to
nozzle clogging or a lack of filament (air printing). Therefore,
the effect of (, )CL5
Table 1, where U5L, max
U and (, )CP
, U5L, min , U
U can be summarized as in
P, max and U are the
,
P , min
threshold for the max and min values of the image five layers
ago and the previous image, respectively.
YOLO-Based Model to Detect Spaghetti
After the IC is obtained, then DL is then used to check for
the spaghetti. In this article, TSD [10], a pretrained YOLObased
model,
M ,TSD is imported. The MTSD
model processes
each image and returns all the spaghetti patterns that it
detects with confidence scores. A threshold in confidence
scores is set to filter out noises, and the current print is classified
as " failed " if the number of defective patterns detected
with a confidence above the threshold is greater than zero.
As shown in the pseudocodes, if no errors (spaghetti, detachment,
air printing) are detected, the printing continues and the
next layer process is executed. Conversely, if any defect is detected,
the printing is forced to stop, followed by the robot executing
Remove and Replace, which will be discussed in the next section.
Remove: Robotic Manipulation
for Removal of the Print
Once the failure detection occurs or the print is complete, the
next step is to use the robot to remove the current print. Usually,
as in the case of manual removal, humans use their
hands to remove the print, or tools (such as scrappers) for
the prints with strong adhesive forces on the heatbed steel
sheet. In this way, different sizes of the prints can be easily
removed. However, imitating such human skills to use the
tool poses a challenge on robotic manipulation. This is
because many factors are then required to be considered for
Table 1. Threshold of the image comparison
for each of the failures.
Detection
Detachment
Air printing
Others or no failures
Results
CL
CL
Others
UU2 (, ),max UU2 P
UU1 (, ),min UU1 P
55L
55L
CP
CP
and (, ),max
and (, ),min
Background Image, IBG
Five Layers Ago, I5L
Previous Layer, IP
Current Layer, IC
Detachment
IBG
I5L
IP
IC
Id(5L, BG)
Id(P, BG)
Id(C, BG)
It(5L, BG)
It(P, BG)
It(C, BG)
(C, 5L)
(C, P)
Figure 5. The IC algorithm, one of the algorithms in Detect (with detachment as the example). Assuming detachment occurs in
the current layer, the images from the previous layer, five layers ago, and the background images are compared with the absolute
difference, threshold, and normalized root mean-square error (NRMSE), respectively, to find the difference. The last two results, (, )CL5
and U classify the conditions of the printing as detachment, air printing, or others.
U
(, ,)CP
JUNE 2022 * IEEE ROBOTICS & AUTOMATION MAGAZINE *
39
4) NRMSE
3) Threshold
2) Absolute
Difference
1) Gray Scale
IEEE Robotics & Automation Magazine - June 2022

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - June 2022
