SunStar HC Series User Manual page 25

2) Upper Thread Tension Adjustment
[CAUTION]
Thread tension adjustment is critical for producing high quality of the embroidery. A balance of 2/3 upper
thread and 1/3 lower thread generally indicates good tension. If the tension is too loose, the upper thread will
loop, causing thread tangles or breaks. If the tension is too tight, puckering may occur as well as thread and
needle breaks.
① The upper thread tension is controlled by the sub
and main thread tension adjusters. Turn clockwise
to increase the tension and counterclockwise to
decrease the tension.
② The sub-tension adjusters should control about 2/3
of the thread tension while the main adjuster should
handle the other 1/3. Set the sub-tension adjuster so
the upper thread flows smoothly through the rotary
tension disks and into the rollers of the main
tension adjuster.
[CAUTION]
If tension at the sub adjuster is too loose, the detector roller may not rotate well and make wrong
detections.
After adjusting the tension, check if the upper thread tension is what can be pulled with little force of
around 100-120g.
[CAUTION]
After adjusting the tension, pull the upper thread to see if the detector roller rotates well.
Adjust the tension according to the type of thread and fabric used.
[CAUTION]
As the upper thread is always fixed by the upper thread holding device, when adjusting the thread tension,
make sure to pull the upper thread holder plate toward yourself for feeding of the thread. (Threading around
the needle)
Adjusting nut
Sub-
tension
adjuster
Main
tension
adjuster
[Fig.4-6]