Checking Of The Knife Unit - JUKI DDL-8000AS Instruction Manual

5-3-3. Checking of the knife unit

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the
sewing machine.
❶
Standby state of the knife
A
5 to 6 mm
❶
❶
Aligning state of salient portion of loop spreading
knife and thread trimming knife
Far end of the hole in
loop spreading knife
❶ aligns with the tip of
thread trimming knife ❷
❶
2 to 2.5 mm
(H type : 2.5 to 3 mm)
State of engagement of knife
❷
❷
❷
❶
❷
A
❷
A
– 61 –
1) Check to make sure that the power switch is in
the OFF state. Remove the gauge (presser foot,
throat plate and feed dog) from around the nee-
dle.
2) In the standby state of loop spreading knife ❶ ,
the distance from center of needle A to the tip of
loop spreading knife ❶ is 5 to 6 mm.
Be aware that, if the distance between
loop spreading knife ❶ and center of
needle A is reduced, thread loop is likely
to interfere with loop spreading knife ❶ .
* Refer to "5-3-4. Adjustment of the knife unit" p.
62 for how to adjust it.
3) The purpose of adjustment of the aligning posi-
tion of loop spreading knife ❶ and thread trim-
ming knife ❷ (far end of the hole in loop spread-
ing knife ❶ and the tip of thread trimming knife ❷ )
is to align the aforementioned aligning position
with center of needle A.
Be aware that, if the aligning position of
the loop spreading knife and the thread
trimming knife does not align with
center of needle A, the length of thread
remaining on the material after thread
trimming will be longer.
4) The amount of engagement between loop
spreading knife ❶ and thread trimming knife ❷ is
2 to 2.5 mm (H type : 2.5 to 3 mm) as measured
from center of needle A.
Be aware that, if the amount of engage-
ment between them is insufficient, faulty
thread trimming can occur.
* Refer to "5-3-4. Adjustment of the knife unit" p.
62
for how to adjust it.
In the case of using a thread that is like-
ly to cause unstable thread loop forma-
tion, the needle thread may be trimmed
extremely short when thread trimming
is carried out at a position where no
material is present.
In this case, correct the aforementioned
problem by increasing the thread take-
up spring stroke to a value that is larger
than the standard value.