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◎ Skipped stitch
　 (The needle thread leftover on needle tip after trimming is too short.)

Check：

The needle thread guide is incorrect. The tension of the needle thread is too strong when trimming.

Adjustment：

Check the needle thread guide. Adjust the thread on the thread guide lever and the position of the thread guide lever on the thread stand.

Check：

The thread tension of the first thread clamp is too strong.

Adjustment：

Turn the thread clamp nut of the 1st thread clamp left to reduce the tension.

Check：

The raising volume of the 2nd thread clamp is not enough while trimming.

Adjustment：

When pushing the lower thread press rod right, check the lifting volume of the 2nd thread clamp to be about 0.5~1.0 mm. Check the parallel of the thread clamp by the adjusting nut under the lower desk plate. If the parallel is not qualified, please try to rotate the thread clamp spring 180° or correct the slope of the spring.

Check：

The cam positions too early.

Adjustment：

Check and adjust the timing of the cam.

Check：

Because of the incorrect position of the lower thread press rod, the needle thread escapes from the needle while trimming.

Adjustment：

Check the tension of the fixed screw of the lower thread press rod.

Check：

The fixed trimmer is too close to the needle. The trimmer tip is too sharp.

Adjustment：

Remove the needle plate, and check the position of the fixed trimmer or fix where the movable trimmer is damaged.

Check：

Trimmer, thread holding plate, movable trimmer or bobbin has problems.

Adjustment：

Check the damaged part of the bobbin and the thread holding plate hole. If there are burrs, polish them with the carborundum paper. If the damage is too serious, please replace it with a new one.

Check：

The timing of the standard cam is too early.

Adjustment：

Adjust to the timing that is suitable for chemical fiber threads.

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◎ Skipped stitch (Improper use of the needle, the needle plate,
　 or the presser foot, or the pressure of the presser foot is too small.)

Check：

The size a of the presser foot is too wide, or the feeding entrance of section b is too large, therefore the seamed needle thread cannot be held. The feeding entrance, A, of the needle plate hole is too large.

Adjustment：

Check the parts a and b, and the shape of the part A of the needle plate.
1. When using chemical fiber threads on the toric cloths, the a<0.8 mm, b<0.3 mm, and the r of A is less than 0.3 mm.
2. When using chemical fiber threads, a<1.2 mm. Also, the clearance between parts b and A should be as small as possible.
3. When using the cotton threads, make the clearance of a, b, and A as small as possible, but do not making the tension improper.
4. The thiner the materials, the thicker the density. In addition, the needle thread will slip easily. The smaller the needle number, the smaller the clearance of a, b, and A.

Check：

The needle is too thick.

Adjustment：

Use the needle as small as possible as long as the thread tension keeps in normal.

Check：

The needle plate eyelet is too big.

Adjustment：

Replace it with a needle plate with smaller eyelet.

Check：

The pressure of the presser foot is too small.

Adjustment：

Strength the tension by adjusting the presser foot adjusting screw, but not to reduce the feeding strength (the fabric shall not be gathered.)

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◎ Skipped stitch (The hook tip cannot hook the needle thread and
　 form skipped stitches.)

Check：

The locations of the bobbin and the needle are not well.

Adjustment：

Check the height of the needle bar. Please try to reach the requirement of 2.0 mm mark line of the needle bar. When using the knitting fabrics, please lower down the needle bar a little and delay the timing.

Check：

The tension of the thread take-up spring is too strong, and its movement is too strong, too.

Adjustment：

Reduce the tension and the movement.（The standard is 5~7mm）

Check：

The thread tip is worn to be flat.

Adjustment：

Fix the hook tip or replace the bobbin.

Check：

The needle is not assembled well.

Adjustment：

Adjust the slope of the needle. When the needle is bent, please replace it on time.

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◎ Skipped stitch
　 (The start of the bobbin thread is too short when sewing starts.)

Check：

Because of the bobbin idle running, the front end of the bobbin thread is pulled into the bobbin case.

Adjustment：

1. Increase the pressure of the bobbin thread press plate.
2. Increase the bobbin thread tension.

Check：

The pressure of the bobbin thread press plate is too strong.

Adjustment：

Reduce the pressure until the bobbin can perform idle running.

Check：

There is a scratch on the bobbin, or the bobbin thread is trimmed too short.

Adjustment：

Polish and grind the scratch, or replace a new bobbin.

Check：

the sewing speed is too fast at the beginning.

Adjustment：

Slow starts (800spm), and stitches 1~2 stitches first.

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◎ The thread lint comes out of the fabric at the beginning. (The needle
　 thread leftover on the needle is too long.)

Check：

The first tension adjusting disc is too weak.

Adjustment：

Strength the first tension adjusting disc.

Check：

The timing of the trimming cam is too slow.

Adjustment：

Adjust the timing of the cam.

Check：

The fixed trimmer moves backward too much.

Adjustment：

Adjust the fixed trimmer.

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◎ Too many lints in the back of the fabric when starting stitching.
　 ( Improper needle, needle plate, or the presser foot. The lint cannot
　 be shortened after trimming.)

Check：

The size a of the presser foot is too wide, or the feeding entrance of section b is too large, therefore the seamed needle thread cannot be held. The feeding entrance, A, of the needle plate hole is too large.

Adjustment：

Check the parts a and b, and the shape of the part A of the needle plate.
1. When using chemical fiber threads on the toric cloths, the a<0.8 mm, b<0.3 mm, and the r of A is less than 0.3 mm.
2. When using chemical fiber threads, a<1.2 mm. Also, the clearance between parts b and A should be as small as possible.
3. When using the cotton threads, make the clearance of a, b, and A as small as possible, but do not making the tension improper.
4. The thiner the materials, the thicker the density. In addition, the needle thread will slip easily. The smaller the needle number, the smaller the clearance of a, b, and A.

Check：

The needle is too thick.

Adjustment：

Use the needle as small as possible as long as the thread tension keeps in normal.

Check：

The needle plate eyelet is too big.

Adjustment：

Replace it with a needle plate with smaller eyelet.

Check：

The pressure of the presser foot is too small.

Adjustment：

Strength the tension by adjusting the presser foot adjusting screw, but not to reduce the feeding strength (the fabric shall not be gathered.)

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◎ The needle thread falls off from the needle at the beginning of
　 sewing. (The needle thread leftover on the needle tip is not enough
　 after trimming.)

Check：

Because the timing of the cam is too late, and the tension of the first thread tension adjusting disc is too strong, the thread has been trimmed before the movable and the fixed trimmers come across to each other. (Trimming in the midway.)

Adjustment：

Stop the motor, and push the thread control set toward the bobbin. Turn the pulley toward your direction (or tread the pedal to turn the pulley) to lift the needle to the upper dead point. If the the remaining thread is less than 10 mm, this means the lint is too short. Set the trimming time short and reduce the thread tension to solve this problem.

Check：

The thread of the thread control set doesn't pass the bobbin center and this causes the thread broken often.

Adjustment：

Correct the position of the thread control set.

Check：

The trimmer is over used and functions abnormally.

Adjustment：

Sharpen the knife or change a new one.

Check：

There is a flaw on thread trimming guard, movable trimmer, or the bobbin.

Adjustment：

Fix the damaged part or replace a new one.

Check：

The needle is too thick.

Adjustment：

Replace wtih a thin needle.

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◎ The needle thread falls off from the needle at the beginning of
　 sewing. (The lint falls from the needle tip as soon as trimming.)

Check：

The cam timing is too early, which causes the thread on the needle tip being trimmed.

Adjustment：

Because the trimmer functions abnormally, the thread on the needle tip is trimmed. Open the plate, and there will have a thread about 20 mm remaining inside. slow down the trimmer cam to adjust it.

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◎ The needle thread falls off from the needle at the beginning of
　 sewing. (The needle doesn't cross the bobbin thread while
　 starting sewing.)

Check：

The speed is too fast at the beginning so that the needle and the bobbing thread cannot cross to each other.

Adjustment：

Slow starting (800spm). Sew 1~2 stitches first.

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◎ The needle thread falls off from the needle at the beginning of
　 sewing. (The needle doesn't cross the bobbin thread while
　 starting sewing.)

Check：

The bobbin thread pressing lever is not assembled correctly.

Adjustment：

Adjust the bobbin thread pressing lever.

Check：

Because the bobbin is idle running, the bobbin thread tension is too loose while starting sewing.

Adjustment：

Adjust the bobbin thread pressing lever. Use a bobbin case with a spring.

Check：

The tensions of the bobbin thread and needle thread are too loose.

Adjustment：

Increase the tensions of the bobbin thread and needle thread.

Check：

The presser foot doesn't not match with the needle plate.

Adjustment：

Check the parts a and b, and the shape of the part A of the needle plate.
1. When using chemical fiber threads on the toric cloths, the a<0.8 mm, b<0.3 mm, and the r of A is less than 0.3 mm.
2. When using chemical fiber threads, a<1.2 mm. Also, the clearance between parts b and A should be as small as possible.
3. When using the cotton threads, make the clearance of a, b, and A as small as possible, but do not making the tension improper.
4. The thiner the materials, the thicker the density. In addition, the needle thread will slip easily. The smaller the needle number, the smaller the clearance of a, b, and A.

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◎ The needle thread can not be trimmed, whereas the bobbin thread
　 can be trimmed. (Skipped at the last stitch.)

Check：

The needle in the needle clamp is assembled incorrectly.

Adjustment：

Adjust the assembly of the needle, and check if the needle is bent.

Check：

The stroke of the thread take-up spring is too wide.

Adjustment：

Lower down the thread take-up stroke about 5-7 mm.

Check：

The hook timing is incorrect.

Adjustment：

Confirm if the thread skips while it is at low thread control sewing. Readjust the stroke of the hook. (This standard is 2 mm faster.)

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◎ The needle thread can not be trimmed, whereas the bobbin thread
　 can be trimmed. (A certain part of the trimmer is not sharp.)

Check：

The trimming parts of the movable and the fixed trimmer cannot engage with each other competely while trimming. (The assembled angle, position, and the slope of the trimmer tip don't match with the movable trimmer.)

Adjustment：

Remove the needle plate, and move the trimmer by one hand. Try to trim 3 cotton threads of #50. If the threads cannot be trimmed, please confirm:
1. the trimmer tip
2. the slope of the fixed trimmer tip
3. Readjust the assembled position of the fixed trimmer.

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◎ The needle thread can be trimmed, whereas the bobbin thread cannot
　 be trimmed. (The backward volume of the movable trimmer is
　　not enough.)

Check：

The movable knife cannot return to the origin fully. The adjustment of the movable knife is incorrect. The relative positions of the two knives are incorrect.

Adjustment：

Check the movable trimmer and all relative process. Adjust the engage range of the two trimmers to be 3.0-3.5 mm.

Check：

The assigned hook is not used in the machine.

Adjustment：

Check the hook to see if there has the hook thread guiding line. If there has no guiding line, please change a new one.

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◎ The thread wiper cannot reach the needle.

Check：

The assembled height of the thread wiper is incorrect.

Adjustment：

Readjust its assembled position.

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◎ The material is puckering while sewing. (Because of the puckers or
　 incorrect line, the materials has puckers on it.)

Check：

The needle is too thick.

Adjustment：

Use thin needles as possible or KN needle (Normal). EX: DB×1#11→DB×1KN#9

Check：

The bobbin thread tension is too strong. The thread path is not smooth.

Adjustment：

Fix the thread path.

Check：

The bobbin thread tension is too strong. The bobbin timing is too late.

Adjustment：

Shorten the bobbin timing as much as possible to improve the process. However, there should be no stitch skipping.

Check：

The bobbin thread tension is too strong. The feeding timing is too early.

Adjustment：

Campared to the needle, delaying the feeding to achieve the purpose of tensing the feeding.

Check：

The thread take-up stroke is too large.

Adjustment：

Move the thread guide on the machine arm right to reduce the supplying thread amount of the thread take-up.

Check：

The stroke of the thread tension adjusting disc is too short.

Adjustment：

Increase the stroke.

Check：

Use the unsmooth threads.

Adjustment：

Use the ethylene fiber threads.

Check：

The pressure of the presser foot is too much.

Adjustment：

Adjust the pressure of the presser foot to the min. （Not to influence the feeding）If the presser foot can be lifted a little, the effects will be better.

Check：

The bottom of the presser foot is not smooth.

Adjustment：

Grind it by a grinding roller.

Check：

The fabric is difficult to be fed.

Adjustment：

Use the teflon presser foot or the presser foot with nitric special treatment.

Check：

Wrinkles on the feeding tapes; the needle plate hole is too large.

Adjustment：

Use the needle with a smaller needle eyelet.

Check：

Wrinkles on the feeding tapes; the tool withdrawal groove in the back of the presser foot is too large.

Adjustment：

Use the presser foot with a smaller tool withdrawal groove or with no groove.

Check：

Wrinkles on the feeding tapes; the presser foot is not parallel.

Adjustment：

Replace the presser foot or the presser lever.

Check：

The needle tip is damaged.

Adjustment：

Replace with a new needle.

Check：

Feeding is not smooth. The feed dog is too high.

Adjustment：

Lower down the height of the feed dog with influencing the feeding.

Check：

Feeding is not smooth. The tips of the feed dog teeth are worn.

Adjustment：

Polish the tips of the feed dog teeth.

Check：

The clearance between each feed dog tooth is too wide.

Adjustment：

Use the feed dog with smaller clearance.

Check：

The slope of the feed dog teeth is poor.

Adjustment：

Make the front part of the feed dog up to improve the effects of front guiding.

Check：

The feed dog doesn't have well parallel situation.

Adjustment：

Replace with a new one.

Check：

The sewing speed is too fast.

Adjustment：

Slow down the speed.

Check：

Others

Adjustment：

1. Use a front roller to assist the feeding device.
2. Pull the fabric backward properly to asist the operation.
3. Use aluminum bobbin (code: B9117552A000)

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◎ The materials are departured. The upper and lower layers has
　 departed in feeding.

Check：

The feed dog is too high.

Adjustment：

Without influencing the feeding, lower down the height of the feed dog as much as possible.

Check：

The feed dog teeth are blunt.

Adjustment：

Sharpen the feed dog teeth.

Check：

The stitch length of the feed dog is too wide.

Adjustment：

Replace with a feed dog with narrower stitch length.

Check：

The slope of the feed dog is not enough.

Adjustment：

Adjust the slope of the feed dog to make the front part to be lower.

Check：

The feeding timing is too late.

Adjustment：

Readjust the timing of the feed dog.

Check：

The pressure of the presser foot is too strong.

Adjustment：

Adjust the pressure of the presser foot to the min. （Not to influence the feeding）If the presser foot can be lifted a little, the effects will be better.

Check：

The bottom of the presser foot is not smooth.

Adjustment：

Grind it by a grinding roller.

Check：

The fabric is difficult to be fed.

Adjustment：

Use the teflon presser foot or the presser foot with nitric special treatment.

Check：

The sewing speed is too fast.

Adjustment：

Slow down the rotating speed.

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◎ The sewed thread is not firm and forms ballons. The threads hooking
　 position is on or under the fabric and forms ballons.

Check：

The thread tension is too small.

Adjustment：

Check and adjust the thread tension.

Check：

The thread clamp spring is not adjusted well. The stroke is too small.

Adjustment：

Increase the stroke.

Check：

The thread clamp spring is not adjusted well. The thread tension is too small.

Adjustment：

Increase the tension.

Check：

The thread clamp spring touches the bobbin case.

Adjustment：

Adjust them to not to touch to each other.

Check：

The stroke of the thread take-up lever is too wide.

Adjustment：

Move the thread guide on the machine arm right to reduce the supplying thread amount of the thread take-up.

Check：

The bobbin timing is too early.

Adjustment：

The standard timing is when using cotton threads. Or, you may adjust the timing to be later a little.

Check：

The bobbin timing is too short.

Adjustment：

While using the chemical fiber threads, it should reach the requirements or be earlier a little.

Check：

The clearance between the bobbin and the bobbin thread press plate is too narrow.

Adjustment：

Increase the clearance from the bobbin to the bobbin thread press plate in order to make the thread come out smoothly from the bobbin.

Check：

The lubricant at the bobbin section is too less.

Adjustment：

Add the oil to make it properly.

Check：

The bobbin doesn't function well.

Adjustment：

If the quality of the bobbin is bad or poor, please replace it.

Check：

The thread cannot pass the thread path smoothly.

Adjustment：

Correct the thread path.

Check：

There are flaws of the thread path.

Adjustment：

Grind or polish the thread path.

Check：

The quality of the thread path is poor. The needle thread is hooked while passing the thread path.

Adjustment：

Grind and polish the thread path.

Check：

The bobbin thread is usually dragged because of the mis-located of the bobbin and the bobbin case.

Adjustment：

Replace with a new bobbin or a bobbin case.

Check：

The quality of wound thread of the bobbin is poor.

Adjustment：

Is the thread tension too strong or too weak? If the quality is poor, please rewind the thread.

Check：

The tension spring of the bobbin doesn't function well.

Adjustment：

Replace with a new bobbin case.

Check：

The bobbin thread inside the bobbin case is idle running.

Adjustment：

Use the bobbin case with spring or place a piece of thin fabric inside the bobbin to prevent idle running.

Check：

The feeding timing is incorrect, or the feed dog is too low.

Adjustment：

When using cotton threads and reeled pongee threads, adjust the feeding timing closer a little than the standard one. In addition, when using chemical fiber threads, raise the feed dog height earlier. (The max is 1 mm.)

Check：

The presser foot is improper. The presser foot lifting phenomenon happens.

Adjustment：

Adjust the height of the presser foot.

Check：

The thread tension adjusting disc is improper. The feeding groove in the bottom of the presser foot is too small or has no groove (for thick threads or wide clearance).

Adjustment：

Use the presser foot with bigger feeding groove.

Check：

The thread tension adjusting disc is improper. The lifting phenomenon happens.

Adjustment：

Adjust the thread lifing timing of the thread tension adjusting disc based on the specification.

Check：

The needle plate hole is too small.

Adjustment：

Use a needle plate with bigger hole.

Check：

Compared to the thread, the needle is too thin.

Adjustment：

Replace whether the needle or the thread.

Check：

The needle is improper. There are flaws at the needle tip.

Adjustment：

Replace with a new needle. (When using chemical fiber threads, it is better to use the needle with round tip.)

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◎ Skipped stitch. Cannot form loops partially, which effects the
　 completion and the beauty of the entire sewing thread.

Check：

The needle is improper. The needle is bent.

Adjustment：

Replace with a new needle.

Check：

The needle is improper. The assembled direction of the needle is incorrect.

Adjustment：

Adjust the direction and re-assemble it.

Check：

The needle is improper. The needle tip is worn to be blunt.

Adjustment：

Replace with a new needle.

Check：

The needle is improper. The needle is too thick or too thin compared to the needle thread.

Adjustment：

Replace wit a proper needle based on the requirements of sewing.

Check：

The hook tip is broken or worn.

Adjustment：

Correct the hook tip or change a new hook.

Check：

The hook timing is incorrect.

Adjustment：

Readjust. (According the materials of fabrics and the threads, readjust to the proper timing. Generally, normal chemical fiber threads and thick materials need an earlier timing, whereas the thin materials need a later timing.)

Check：

The height of the needle bar is incorrect.

Adjustment：

Adjust the hook tip up and down. (For normal chemical fibers, adjust it upper. For thin materials, adjust it lower.)

Check：

The bobbin functions poorly. The clearance between the hook tip and the nnedle is too wide.

Adjustment：

Adjust the clearance as small as possible.

Check：

The bobbin is poor. The motion of forming balloon is unstable.

Adjustment：

Wind the thread on the needle.

Check：

The tension of the needle thread is too strong.

Adjustment：

Reduce the tension and adopt the cooling device.

Check：

The rotating speed of the sewing machine is too fast.

Adjustment：

slow down the sewing speed.

Check：

The feeding is not correct because the needle is bent.

Adjustment：

Replace with a new needle. Readjust the positions.

Check：

The thread clamp spring is not adjusted well. The stroke of the thread clamp is too wide.

Adjustment：

Narrow the stroke.

Check：

The thread clamp spring is not adjusted well. The tension of the thread clamp is too strong.

Adjustment：

Narrow the stroke or reduce the tension on poor sections.

Check：

Not match the requirements of the sewing. The presser foot starts lifting.

Adjustment：

Adjust the height of the presser foot based on the characteristics of the materials.

Check：

Not match the requiements of sewing. The needle plate eyelet is too big.

Adjustment：

Use the needle plate with small needle plate eyelet as possible.

Check：

Not match the requirements of sewing. The feeding groove in the bottom of the presser foot is too large.

Adjustment：

Use the presser foot with smaller feeding groove or no feeding groove.

Check：

The parallel situation of the presser foot is not good.

Adjustment：

Readjust the presser foot or the presser foot lever.

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◎ The needle thread is broken. The needle thread is broken or worn-off
　 during sewing.

Check：

Problems happened in threading. (Including needle plate, feed dog, presser foot, and so on.) The thread path is not smooth.

Adjustment：

Fix the thread path.

Check：

Problems happened in threading. (Including needle plate, feed dog, presser foot, and so on.) There are some flaws in the thread path.

Adjustment：

Fix the thread path.

Check：

Problems happened in threading. (Including needle plate, feed dog, presser foot, and so on.) The needle thread is hooked by the part of the thread path.

Adjustment：

Fix the thread path.

Check：

The tension of the needle thread is poor. The needle thread tension is too strong or too weak.

Adjustment：

Adjust the needle thread tension properly.

Check：

The needle thread tension is not well. The tension of the first thread clamp is too small.

Adjustment：

Adjust to the proper tension.

Check：

The thread clamp spring is not adjusted well. The stroke of the thread clamp spring is too wide or too narrow.

Adjustment：

Readjust the stroke of the thread clamp spring. Readjust the tension of the thread clamp.

Check：

The needle is bent.

Adjustment：

Replace a new needle.

Check：

There is flaw on the needle.

Adjustment：

Replace a new needle.

Check：

The needle is poor, and the needle tip is worn to be flat.

Adjustment：

Replace a new needle.

Check：

The needle is assembled in wrong direction.

Adjustment：

Remove the needle and re-assemble it.

Check：

The needle is too thick or too thin to the needle thread.

Adjustment：

Replace a new needle.

Check：

The needle tip is too sharp.

Adjustment：

Replace with the needle that has round tip (KN、S、J、B、U、Y).

Check：

Malfunction of bobbin. There is a flaw on the bobbin thread path.

Adjustment：

Correct the flaw on the thread path.

Check：

Malfunction of bobbin. The hook tip is worn to be flat or damaged.

Adjustment：

Correct the hook tip or replace a new bobbin.

Check：

Malfunction of bobbin. The clearance between the bobbin and the bobbin thread pressing plate is too small.

Adjustment：

Enlarge the clearance so that the thread can be off from the bobbin easier.

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◎ The needle thread is broken or worn-out during sewing.

Check：

The lubricated oil is too less in the bobbin.

Adjustment：

Adjust the lubricated oil volume properly.

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◎ The thread is broken when back stitching,

Check：

The needle is not assembled well. The needle is assembled off the center.

Adjustment：

The side having a long groove of the needle should face straight forward. Or, turn the long groove side facing the operator a little.

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◎ The thread is broken while idle running.

Check：

The needle is not assembled well. The needle is assembled off the center.

Adjustment：

The side having a long groove of the needle should face straight forward. Or, turn the long groove side facing the operator a little within 10°.

Check：

The location of the trimmer guard is incorrect.

Adjustment：

Make the needle stitching at the center of the eyelet.

Check：

The needle bar is too low.

Adjustment：

Lift the needle bar higher.

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◎ The stitches are abnormal, the sewing line is not straight, and part of
　 the stitches are not in a straight line.

Check：

The tension of the needle thread is too strong.

Adjustment：

Reduce the tension.

Check：

The needle is bent.

Adjustment：

Replace it with a new needle.

Check：

The needle tip is worn flatly.

Adjustment：

Replace it with a new needle.

Check：

The needle is too thin.

Adjustment：

Use the needle with thicker specification. When using the needle, KN (single section), please replace it with a needle that has two sections.

Check：

The needle is too long.

Adjustment：

Use a shorter needle, or use the needle with longer bar section (DA×1).

Check：

The sewing speed is too fast.

Adjustment：

Slow down the sewing speed.

Check：

The feed dog teeth are not in parallel.

Adjustment：

Replace a new feed dog.

Check：

The feed dog wasn't assembled well.

Adjustment：

Re-assemble the feed dog correctly.

Check：

The feed dog is loose in left and right directions.

Adjustment：

Solve the loose situation of the feed dog.

Check：

The presser foot is lifting.

Adjustment：

Adjust the height of the presser foot.

Check：

The presser foot doesn't have well parallel situation.

Adjustment：

Adjust the presser foot or the parts of the presser foot bar.

Check：

The pressure of the presser foot is too less.

Adjustment：

Increase the pressure of the presser foot.

Check：

Incorrect threading of the needle thread.

Adjustment：

Correct the threading.

Check：

The thread hook of the needle bar is poor.

Adjustment：

Try the B1418227T00, and B1418552A00.

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◎ The lower thread is broken.

Check：

The temperature of the needle is too high.

Adjustment：

Use the needle cooling device.

Check：

The needle is too thick.

Adjustment：

Try to use a thiner needle as possible.

Check：

The needle tip is worn.

Adjustment：

Replace the needle.

Check：

The needle tip has bad shape. (incorrect needle is chosen)

Adjustment：

1. Use the needle with round tip (KN, S, J, B, U, or Y, etc)
2. Lower down the rotating speed. (To prevent the needle getting hot)

Check：

The tension of the fabric is too much; the needle plate hole is too small.

Adjustment：

Use a needle with a larger needle eyelet.

Check：

The tension of the fabric is too much; the pressure of the presser foot is too much.

Adjustment：

Try to reduce the pressure as much as possible.

Check：

The tension of the fabric is too much; the feed dog is too high.

Adjustment：

1. Try to lower down the height.
2. Keep the humidity around 65%.
3. Enlarge the stitch length as long as possible.

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◎ Imperfect thread winding

Check：

The oil on the bobbin is too much or too less.

Adjustment：

Make it well situated.

Check：

Bad bobbin (been hooked, bad thread path, etc.)

Adjustment：

Replace the bobbin and fix the thread path.

Check：

The bobbin doesn't assemble well into the bobbin case and this makes the functions of the lower thread poor.

Adjustment：

Replace the boobin or the bobbin case.

Check：

The bobbin doesn't wind thread well and cause the lower thread being hooked.

Adjustment：

Adjust the lower thread winding tension or adjust the location of the lower thread winding clamp.

Check：

The lower thread is idle running inside the bobbin case.

Adjustment：

Use a bobbin with idle-running-proof spring or place a thin fabric inside the bobbin to prevent idle running.

Check：

The tension adjusting spring of the bobbin doesn't function well.

Adjustment：

Replace the bobbin case.

Check：

The assembly of the bobbin into the bobbin case is incorrect.

Adjustment：

1. Enlarge the tension of the pressing plate of the bobbin.
2. Enlarge the tension of the lower thread.

Check：

The stroke is too wide or too narrow.

Adjustment：

Adjust the stroke.

Check：

The tension is too much or too less.

Adjustment：

Adjust the tension.

Check：

The surface of the thread path is not smooth.

Adjustment：

Fix the thread path.

Check：

Blemishes exist on the thread path.

Adjustment：

Fix the thread path.

Check：

Hooked by the thread path.

Adjustment：

Fix the thread path.