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◎ The tension of sewing is not good.

Check：

Does it thread correctly ?

Adjustment：

If the threading is incorrect, please thread the threads to correct positions.

Check：

Is the operation stroke of the spring of the thread tension controller too small?

Adjustment：

Adjust the operation stroke of the spring of the thread tension controller.

Check：

Is the tension of the needle thread or the bobbin thread too small?

Adjustment：

Adjust the tension of the needle thread or the bobbin thread.

Check：

Is there any scratch on the bobbin?

Adjustment：

If the bobbin is damaged, polish it by an oil stone or replace it with a new bobbin.

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◎ Needle thread or bobbin thread broken

Check：

Is the needle tip bent? Is the needle tip blunt?

Adjustment：

If the needle tip is bent or is broken, please replace with a new one.

Check：

Is the needle assembled well?

Adjustment：

If the needle is not assembled well, please re-assemble it to the correct position.

Check：

Does it thread correctly?

Adjustment：

If the threading is incorrect, please thread the threads to correct positions.

Check：

Has the bobbin been properly lubricated?

Adjustment：

If the oil line is lower than the bottom line of the oil window, please add some more oil.

Check：

Is the tension of the needle thread too strong or too weak?

Adjustment：

Adjust the tension of the needle thread.

Check：

Is the hook, feed dog or any other part worn?

Adjustment：

If any of the parts mentioned above is worn, please polish it with an oil stone or replace it with a new one.

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◎ Skipped stitches in sewing

Check：

Is the needle tip bent? Is the needle tip blunt?

Adjustment：

If the needle tip is bent or is broken, please replace with a new one.

Check：

Is the needle assembled well?

Adjustment：

If the needle is not assembled well, please re-assemble it to the correct position.

Check：

Does it thread correctly?

Adjustment：

If the threading is incorrect, please thread the threads to correct positions.

Check：

Is the tension of the presser foot too weak?

Adjustment：

Adjust the pressure of the presser foot.

Check：

Is the sewing speed too fast?

Adjustment：

Check if using a correct belt that suitable for the max speed of the machine, frequency, and sewing characteristics, which means the outer diameter of the belt is correct. If using an incorrect belt, please replace with a correct one.

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◎ The stitches skipped at the beginning of sewing, or the thread
　 leftover is too loose at the beginning of sewing.

Check：

Is the upper stop position of the needle too high?

Adjustment：

Adjust the needle position adjusting knob.

Check：

Does the bobbin thread clamp spring plate press on the bobbin thread after trimming?

Adjustment：

If not, please adjust the position of the movable trimmer.

Check：

Is the height of the feed dog correct?

Adjustment：

Adjust the height of the feed dog to be 1 mm above the needle plate.

Check：

Is the pulling tension of spring of the thread controller too strong?

Adjustment：

Lower down its pulling tension.

Check：

Is the moving stroke of the spring of the thread controller too wide?

Adjustment：

Narrow down its moving stroke.

Check：

Is the leftover of the upper thread after trimming too short?

Check：

The thread is not trimmed completely?

Adjustment：

Polish the fixed trimmer. If possible, replace the fixed and the movable trimmer with new ones.

Check：

Is the needle too wide?

Adjustment：

Try using a needle with a count that is one lower than the current needle.

Check：

When sewing thin or medium heavy materials, is the using presser foot specilized for heavy materials?

Adjustment：

Use the presser foot with no chinks, as well as use the feed dog specilized for thin and medium heavy fabrics.

Check：

Is the sewing speed too fast at the beginning of sewing?

Adjustment：

Take slow-start mode at the beginning of sewing.

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◎ The sewing is not smooth.

Check：

Is the pressure of the presser foot too weak?

Adjustment：

Adjust the pressure of the presser foot.

Check：

Is the feed dog height too low ?

Adjustment：

Adjust the height of the feed dog.

Check：

Is there any scratch on the bobbin?

Adjustment：

If the bobbin is damaged, please polish it with an oil stone or change a new one.

Check：

Is the belt tension not enough?

Adjustment：

Adjust the belt tension. The belt should have a 10~20 mm slope when pressing the belt inward by a finger.

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◎ Big shirrs（Over-tensed）

Check：

Is the needle thread over-tensed?

Adjustment：

Lower the tension of the needle thread as small as possible.

Check：

Is the bobbin thread over-tensed?

Adjustment：

Lower the tension of the bobbin thread as small as possible.

Check：

Is the pulling tension of the spring of the thread tension controller too strong?

Adjustment：

Reduce the moving stroke of the spring of thethread tension controller as much as possible.

Check：

Is the pressure of the presser foot too weak?

Adjustment：

Increase the pressure of the presser foot..

Check：

Is the sewing speed too fast?

Adjustment：

Slow down the sewing speed a little.

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◎ Deviation of needle thread after trimming.

Check：

Is the movable trimmer tip damaged or bent?

Adjustment：

Replace the damaged movable trimmer.

Check：

Is the clearance between the movable trimmer tip and the hook plug too wide?

Adjustment：

Adjust the clearance to be between 0.05~0.2 mm.

Check：

Does the pressure releasing mechanism/device function correctly?

Adjustment：

Adjust the pressure releasing mechanism/device.

Check：

Is the movable trimmer tip at the correct position?

Adjustment：

Adjust the position of the movable trimmer .

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◎ Deviation of bobbin thread after trimming.

Check：

Is the movable trimmer tip too low? Is the movable trimmer tip damaged or bent?

Adjustment：

Replace the damaged movable trimmer with a new one..

Check：

Is the hook too positioned too high?

Adjustment：

Push the hook downward to make the assembly correct.

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◎ The bobbin thread enwinds at the beginning of sewing

Check：

When the bobbin thread is pulled, is the rotating direction of the bobbin correct?

Adjustment：

Correct the bobbin. The rotating direction should be in reverse with the hook.

Check：

Is the thread quantity on the bobbin too much?

Adjustment：

The total quantity of each bobbin shall not exceed 80%.

Check：

Does the anti-enwinding spring connect already?

Adjustment：

Connect the anti-enwinding spring .

Check：

Does the bobbin not function well?

Adjustment：

If the bobbin cannot function smoothly, please replace it with a new one.

Check：

Is the bobbin a light alloy bobbin that is assigned by SIRUBA?

Adjustment：

Use the bobbin that is assigned by SIRUBA.

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◎ The needle thread leftover is too short after trimming.

Check：

Does the thread come out from the thread stand easily?

Adjustment：

If not, please check if there is anything holding the thread.

Check：

Is the tension of the spring of the thread tension controller too strong?

Adjustment：

Adjust it to be weaker a little.

Check：

Is the moving stroke of the spring of the thread tension controller too wide?

Adjustment：

Narrow down the moving stroke of the spring of the thread tension controller.

Check：

Is the hook of the movable trimmer damaged?

Adjustment：

Polish the damaged part, or replace with a new one.

Check：

Does the pull disc rotate or not while trimming?

Adjustment：

If it doesn't rotate, adjust the tension release mechanism/device.

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◎ The thread wiper keeps hitting on the needle. The upper stop
　 position of the needle does not remain at the same position.

Check：

Is the thread wiper assembled at the correct position? (Located correctly)

Adjustment：

Adjust the thread wiper .

Check：

Is the upper stop position of the needle too low?

Adjustment：

Adjust the stitch length adjusting knob.

Check：

Is the belt tension not enough?

Adjustment：

Adjust the belt tension. The belt should have a 10~20 mm slope when pressing the belt inward by a finger.

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◎ Needle broken

Check：

Is the fabric pulled or pushed by some excessive strength while sewing?

Adjustment：

If the needle tip is bent or broken, please replace it with a new one.

Check：

Does the needle pass through the center of the needle hole of the feed dog?

Adjustment：

Check the needling position. If the needle didn't fall on the center of the needle hole of the feed dog, please re-assemble the feed dog.

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