An important sewing defect in footwear manufacturing is thread breakage. It can cause shoe production downtime, inconsistent stitching, waste material, and impact the shoe’s strength and appearance. A minor problem that can be a major issue when repeated in several machines/lines of footwear production is a broken thread even when it only happens every so often.
It typically occurs due to the quality of the sewing machine thread, specifications of the machine, choice of needle, fabric properties, sewing speed, and the handling quality by the sewer. Unlike patching the hole, finding the source of the failure can enable manufacturers to get more consistent production.
Table of Contents
Incorrect Thread Tension
One of the first places to look if the thread breaks is the tension of the thread. The tension is too high, causing further tension on the thread in the machine and with the risk of snapping again.
Too loose, and stitches could be irregular or won’t ‘catch.’ As well, if it is overly congested, the thread may suffer too much stress.
- Troubleshooting tip: Change the upper and bobbin tension slowly and watch the results of the stitch formed. The goal is to produce even stitches without stressing the thread unduly.
Wrong Needle Size or Type
If it is a very fine needle, a lot of friction may result, and the thread may get jammed between the needle and the eye. If it is too large, it can cause too big holes or impact the stitch appearance.
- Troubleshooting tip: Using a needle with the best size and point is appropriate for the thread and material of the shoes. Swap out broken or torn pieces of ropes or chains as needed and do not accept damaged rods or stallions.
Poor Thread Quality
The quality of thread directly affects sewing. Frequent breaks may result from inconsistent thread diameter, weak spots, excessive hairiness, poor lubrication, or damage to the winding.
In footwear various fabrics like leather and heavy synthetic are a major source of stress on the thread, so it is especially important in shoe uppers.
- Troubleshooting tip: Check thread specifications, strength, elongation, finish, and consistency. Repeatedly if breaks are happening with one lot of threads, then compare that lot to another lot or thread that is known to be good (nylon sewing thread).
Excessive Sewing Speed
Friction is caused by the high rate of machine speed, which creates heat. This stress, if too much for the thread, could cause it to weaken or break.
This may be more apparent when working with thick leather, multi-layer seams, or dense constructions.
- Troubleshooting tip: Reduce machine speed temporarily and observe whether the breakage rate decreases. Before trying to increase the rate of production again, check the thread size, machine setting, and sewing condition when it is increased again if the performance improves.
Friction in the Thread Path
Between the needle and thread are a number of components. Friction can be caused by rough surfaces, damaged guides, sharp edges, or tension discs being positioned incorrectly.
- Troubleshooting tip: Check the entire thread path and test the thread by running it by hand through the guides. Look for rough surfaces, broken machinery, or any buildup of dirt or improperly threaded items.
Incorrect Thread Size
A thread too thick to pass through the needle eye can cause undue resistance. Alternatively, a thread that is too thin for the job could fail to endure the tension of the seams.
- Troubleshooting tip: Change the thread size based on the material, thread type, needle, and strength of the stitch wanted. Make sure that there is enough room for smooth thread movement with the needle eye.
Difficult Footwear Materials
Sewing can occur with varying resistances with leather, coated textiles, rubberized or synthetic materials. Needs may penetrate the material more forcefully and introduce more thread stress into the material with thick or uneven material.
Repeatedly, there are areas of hard plastic, seams, folds, and multiple material layers, which can also result in intermittent breakage.
- Troubleshooting tip: Sew with the actual footwear material and construction for the test. Make any necessary changes to needle, presser-foot pressure, machine speed, and thread tension.
Bad Thread Handling and Storage
Before the thread gets to the sewing machine, it can be damaged. Thread performance may be influenced by excessive moisture, heat, dust, sunlight, or improper storage.
The thread package can also be damaged or contaminated when not packaged properly.
- Troubleshooting tip: Store thread in a dry, non-excessive heat and direct sunlight location. Until ready for production, protect packages.
A Real-World Troubleshooting Strategy
Changing the thread as soon as the breakage has happened is not always the best choice when you have thread breakage. It is better to follow a systematic approach.
The first step is to record where and when the break is then check:
- Quality of thread and package condition
- Needle type and condition
- The thread size and needle compatibility
- Upper and bobbin tension
- Provide paths & guides
- Machine speed
- Stitch density
- Material thickness and construction
- Operator threading technique
After changing one thing at a time, run a controlled trial. This will help you to pinpoint the real issue and not make too many changes at once.
Final Thoughts
Your line of footwear won’t last long, but there’s a solution, and there’s also a signal. Frequent breaks may be because of poor quality thread, machine setting, needle type, material suitability, or equipment maintenance.
With a systematic troubleshooting process and proper material pairing between thread, needle, machine, and footwear, manufacturers can minimize downtime, stitch uniformity, and waste and also result in a strong, reliable footwear seam. Regular testing and preventative maintenance can greatly transform Thread’s life from a production problem to a business-enhancing tool.