How Footwear Finishing Processes Can Affect Thread Performance
Footwear manufacturing involves much more than stitching materials together. Shoes may then go through a number of shoe finishing processes that enhance the looks, comfort, protection and durability of the finished product. This can include polishing, cleaning up, coating and heat treatment, washing, and pressing, along with chemical finishing.
Both these processes enhance the product but can also influence the performance of sewing threads. Colour, strength, flexibility and surface properties of the thread can be changed by heat, moisture, chemicals, friction, and pressure. They are the dynamic relationships of these interactions that must be comprehended in order to create footwear that is designed for high-quality and durable seams.
Why Finishing Matters for Sewing Threads
The kind of sewing thread is chosen depending on the expected conditions in the process of footwear manufacturing and utilisation. A thread that may work well during sewing, however, can have certain effects when finished for later use.
The effect of excess heat on some synthetic threads, for instance, or the effect of harsh chemicals on some types of thread are examples of these. Another source of abrasion can be caused by mechanical finish on exposed stitches.
The choice of thread for the sewing operation should be related to the whole manufacturing procedure.
Heat Treatment and Thermal Exposure
Various footwear processes, such as moulding, pressing, drying, and adhesive activation, utilise heat. Some sewing threads may not have the necessary dimensional stability or mechanical properties when subjected to too much or too long heat.
Synthetic threads like polyester sewing thread or nylon sewing thread tend to have good thermal properties, depending on a number of factors related to the construction of the thread and the ambient temperature.
Practical method: Manufacturers should specify the actual temperatures and drying times during finishing and verify that the chosen thread would resist these conditions without substantial shrinkage, melting or strength decrease.
Chemical Finishing and Thread Compatibility
Chemicals can be applied to footwear and be present in activities like cleaning, dyeing, coating, polishing and surface processing. Some chemicals could cause the thread to change colour, lose strength, dry, or be less lubricated or more oversized or flexible.
The other chains that may be required for leather shoes can be exposed to various types of care. A thread that is not chemically compatible could cause performance problems in the long term.
Practical approach: Run tests with the real chemicals and products utilised in production. Suppliers will be able to give information on the chemical resistance and suggested applications where appropriate.
Washing and Cleaning Processes
In some types of footwear, washing or wet processing is carried out prior to the consumer. Other stresses that water, detergents, mechanical movements and drying exert on the thread.
If the thread is not dimensionally stable, then it can shrink or adjust tension, causing buckled areas or buckled seams after washing.
Colourfastness and resistance to the cleaning process that is targeted can help to preserve seam performance and appearance.
Polishing and Surface Finishing
High-quality goods and leather footwear might be finished or polished to give them the appearance desired. The processes involve exposing exposed thread to waxes, dyes, oils or finishing compounds.
Some finishes may take little effect, others may change the colour or appearance of the surface of the thread.
This is significant for decorative sewing, as little changes can become noticeable against the material used in making the shoes.
Mechanical Finishing and Abrasion
Exposed stitching can cause friction in mechanical processes such as brushing, buffing, trimming, and polishing.
Using thread that is repeatedly rubbed during the finishing process can lead to a fuzzy or damaged surface on the thread. This can compromise image quality and may impact the long-term seam strength as well.
Decorative seams or seams that are exposed must be examined and should be analysed and evaluated more carefully than other seams, as they are exposed to mechanical finishing to a greater degree.
Impact on Thread Colour and Appearance
A thread is not only a structural component; it can also be an important design element. In some cases, where a ‘colour consistency’ is essential, luxury footwear may be stitched or decorated in contrasting colours.
The colour of the threads can be impacted by finishing chemicals, heat, cleaning, and light.
Similarly, consistency is ensured if the manufacturers look into the colourfastness sets as per the finished rainwear.
Choosing Threads for the Complete Process
In the entire process of footwear manufacturing, the best thread should be chosen.
Manufacturers should consider:
- Sewing conditions and machine speed
- Heat exposure
- Chemicals and adhesives
- Washing and cleaning
- Mechanical finishing
- Expected wear conditions
- Required colourfastness
- Final appearance
It’s not a good thread if it is successful in sewing but not successful in finishing.
Practical Testing Before Production
The manufacturers should perform a thread – material – finishing test before they start bulk manufacturing.
The following is a helpful testing process to adopt:
- Sew the selected thread on the actual footwear material.
- Apply the intended finishing processes.
- Inspect the thread for colour, fuzzing, shrinkage, and damage.
- Check for seam strength and flexibility.
- Analyse the comparison with results from an untreated control sample.
- Make necessary adjustments to thread or finishing conditions.
It can be used to determine the key issues before they impact upon big production volumes.
Final Thoughts
The effects of finishing treatments on sewing thread can be dramatic. The strength, flexibility, colour and appearance of the thread can be affected by the application of heat, chemicals, moisture, washing, mechanical friction and surface treatments.
Therefore, it is important that the selection of threads when making footwear be more than just for sewing in order to achieve durable footwear production. By testing the thread through the complete manufacturing and finishing process, manufacturers can minimize seam failures, maintain appearance, reduce rework, and improve the durability of the finished footwear.
The right thread should not only sew well; it should sew well after the shoe is finished!