Introduction to Shoe Welt

The shoe welt is a thin strip of leather that surrounds the outer edge of the outsole, and then the sole is sewn to the welt. It is a leather strip used to connect the insole and the upper, which increases the combination of the upper and the sole and can also cover the wrinkles of the lasted upper. The welt structure not only makes the shoes strong and durable, but also has the advantage of being able to replace the outsole. The most easily worn - out part of leather shoes is the outsole, and the introduction of the welt further extends the service life of the shoes. As long as the upper is not damaged, a pair of shoes can be worn for a long time. Here are some common types of welts:

• High - edge welt: Actually called the cut - and - turned high - edge welt. When making it, the welt needs to be cut from the edge to the middle section without cutting it off completely. Then, turn it over along the cut. One side is sewn to the upper from the bottom of the shoe, and the other side is turned to the back to fit the sole. The uncut part spreads outwards. After completion, the cut welt is flush with the upper and then ironed into the upper for further trimming. This is the most weather - resistant welt and is often used in the production of country boots.

• Barbour welt: Similar to the high - edge welt, but it has a thick edge cast by the manufacturer itself and does not need to be cut from the middle. When sewn to the upper, the thick edge is flush with the upper.

• Flat welt: It is a straight leather strip without the vertical leather strip between the sole and the side of the upper. It is most commonly used in the production of city shoes.

• MSSR (Super - tough) welt: Similar to the reverse - split welt, but made of softer tanned leather, so it is softer and more elastic, and is used in super - tough series shoes.

Introduction to the Materials of Shoe Welt

The materials of shoe welts are diverse, and different materials have different characteristics and application scenarios. Here are some common materials for shoe welts:

• Natural leather: Natural leather welts are special leathers used for making the outsoles and insoles of shoes and boots. According to the raw materials used, they can be divided into yellow cattle leather soles, buffalo leather soles, pig leather soles, etc.; according to the uses, they can be divided into outsole leathers, insole leathers, main heel leathers, inner toe cap leathers, etc.; according to the tanning methods, they can be divided into chrome - tanned leathers, vegetable - tanned leathers, combined - tanned leathers, etc.; according to the layers and parts, they can be divided into cattle heart leathers, cattle head leathers, cattle side leathers, cattle shoulder leathers, etc. The advantages of natural leather welts are good texture, excellent breathability, and strong durability, which can add a high - quality feeling to the shoes. For example, vegetable - tanned sole leather has a thick and large body, strong nail - holding force, small water absorption, and strong plasticity, but poor cushioning performance; chrome - tanned sole leather has good wear resistance, large water absorption, high strength, and good heat resistance; the surface performance of combined - tanned sole leather is basically the same as that of vegetable - tanned sole leather, but its heat - resistance strength and wear - resistance are improved. However, natural leather welts are relatively expensive and require certain maintenance.

  
  

• Rubber: Rubber welts have good wear resistance, elasticity, and waterproofness, and can adapt to various complex road conditions and environments. The rubber - based materials used in shoe - making have certain wear resistance, high elasticity, waterproofness, acid and alkali resistance, etc. Classified by composition, they can be divided into natural rubber and synthetic rubber. Natural rubber is very soft and has excellent elasticity, suitable for various sports, but it is not wear - resistant, and indoor sports shoes often use natural rubber; synthetic rubber can be further divided into wear - resistant rubber, environmental - friendly rubber, air rubber, sticky rubber, hard rubber, carbon - added rubber, etc. Classified by finished products, they can be divided into rubber sheet materials, strip materials, rubber compounds, molded soles, etc. Among them, strip materials such as outer rubber strips and welt strips for stitched shoes. The disadvantage of rubber welts is relatively poor breathability, and the feet may feel stuffy after wearing them for a long time.

  
  

• Thermoplastic elastomer (TPE): TPE is a new type of polymer material between rubber and resin. It has the functions and properties of traditional heat - reversible rubber (soft, elastic, good touch) and the advantages of general thermoplastic plastics, such as easy processing, fast speed, and recyclability. TPE welts have the characteristics of environmental protection, non - toxicity, safety, a wide range of hardness, excellent coloring, and soft touch; they have superior weather resistance, fatigue resistance, temperature resistance, and processing performance. They do not need vulcanization, can be recycled to reduce costs, can be injection - molded twice, and can be coated and bonded with matrix materials such as PP, PE, PC, PS, ABS, or can be molded independently. TPE welts are strong enough while maintaining a light weight and can provide long - lasting durability even with wear over time.

  
  

• PVC: PVC welts are mainly made of polyvinyl chloride. They are lightweight, easy to install, waterproof, and moisture - proof, and the price is relatively affordable, suitable for shoes for general household use. However, the texture and durability of PVC welts are relatively poor, and they may age and harden after long - term use.

• Linen materials: Linen welts are made of natural linen threads and have the advantages of environmental protection and breathability. After special treatment, linen welts can also have a certain degree of strength and durability. For example, a kind of linen welt includes multiple strands of woven unit linen ropes, and the outer periphery of each unit linen rope is covered with a unit glue layer, and there is also a main glue layer on the outside of the body to enhance its strength. Linen welts are suitable for consumers who pursue environmental protection and breathability.

Introduction to the Process of Attaching the Welt

Steps of Attaching the Welt in the Goodyear Process

1. Preparation: First, shape the toe cap. Then, use the forepart lasting machine to adjust and rotate the claws at preset angles to bond and fix the shaped toe cap to the insole nailed on the last.

2. Sewing the inner welt (inner thread): This process is crucial. The inner thread is sewn between the welt, the upper edge, and the inner mid - sole welt, which fixes the three parts.

3. Sewing the outer mid - sole: Use the Goodyear welt outer - thread machine to sew the outer mid - sole that is bonded to the welt to fix the welt and the outer mid - sole.

4. Roughening the contact surface between the outsole and the outer mid - sole: Roughening can increase the adhesive force between the two surfaces.

5. Applying glue: According to international standards, the outer mid - sole and the outsole need to be brushed with glue twice. To ensure the shoes are more secure, it can also be brushed three times.

6. Attaching the sole, pressing, and welt rolling: Ensure that the outer mid - sole and the outsole are fully attached. After attachment, cut off the excess part of the outsole along the welt.

Steps of the Processing Method Using the Sole Welt Pressing Die Auxiliary Scissor Structure

1. Open the sole mold: Prepare the upper mold and the lower mold. The upper mold has a welt groove for placing the welt, and the lower mold has a sole groove for placing the sole.

2. Insert the starting end of the welt: Insert the starting end of the welt into the welt groove of the upper mold.

3. Press the welt: Hold the scissors and press the ball bearing against the welt that has been inserted into the welt groove. Move the scissors back and forth to make the ball bearing roll and press the welt into the welt groove.

4. Cut and connect the welt: Cut the welt with the scissors and press the end of the welt into the welt groove to connect the end and the starting end of the welt.

5. Place the sole and heat: Place the sole in the lower mold, close the upper mold, and enter the heating process to bond the sole and the welt together.

6. Sole demolding: After heating, insert the barrel of the air gun into the anti - falling rubber tube and turn on the air gun. The air blown by the air gun enters the chamber and the first channel through the anti - falling rubber tube. The sole is blown up and separated from the sole groove by air pressure, and then the air gun can be pulled out.

Precautions for Attaching the Welt

• Material selection: Non - decorative welts must be strong and tough, with moderate hardness and plasticity, and have a flat appearance without obvious defects to ensure clear and beautiful stitch lines. When cutting, choose the appropriate direction according to the material used. For example, when using cowhide sole leather, cut it horizontally; when using pigskin sole leather, cut it vertically.

• Operation accuracy: The positioning and sewing position of the welt should be precise. For example, the distance of the insole welt needs to be changed at least 5 times, and it must start and end at precise points. When sewing the welt, ensure that the awl penetrates the upper and the inner welt at a consistent angle into the upper edge line to prevent the phenomenon of the sole showing.

• Equipment use: Different processes may require the use of specific machines, such as the inner welt attaching machine, the welt sewing machine, the outer sole beveling machine, etc. Be familiar with the operation of the equipment and ensure the normal operation and maintenance of the equipment. For example, some old machines may be noisy, and equipment with automatic lubrication and low - noise, low - vibration variable - speed engines can be selected.

• Environment and subsequent maintenance: If the climate temperature is lower than 10°C, it is best to use the hot air of a hair dryer to heat the relevant parts before pasting. After pasting, heat it again and press it appropriately by hand to ensure firm adhesion. In addition, after attaching the welt, pay attention to the maintenance of the shoes, avoid excessive wear and moisture to extend the service life of the shoes.