Need more comfortable Shoes : Importance of Ribs of Shoe sole and Sole Mould

What are Ribs in a Shoe Sole?

Rib (popularly called as jaal or line) in a shoe sole is made to reduce the weight of the sole. It is technically made so that the shoe last(Lasted Upper) sits on the ribs. The ribs should thus take the shape of the shoe last(Lasted Upper) both in 3d and curvatures at various cross sections including the seat, the waist and the forepart.( later I will explain this in the post)

How ribs are made on the sole?

1. Inputs from the shoe last are taken. The shoe last is digitized and a copy is made in CAD. Margins for upper are added.  The sole sits on the lasted upper hence the bottom side of the lasted upper matches the fitting side of the sole.

2. Bottom side of the sole is designed as per specification of shoe design

3. To keep the weight of the sole minimum and to keep the shoe as light as possible the thickness of the sole is kept as per SATRA standards. Ribs are made so that the lasted upper sits comfortably on the sole without dancing. The final sole CAD is generated

4. Now the mould is made and the ribs are machined on the mould. There are two ways to machine ribs on the mould.
a. Pantograph Machining : Manually the ribs are machined on the mould using pantograph machines. This is a very cheap method and produces extremely low quality ribs.
b. CNC Machining : A cnc milling machine is used to make the ribs which are perfect in curvature. This is expensive and produces high quality ribs

Quality Of Ribs

Ribs have 3 important points on which quality is evaluated

1. Curvature of ribs at heel to match the lasted upper
2. Curvature at ribs at forepart to match the lasted upper
3. 3D profile of ribs from heel to forepart to match the lasted upper

 

Problems that comes when ribs are wrongly made or are poor in quality

1. The Last can go inside the sole more than specification(ribs are lower in sole than needed)
2. The last can remain outside the sole more than the specification
3. Heel area can be lower and forepart can be higher than specification or vice versa
4. The last can be resting in air in heel part , waist or forepart.
5. Due to poor quality and rough surface of the ribs when the shoe is made it can make the shoe wearer feel uncomfortable(like little pins are hurting)

Suggestions to improve the comfort

1. Use sole moulds that are machined using CNC only. Pantograph moulds may look cheaper on the first instance but they will end up costing more since they provide very poor quality.
2. Use shoe last for designing of the soles in case shoe lasts are already made for project
3. Best way to control this problem is to first get a mould in which ribs are machined from cnc and then develop a shoe last from the sole that comes out of the mould. This way the comfort of the shoe will be maximum.

 

For any queries please feel free to contact me on WhatsApp : +919627774488 or visit http://www.solemould.com.

Rise & Shine Together

3D Printer & Shoe Sole Moulds

Knowledge about 3d printer

3D printers are based on additive manufacturing. This means material is added layer by layer to get the desired shape. In our traditional manufacturing style of CNC machining which is subtractive manufacturing, the material is removed to get the desired shape. All photos on this blog are 3d printed sole models.

There are many types of 3d printer available depending upon the technology they use and the material they can print. The most popular are FDM, SLA, DLP, SLS, DMLS, SLM, EBM, Material Jetting, DOD, and Binder Jetting.

Selection of the right 3d printer for Sole Moulds

The Printer is used to print Shoe sole Models which are in turn used to do the casting of moulds. Requirements for Sole mould models.

1. Surface finish should be high
2. Textures such as diamond and leather can be printed
3. Quality at sharp corners should be high
4. Features should be sharp
5. Logo and branding should be neat
6. The Resin should be hard so that it does not bend in casting process
7. Cost should be low

Considering all the points and extensive research for over 2 years, Valor Engineering (www.solemould.com ) picked a SLA (Stereolithography) printer. All the photos in this blog are of SLA Printed Shoe Models

About SLA 3D Printers

Stereolithography is an additive manufacturing process that works by focusing an ultraviolet (UV) laser on to a vat of photopolymer resin. With the help of computer aided manufacturing or computer-aided design (CAM/CAD) software, the UV laser is used to draw a pre-programmed design or shape on to the surface of the photopolymer vat. Photopolymers are sensitive to ultraviolet light, so the resin is photochemically solidified and forms a single layer of the desired 3D object. Then, the build platform lowers one layer and a blade recoats the top of the tank with resin. This process is repeated for each layer of the design until the 3D object is complete. Completed parts must be washed with a solvent to clean wet resin off their surface

Advantage of using 3d Printer in Shoe Sole Moulds compared to CNC

1. Printer can make all types of textures while CNC cannot
2. Printing model is cheaper than making a CNC model
3. Printing Model takes Less Time than CNC machining
4. Printed Model Quality is better than CNC machined model
5. Printing a size set(Series) model is much cheaper and consumes much less time than CNC
6. Printing Model is Dust free while CNC machining produces dust.
7. Printer does not need any tools while for cnc you have to buy tools and also make customized tools

 

Disadvantages  Of Printer

1. Manual correction of model not possible in Printed models while it can be done in CNC models
2. Accuracy of CAD should be perfect else chances of rejection of model
3. Existing designers need to learn Texture making and wrapping on Model in CAD
4. New Softwares like Magic which are used in slicing of CAD model need to be learnt.
5. Printer laser has lifetime.

 

Weighing the Advantages and Disadvantages

3d printing is a Sunrise Industry. More technical advancement are likely to come in coming years. The quality will increase, the timings will be better for printing while the cost is sure to fall.  Investing 3d Printing now is the right way forward. Initially there will be some challenges but once those are overcome then this technology will surely change how the mould making industry looks. The most important point is shoe sole moulds is one of the first commercially feasible product of 3D printing.

If you have any query please mail me at valorindia@gmail.com or contact me on WhatsApp +919627774488.

 

Photos Credit : Kings 3d Printer China, Manufacturer of SLA Printer.

How Shoe Sole Moulds are Manufactured

Order Receiving : Executives understand the needs of the sole manufacturer in detail.

CAD : The Designer design the sole as per requirement of customer in 3d modelling software

Blueprint : Blueprints are generated which are then confirmed by sole manufacturer. In case of corrections the CAD model are updated

CAM : The milling toolpaths are generated with the help of CAM softwares

Model from CNC : Model of Sole are machined on cnc. A good model is machined on all 6 settings and no hand work is left.

Model Finishing : Sheet pasting of textures is done on models. The model is approved by the sole manufacturer

Silicone Mould/ Plaster Mould : Silicone Rubber mould are prepared using the final model. Afterwards plaster moulds are made. The plaster moulds are then baked.

Casting : Molten Aluminium alloy of shoe mould specification are used. Patented technology of casting is used for best results

CAD/CAM/CNC RDB : Reverse engineering of the casting is done. Technology like 3d Scanner and Digitisers are used for reverse engineering. Cavity, Ring and core are designed and manufactured using cnc. All the quality is dependant on this step

Fitting/Sole Testing : The different parts of moulds are assembled by experienced Technician and sent to testing machines for producing samples.

Quality Report : The samples are checked thouroughly with sole requirements. 100’s of dimensions are checked and documented. Only the perfect moulds are dispatched.

 

http://www.solemould.com

 

TPR Sole Moulds

How to select your TPR Mould vendor / Important points to remember while selecting your TPR Mould

• Communication : Select your vendor who you are comfortable with explaining what specification you need in mould and sole
• Technical Drawings / Blueprint : Sole is a very complex technical part of the shoe. Technical drawings and blueprints are like architects map that you need before building the house. No matter what, a mould can never be built without a blueprint. So always ask for blueprint of sole and mould from your mould maker.
• Casting Moulds vs Direct Machining Moulds :  A shoe sells from its side look. A direct machining mould has its sides engraved manually. A casting mould has much better curvatures and finishing as compared to Direct machining mould
• 2 Setting Models vs 6 setting Models : 2 Setting models are manufactured by the mould maker to cut costs . Manual engraving is done on the model for side looks. While a 6 setting model all the 6 sides are machined by cnc. The quality of the model is very high and also while making the size set the repeatability is very high
• Ribs machined by Pantograph Vs Ribs CNC : The design of ribs on the fitting side of the sole is very important for the comfort of the shoe. The curvature can only be matched by CNC. Pantographs ribs are cheap and uncomfortable alternatives.
• Manual Matching of Cavity and Ring vs CNC Matching : Manual matching is a big No. Always select the moulds in which matching is done by cnc.
• 2d Moulds vs 3d Moulds : 2d moulds are moulds with deep cavity. The problem with these moulds is that the sole gets distorted while pulling out of cavity. In 3d Moulds the depth of cavity is no more than 6mm.
• Quality Reports : Local mould makers tend to send the moulds for TRIAL at your factory. This waste your time , labour and material cost. Then they manually correct the mould. Avoid such mould makers. Always choose a mould maker who provide you with detailed Mould and Sole report with tolerance analysis

About TPR material from Footwear Industry/ Sole Manufacturing Perspective

TPR or TR stands for thermoplastic rubber. The advantage of this material in shoe soles

•   It stretches hence the comfort is high
•   Life of the sole is long
•   It can be injection moulded thus reducing the lead times in production and cost of production
•  The material can be recycled thus cost of rejection is low.
•  Available in many colors. Customised colors can also be developed.
•  Material is available as granules in packing of 25kg and 50kg.

These are the most important points while selecting the TPR Moulds. If you have any query please mail me at rishijain.me@gmail.com.

 

Visit http://www.solemould.com

 

 

 

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