Last technology developer Framas makes a case for automation in direct-injection processes, but points out that specially  developed lasts are an essential part of this transition.

The footwear industry is currently navigating a landscape filled with new challenges. Key issues include rising production costs, ever-more demanding quality standards, and a strong emphasis on sustainability. To address these challenges, many companies are looking towards automation to help them find solutions.

Integrating automated processes into production can significantly enhance quality and speed, making it a compelling option for manufacturers. One innovative approach gaining traction, and which Pirmasens-based lasting technology specialist Framas is actively exploring, in collaboration with its partners, is the integration of direct-injection processes into footwear production.

This method involves directly moulding the outsole onto the upper of the shoe, which eliminates the need for complex adhesive applications. This also contributes to reducing the volume of waste that the footwear manufacturing process naturally creates. However, the direct-injection process presents its own set of challenges, particularly regarding the precise alignment of the last, which shapes the shoe, of course, with the reference points of the automation equipment and the direct-injection tool.

Variations in material thickness and cutting tolerance can lead to additional measurement tolerances that must be meticulously managed. To ensure a smooth operation in automated systems, it is crucial that every functional area is manufactured with high precision. In metalworking, tolerances are typically maintained within hundredths of a millimetre, whereas the footwear industry generally operates with tolerances of plus or minus 1 millimetre. While these tolerances may suffice for traditional footwear production, they are inadequate for highly automated processes.

Deviations in alignment can result in over moulding or improper fit, underscoring the necessity for specially developed lasts. To meet these demands and to present itself as an ideal partner for footwear producers that want to implement advances in automation, Framas has implemented the use of high-precision (HP) lasts.

The structure of HP Lasts

HP lasts serve as moulds for shoes, just as conventional lasts do, but they come equipped with advanced features specifically designed for automated manufacturing processes.

A central element of an HP last is the top plate. This component is crucial for holding the last securely within the production system and ensuring precise positioning throughout the manufacturing process. The design of these top plates varies according to the specifications of the automation plant supplier, reflecting the unique requirements of different systems. In addition to their primary functions of holding and positioning, HP lasts incorporate several additional components that enhance their functionality:

• Integrated lace holders: These holders facilitate the lacing process, making it more efficient;
•  Automated opening mechanisms: Featuring sliding components, these mechanisms help reduce wear and tear during production;
•  Robotic mounts: These mounts enable seamless integration with automated systems, further streamlining the manufacturing process.

Framas provides a variety of modifications tailored to meet specific production process needs. This customisation allows manufacturers to optimise their workflows effectively. Unlike traditional turned lasts, which are limited in design possibilities owing to their manufacturing constraints, HP lasts offer greater design freedom. This flexibility empowers designers to create innovative shoe styles that can be efficiently produced in an automated environment.

Manufacturing process 

Constructing HP lasts involves a manufacturing process that diverges from the one for standard lasts. The primary distinction is that additional steps are required for positioning and aligning the top plate on the HP last. This process also emphasises achieving extremely low tolerances during fine milling. The steps involved as follows.

First comes some CAM work. The process begins with digital modelling of the last and the top plate. This digital modelling is essential for ensuring precise adaptation of components to meet the specific requirements of the production system.

Then there is rough milling, what can also be called vague milling, an initial phase to create the basic shape of the last.

After this, cutting the last is the next step, with a focus on processing specific opening mechanisms that are integral to the design of the last. Precise cutting of the cone is also necessary to prepare it for screwing in the top plate, ensuring a secure fit.

Then fine milling can take place. To adhere to stringent tolerance requirements, Framas HP lasts are manufactured using a Röders 5-axis milling machine. This advanced machinery replaces traditional fine-milling machines. It has a robust construction, which minimises vibrations. Coupled with the precision offered by machines from Italian technology provider Newlast, this setup allows for a tolerance of plus or minus 0.03 millimetres.

Given the low tolerances and high standards, a 100% quality inspection process is also implemented, accompanied by detailed reports. Measurements can be conducted directly within the 5-axis milling machine, effectively eliminating human error in measurement.

Finally, each last is stamped for identification purposes during production, ensuring traceability.

Package of services

Extensive expertise in the footwear industry, Framas says, also helps position the group as an ideal partner for shoe manufacturers introducing direct-injection process. In addition to the development of lasts, its package of services includes the design and manufacturing of direct-injection tools and the supply of injection-moulded shoe components such as heel counters.

By offering these services from a single source, it argues that it can ensure a central point of contact and maintain “extremely short communication paths” to enhance efficiency and collaboration. Operating globally at strategically advantageous production sites, including Indonesia and Vietnam, it is well-equipped to meet supply demands effectively, it says. The company’s international presence allows it to leverage local resources while maintaining high standards of quality and service.

To demonstrate the breadth of its product range and capabilities, Framas has worked with two partners, Taiwan-based last developer Yinhwa and Germany-based footwear  technology developer Desma, to develop a shoe that it says showcases its innovative approach and technical expertise in footwear manufacturing. This collaboration highlights its commitment to delivering high-quality solutions that are tailored to the needs of clients in the footwear industry, it claims. 

Craftsmanship is combined with cutting-edge 3D technology to create precision lasts for sports, fashion, health, and safety footwear, including custom and innovative designs.
All Credits: Framas

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