Resin is a delicate material that is more easily affected by environmental factors than metal. In addition, precision resin machining requires careful consideration of various factors, including machining equipment, techniques, and environmental conditions, and it is important to apply the most suitable processing method for each component.

At City Pla (Thailand), we handle more than 120 types of resin materials. Drawing on the know-how we have developed over the years in resin processing, we apply tailored machining methods for each component, taking into account the specific characteristics of each resin material.

▲ Example of resin material inventory at City Pla (Thailand)

In this article, we introduce resin machining at City Pla (Thailand), including specific examples of our work.

City Plastic, a Leading Japanese Manufacturer in Resin Machining

The parent company, City Plastic Co., Ltd., headquartered in Hiroshima Prefecture, is a Japanese precision plastic machining manufacturer with the largest facilities in the industry. Equipped with more than 70 advanced machines, including large machining centers, simultaneous 5-axis machines, and multi-tasking lathes ranging from small to large sizes, City Plastic can handle complex shapes and high-precision machining with short lead times. City Plastic operates manufacturing sites in Hiroshima Prefecture (site area: 35,000 m², total floor area: approx. 13,000 m²), Shimane Prefecture (site area: 6,000 m², total floor area: approx. 3,200 m²), and Kumamoto Prefecture (approx. 400 m²), producing mechanical components for a wide range of industries, including semiconductors, medical devices, and industrial robots.

▲ Aerial view of city plastic Hiroshima Factory

▲ Example of equipment at City Plastic Hiroshima Factory

Machining and Environmental Control Tailored to Resin Characteristics

Resin is generally sensitive to environmental conditions, and its dimensions can easily change due to slight variations in temperature or clamping force. For this reason, we maintain strict daily temperature control in the factory (24–25°C) to prevent expansion or distortion caused by temperature fluctuations.

In addition, the selection of machining jigs is crucial. Since metal jigs can deform the material under clamping, we sometimes custom-make resin jigs to minimize stress on the workpiece. Depending on the type of resin, dimensions may change due to the force applied during caliper measurements, or deformation may occur if coolant contacts the material. For example, in drilling operations, holes are made slightly larger than the design dimensions to account for the material’s properties. Process adjustments based on the properties of the resin.

▲ Measurement of machined parts using calipers

Adopting Machining Methods Tailored to Resin Properties: Glass-Filled PTFE Case

One of the resins that is difficult to machine and handle is PTFE (Teflon). This high-performance resin combines heat resistance, chemical resistance, and low friction, making it highly sought after in industries that demand high precision, such as medical devices and semiconductor equipment. Glass-filled PTFE, which is reinforced with glass fibers, further increases strength and rigidity, making it suitable for applications in harsher environments. However, it is prone to chipping under machining loads, so careful tool selection and process management are essential.

▲ Glass-Filled PTFE Before Machining

Milling and Turning Performed Without Setup Changes

▲ One-stop turning (left) and milling (right) on a Mazak INTEGREX multi-tasking machine

After repeated trial and error, while taking into account the tendency of chipping, we arrived at the optimal solution: simultaneous machining using a multi-tasking machine. Turning and milling operations are performed consecutively in a single setup, achieving both stable precision and reduced machining time. By minimizing setup changes during machining, we further ensure consistent accuracy. For high-difficulty parts—such as those refused by other companies—5-axis machining is often employed.

▲ Mazak INTEGREX multi-tasking machine at City Pla (Thailand)

The Key to Achieving High-Precision Machining: Training Skilled Operators and Finishing Specialists

In addition to utilizing high-precision machining equipment, we place great emphasis on training the staff who operate them. Our operators are generally capable of creating drawings using CAD/CAM software and possess the knowledge required to select the most appropriate tools and jigs for each project. Furthermore, we have established a comprehensive training system in which even non-production staff—such as sales and accounting personnel—are taught to read and understand technical drawings.

Equally important, manual finishing after machining is a vital part of the process. Our specialized finishing staff handle delicate tasks such as deburring and fine adjustments that cannot be performed by machines.

▲ Manual deburring and finishing work

In Japan, it is standard practice to have drawings for each part, but in Thailand, we often receive inquiries without any drawings, such as “We want something the same as this (actual part)” or “Can you make something like this?” We respond flexibly to such requests by working directly with the actual parts, carrying out repeated trial and error as needed.

If you are having trouble finding suppliers for resin parts in Thailand, or if other companies have declined your request, please feel free to consult City Pla (Thailand).