On-site customer feedback from precision semiconductor resin part manufacturer leads to product development of SEP-EL end mill optimized for super engineering plastic applications
Akinori Sumi, Koichi Ida & Shotaro Noda | OSG Corporation
Super Engineering Plastics
In recent years, the semiconductor manufacturing sector has taken steps to advance the use of super engineering plastics (SEPs). SEPs are high-performance plastics with properties that can withstand high temperature and tensile strength. Equipped with exceptional thermal and mechanical characteristics, SEPs excel even in harsh environments. In many cases, SEPs can effectively replace metals as they are lighter in weight. Today, SEPs are commonly employed in electronic appliances, home electrical appliances, automobile, medical instruments, airplanes, industrial machines, and more.
Cutting Resin
Firstly, most of the plastic products that surround us today are made by injection molding, not cutting. Because resin has a low melting point, injection molding, which involves pouring molten plastic into a mold and shaping it, is the most efficient method for mass production and has the least material loss. However, since the production of molds is very costly, it is not suitable for small-lot, high-mix production. It is said that cutting can reduce costs for part production quantities up to about 700 pieces.
In addition, some resin materials have very poor fluidity when liquefied, and many are only available as plates or bars due to their manufacturing methods. These materials have no choice but to be cut, so there is a certain demand for cutting resin.
Machinability of Resin
The mechanical properties of SEPs are significantly different from those of metals, and the performance required of cutting tools is also different from that of metals. General resins have different characteristics than metals in various ways, such as being softer, more stretchable, having lower thermal conductivity, and lower heat resistance. The points to be careful of when cutting are also different from metals, and cutting resin requires unique techniques. The main problem with cutting resin is not chipping or wear of the tool, but burrs, warping, and expansion and contraction on the workpiece. As depicted in figure 1, the cutting resistance of resin is quite small, about 1/20 that of metal, so abnormalities on the tool are unlikely to occur, but various problems can occur on the workpiece.
Figure 1. Comparison of bending moment in different materials using the same tool and cutting condition
Additionally, in the case of transparent resins, a highly transparent surface is required, and a processing method that is appropriate for the resin material is vital. Furthermore, some resins contain reinforcing materials such as glass fiber and carbon fiber. These materials can cause significant tool wear during processing. When the tool wears and the cutting edge becomes curled, the cutting ability decreases, leading to increased burrs and deformation, so even slight wear is not tolerated for cutting tools used in SEP processing.
Cutting Tools for Resin Processing
Currently, the majority of end mills for resin processing sold by tool manufacturers are positioned as end mills for acrylic. End mills for acrylic are generally uncoated and have a strong rake angle to improve sharpness. However, since these end mills are designed to be almost wear-free, they quickly wear out when processing fiber-reinforced SEPs, and are incapable of meeting quality requirement.
Diamond coating is the most effective way to improve the wear resistance of SEP processing. However, diamond coating has a large film thickness and the cutting edge tends to curl, making it difficult to maintain sharpness, so it cannot be used in applications that require high precision. Furthermore, diamond coating products are also more expensive than general tools, making them less attainable.
Mori Craft – The SEP Application Expert
To better understand the usage and machining challenges involving SEPs, OSG consulted with Mori Craft Co., Ltd., a company that specializes in precision resin processing.
Founded in 1991, Mori Craft is a metal and high-performance plastic solution provider. Using some of the latest precision processing technologies, Mori Craft supports its clients’ product development from prototype to modeling.
Founded in 1991, Mori Craft is a metal and high-performance plastic solution provider. Using some of the latest precision processing technologies, Mori Craft supports its clients’ product development from prototype to modeling. Mori Craft can perform processing with an accuracy of ±0.01 mm and offers solutions for mass-produced parts, small-lot, as well as multi-variety products. The annual production volume of parts may vary from 10 pieces to more than 36,000 pieces. The volume of each batch may range from a single piece to 3,000 pieces. In terms of size, workpieces may range from 5 mm by 5 mm up to a maximum of 70 mm by 120 mm. Although requirements vary depending on the client, the precision requirement is usually around ±0.02 mm. Currently, the company’s main products are test sockets, which are inspection jig components for the semiconductor industry.
Mori Craft’s inspection room. Mori Craft has obtained the ISO 9001 certification since 2023, a proof that its products and services are provided under a quality control system at an international standard level.
Employing 17 staff, Mori Craft’s manufacturing plant is located in the city of Tomioka, Gunma, Japan, with an estimate production area of 384-square-meter. Its production facility is equipped with a variety of machining centers, including a Roku-Roku Sangyo MEGA-S micro machining center (HSK-25), a DMG Mori CMX 800 V vertical machining center (BT40), a Mori Seiki DuraVertical 5060 machining center (BT40), and 12 FANUC Robodrill compact machining centers (BT30). Mori Craft has obtained the ISO 9001 certification since 2023, a proof that its products and services are provided under a quality control system at an international standard level.
OSG first visited Mori Craft in May 2022 by the introduction of cutting tool distributor Sato Kiko Co. Ltd. Mori Craft has been manufacturing SEP products since the company’s founding more than 30 years ago. As an expert in SEP applications, Mori Craft Plant Manager Takeshi Tamura shared his insights revolving the processing of this material.
From left, Mori Craft plant manager Takeshi Tamura shares his insights revolving the processing of super engineering plastics with OSG representatives.
“There are many kinds of resins, and among them, materials classified as super engineering plastics (SEPs) are very expensive, hard to obtain, and very difficult to cut due to their material properties,” said Tamura.
“Above all, the durability of cutting tools used for processing SEPs is extremely poor,” Tamura adds.
There were many malfunctions due to tool wear and chipping, as well as noticeable time lost due to accuracy inspection and tool replacement. Mori Craft has always been troubled by the limited cutting tool options for the processing of SEPs. Up until recently, the company would use a competitor tooling series specialized for machining copper alloy with DLC coating. The competitor tools are available in small diameter sizes and are inexpensive. However, Mori Craft has been dissatisfied with the tool life and processing quality.
Prototype Tool & Test Cut
With valuable feedback and cooperation from Mori Craft, OSG conducted cutting tool trials on SEPs for approximately nine months, from May 2022 to February 2023. Two prototype end mills were developed in 1.5 x D length of cut and 3 x D length of cut.
From left, figure 2. Krefine PEI (polyetherimide) is a common SEP material that Mori Craft works with. | Figure 3. Visual reference of approximate shape and dimensions of the test part made of Krefine PEI.
The test part was a tray made of Krefine PEI. The processing involved plunging into the solid surface in Z direction, followed by milling at a depth of 1.8 mm to create a pocket. An OSG diameter 3 x 4.5 length of cut (1.5 x D) prototype DLC coated end mill and a competitor diameter 3 x 10 x 6 length of cut DLC coated end mill were used for the testing. The cutting trial was conducted using a FANUC Robodrill compact machining centers (BT30) with coolant emulsion (20 times diluted).
For plunging, the tools were tested at a cutting speed of 5,000 min-1, a feed rate of 200 mm /min, and at an axial depth of cut (ap) of 1.8 mm. Both tools ejected elongated cutting chips. For pocket milling, the tools were tested at a cutting speed of 5,000 min-1, a feed rate of 200 mm /min, an ap of 1.8 mm, and a radial depth of cut (ae) of 3 mm. For the pocket milling process, cutting began with slotting, which subsequentially turned into contouring at a radial depth of cut 3 mm. Since the radial depth of cut is the same as the slotting process, the cutting resistance has a tendency to rise, and the tool deflection also tends to increase.
The competitor tool was able to complete pocketing two workpieces (milling distance of 2.3 m). However, the bottom of the pockets exhibited cracks and galling also occurred. The OSG prototype end mill, on the other hand, was able to complete pocketing 15 workpieces (milling distance of 17 m). Although there were stripes and chattering on the bottom of the surface, they do not affect the quality of the product. The OSG prototype tool exhibited normal wear and can continued to be used depending on the required machining precision. At the end of the trial, OSG’s 1.5 x D prototype was able to achieve more than seven times the durability versus the competitor tool in Krefine PEI, demonstrating the superiority of the tool’s cutting edge geometry and the DLC-IGUSS coating.
With tremendous support from Mori Craft, the OSG product development team was able to develop the SEP-EL DLC-IGUSS coated carbide end mill optimized for super engineering plastic applications.
With this cutting trial success and the tremendous support from Mori Craft, the OSG product development team went on to standardize the prototype tool, which would become the SEP-EL, DLC-IGUSS coated carbide end mill optimized for super engineering plastic applications.
Key Features & Benefits of SEP-EL
The SEP-EL is OSG’s latest milling innovation specialized for high-quality processing of SEPs that are prone to wear. The first key feature of the SEP-EL is the application of OSG’s original DLC-IGUSS coating, which has a film thickness of approximately 8 μm. Thicker than conventional DLC coating but thinner than typical coatings for steel, the DLC-IGUSS offers the perfect balance of lubricating effect, wear resistance, and cutting edge sharpness.
As depicted in figure 4, a second key feature of the SEP-EL is its 3-flute specification, which reduces the load on the cutting edge compared to 2-flute configuration. The low helix geometry of the flute suppresses the generation of burrs, lifting or peeling of the workpiece when fixed with double-sided tape, resulting in stable processing. The 3-flute and sharp cutting edge specification enables high-speed and high-efficiency processing of various SEP applications.
Figure 4. SEP-EL DLC coated carbide end mill for super engineering plastics.
Last but not least, the sharp cutting edge configuration of the SEP-EL reduces heat generation and enables high-quality resin processing. With excellent sharpness, general-purpose plastics, engineering plastics and SEPs can be cut through with a single stroke.
Cutting Data
A cutting test was conducted in a resin called Unilate to compare wear on the cutting edge and the machined surface between three tools – an end mill designed for machining aluminum, an end mill designed for machining steel, and the SEP-EL.
Figure 5. Cutting edge and machined surface conditions after milling 60 m of Unilate.
As illustrated in figure 5, after milling 60 m of Unilate, the SEP-EL exhibited significantly slower progression of wear and has the least amount of burrs on the machined surface versus the other two end mills.
From left, OSG application sales representative Akinori Sumi and OSG sales representatives Koichi Ida explain the features of OSG’s SEP-EL DLC-IGUSS coated carbide end mill to Mori Craft plant manager Takeshi Tamura.
It is true that resin is a soft material and can be processed somehow if time to spent on deburring and annealing. However, considering the increasing precision and demand for resin parts in the semiconductor manufacturing industry, the need to improve efficiency of SEP part production is evident.
The SEP-EL is OSG’s latest milling innovation specialized for high-quality processing of super engineering plastics (SEPs).
“After adopting SEP-EL, running costs improved significantly, which greatly contributed to improving productivity,” said Tamura.
“This experience also helped our staff foster a professional mindset by emphasizing on the importance of proper tool selection,” Tamura adds.
From left, OSG sales representative Koichi Ida, Mori Craft plant manager Takeshi Tamura, OSG application sales representative Akinori Sumi and OSG applications engineer Shotaro Noda pose for a photograph at Mori Craft’s manufacturing facility in Gunma, Japan.
OSG always strives to deliver optimal cutting tool solutions for the ever-changing manufacturing industry. Through research, development and strategic collaborations, OSG will continue its journey of innovation to expand its offering of highly productive, energy efficient and environmentally friendly products.
For more information on OSG’s SEP-EL DLC coated carbide end mill and Mori Craft (Japanese only)
About Mori Craft Co., Ltd.
Founded in 1991, Mori Craft is a metal and high-performance plastic solution provider. Using some of the latest precision processing technologies, Mori Craft supports its clients’ product development from prototype to modeling. Mori Craft can perform processing with an accuracy of ±0.01 mm and offers solutions for mass-produced parts, small-lot, as well as multi-variety products. The annual production volume of parts may vary from 10 pieces to more than 36,000 pieces. The volume of each batch may range from a single piece to 3,000 pieces. In terms of size, workpieces may range from 5 mm by 5 mm up to a maximum of 70 mm by 120 mm. Although requirements vary depending on the client, the precision requirement is usually around ±0.02 mm. Currently, the company’s main products are test sockets, which are inspection jig components for the semiconductor industry.
Mori Craft employees pose for a photograph at the company headquarters in Tomioka, Gunma, Japan.
Mori Craft performs resin processing using lathes and machining centers. With the introduction of 3D CAD, the company now also processes complex three-dimensional shapes. In particular, Mori Craft is an expert of cutting high-performance SEP products. For resins, the company actively proposes conductive and antistatic materials and ideas for improving processability. For metals, it mainly processes aluminum, brass, SUS, etc., mainly for circuit inspection parts, and can also accept various surface modifications.
Mori Craft’s operator prepares for the machining of parts.
Staff from Mori Craft’s sales order management department.
Employing 17 staff, Mori Craft’s manufacturing plant is located in the city of Tomioka, Gunma, Japan, with an estimate production area of 384-square-meter. Its production facility is equipped with a number of machining centers, including a Roku-Roku Sangyo MEGA-S micro machining center (HSK-25), a DMG Mori CMX 800 V vertical machining center (BT40), a Mori Seiki DuraVertical 5060 machining center (BT40), and 12 FANUC Robodrill compact machining centers (BT30). Mori Craft has obtained the ISO 9001 certification since 2023, a proof that its products and services are provided under a quality control system at an international standard level.
Precision Processing Work Examples
From left, a part made of PEEK and parts made of PAI. Mori Craft can perform processing with an accuracy of ±0.01 mm and offers solutions for mass-produced parts, small-lot, as well as multi-variety products.
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