When it comes to processing composite materials, there is no secret, and specific methods must be adopted for specific materials and specific applications. Therefore, people continue to explore progress in practice and find specific processing methods. Whether it is carbon fiber reinforced plastic (CFRP) or CFRP metal laminates (such as aluminum and / or titanium) processing; whether it is automatic feed equipment, or CNC fixed bed machine tools, Sandvik Coromant can work together with Precorp Provide leading composite machining tool solutions to help customers maximize process performance and process quality.
In recent years, the most discussed tool innovation in composite drilling tools is PCD direct compression sintering technology. To understand this concept, you first need to understand the PCD and its previous limitations. Generally, a flat sheet PCD is attached to the cemented carbide layer, and the PCD is brazed to the cutter body during the production of the cutting tool.
This method has two major drawbacks: 1. The tool geometry is limited because it is made of flat sheet; 2. The flat sheet is welded to the copper brazed joint of the tool very close to the cutting edge. If the temperature is close to the melting point of the brazing, heat is generated during processing, which can cause the welded joint to fail.
Strategic Positioning
In order to overcome these shortcomings and make full use of the advantages of PCD, Sandvik Coromant and Precorp have devoted themselves to the strategically focused manufacturing of PCD tool blanks using direct compression sintering technology of PCD materials. When making such a blank, the diamond powder is placed in a groove opened in the cutter body of the cemented carbide tool, and the diamond and the hard alloy are sintered together under high temperature/high pressure, and the sintered tool blank is brazed. On the handle. Finally, precise tool edge machining is performed according to the design requirements of the tool edge shape.
This is good news for the shop, because the characteristics of the sintered PCD allow for accurate positioning of the PCD blade during tooling. In addition, spiral cutting edges or other complex cutting edges can be made accurately, which is not possible with welded PCD flat sheets. Sintered PCD technology provides Sandvik Coromant with a design-optimized cutting edge that is optimized for under-rigid settings and for precision, stable, high-volume machining. The use of PCD direct compression sintering technology can also solve the above problems of copper solder joint failure. It is true that the direct compression of the sintered tool still has a brazed joint - this is only located above the shank, far from the cutting point, and is not affected by heat.
Special tool edge
In general, the PCD direct-pressing tool has a sharp cutting edge that maintains a sharp edge even when machining composites with the highest wear resistance. This technique can even be further enhanced, such as strengthening the rounded corners of the tool to increase the cutting speed without affecting surface quality or dimensional tolerances.
For processing composites and metal laminates, PCD direct-sintering tools can be micro-grinded to process high stress concentrations and help maintain sharpness and extend tool life. When the sharp edge of the tool cuts synthetic fibers, the required thrust is small, which minimizes machining defects such as delamination, substrate melting/softening, fiber pull-out and surface scorching.
Core driving force
Hole machining continues to dominate in composite and part processing. For example, in the aerospace industry, it takes a lot of time to prepare fasteners for composite frames and parts. Even with the latest uniform structure that reduces assembly requirements, drilling is still the dominant factor in terms of process efficiency and cost.
Sandvik Coromant's PCD drills use direct compression sintering technology. The cutting edges can be made into a variety of groove types to minimize the tendency to delamination into and out of the hole, but the application method is still a major factor in tool selection. For example, when using automatic feed equipment, the PCD directly presses the sintered drill bit (such as the 85 or 86 PT series CD10) and uses the PCD blade protection design to increase the stability of the process. At this time, a protective layer is added to the cutting edge of the cutting tool PCD, which shortens the total length of the exposed portion of the PCD. This prevents the cutting edge from cracking and extends the life of the tool. These drills can also be internally cooled, which is especially recommended for composites that process aluminum and/or titanium alloy stacks.
CNC machine tool
When machining CFRP parts on a fixed-bed CNC machine, we have optimized another CD10 PCD direct-pressed drill bit, CoroDrill ® 859V, for unidirectional tape materials such as M21E, and epoxy and BMI ( Maleimide resin. This drill has a sharp double-angled edge that reduces delamination and provides excellent performance when drilling on coated CFRP (eg fiberglass and copper).
When machining CFRP/metal stacking materials on fixed-bed CNC machines, CD10 PCD is required to directly press sintered drill bits, such as the 86A and 86B series. The former has a 118° centering point for CFRP/aluminum alloy stacking materials, while the latter has a 135° centering point for CFRP/titanium alloy stacking materials, both designs reduce burrs and fibers Fragmentation.
Carbonized fibers stacked with titanium alloys are one of the most difficult material combinations to be processed, but Sandvik Coromant and Precorp work together to overcome the difficulties and improve the hole processing efficiency of such materials. In order to give the idea of ​​direct compression of sintered PCD performance by CoroDrill, a 15 mm thick CFRP interlayer and a 10 mm titanium alloy sheet were used to cut the through hole with a cutting speed of about 12 m/min and a feed rate of 0.05 mm/rev.
One drilling
In order to reduce downtime, improve the surface quality and pore size error of CFRP (carbon fiber reinforced plastic) or CFRP/metal stacking materials, it is essential to use the direct compression sintering technology of optimized drill tip configuration for PCD drill bits and optimized machining processes. of. Although it is desirable to use a one-time tool for drilling to reduce production time, when high precision is required, the drilling requires two or three operations, namely pre-drilling, drilling and reaming.
Although it has always been believed that precision drilling on composite materials is difficult to achieve through a stable, reliable and repeatable one-shot drilling process, this concept is about to change. Sandvik Coromant is conducting extensive trials to reduce machining time and reduce tool usage when drilling aerospace parts. These tests focus on a single-pass drilling process using a power-feeding machine that drills through CFRP (CFRP/Ti/Alu) materials in an aluminum/titanium alloy stack. The results of the first test made the large aviation industry see hope that the quality of the drilling can fully meet the desired level of demand.
The direct press-sintering PCD technology helped Sandvik Coromant meet the needs of such companies and developed a special geometry to suit the different conditions required for different materials.
However, PCD direct compression sintering tools are not only used for hole machining, but also for surface machining and edge machining. A typical example is the vertical tail of an aircraft made of composite material. The edge machining of this material is quite difficult. However, CoroMill ® Plura end mills with PCD direct compression technology are best suited for this type of processing, reducing fiber fragmentation and increasing metal removal rates.
From the perspective of composite processing capability and cost reduction, PCD direct compression sintering technology is undoubtedly the biggest technology driver, with great potential and competitive advantages for various applications.
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