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Composite Tools

  • What is composite material?
  • Composition and directivity of composite 
  • The main issues of composite machining
  • Milling tools
  • Holemaking tools
  • Superhard diamond tool: CVD and PCD

What is composite material?

A composite material is an engineering material, often referred to as a composite, made of at least two or more materials with significantly different physical and chemical properties, including a substrate that acts as a bond and a reinforcement that acts as a force. At the macro level, composite products can maintain and embody the different properties of their constituent materials.
According to the different substrates, composite materials can be divided into polymer base composite, metal base composite, and ceramic base composite three categories:
PMCs, that is, polymer-based composites, is a typical composite material, usually referring to FRP, that is, fiber-reinforced plastics. FRP is made of thermosetting or thermoplastic resin as the matrix, with short or continuous fiber and its fabric as the reinforcement phase, by composite. Common reinforcements include glass fiber, carbon fiber, and Kevlar (aramid fiber).
MMCs, or metal-based composites, are increasingly used in the automotive industry, where the base material is a metal, such as aluminum, and the reinforcement is usually silicon carbide.
CMCs, that is, ceramic-based composites, commonly used in high-temperature environments, the substrate is ceramic, and the reinforcement is short fiber, silicon carbide, or boron nitride.

Directivity of composite materials

The fiber reinforcement can be made into unidirectional rope, band, or woven into isotropic fabric.

Main ingredient and characteristics of substrate material

  • Epoxy resin: high-quality standard;
  • Phenolic resin: fireproof;
  • BMI cyanate resin: high-temperature resistance;
  • Polyester fiber (polyester), polyethylene: low cost;
  • Thermoplastic (PEEK, PEKK): strong impact resistance.

In the aviation industry, epoxy resins are used as structural substrates or binders for composites, which are entirely transparent. As the reinforcement of carbon fiber, the single diameter is minimal. Usually, only 0.005-0.010 mm are formed by carbon atoms in a microcrystal structure.
In addition to carbon fiber, composite reinforcement refers to glass fiber and Kevlar (aramid fiber). Carbon fiber is black, fiberglass and Kevlar are white and yellow, respectively. The fiber reinforcement can be made into unidirectional cables and belts and spun into isotropic fabrics.

The major problem of machining composites

Compared with the processing of metals and other conventional materials, because of the above characteristics, there are some unique difficulties for composite materials, mainly including:

Splintering

Fraying

Quick Tool Wear

Delamination

Composite Milling

The composite routers produce clean shearing of material fibers due to the upcut and downcut diamond-cut flute pattern design. Chipbreakers of the routers ensure that the carbon fibers are reduced to powder for rapid evacuation, ensuring minimal heat generation and aggressive removal rates with minimal delamination and splintering. CVD diamond coating provides expectation protection on the cutting edge, resulting in a long tool life.

A type: No end-cut fiberglass router bit is ideal for contour finishing flat surface removal.

B type: Bur-end fiberglass router bit is suitable for removing contour and right-angled corners.

C type: Mill-end fiberglass router bit is suitable for processing grooves, terraces, etc.

D type: The drill-end fiberglass router bit is suitable for drilling, making random cuts, and grinding.

Composite Router-Diamond Teeth

Applications

Avoid Delamination and Splintering

D type router

  The drill-end fiberglass router bit is suitable for drilling, making random cuts, and grinding.

C type router

Mill-end fiberglass router bit is suitable for processing grooves, terraces, etc.

Milling cutter for composite laminates

composite materials use more and more in aviation, yachts and luxury car interiors, to reduce weight while ensuring strength. The composition of composite laminates varies greatly, and the main problems in processing are delamination and splintering. Therefore, the tool must be sharp, and it needs to have a good chip removal design.

Composite Holemaking

Holemaking accounts for 60-80% of composite processing, including through holes, step holes, reaming, threading, chamfering, countersunk holes, and so on.
Similar to milling, the main problems in the hole processing of composite materials are tool wear, delamination, splintering, fraying, and the tool design needs to focus on these problems.
Indexable hole-making tools are also common. On the basis of the traditional indexable bit such as module drill, U drill, shovel drill and gun drill, the matching blade is welded to the PCD cutting edge, and the appropriate geometry is selected, which can greatly improve the tool life, improve the cutting efficiency and cutting quality, and reduce the processing cost per hole.

Popular composite drill bit

Devlar drill, Aircraft drill
Custom:dagger drill, step drill, piloted countersink

Superhard Tools:CVD and PCD

Adding reinforcement materials to composite materials, including carbon fiber, glass fiber, Kevlar fiber, SiC, etc., significantly improves the strength of the composite material but also dramatically increases the difficulty of processing and accelerates tool wear. The use of superhard tools has largely solved the problem of rapid tool wear. Through the physical method of high temperature and high pressure, carbide tools are brazed with PCD edges. This is a proven technology and cost-effective. So, it’s usually the first choice for composite processing. The technology of “growing” a pure diamond coating on the surface of solid carbide tools by chemical vapor deposition (CVD) is also proven, and the cost is acceptable. CVD is the coating on the already ground tool, so the shape of the CVD tool depends on the CNC grinder, which can be very flexible. This is what the PCD tool does not have. For small diameters and sizes and tools with complex geometry, the CVD process has obvious advantages over the PCD process.

CVD coated cutting tools

The geometry of the CVD tool can be very complex. The diameter and overall size can be small. CVD diamond-coated tool has apparent advantages over the PCD process

PCD cutting tools

PCD cutting tools are available in two types: monopiece and indexable. Braze PCD at the cutting edge of the cutting tools is the most economical method. The PCD edge is welded at the edge of the integral tool to achieve the highest overall accuracy. Because a CNC grinder is ground to size after welding, the integral PCD tool can also make a tool with more complex geometry.