Tools in polycrystalline diamond and tungsten carbide: when and why to choose them

Tools made from polycrystalline diamond and tungsten carbide

 

When it comes to choosing cutters for machining wood, a decision must be made between two main categories: tungsten carbide tools and polycrystalline diamond tools.

The most frequently asked questions regarding the choice of one type of tool over the other essentially focus on the differences between the two materials in terms of price, characteristics and intended use.

While it is undeniable that PCD polycrystalline diamond cutters cost more to buy than their tungsten carbide equivalent, as we will see in a moment, it is also true that the initial difference in cost is reabsorbed over time, and is justified by the specific characteristics of PCD.

Below, we will analyse the peculiarities of PCD and tungsten carbide cutters and provide a series of useful tips for assessing when it is best to choose a polycrystalline diamond cutting edge, and when it is more appropriate to opt for tungsten carbide.

But first, it is important to start by saying that the choice of tool can be influenced by a range of variables, some of which are related to specific machining operations, and others of which are dependent on the requirements of the individual user. For this reason, it is always advisable to seek the advice of experienced suppliers who can provide valuable support in choosing the most suitable type of tool for you.

 

Tools-made-from-polycrystalline-diamond-and-tungsten-carbide-when-and-why-to-choose-them

 

What is polycrystalline diamond (PCD)?

Polycrystalline diamond is a composite material which consists of diamond particles sintered together with a metallic binder.

Diamond is an extremely hard material, a quality owed to its very compact cubic crystalline structure, composed entirely of tiny carbon atoms arranged in a tetrahedral shape, which creates very strong bonds with all the surrounding atoms.

From the early 1800s, after the discovery that diamond was composed of pure carbon, and for over a century afterwards, numerous attempts were made to reproduce the extreme conditions for creating synthetic diamonds, but it was not until around 1940 that the first industrial diamonds appeared, manufactured by General Electric. 

GE subjected graphite (the other crystalline form of carbon with a hexagonal structure) to temperatures of 2-3000°C and pressures of 50-100,000 bar, using catalysts made from nickel, iron and cobalt. In the 1970s, General Electric created CBN (Cubic Boron Nitride) and later Polycrystalline Diamond (PCD) and Polycrystalline CBN (PCBN).

Since then, applications have grown exponentially, leading this material to become one of the most versatile in the wood machining industry.

The natural hardness of polycrystalline diamond makes it an excellent cutting material, ideal for producing routing, sizing and boring tools.

When and why to choose tools made from polycrystalline diamond

Of the primary characteristics of tools made from polycrystalline diamond, the following are of particular note:

  • extreme hardness
  • low friction
  • high resistance to wear
  • greater cutting duration
  • optimal finish quality

Due to their exceptional ability to withstand high levels of wear, PCD tools are a valuable help when machining all the abrasive composite materials that are sometimes difficult to machine using tungsten carbide tools. 

They are best used on the following materials: 

  • chipboard
  • laminated materials
  • MDF/HDF
  • phenolic
  • fibreglass
  • carbon fibre
  • PVC
  • CORIAN
  • HPL

However, it is not recommended for use on ferrous materials.

If you are considering purchasing a polycrystalline diamond tool, it is important to talk to the manufacturer, discuss in detail what you will be using it for and explain your expectations with regard to the machining results you want to achieve. 

Indeed, buying a PCD tool is not sufficient to guarantee a good result. You also need to know how to use it!

This is why it is essential to speak to the manufacturer: to discuss the specific characteristics of the PCD cutter, saw blade or bit in relation to the material to be machined and the type of machining operation to be carried out.

Based on this information, the supplier will be able to provide advice with regard to:

  • the most suitable PCD grain size
  • the optimum tool geometry

These assessments are essential not only to achieve the best possible results, but also to optimise the purchase cost of the diamond tool.

 

characteristics of tools made from polycrystalline diamond

 

What is tungsten carbide (HW)?

Tungsten carbide (also known as Widia) belongs to the cermet category of materials, and is composed of of hard particles, usually of tungsten carbide, incorporated into a metal matrix (often cobalt), which combines hardness and resistance to wear with resistance to cracking.

It was Karl Schroeter and Henrich Bauhmhauer from Germany who first sintered tungsten carbide at the Osram Lamp Company in 1923, in an attempt to produce a material capable of cutting tungsten into thin filaments for use in lamps. Friedrich Krupp acquired the patent for this process, and in 1926, his company began producing this material, which was referred to as Widia (from the German “Wie Diamant”).

In 1928, the American company General Electric bought the rights for the production of this material in the USA, where it was marketed as Carboloy.

Tungsten carbide tools: when is it best to use them?

Cutters made from tungsten carbide or carbide tend to wear slower than steel cutters, and can withstand higher temperatures. 

Tungsten carbide tools are characterised by high resistance to wear and extreme toughness, and are recommended for machining materials with a greater chip discharge, such as hardwoods.

In addition, they are effective when used in machining operations where the tool is required to process different types of material during a single day, and where a high finish quality is not required: the cutting edge of carbide tools deteriorates right from the very first stages of cutting.

 

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Polycrystalline diamond vs. tungsten carbide: costs and benefits

In addition to these technical considerations, the choice between polycrystalline diamond and tungsten carbide tools is often influenced by cost.

As mentioned previously, tungsten carbide tools have a lower purchase price than polycrystalline diamond tools. But does this actually represent a real saving in terms of total production costs?

In order to answer this question, we must look at the "purchase cost" in relation to the actual benefits and advantages that can be obtained by opting for one solution over the other.

While carbide tools offer a cost advantage in terms of the initial sum invested, for some companies, polycrystalline diamond cutters may prove more advantageous in the long term. 

Although at first glance PCD tools are more expensive, when we calculate the cost per linear metre machined, with the correct application, a diamond tool proves to be a wiser choice, and an investment that pays for itself relatively quickly.

PCD saw blades, cutters, router bits or boring bits not only offer high performance in cutting applications - they can also significantly reduce a company's overall tooling costs. These costs can be further reduced by proper use and maintenance.

After a careful calculation, it transpires that the cost of a polycrystalline diamond tool is only one-fifth of the equivalent cost of a tungsten carbide tool, due to the fact that right from the first life cycle, diamond tools can reduce costs by 30-50% compared to carbide tools or tools with inserts.

However, not all companies need to use PCD tools. It is important not to fall into the opposite trap: if a company performs frequent machining operations on different types of material, PCD cutters are not always recommended. 

As such, the cost-benefit analysis must always be placed in the context of the type of activity in question and the machining operations most frequently carried out.

 

characteristics of tools made from tungsten carbide

 

How to understand which tools are most suitable 

As we have already noted, it is essential to get to know the characteristics of the tools on the market in detail. Indeed, in-depth knowledge of the product enables this to be evaluated correctly, and minimises the risk of errors.

In this sense, it is vital to rely on advice from professionals in the sector, as the only individuals capable of guiding customers towards the most suitable solution for them, after looking at the different variables: material to be processed, type of machining operation, user needs and expectations.

PCD cutters, for example, are not recommended where the main requirement is to be able to machine all types of material. 

A major advantage of PCD tools, meanwhile, lies in the fact that they offer a much higher finish quality than tungsten carbide, and therefore require less sanding.

Before purchasing a tool, you should therefore ask yourself: how many times can I sharpen this tool? How much will it cost me to sharpen it? How long will it take me to assemble/ disassemble and reset the machine during sharpening?

These questions can be answered by analysing the main differences between diamond and carbide tools in individual areas.

  • Cutting time

On average, diamond tools have a cutting time that is 50 times greater than that of tungsten carbide tools (the figures man vary in accordance with the material being machined, the machining speed etc.)

  • Cutting quality

Both diamond and tungsten carbide tools initially offer very high levels of cutting quality; however, tungsten carbide begins to deteriorate from the very first stages of cutting, while the quality of the diamond remains unchanged until the first time it is sharpened.

  • Re-sharpening

Tungsten carbide tools need to be resharpened more often than those made from polycrystalline diamond. This means:

  • more machine downtime
  • longer machine reset times
  • greater number of spare tools required.

 

Utensili in diamante

 

The experience of Wirutex 

As we have just seen, when choosing the right tool material for your needs, it is important to consider a number of elements, such as the type of material you will be machining, the composition of the batch in question and the machining finish you require, as well as performing a careful analysis of the costs involved.

Making a mistake during the evaluation process could have a negative effect on the production process, both in terms of machining quality and operating costs. 

Precisely for this reason, it is beneficial for customers to find a tool manufacturer they can rely on, with the ability to direct them towards the products most suited to their requirements.

Wirutex hi-tech tools is the ideal company for operators who want to be able to place their trust in a technological partner with a wealth of experience in the field. 

The extensive range of high-quality polycrystalline diamond and tungsten carbide tools available is a direct result of the company's ongoing investment in innovative technologies, which enable the application of cutting-edge design, development and production processes.

Wirutex hi-tech tools produces and distributes:

Whatever the choice of tool - diamond or carbide - it is essential to know how to use it correctly: even the best tool on the market will not perform to its full potential if it is not used according to the set parameters.

For this reason, it is essential to seek advice from an experienced tool manufacturer who can provide guidance on how to achieve the optimum balance between the various machining parameters.

If you have any questions regarding which cutting material is best suited to your machining requirements, please contact us by clicking here.



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By Redazione |
21 November, 2018
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Utensili hi-tech