Select The Right CNC Cutting Method For Your Parts

cnc cutting method

It can be challenging to choose the best CNC cutting method for your part design. CNC (Computer Numerical Control) encompasses a range of manufacturing processes — all aimed at producing parts by removing materials. Here are our tips to help you choose the right CNC cutting method for your custom parts.

Select CNC Cutting Method Based On the Material Used

Material selection is an important decision in designing new parts. It also determines the CNC cutting methods you can use to machine your part.

For Hard Materials

In the last few decades, there has been a rise in the development of specialty metal alloys. This is due to a greater understanding of materials science at the atomic level and innovative technologies. There is a super hard material class that has hardness values above 40 GPa (Vickers Hardness). They are almost incompressible solids with superior, high-electron density and covalent bond strengths. Diamond, for comparison, has a hardness between 70-150 GPa and a 2021 project developed an alloy that can harden up to 2500 GPa.

While all types of CNC cutting can cut hard materials, EDM and CNC Milling have been specifically optimized for this task. Remember that the cutting tool or wire must be as hard as the cut material. The durability of your cutting tools or wire can also be an issue. This is why it’s important to choose the right one. Not all cutting tools are designed for cutting through hard material. Cutting through harder materials can produce more heat, which requires more energy.

Tips for Hard Materials With EDM

  • Select the right wire For wire EDM. Zinc coatings are used to coat the wire. This improves the wire’s stiffness and helps with the cutting speed.
  • Use adaptive controls to reduce the volume of the recast layer and heat-affected zones.
  • For sinker EDM applications, it is important to change the dielectric fluid and the tooling more frequently, as tooling wears more quickly when made of harder materials.

Tips for Hard Materials with CNC Milling

  • Select the right tool type to cut through hard materials. Ball end mills are ideal because they reduce heat loss and minimize the chance of deforming the workpiece.
  • Do not heat treat parts until they are complete.
  • To help dissipate heat during CNC cutting, use the right type and amount of coolant or Lubricant. The spindle cooling system offers excellent heat dissipation.
  • Make sure the radial step-over distance equals 10-20% of your tooling diameter.
  • Use high-quality tool holders to reduce runout. Dovetail holders can also reduce vibration and provide higher precision cuts.

Select Based On Tolerance & Geometry

EDM generally has tighter tolerances than CNC turning or CNC milling. With CNC gear hobbing, our experienced CNC machining manufacturers can achieve tight tolerances of as little as a millimeter (around 0.0004 in) — which is exactly what precision companies such as Hebi Robotics need. EDM is the best option for extremely precise requirements. However, CNC milling and turning can achieve tighter tolerances than hobbing.

EDM

EDM is best for parts with complicated geometries. These parts require precise through-holes (wire EDM) machining and complex internal cavities (sinker EDM). EDM is a great choice for parts that have small features and inside corners. EDM is more expensive per part, so it is often used for low-volume production.

CNC Milling

CNC milling is ideal for creating geometric features that are not extended through the thickness of the material. CNC milling can create geometric features on multiple parts faces or planes simultaneously in one fixturing/machining setup, depending on how many axes are used for each type of CNC machine.

CNC milling is also a great option for complex contour geometries. The tool shapes that remove material can create smooth radii and curves, counters, or similar features. CNC milling can create different edge profiles, including rounded and chamfered edges.

Gear Hobbing

Gear hobbing, a CNC machining process used to create a wide range of gear shapes on non-metal and metal parts, is one of the most common gear manufacturing methods. The gear hobbing process involves cutting the teeth (or splines) into a circular piece of material using a cutting tool called a hob. Hobbing can create complex shapes and sizes of gears such as spur, worm, and bevel. Gear hobbing is great for prototyping small quantities but is not suitable for larger volumes.

CNC Turning

Finally, CNC turning can turn shapes with cylindrical mirror symmetry. This is because the part rotates on its axis as the cutting tool is in contact with it. CNC turning is also a great option for complex geometries like threaded bodies. A CNC turning machine is also used for tunneling and tapering.

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