Engineers have long been told to “design for manufacture”. 5-axis machining frees them from that diktat, at least in terms of producing complex metal components. Today, rather than breaking a part or design into multiple pieces, each of which is machined by conventional 3-axis methods, 5-axis lets engineers keep parts closer to the design intent.

In this blog we’ll explain how 5-axis machining allows greater part complexity and higher precision. That has to begin though, with an introduction to CNC milling.

What is CNC Milling?

The two primary metal cutting processes are turning and milling. Turning is done on a lathe with a single cutting edge and produces what are essentially cylindrical shapes. Milling is done on a milling machine or “mill”, with a rotating multi-toothed cutter that creates flat surfaces and prismatic shapes in a workpiece clamped to the table.

Most milling machines can move the table and workpiece in three axes relative to the cutter. These are left-right, in-out, and up-down, or in CNC machining nomenclature, the x, y and z axes. Interpolation between two axes, (synchronizing their movements), allows production of curves.

For an example, consider milling a pocket. The machine controller moves the x and y axes so the cutter follows a path over the surface of the workpiece that creates the pocket shape. X-Y interpolation moves the cutter in an arc to give the pocket radiused corners while Z-axis movement pushes the cutter down to add depth to the pocket.

3-axis milling like this can’t produce:

• Non-orthoganol features: If the design calls for a feature not parallel or perpendicular to the table, the workpiece must be taken off and relocated on a fixture holding it at the required angle.
• Contoured surfaces: The relationship between workpiece and cutter is fixed.

5-axis machining addresses these limitations, but does a lot more besides.

5-Axis Machining Basics

A 5-axis milling machine adds two rotational axes to the three orthogonal axes. There are various configurations, but all have the same goal: to tilt the workpiece relative to the cutting tool spindle.

This capability can be used in two ways:

• Reorient the workpiece between cuts (tilting it to enable milling of non-orthogonal flat surfaces)
• Rotate the workpiece during cutting, which creates contoured surfaces

Advantages of 5-Axis Machining

A host of benefits flow from adding this ability to control workpiece-cutting tool orientation. These start with:

• Do more machining in a single setup
• Consolidate otherwise separate parts into a single piece
• Use shorter tools
• Generate smooth contours

Let’s take a closer look.

Single setup

Doing more machining in a single setup provides an immediate productivity boost, (less setup time), but it also improves precision. This results from avoiding the inaccuracies that result from lifting a part off the table and remounting it.

Part consolidation

The ability to machine more complex features frees designers from the limitations of 3-axis machining. This means, rather than machine separate parts and assemble or weld them into one, they can be produced as a single item. (This can also reduce weight and increase stiffness and strength.)

Shorter tools

Freed from the need to reach deep into pockets and other features, the CNC programmers can use shorter tools. These deflect less under cutting loads, which results in higher precision machining and better surface finish.

Smooth contours

Required in fluid flow applications, from hydraulic valves and medical devices to the vanes and blades in gas turbines, smooth contours improve performance but have been very difficult to produce. In some cases, hand-polishing was the only option. 5-axis machining readily produces features like these.

Machining Processes Needn’t Dictate Part Design

5-axis CNC machine tools are expensive and require high-level programming skills, but for producing complex machined parts they offer increased productivity and high precision. If you’re in the business of designing metal components for challenging applications – think aerospace, chemical processing or medical devices – 5-axis machining creates more options.

Impro performs high-precision machining on modern CNC machine tools, including those with 5-axis capabilities. If you’d like more information or a quote for machining your parts or designs, please contact us.