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The CNC Precision Honing Process Explained

Posted by Andrea Rodney on Apr 17, 2018 9:07:18 AM

The CNC Precision Honing Process Explained

CNC honing, like mostcomputer-controlled processes in general, presents some significant advantages over conventional techniques:

  • Consistent and repeatable accuracy and quality
  • Very fine and exacting dimensions possible
  • Surface finishes of 0,05μ
  • Built-in metrology controls stock removal
  • Ideal for components that require the highest possible level of precision

Features and capabilities vary from machine to machine but they all deliver hands-off honing to exceptional tolerances and the ability to sense and establish the dimensions of an environment such as a target bore.

The standout advantages of a CNC honing machine are the speed and ease of setting it up for a job, size accuracy and bore geometry control.

Typical industry-wide applications are where high bore geometric tolerance is critical, for example some bearings and valve components, fuel injectors and so on. Here at Hone-All it enables us to deliver exceptional quality and balance for the wide range of components we machine and industries we serve.

General Observations

Honing generally always follows an existing machined bore. However, you may have been told that straightness and cylindricity cannot be improved upon and this is certainly the case with standard tooling used for the majority of components but specialist tooling can be designed to overcome these parameters but at an increased cost which is not always a viable option with smaller batches.

The purpose of honing is a process intended to refine a surface in terms of any or all of:

  • accuracy of size
  • it’s geometric form
  • apply a specified surface finish, such as cross hatching
  • efficient plateau honing when double acting tooling is used

What it does mean is that the position of the bore will not change relative to the external dimensions when honing to a consistent size.

What The Process Entails

The operator enters data such as parameters and material of the workpiece, initial and desired diameter, finish required, bore length, sets starting positions for stroke and feed, and presses the Start button. The rest is automatically done by computer as it calculates the stroke rate, length and spindle speed. It can optionally adjust automatically for diamond wear after the size is proven to be correct.

Within the hone head, a coned shaft is driven by either electric or hydraulic power which actuates the cone shaft to linear movement. The stone set has corresponding cone angles and the core shaft expands or contracts when the shaft is pulled or pushed. Due to the slow angle of the cones, greater accuracy is achieved.

This is powered by a motor that dynamically positions the cone, which expands or contracts to control the diameter of the stone set. It executes bore size adjustments of sub-micron proportions.

The machine self-centres in the bore to begin exploring its environment vertically and horizontally. That way it “learns” it’s starting position in relation to the part’s position and dimensions. Then it expands the stones on the hone head and is ready to execute the honing under the control of the computer and guided by the parameters entered by the operator. The honing process deploys two forces on the part - hone rotation generates torque and the push-pull stroke action provides a lateral force. Together they abrade the surface which is constantly measured by the controlling computer.

The Bottom Line

CNC honing machines deliver consistent superb precision time after time. They require little supervision after the initial setup and can repeat a program identically time after time on similar parts that may have microscopic differences in diameter or present different taper characteristics, for example. There are always those rare applications where an old-fashioned manual machine and years of engineering experience will permit a more nuanced approach. But CNC honing is fast and precise - perfect for premium quality engineered parts.

Contact Us

Take the opportunity to contact us today for an informal initial chat about your particular requirement and scenario. We are always happy to consider new and challenging jobs and delivering customer satisfaction again and again is one of our greatest strengths.

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Topics: CNC Honing

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