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Easy Machining of Hard Materials

Easy Machining of Hard Materials (EMHM) is a laser assisted machining process that can make the post sintered machining of hard materials a cost effective alternative to traditional diamond wheel grinding.  The system integrates a fiber diode laser with a CNC lathe.  The laser preheats the material, softening the material, and therefore reducing the cutting forces required for machining.

Heating of the surface locally raises the temperature of the glassy ground boundary phase, which is the remainder of the oxide sintering aids used to obtain liquid phase sintering.  The system applies sufficient heat to soften the grain-boundary phase and produce the desired ductile deformation to allow machining using a single point cutting tool.  This ductile deformation enables reduced cutting forces, high material removal rates, minimal surface damage, and long tool life.  

The setup is a practical, industrially rugged production laser assisted machining system.  Special installation of the system permits the use of a tool changer allowing machining of the workpiece without the removal of part or breaking of the setup.  When not machining ceramics the system can be used as a normal turning center.

EMHM Benefits

Ceramics offer unique physical properties. In certain applications they can provide many benefits that traditional materials such as steel and super alloys cannot offer. Despite their many benefits ceramics remain extremely difficult materials to machine due to their high hardness and brittle nature. The expensive cutting tools and long machining times that are required to machine these materials make these materials cost prohibitive in all but the most demanding applications. Regardless of these challenges ceramics remain a desirable alternative for metal components. The ability to machine ceramics easily and cost effectively can be a monumental leap in industries where critical material properties for resisting extreme environments is a must. EMHM helps mitigate some of the costs associated with these materials and makes them a more affordable solution for current applications as well as applications where cost of machining was previously a barrier.

Due to the various benefits that technical ceramics offer they are used in a wide range of industries and applications. Some of these industries/applications include but are not limited to:

Automotive

  • Cylindrical rollers
  • Engine Cam rollers
  • Fuel Pump rollers
  • Jet engine igniter insulators

Military/Defense

  • Body armor
  • Missile radomes

Electronics Manufacturing

  • Microwave products
  • Semiconductor equipment

Industrial Applications

  • Industrial wear applications
  • Bearing rolling elements
  • Boiler ferrules
  • Metal forming rolls
  • Sand blast nozzle liners
  • Aluminum casting products
  • Dressing plates for polishing pads
  • Thermocouple sheaths
  • Welding nozzles
  • Welding jigs
  • Glow plugs
  • Cutting tools

Integration Made Easy

In production environments that currently use diamond grinding to machine ceramics, EMHM will be a comfortable addition to the shop floor. If you are currently using a CNC lathe in your process we can integrate a system with your existing machining center as long as there is adequate cabinet space to contain the unit.

If a CNC lathe is not currently part of your process, we work with our machine center supplier to provide you with a lathe that is a perfect fit for your size operation. In addition to designing a custom system for your operation we will also install the system at your facility and train your staff how to operate the machining center. This will ensure that your system is running as quick as possible and you are receiving the benefits of EMHM as quickly as possible.

Improved Surface Quality

Testing was performed with samples provided by two leading suppliers of silicon nitride.  These samples were tested under five different surface conditions. For ceramic rod B the conditions were: As received, diamond ground (800 grit), laser only, and laser assisted machined. For ceramic rod K the conditions were: As received, diamond ground (100 grit), and laser assisted machined. 

These samples were analyzed for surface finish using the advanced digital moire contouring method. A total of 27 images were taking for each of the two ceramic samples. Tests indicate that EMHM provides the best results in terms of surface finish.

While improving surface finish is definitely important, it is the consistency of that finish that leads to a better performing part, especially in applications where reducing friction is key. Weibell analysis of the two silicon nitride samples that were tested show us that the spread between the upper and lower bounds (Ra) for laser-assisted machining are much tighter than they are for the samples machined using diamond wheel grinding. This means that overall a better and more consistent surface finish was achieved by laser assisted machining. Digital moire contour testing of the samples show that overall EMHM creates less peaks and valleys, and where there is contrast there are smoother peaks and shallower valleys than those that were produced by diamond wheel grinding. This can have a significant impact on reducing friction and enabling the part to perform more efficiently.

Even Stronger Than Before

Testing was performed with samples provided by two leading suppliers of silicon nitride. The samples were tested for flexure strength using a four point bending method. These samples were tested under five different surface conditions. For ceramic rod B the conditions were: As received, diamond ground (800 grit), laser only, and laser assisted machined. For ceramic rod K the conditions were: As received, diamond ground (100 grit), and laser assisted machined. After machining each rod was sectioned into three 19 mm x 50 mm arc segments.  The results from flexure testing indicates that EMHM provides the best results in terms of bending strength.

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Contact

For more information about licensing, machining services, or for a quote for a laser assisted ceramic machining center, please contact:
Rita Yusko
Northern Illinois University
Technology Transfer Office
815-753-9281

Contact Us

Department of Mechanical Engineering
Engineering Building, Room 226
590 Garden Road  

Northern Illinois University
DeKalb, IL 60115
Phone: 815-753-9979

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