Advanced High Speed Machining Methods

Introduction

There are many new technologies that make machining faster. This document introduces some of these new methods of advanced machining. By the end of the document, you will have some knowledge of:
  • High-feed milling
  • Trochoid milling
  • Hard turning
  • Thread milling
  • Urma high-speed reaming
  • Integrated toolholding
  • Shrink-fit toolholding
  • Sources for more information

High-Feed Miling

High-feed milling pairs shallow depth of cut with high feed per tooth.

The result is up to three times faster machining, reduced wear on the tools, and near-net shapes.

The system uses small setting-angle inserts that focus cutting forces only in the spindle axial direction, which reduces vibration and increases tool stability. Tool life is extended through the axial focus, increased stability, and strong insert geometry.

This Seco video shows a good example of High Feed Milling: http://www.youtube.com/watch?v=vyT8UTkCc4k

Trochoid Milling

 

Trochoidal, or peel, milling is circular milling with simultaneous forward movements. The cutter removes repeated slices of material in a sequence of continuous spiral tool paths in its radial direction.

A large axial cut with a small radial cut depth (5% to 10% of the tool diameter) is used. This allows for a cutter with a close pitch (more flutes).

Use this method to cut slots in hardened material. It also works well for milling deep slots and pockets.

The high number of passes reduces cutting load on the tool and extends its life. The controlled arc of engagement and chip thinning reduces heat.

Trochoidal milling is not a faster method of machining, but can improve the quality of the cut.

This Sandvik/Coromant video shows a good explanation of trochoidal milling: http://www.youtube.com/watch?v=Pkgw-w_AoOo

Finish Hard Turning

 

Finish Hard Turning refers to the process of single point cutting of hardened pieces less than 2 microns, with hardness between 58 and 62 HRC. Finish hard turning is an alternative to the more expensive and time consuming grinding.

With the development of Carbon Boron Nitride (CBN), polycrystalline cubic boron nitride (PCBN) and ceramic inserts, finish hard turning replaces grinding operations on hardened materials.

Finish hard turning lets you machine parts in one setup. This gives greater accuracies on features such as concentricity, squareness and roundness.

With a single standard tool and clamping setup you can machine a wide variety of products with different forms and sizes. This increases flexibility in production environments and reduces the number of changeovers.

Finish hard turning can remove more material per machining operation than grinding. This can make finish hard turning 3 to 4 times faster compared to cylindrical grinding.

Thread Milling

 

Thread mills look similar to taps, but function entirely differently.

Taps feed into the part at the rate of the lead of the thread, utilizing the chamfer and first full thread beyond the chamfer to cut and enlarge the thread to finished size.

A thread mill has no chamfer. The thread mill enters the hole along the axis of the spindle, deep enough to produce the full thread depth required. The controller moves the thread mill out to the hole diameter until the threads cut into the sidewall of the hole. The thread mill then moves in a 360° circular motion until it is back to it starting position.

During this circular motion the thread mill must be lifted toward the top of the hole or moved along the Z-axis of the machine one thread pitch (or lead) to produce a thread. This lifting movement together with the circular motion is called "helical interpolation". After the 360° rotation, the tool returns to the center of the hole and exits from the part.

In general, for production threading up to 3/8", taps are more efficient.

If you make a wide variety of parts, threads, and materials on the same machine, thread mills are far more versatile. They produce right or left hand, internal or external threads, single or multiple leads from #2-56 with the same mill. Materials range from soft, non-ferrous alloys to heat-treated steels, or tough alloys such as inconel and titanium, where tap breakage often occurs.

Easily make pipe threads without leaving the normal "stop lines" and creating the troublesome stringy chips normally produced by taps. In addition, thread mills can produce full threads to within one pitch of the bottom of the drilled hole.

Urma High-Speed Reamer

 

High-speed reamers from Urma and other manufacturers have a greater number of cutting edges in an easily replaceable disk-shaped insert. The larger number of cutting edges lets you increase the feed rate, which reduces cycle time. The cutting disks replace quickly, similar to traditional inserts.

This video shows a high speed reamer in action: www.youtube.com/watch?v=2YvYFKoq17A

Integrated Toolholders

 

A growing number of manufacturers make cutting tool tips that are easily installed into a standard mandrel or toolholder. This system is called "integrated toolholding."

With integrated toolholding, the operator can quickly change tool tips without a tool change. When you change the tip, it is not necessary to remove the mandrel. Thus the tool length offset usually stays the same.

Shrink-Fit Toolholding

 

Shrink-fit uses the expansion and contraction properties of metal to give very strong toolholding. The bore is slightly smaller than the tool shank. Heat expands it enough to let you insert the tool. When it cools, the contraction of the metal holds the cutting tool with 10,000 lbs of force.

Shrink-fit toolholders decrease vibration. Cutting is faster and smoother. Manufacturing times can be reduced while maintaining quality and accuracy.

This video from Techniks shows the process of shrink-fitting: http://www.techniksusa.com/videos2008/SF_Demo/Technoshrink_demo.htm

Machining Methods Not Recommended for Haas Machines

MACHINING METHODS NOT RECOMMENDED FOR HAAS MACHINES

  • Gear Hobbing: Hobbing accurate splines is a machining method that should not be used on the Haas Lathes because we do not synchronize the C-axis with the live tooling motor.
  • Abrasive Materials: Grinding and machining abrasive materials like graphite and ceramic should not be done because the way covers, electrical, and coolant systems are not designed for these applications. The warranty is void if a customer uses a machine for these types of applications.
  • Broaching: Traditional broaching operations when the spindle does not rotate can damage spindle bearings.
note: Only rotary broach tools can be used on Haas machines, because they allow the spindle to turn. Visit www.slatertools.com for information on these tools.

How to Learn More about Advanced Machining Methods

  • Search the Web for videos of different machining methods.
    • YouTube is a valuable resource for videos.
  • Stay up to date on new toolpath types
    • High feed toolpaths can reduce feed time
    • Plunge mill toolpaths are a very effective way to remove large amounts of material very quickly.
  • Visit Trade Shows
    • Trade shows are a good place to:
      • stay up to date on new tooling and workholding
      • develop relationships with new tooling suppliers
      • work with multiple suppliers to make the best recommendations for customer applications.
  • Use the Haas website to stay up to date on machine and control options.
  • Ask Haas Applications.
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Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.