Milling Tools

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Luke Pollock, Product Manager

Shop Metalworking Technology Magazine speaks with Walter Tools’ Luke Pollock about advances, cutting strategies and challenges



What in your opinion have been the most significant advances in milling tools and milling technology in recent years?

Insert Grades (substrates and coatings), such as ultra low pressure CVD coatings with high aluminum content in TiAIN coatings. A high Al content gives the coating good resistance against heat allowing machining at higher sfm. This increases the production rate and improves the tool life in number of pieces produced.

Dynamic milling strategies: they allow for smaller, lower HP machines to increase the material removal rate over traditional machining techniques while keeping the HP consumption low.  However, this process requires three main components to work in sync: the machine must have capability in both movement and processing power; the programming software package must have capability to calculate complex dynamic milling tool paths; and the cutting tool must be capable of handling the depths of cut and the feed rates required.  Development in all three of these areas has fostered the growth of dynamic milling strategies.  However, it is still considered “new” and many end users either do not have the capacity to utilize this strategy, or they have not been educated enough to have confidence to incorporate it into their production.

What are the top three strategies manufacturers must consider to optimize milling tool performance?

Well thought out tool paths. Regardless if it is dynamic milling or traditional tool paths, an intelligent approach to the tool path and how the tool is presented to the part must be considered. For example, simply entering the part could be approached by feeding straight in which could introduce some vibration and unnecessary impact. An alternative would be to “roll” onto the cut creating better chips and less shock to the operation. Similarly, it’s better to work continuously in one direction maintaining a constant conventional/climb milling versus a back and forth tool path which would alternate between climb and conventional milling.

Correctly applied grades and geometries .A lot of development goes into grades and insert geometries for a specific material or application. Details that cannot be seen by the naked eye are critical to the performance. Many times we see insert grades and geometries misapplied: using the wrong grade for a specific material. While it’s much easier to have just one grade and geometry in the shop, it is extremely unproductive to not adjust the characteristics when changing to a different material. Sometimes, even a change in the style or type of cutter can make a huge difference in performance, but at a minimum, the inserts should be reviewed for correct application.

Rigid fixturing. Care should be taken to optimize the workpiece clamping and the reach required when machining parts. Long overhangs can require tremendous slow down in production rates or can greatly reduce the quality of the cut. The direction of cut and the associated cutting forces should also be considered. For example, a high feed mill, a 45° lead cutter and a shoulder milling cutter will push on the part in different directions (relative to the spindle axis).

What machining advances have had the greatest impact on developments in milling tools/inserts?

Multi-axis machining . These machines are completely versatile compared to traditional three or five axis milling centres. The tools must be adaptable from the spindle connection to the type of cuts the machine will take. 

Dynamic milling. This milling strategy is advancing with the development of the machine capability. The tools must be capable of taking the types of cuts required.

What types of milling tools have emerged as a result of responses to these advances?

 Broad range of high feed mills.

Cutting tools designed to take the cuts required (long depths of cut, higher number of cutting teeth, inserts that can handle higher sfm, etc…)

What should a manufacturer consider when selecting a milling tool supplier?

Level of service
Engineer capabilities to create either simple specials or complete specials. These tools can greatly reduce production times by combining multiple tools into one operation. But even if you don’t have a regular need for this capability, I think your tooling supplier should at least have this expertise to continuously build their knowledge and application experience.

Application assistance 
Your cutting tool supplier should be there to support the application of the product. A technical product like a milling tool needs to be used in a specific way. They should have the expertise and the availability to help with the specific application after the sale of the tools.

Technical support via phone or personal visit
This could include application data, product selection, grade selection and machining strategy. The supplier should be available to help improve your overall expertise in the application.

Can they offer complete solutions? It’s better for the end user if the cutting tool supplier can provide all the tools to machine a specific part. 

Are their products innovative? Technology is always advancing. To stay productive and help keep production costs under control, constant improvement is a must. Partnering with a cutting tool company that is constantly improving the performance of their products will always benefit the shop floor. This is an easy way to keep taking credit for constant cost savings.

What key factors in milling tools impact performance?

Materials (both carbide inserts and steel bodies). Carbide substrates and insert coatings can obviously impact the tool life since it is what makes contact with the part. Using the correct substrate and coating for the material and application is critical to maximizing tool life. Subtle geometry such as hone size also plays a role, which is another reason to review the manufacturer’s material recommendation for specific grades. Also, the steel body can affect performance: Is the steel body case hardened or through hardened and to what hardness? This will have a direct impact on the life of the steel body. 

Quality of production that includes tight tolerances and consistent geometry. Manufacturing quality such as how flat the insert pocket is machined can affect the rigidity of the milling system and how hard the tool can be pushed before chatter or insert failure occurs. Repeatability of insert pocket location is important as excessive runout could result from poor manufacturing quality. Excessive runout will affect the part produced quality and directly impact tool life.

What are the key areas of R&D for milling tools for Walter?

  • Insert rigidity for higher HP cuts
  • Insert coatings that can handle higher sfm
  • Higher density high feed mills SMT
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