Can 3D Printing Increase Milling Feed Rates?

With PCD tooling, yes it can. The diamond cutting edges demand a large number of flutes to realize their full effectiveness. While traditional methods for making cutter bodies limit the number of flutes, 3D printing delivers tools with higher flute density and other enhancements
as well.

The promise of additive manufacturing will be found in products that are designed for additive manufacturing—that is, products that take full advantage of the geometric freedom that 3D printing can realize. A recent successful example of this relates to milling cutters. Komet’s “Revolution” line of milling tools includes tool bodies made through metal additive manufacturing to realize design features including a flute density higher than what is practical to achieve on conventionally manufactured tools. When it comes to cutting edges made of PCD (polycrystalline diamond), more flutes on the tool translates directly to faster feed rate.
Thus, Komet is actually using additive manufacturing to make subtractive manufacturing more productive.

Additive manufacturing: a more efficient option

Cullen Morrison, Director, Production, Komet, sees making tool bodies through 3D printing as being the way of the future, at least for PCD. This cutting tool material often can take advantage of all the flutes it can get, he says. It is capable of such high material removal rates in the materials it typically cuts—aluminum and carbon fiber composite—that the number of flutes can be the limiting factor on feed rate and productivity. This is increasingly true as facilities using this tooling adopt modern machine tools with high acceleration rates. However, obtaining a high number of flutes is problematic in cutter bodies made through machining, because the small pockets resulting from high flute density have to be milled out painstakingly using light cuts with small tools. Additive manufacturing offers a more efficient option.

Now, high-flute-density bodies are grown several at a time at Komet’s headquarters in Germany on a selective laser melting machine from Renishaw. After these bodies are separated via EDM from the build plate used in the additive process, they are ready for the PCD edges to be brazed on. Komet grows only the heads of the tools this way, laser welding them onto the shanks, because the shanks can be manufactured more economically in conventional processes.

Benefits abound

Morrison says the advantages of additive manufacturing for the cutter heads go beyond flute density. There is also the flute pitch. Previously, a pitch of 4 to 5^o is the best the company could efficiently achieve, because the clearance challenges of reaching a cutting tool past the flute in order to mill out the pocket precluded a steeper angle than this. But in this case as well, the geometry consideration poses no challenge for additive. On the new tools, Komet has produced flute helix angles
up to 20^o. The 3D printed tools likely will also realize longer life, he says. The reason is coolant delivery. With additive, coolant channels can be grown inside the tool along snaking paths that exit precisely where the fluid can be most effective. On previous tools, the positioning of coolant channels was always a compromise resulting from the need to drill a straight hole past the clearance obstacles in the way of this drilling.

One other advantage of additive manufacturing might be the most transformative of all, Morrison adds: It will permit faster lead times for special tools. With 3D printing, the range of design options for these special tools increases, and unusual designs specified by special-order customers can move into production pra-ctically as soon as they are modeled.

No hindrances

It will take more additive manufacturing capacity to fully realize the promise of the capability for special orders, informs Morrison.
The company is exploring how far to advance with this means of production, and how quickly.

Author

Peter Zelinski
Editor-in-Chief
Modern Machine Shop
pzelenski@mmsonline.com