27-Jul 2017: Application Report: High-end Universal cutting tool convinces Audi - HAIMER’s solid carbide end mill cutters pass the test at the Audi Pre-Production Center
The Audi Test Part Production Center in Ingolstadt produces challenging components as prototypes in small quantities. The responsible production engineers at Audi rely on HAMER solid carbide end mill cutters, which are suitable for a wide range of machining applications due to their geometry and quality. Their excellent dampening properties and runout accuracy guarantees a considerable increase in productivity.
Innovations have great significance for the Audi Group. About 8,600 employees in Ingolstadt and 1,700 more in Neckarsulm are specialized in the field of "Technical Development". The Audi Group also has additional development centers located in Gyor, Beijing and San José Chiapa where they are working continuously to maintain innovation leadership in classical and alternative drive systems, in lightweight construction and production processes, as well as lighting technology.
The Pre-Production Center is part of the Experimental Production Department and is located almost at the end of the development chain. In Ingolstadt there are 75 employees that ensure various gear, engine and chassis parts are available as prototypes or in small quantities for first, practical trials.
Reinhard Kindl, Workshop Manager, explains: "For our prototypes, we have to achieve near to serial-production quality in regards to both precision and surface finish. This has to be possible without the use of any special tools which would simply be too expensive for our small quantities - both in terms of purchase and programming. That's why we require high-performance, universal tools." Dragan Pejcinoski, responsible for purchasing new tools, adds: "We prefer to work with tool manufacturers who only offer a small catalog selection and whose tools are designed for universal use. Good customer service, including application support and short delivery times, are very important for us."
For more than a year HAIMER GmbH, Igenhausen, has been the preferred supplier of solid carbide tools. However, the actual cooperation between the two companies started about 20 years ago. Shop Manager Kindl remembers: "In the beginning we only worked with HAIMER tool holders and then started using their shrinking machines as well. In 2002, we invested in a HAIMER balancing machine to optimize the runout of our clamped tools." Three years ago, when HAIMER expanded its product portfolio with its own solid carbide end mills, the machining specialists at Audi closely followed this development. In 2015, the Audi Pre-Production Center was tasked to produce a balance shaft for a gear box prototype. During this process they had to face some difficulties which according to Jakob Mosandl, Head of the Technical Center, had to do with the geometry required for turning and milling. "The clamping conditions of our turning and milling center WFL M 35 G was unfortunately unstable. In addition, we did not have much experience with the material of the balancing shaft, highly-hardened 42CrMo4 steel. Almost 90 percent of our milling operations are related to aluminum alloys."
Only 1 mm radial depth of cut and extreme tool wear
The first attempts to machine the balancing shaft were by no means satisfactory. For roughing, a standard milling tool with a 12 mm diameter and a standard shrink fit chuck were used. In order to meet the required tolerances, which were a few hundredths of a millimeter, only a maximum cutting width of 1 mm could be realized (see comparison table of cutting data). Despite these "conservative" cutting parameters, another problem arose: after machining just one part, the cutting tool life was done.
Thus, Reinhard Kindl and his team consulted their HAIMER contact person. Since there was no positive change regarding the poor clamping conditions, Oliver Lechner, HAIMER Sales Manager for Southern Germany, recommended reconfiguring the complete tool. According to his experience "for such demanding applications, it is often not enough to simply exchange the cutting tool. Ultimately, the tool holder has the same impact on the process as the cutting edge itself."
A team of Audi and HAIMER employees finally replaced the standard cutting tool with a HAIMER Power Mill solid carbide end mill diameter 12 mm and clamped it into a HAIMER Power Shrink Fit Chuck with Safe-Lock. While the Power Shrink Chuck ensures maximum vibration dampening, the Safe-Lock pull-out protection system by HAIMER prevents the milling cutter from spinning during extreme machining or from being pulled out of the chuck. The Power Shrink Chuck is equipped with the Cool-Jet system, which ensures that the coolant is transported at 80 bars to the cutting edge through bores in the holder.
High performance tools increase cutting widths
Together, the team planned the machining process, chose a suitable programming strategy and optimized the cutting parameters (see comparison table for cutting data). The incredible results showed that at slightly increased speeds, the cutting width could be increased to 9 mm (nine times higher than before). Dietmar Ungar, Team Leader of Application Engineering at HAIMER, explains: "We were able to dampen the vibrations that occur during the machining process by using our Power Mill end mill - made of high-performance solid carbide and tough cobalt content - in combination with our Power Shrink Chuck." The smooth operation resulted in visibly better surface quality and less tool wear. The tool life tripled which subsequently resulted in quicker tool change and less machine stops. Since the wear is evenly distributed on all cutting edges, the HAIMER service department can subsequently re-grind the tool. This way the tool can be reused. Additionally, in a second operation - roughing and finishing of pocket grooves with a similar complete HAIMER tooling assembly with an 8 mm diameter - productivity increased by 300 percent. Both of these milling improvements have an extremely positive effect on the total machining time and overall productivity: while previously it took 8 hours to finish the component, the overall time was reduced to five hours.
Good results with Basic Mill and Duo-Lock
These results were convincing enough for the Audi Test-Part Center to justify testing more HAIMER tools. Especially with the need for universal end mills, which are suitable for different applications and materials, the second cutter geometry offered by HAIMER came into focus. The Basic Mill solid carbide end mills are reduced to the basics in terms of product characteristics and can be used in almost all materials. They are suited for a broad range of applications such as roughing, finishing, slotting, ramping (up to 45°) and even direct drilling. The Basic Mill end mills are less expensive, but provide the same, well-known HAIMER quality. The Basic Mill end mills are characterized by an h6 shank and a runout accuracy <10 μm. After a number of projects, Tool Specialist Dragan Pejcinoski is very satisfied with both lines of HAIMER solid carbide end mill cutters: "We use the Power Mill for particularlydemanding materials, and for normal materials - like aluminum alloys and steel - we use the Basic Mill geometry." Recently, the Audi Machining Team and Workshop Manager Reinhard Kindl went a step further and tested the HAIMER solid carbide Duo-Lock system: "We are still at the experimental stage, but everything so far has worked out very well. It seems that this patented interface keeps what HAIMER promises". Based on an innovative thread design with double cone interface and an additional third support surface at the rear end of the interface, the Duo-Lock technology delivers high runout accuracy, stability and resilience.