Reliable implementation of high time savings

Helical thread forming tool Punch Tap


Perfected and reliable in mass production

Since 1993 Audi Hungaria Zrt. has developed and produced engines in Györ for Audi AG and other companies of the Volkswagen group. Today, the company also covers the complete production process for automobiles. EMUGE-FRANKEN has been a supplier of threading tools for this production.

Audi Hungaria Zrt. produced around two million engines and almost 165,000 cars in 2019. 70 % of the engines were three- and four-cylinder petrol and diesel engines, the six-cylinder petrol and diesel engines together account for about 20 % of production. The five, eight and ten-cylinder engines, which are primarily used for sports models, together account for around 2%. In addition, electric axle drives now account for a significant proportion of production in Hungary, now at 8%.

Audi Hungaria Zrt. thus produced five different petrol and three different diesel engine variants in 2019, as well as an electric drive family with a power range from 63 to 470 kW. The cars produced completely in Györ since 2013 include the Audi A3 as a limousine and convertible as well as the Audi TT Coupé and the Audi TT Roadster as well as the Audi Q3 and the Audi Q3 Sportsback. Since 2019 the enterprise has produced the models with electrified powertrain (hybrid technology).

Firmly integrated in a new production line

Part of the Audi Hungaria Zrt. product range is a 3-litre V6 petrol engine, which was originally used in the Audi S5 and RS5, but is now also installed in the Porsche Macan, VW Touareg and various S and RS models from Audi. Production of this TFSI engine started in 2016 on a completely redesigned production line.

From the beginning, thread forming with the EMUGE-FRANKEN punch-tap cycle as a machining step was also integrated into this production environment. The integration of the process into the new line was preceded by a detailed analysis of the process. Proofs of quality as well as static, dynamic and fatigue strength tests were included as well as tests regarding the mountability and assembly strength up to the running characteristics and the release of the complete engine.


Chipless and MQL-capable threading

The fact that threads are preferably cold-formed in Györ today is one of the important production strategies of Audi Hungaria Zrt. At the same time, the company is increasingly working with minimum quantity lubrication (MQL). The main reasons for Audi to integrate the punch-tap technology into the line were the chipless process, but also the time- and energy savings.

An additional advantage of the Punch Tap is the significantly shorter tool path compared to conventional thread forming or cutting, thus saving a lot of time with the tool. Furthermore, the thread cycle saves up to 90 percent of energy due to the shorter tool path.

200 threads per engine

The Punch Tap is used to machine the two cylinder heads and the cylinder crankcase of the V6. Both component groups are made of cast aluminium, but of different alloys. While the cylinder heads are made of AlSi7Cu0.5Mg, the crankcases are made of AlSi8Cu3. The cylinder head and crankcase use mainly M6 threads which are to be formed. In the complete engine the total number of threads amounts to almost 200 pieces.

There is a separate production line for both component groups, in which the threading is synchronised on Grob G320 and G520 machining centres with a Siemens control unit. As with threading in general, a 6H tolerance of the pitch diameter must be ensured and the minor diameter must be implemented with a 7H tolerance. Both specifications are reliably achieved with the Punch Tap, which also applies to the requirements for surface quality.

A usable thread depth of 2.5 x D is available for forming threads of different depths. In any case, the tool must be clamped in a stable manner, which is why EMUGE-FRANKEN has developed the special PT-Synchro tool holder for the Punch Tap.

A new dimension in productivity

Punch-tap technology represents another original technology for the production of internal threads in addition to classical tapping, forming and milling. The tool path of the Punch Tap compared with the path of conventional taps or cold-forming taps is approximately 15 times shorter for an M6 thread with a usable thread depth of 15 mm.

This results in a time saving in the thread cycle of up to 75 percent. In the first step, the Punch Tap plunges helically into the workpiece and creates a helical groove before the actual threading, while simultaneously moving to the intended depth of thread. In the second step, the thread is formed by the special tooth geometry with a half a rotation in one step, before the tool retracts in the third step.

This results in a 90 percent reduction of the tool path compared to conventional threading processes. The time saving ultimately achieved depends on the specific thread. "At Audi, we have saved 0.7 s per thread compared to conventional thread forming," reports Attila Bugár, who works in the area of production technology drives at Audi Hungaria Zrt. and is also involved in the development of punch-tap technology and the optimisation of tool life in the production lines. "Depending on the thread depth, the process time was reduced from 1.3 to 0.6 or 1.2 to 0.5 s".

Continuous optimisation

In 2016, Audi announced at the AMB exhibition that they would start production of the V6 with the Punch Tap. Since then, the tool as well as the process control have been systematically optimised. For example, the heat treatment of the high-speed steel in order to harmonise hardness and toughness. "But the geometry, coating and finishing have also been optimised. Coating tests with AlSi8Cu3 and AlSi7Cu0.5Mg alloys for example, had shown different wear behaviour.

​​​​​​​Therefore, a TiN coating was subsequently used for cylinder head machining and a TiAlN coating with a special finish for the crankcase," says Christian Beer of EMUGE-FRANKEN, who as a development engineer is involved in the development and optimisation of Punch Tap.

EMUGE-FRANKEN also made the process MQL-safe with the implementation of the Punch Tap in the new production line. While the process had previously been implemented mainly with emulsion, the young technology was now to be put into series production for the first time with minimum quantity lubrication. "We need good lubrication for the Punch Tap because all threading teeth are engaged at the same time and consequently a high torque occurs," says Peter Kopton, who has been a driving force behind Punch Tap technology and has worked in the field of production technology drives at Audi AG from the very beginning, indicating an important aspect of the matter. "However, it soon became clear that the Punch Tap also works reliably under these conditions.

The overall conclusion was: "The Punch Tap works very reliably in series production with MQL and has a long tool life. The explanation for this is that the tool is only in contact with the material for a short time. Due to this half thread rotation, no welding occurs on the thread teeth. At the same time, the pressure on the individual tooth is very high, so that a large forming zone is created, which additionally counteracts cold-welding.

The next step

The V6 engine has been in series production for four years now in Györ, where the Punch Tap has been used from the very beginning. With a high process reliability and a long tool life. At present, 200,000 threads are formed with one tool in cylinder heads, and 90,000 in cylinder crankcases, "And all this is accomplished with an HSS tool," emphasises Nándor Nárai, technical advisor to EMUGE-FRANKEN Hungaria. "That is quite a highlight." But that is not the end of the development.

Currently, a step from 90,000 to 120,000 threads for the cylinder crankcase is being discussed. The tests have already been completed and the results showed that 120,000 threads can be formed. "The current discussion is whether the production line will be amended for this," reports Zsolt Hulik, who is responsible for optimising tool life on the V6 Otto EA839 cylinder block production line. Csaba Bittmann adds: "For the cylinder head at least, a peak tool life of 250,000 threads is no exception". For some years now, he has accompanied the process to ensure the tool life on the parallel production line for cylinder heads.

The partner as inspiration

Introduced as an innovative process, Punch Tap has proven to be a highly efficient technology for mass production, which runs reliably under demanding conditions and has a long tool life. "The process enables the mentioned savings in time – and therefore investment costs and the ongoing operation does not incur higher costs than a conventional tool," estimates Kopton. The punch-tap process currently presents itself with a significantly higher technology status after four years in series production.

EMUGE-FRANKEN has accompanied the path to this status from the very beginning. To this day, a technician in Györ is the direct contact for technology optimisation. Kopton points out the framework for the joint development between Audi and EMUGE-FRANKEN: "The close cooperation is also reflected in a development partnership in which we develop new drilling and threading processes. A current example is Taptor, a new threading technology that combines a spiral drill with a tap, thus enabling massive savings in machining time".

In addition, Dietmar Hechtle, head of the technical office at EMUGE-FRANKEN, agrees: "The close partnership and openness made this technology development possible in the first place. The customer is our inspiration. He shows us which components will be machined in the next five to ten years and which tools will be required for this. At Audi, this cooperation led to an innovative technology development".

(Image sorces:  Image 1 Audi AG, Images 2,3,4,7,8 Audi Hungaria, Images 5,6 EMUGE-FRANKEN)


EMUGE-Werk Richard Glimpel GmbH & Co. KG

Mr. Jörg Teichgräber

Nürnberger Straße 96-100
91207 Lauf an der Pegnitz

Phone:  +49 9123 186555
Audi Hungaria Zrt

Audi Hungária út 1
9027 Györ

Phone:  +36 96 66 1000