Customer story with extensive interview: When producing hobs SAAZOR relies on carbide from CERATIZIT
download original picture | picture with 300pxProfile grinding of hobs. Picture: SAAZOR
download original picture | picture with 300pxIsostatic pressed carbide blanks. Weight approx. 20 kg. Picture: CERATIZIT
download original picture | picture with 300pxGrinding of tooth profile and chip grooves with diamond disks of the pre-sintered carbide blank. Picture: CERATIZIT
download original picture | picture with 300pxChecking the concentricity of pre-sintered hob blanks. Picture: CERATIZIT
download original picture | picture with 300pxNon-ground carbide blank with pre-formed thread profile, module 3.0. Picture: CERATIZIT
download original picture | picture with 300pxReady-for-use hob with coating. Picture: SAAZOR
download original picture | picture with 300pxCERATIZIT S. A., Mamer, Luxemburg (headquarters), February 2010
CERATIZIT offers a wide range of hobs. The blanks weigh between 2 g and 80 kg and are finish-ground by the customer. Hobs are applied in a variety of industries such as the automotive sector, in watch production and wind turbines – in fact wherever gear wheels are required. The most frequently used grades for hob production are CTS20D (previously known under the name TSM33) and the more robust new grade CTS18D. These grades cover 80% of the demand.
Careful handling during machining and transport
After isostatic pressing and the subsequent pre-sintering operation the blanks show a strength comparable to the one of chalk. “The sensitivity of the product itself combined with the complex shape of the hobs (preformed tooth profile) requires careful handling during the machining operations as well as during the transport from one machining station to the next“, says Reinhard Kuhn, product manager in the CERATIZIT segment ‘Solutions for mould and die production’. “Most milling cutters for the automotive industry weigh between 5 and 10 kg. Just putting the blank down may mean breakage of the edge of a tooth, in which case further processing of the tool is pointless as it can be scrapped."
SAAZOR relies on carbide from CERATIZIT
In Pforzheim, Germany, SAAZOR has around 60 employees and produces hobs and special tools for leading automotive and gear manufacturers worldwide. Extremely high market shares and the desire to provide the French automotive industry with a national supplier led to the foundation of SAAZOR S.A. in France in 1975 (35 employees).
The hobs are available in solid carbide or high-alloyed high-performance high-speed steels (HSS) or as hobs with inserted blades made of carbide or HSS. In this field SAAZOR relies on carbide from CERATIZIT. The calculation of the tool profiles and cutting data according to the requirements of the customers, machining before heat treatment (green machining), heat treatment and grinding as well as the PVD coating process are all carried out on up-to-date facilities directly at SAAZOR.
Additionally, SAAZOR also offers a complete regrinding and coating service for tools after every application. For their special application, after specific machining operations a TiN, TiCN, TiAlN or other PVD hard coating is deposited on the cutting edges. In this way it is guaranteed that the hob provides maximal cutting performance combined with consistent tool life in any application.
The dry machining process which was introduced some years ago in the high volume production of gear wheels as a result of the higher cutting speed and the increased thermal stress requires every higher quality of both the cutting materials and coatings. Carbides are also increasingly used as cutting material for hobs.
Interview with Bernd Zorn, managing director of SAAZOR
What is important in the machining technology of this sector and what does that mean with reference to the carbide?
Zorn: Let’s talk about the machining of carbide first. Hobs are almost exclusively produced upon order. In close cooperation with the supplier we define the tolerances which can be achieved on an economic basis and also the degree to which the blank is machined. A compromise has to be made between price, delivery time and maximum possible geometric accuracy of the blank. The more precise the form of the blank, the faster and less expensive is the complex grinding procedure which is necessary to finish the hob.
As for machining operations with hobs made of carbide I can say that the typical conditions for the production of gear wheels are minimum machining times, dry machining, high cutting speed, very close tolerances and large quantities. Carbide is an extremely well-suited cutting material for this application range. Consistent tool life however can only be guaranteed through the optimal condition of the tool, the machine and the clamping device. Furthermore, the interrupted cut in the hob milling process and the various different chip thicknesses lead to constantly changing stress on the cutting edge. An unstable system and the resulting vibration together with inhomogeneous work piece material additionally put stress on the cutting edges.
The sharp teeth on the periphery of a hob of typical dimensions, which weighs more than 10 kg, require very careful handling on the part of the operator and during production, as the sensitive cutting edges may otherwise be subject to damage even before they are applied on the machine, a fact which often leads to the destruction of the tool.
Where are the CERATIZIT products applied and under which conditions do they show maximum efficiency?
Zorn: Hobs produced from CERATIZIT blanks are mainly applied in high volume production of gear wheels for automotive and gear manufacturers. The pre-condition for the successful application of a precision tool is a CNC hob milling machine with stable work holding, the choice of optimized cutting parameters for this specific process and of course extremely careful handling of the hob outside the machine. In order to guarantee consistent tool life and roughly constant wear, the tool manufacturer should carry out both the regrinding and coating process as a single source supplier. If these pre-conditions are strictly fulfilled, carbide hobs allow notably increased cutting speeds combined with reduced manufacturing time of the gear wheels.
What are the requirements concerning the carbide?
Zorn: The carbide characteristics required by the hob manufactures today are high hardness combined with sufficient toughness, high heat resistance (resistance to thermal stress caused by the high cutting speed in dry machining operations) and high edge strength, thus good wear resistance and deformation resistance. The carbide manufacturer is also expected to see to permanent further development and adaptation of the grades to changing application conditions.
For the economic production of the hobs the manufacturer demands precise machining in terms of geometric accuracy and on time delivery of the blanks which have to be suitable for grinding, for coating and for the removal of the coating (low cobalt leaching). Of course the price of the blanks should also take the customer’s wishes into account. This sounds like a lot – and it is a lot. I want to underline that all this is only possible when there is close cooperation between the carbide producer and the tool manufacturer.
What is the relation between steel milling cutters and milling cutters made from carbide, and what are the advantages of the carbide?
Zorn: On average we produce 600 monobloc hobs, out of these around 15% are made from carbide. The same geometry of a carbide hob is on average 2.5 times more expensive than a hob made of steel. That is mainly due to the higher price of the raw material together with the fact that carbide milling cutters can only be machined with diamond tools. But milling cutters in carbide are not always more expensive: a steel milling cutter with a top quality coating may be more expensive. The big advantage of hobs made from carbide is their suitability for high cutting speeds up to about 1,000 m/min. (Steel from around 350 up to 400 m/min) and a long tool life, approx. 8 – 10 metres per tooth (steel about 4 to 6 m). This means more stable processes and less machine downtime caused by the need to regrind the tool.
Since when have you been working together with CERATIZIT and how did this business relationship start?
Zorn: We had already begun to buy carbide products from CERATIZIT in Switzerland in 1999, and later transferred the business relationship to CERATIZIT Austria. This grew in intensity, mainly thanks to the personal commitment of Mr. Reinhard Kuhn, product manager at CERATIZIT.
Why did Saazor decide on CERATIZIT products?
Zorn: Through the first test orders and the visit to a production site by our management, we became convinced by the production possibilities and the quality of CERATIZIT. The efficient business relationship with CERATIZIT essentially improved the geometric accuracy of the blanks ensuring clearly reduced grinding times.
And in the field of continuous further development of specific cutting materials, reliable product availability and delivery CERATIZIT has distinguished itself within the group of leading carbide manufacturers.
The carbide specialist CERATIZIT is synonymous with “hard material matters”
CERATIZIT S. A. – is a pioneer and global player in sophisticated hard material solutions. The company operates from Mamer, Luxembourg. CERATIZIT is the world market leader in unique and consistently innovative hard material products for wear protection and cutting tools and is present in more than 50 countries worldwide. CERATIZIT provides hard material solutions to customers in selected industrial sectors including the automotive industry, mechanical engineering, oil industry, medical systems, electronics as well as mould and die making. With more than 400 active patents, a sales volume of 600 mill. EUR and over 4000 employees, CERATIZIT is your strong partner worldwide.
--------------
Number of characters including spaces: about 9100
Reprint of this press release is free of charge. We would appreciate a sample copy of any reprints.
--------------
Pressekontakt:
- Artikel drucken:
- Drucken Sie diese Seite aus.
- Artikel als PDF generieren:
- Artikel als PDF generieren
- Links:
- www.ceratizit.com
