09/07/2007
CERATIZIT helps with the largest cast iron parts in the world!
Tailor-made tooling solutions for British heavy machining sector |
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When machining some of the largest castings in the world, both milling cutter and supplier have to be able to keep their promises. In order to be able to face the challenges of such huge cast iron parts, Davy Markham, a UK-based heavy machining company in Sheffield, cooperates with the carbide expert CERATIZIT.
Davy Markham is a supplier of heavy castings for large press components and the steel rolling mill industry, the castings frequently weighing several hundred tons. Nevertheless the finishing tolerances have to be in the region of a few microns. Often more than 1000 machining hours are necessary to produce the finished item. Sometimes it can take days to turn a casting over to machine a different face. Time saved in machining can therefore prove vital. John Watson, Davy Markham’s production manager says: “Improving cutting tool performance is a major factor in our drive to deliver our Total Punctuality Concept, whereby everything we do is delivered on time – every time.”
Saves time and money: one milling cutter only for all machining operations
One of the first areas that CERATIZIT investigated for Davy Markham was the finish milling of large castings. This particular challenge was one that required confidence in the competence of the carbide experts, as these expensive components are not something that can be ‘experimented’ on. Every attempt at improvement must immediately fit.
“Initially we saw an opportunity to develop the existing process,” says Adrian Eagle, CERATIZIT’s cutting tool account manager. “The original milling cutters were designed as a double negative cutter, which is not ideal for a finishing operation. Therefore, we designed a cutter with a 45 degree approach angle and a positive rake. The effect this had was to improve cutting data on the 250 mm diameter cutters dramatically. The feed rate was immediately increased from 400 mm/min to 1200 mm/min, with the potential to take this even higher, and all this with only one tool. This finishing cutter can be applied for the typical average medium cuts at Davy Markham (depth of cut up 6-8 mm), then a finishing operation at 0.1 mm follows.
Balance differences in the material, maintain speed and feed rate
Once the finishing cutters had proved their worth, CERATIZIT was tasked with investigating the roughing operations. “The biggest challenge facing CERATIZIT in this area was one of consistent metal removal,” says Kevin Parkin, managing director of Davy Markham. “Due to the scale of the castings being machined we are often faced with sand inclusions and differential hardness of the cast material. The goal is that any tool design must be ableto absorb these material changes without the requirement to adjust speeds and feeds.”
CERATIZIT met this challenge by developing an individual tool design. To solve this particular problem CERATIZIT has developed a negative rake cutter body that uses a non-standard insert that provides multiple cutting edges as with the finishing cutters swarf removal is a major issue, and CERATIZIT has developed specific insert geometry designs to ensure that chip breaking is achieved in a controlled manner. This is achieved by the specific land and edge preparation undertaken on the inserts.
CERATIZIT as a strategic partner in the transition process
“Heavy industry is often viewed as very traditional and reluctant to change,” says managing director Kevin Parkin. “However, we had to make these changes in order to compete with low-cost economies around the globe. In the past 18 months we have focused our efforts on being a customer-facing business and have implemented a 100 per cent on-time delivery programme to ensure that we continue to win repeat business. This strategy has created a full order book. Crucial to this strategy are the partnerships that we have with our suppliers. In the past we have had what can be described as passive relationships with tooling suppliers. What we now have with CERATIZIT as a partner is a very professional relationship. We definitely see CERATIZIT as an attractive partner in our business.”
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