Striving to establish itself as the leading subcontract manufacturing business in the South West of England, Metaltech Precision Engineering Ltd is certainly heading in the right direction with three factory extensions in the last 20 years and over £3m invested in eight machine tools in the last three years. Part of this recent investment drive has now included a new L20 LFV sliding head turning centre from Citizen for tackling a particularly challenging long-term project manufactured from Swedish Iron.
With more than 50 CNC machine tools and over 70 staff, Chard based Metaltech works with customers in the rail, automotive, petro-chemical, nuclear, hydraulic, oil & gas and motorsport sectors, delivering cost-effective manufacture and consistent growth. So, when the ISO: 9001, ISO: 14001, ISO: 18001 and AS: 9100 manufacturer witnessed production issues with a particular long-term contract that couldn’t be resolved purely by cutting tool changes and machining strategies, the Somerset Company spoke with Citizen.
Commenting upon the particularly challenging range of parts, Andy Riste, the Operations Director at Metaltech Precision says: “We’ve been making families of components for numerous assemblies for over 15 years and back in the day, we were making them on a 2-axis CNC lathe with second-ops facing the heads. About 10 years ago, we were introduced to sliding head technology and were shown how to improve cycle times and tool life whilst taking the process to a single operation with the sub-spindle configuration. The time studies were very encouraging and we bought our first machine. Shortly after that; we bought a second sliding head machine due to customer demands.”
Cutting ‘One of the Worst Materials Ever’
Since the arrival of its first sliding head machines, Metaltech has added a Citizen A20 and an A32, 8 and 5 years ago respectively. However, neither the machines from Citizen or alternate vendors were capable of resolving poor tool life and swarf wrapping issues created by machining Swedish Iron. “We have struggled with swarf control on this Swedish Iron project for many years. It is probably one of the worst kinds of material that you are ever going to try and cut in your life! This is down to the swarf control and random characteristics of the material. It can react in different ways across a single length of bar. So, you may think you have a solution with speeds and feeds and the right insert or chip-breaker for cutting, and then half way through, the bar can change its characteristics. You just never know what you are going to get.”
“We have tried many types of carbide inserts and chip breakers from a multitude of vendors and nobody has ever come up with a perfect solution. At present, the Iscar indexable line has proven the most successful. In some circumstances, Swedish Iron can cause fires and we have personally experienced this. With all this in mind, we had to look for a new solution to machine the parts. Simultaneously, we needed to increase our machining capacity. We approached Citizen and they were fantastic from start to finish, they did trials for us whereby we supplied the material, the Iscar cutting tools and even the Houghton coolants that we use.”
Citizen Sails to a Solution
Supplied with all the tools and parameters that are applied at Metaltech, Citizen cut the material without the LFV (Low Frequency Vibration) system – and they knew they had a battle on their hands. Numerous tests were conducted and by applying the LFV cutting technology, Citizen reduced cycle times by over 30% whilst gaining a similar improvement in tool life. “We used to get 30 components per edge and now we get over 100 and the surface finish has also improved.”
“By using our previous method of machining, you just didn’t know what you were going to get. All of a sudden, inserts would be chipping and you would quickly gather a birds-nest of swarf. If the operator turned his back to check another part whilst the sub-spindle is arriving to collect a part with a nest of swarf, you could quickly have a problem on your hands.”
Operating a two-shift pattern, Metaltech is manufacturing upwards of 5,000 components each month from Swedish Iron for this particular customer on a KANBAN basis. The huge variety of parts can have cycle times from 1 to 8 minutes depending upon the complexity and operations involved. “Citizen has been outstanding. They took our machining parameters, conducted the trials and time studies and came back to us with a turnkey solution that suited our exact needs.”
Regarding the time and tool-life savings, Mr Riste continues: “The nature of the material meant that every surface had to be rough and then finish machined as the aesthetic qualities of the parts is a critical factor. HoHoho However, by applying the LFV technology, Citizen could re-program the machining cycles to combine many of the rough and finish cycles into a single tool pass. Despite fewer tool passes, surface finishes improved considerably with the LFV technology. In addition, the tool life improvement from 30 to 100 parts per edge, further improved productivity as the sliding head turning centre wasn’t being stopped as frequently for insert changes.”
“We have moved from a position that we were struggling to meet customer demand and now with the new Citizen L20 and its LFV technology, we are in a position that we can actually stock parts. We don’t currently need to machine lights-out as our 2-shift pattern and the productivity of our machines can comfortably cope with capacity. However, if we did need to instigate unmanned machining, we are confident that the LFV Technology would retain excellent tool life characteristics and longevity, prevent swarf wrapping and give us the confidence that there would be no over-heating or fire-risk hazards. Additionally, the continuous chipping of the swarf is compacting our chips and making disposal considerably easier.”
“We are delighted with the Citizen service levels and application expertise and we are now waiting for the LFV technology to be applied to the 32mm diameter machines - so we can look at taking another machine tool,” concludes Mr Riste.