TPT January 2008

Case study A low volume, high product mix tube mill operation (providing tube to the automotive ride handling and exhaust sector) needed to reduce the cost of its tube making operations. The operation had to make 120 different products and keep total stock levels below 6 days. The mill had to be suitable to handle stainless steel 409 436, aluminium coated mild steel, high tensile carbon steel and deep draw quality carbon steel. The mill would have to handle 18 diameters between 36 and 60.5mm and 10 wall thicknesses from 0.8 to 3.2mm. These activities were undertaken and a project to purchase a new tube mill line was developed and approved. The existing tube mill was 50 years old with many modifications. Reject levels were still high and productivity low. Both of these indicators had improved tremendously over a two year period but were still a long way from world class. To meet the requirements of a just-in-time (JIT) environment, there was a need for high quality and accurate tube where defects are counted in parts per million. There was also the challenging task of reducing the cost of manufacture. The tube mill, that was specified and then met and surpassed the targets, is described below. 1. An automatic double-sided vertical uncoiler that was loaded using c hook and crane 2. Leveller to flatten the nose and tail of the coils (fully automatic) 3. Shear and welder TIG (fully automatic), hole punch for end weld detection and mistake proofing 4. Strip accumulator to ensure the mill did not stop for end welds 5. Flying strip shear to minimise changeover times and scrap 6. Break down stands 1 and 2 where mounted on a turret to allow for quick change and offline tooling setup 7. A cage was used to form the tube from the break downs to the fin passes 8. Fin passes 1 and 2, fin pass side stand and the inverted 3 roll squeeze stand where mounted on a Turret similar to the breakdowns. There was limited space for the installation and the Turret provided the maximum utilisation of the space. No seam guide was used 9. A solid state HF welder was installed. The repeatability of the settings was critical for the stainless steel manufacture 10. A Pyrometer and squeeze pressure monitoring and feed back control system was installed 11. SCADA system installed to track 16 variables at 1 second intervals and also down load variables from the master data base to the PLC 12. Internal fin cutting was installed with monitoring equipment 13. An ironing pass stand was installed to assist control the internal fin cutting depth required to produce tubing for cylinder bore product Tube mill specifications (quick change high quality tube mill)

› Figure 6 : Quick change high quality mill for the automotive industry

14. Eddy current was installed after the cooling tunnel however its use was discarded as other systems ensured that faults that the eddy current could find were not produced 15. The sizing section consisted of a single Modular Sizing Mill (MSM). This provided OD tolerance better that a conventional mill. However, OD tolerance can be further improved by adding additional MSM stands or a rotary sizing mill or some combination of these technologies 16. A simple motorised turkshead was used as a straightening stand 17. Ink jet printers were installed and linked to the master database and the clocks synchronised with the one used by the SCADA system. Tubing was continuously identified with date and time to the second. Any faulty tube could then be tracked and investigated with ease 18. A flying double shear type cut off was used. Due to the high speed and short lengths. 100 metres per minute at 4 metres 19. The tube was then sorted automatically on the run out conveyor 20. The internal swarf was removed used high pressure water and then drained 21. The tube was then stacked into stillages and sent to the cutting machines, storage or packing 22. The mill layout was such that the uncoiler’s station was next to the mill operator’s station. This enabled either operator to run both stations when the other was away on other duties. The operation was very successful and met and exceeded all expectations. The success of these types of projects is the result of understanding what is required, what is possible, what is available and working closely with the suppliers to get the desired result.

Kusakabe Electric & Machinery Co Ltd 11-2, 2-chome, Murotani Nishi-ku, 651-2241, Hyogo, Kobe, Japan

Tel : +81 78 992 9100 Fax : +81 78 992 9139

Email : sales@kusakabe.com Website : www.kusakabe.com

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J anuary 2008

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