Saturday, March 29, 2014

Sequential Operations in assembly conveyor for closed shoes

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This is the first part of the article. After completing sewing, all the upper come to lasting and finishing section to assemble and packing shoes. Now lets see how to assembly a closed shoe.
  1. Preparation: Before assembly one final check on the quality of uppers, insole, soles and fillers is important. If required action should be taken in good time before assembly to exchange poor quality components. the last must be correct according to the specification and also be cleaned of any adhesive or other extraneous materials.
  2. Attaching insole: Insole to be attached with the last properly by staples or tacks at least in two locations. It should not be in the edges so that during lasting no problem appears.
  3. Applying primers: Primer should be applied on soles for better adhesion say for plastic sole -M.E.K, for rubber sole- Solutions of tricloro isocynuric acid 3-5% in ethyl acetate and Bostik for E.V.A.
  4. Mulling of uppers: One of the most important operations before assembly is the mulling of uppers. It is a process of impregnation of moisture on the uppers to make the leather soft and pliable. The moisture content of upper leather must be 24-28% again it depends on the type of material. This can be done in a continental muller or simply by storing the uppers in a closed room with high humidity. In case of Anzani conveyor there is a mulling chamber with controlled facilities.
  5. Moulding of counters: The shape of the back part and its shape retention in use, depends upon the use of good counter material. After selecting the right material, it is necessary to mould it correctly. The counter must firstly be reactivated and then moulded in the frozen  last.
  6. Lasting: The upper takes the correct form of last in toe lasting by correct amount of pulling by pincers. For good lasting a regular 12-14mm margin around must be attained. During heel lasting the height of the back part is with in the mark of the last. There fore for different type of last the bands and wipers must be changed. The tacks which held the insole in place on the last must be remould. Otherwise it can injure the wearer. In case of vamp lining, the lining should be 8-10mm shorter than the vamp, pasted uniformly allowing a free leather lasting margin and must ensure that the shoe is lasted on the leather and not on the lining.
  7. Heat setting: For a good appearance and sales appeal good heat setting is required. Without good heat setting there will be no shape retention. In case of Anzani Conveyor(Almost all lasting conveyor), there is a controlled preheating unit. Again the heat setting depends on material. There is also a timer with pre-heater. The pre-heating time and temperature depends on different       type         of leather and plastic material used.Pre-heating temperature maintained as bellow
                               For leather- Heather temperature-------------80degree to 100 degree centigrade
                                                  Blower temperature-------------180 to 200 degree centigrade
                               For Plastic-Heather temperature-------------40 degree to 50 degree centigrade
                                                  Blower temperature-------------140 to 150 degree centigrade

           Stay on touch and read the last part. Thanks everybody. 
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