 Introduction  Designing of Die Block  Process of making Press Form Points to be Covered PRESS FORM AND RUBBER TECHNOLOGY

 Rubber parts are used in aircraft.  Rubber parts are moulded under heat and pressure in a die.  The dies or moulds are commonly called as Press Forms.  Moulds are made from mild steel by machining, milling and finishing by hand. Introduction PRESS FORM AND RUBBER TECHNOLOGY

 Design of die block depends upon work piece size and thickness.  Overall dimensions of the die block will be determined by the minimum wall thickness of the die required for strength.  Sharp corners may lead to crack during heat treatment, therefore it requires greater wall thickness. Designing of Die Block PRESS FORM AND RUBBER TECHNOLOGY

 Two dowels should be provided in each block, for accurate and permanent positioning.  Thickness of the die block depends upon the size of the seals to be manufactured.  The minimum thickness of the die should not be less than 12.5mm.  In the process of rubber moulding, the accuracy of the product depends upon the construction of the dies. PRESS FORM AND RUBBER TECHNOLOGY Designing of Die Block

 The two pieces or a split die is most common.  Two-piece dies are turned on lathe first.  It is always not necessary that all dies are in circular form.  It may be in rectangular form also.  Special care must be taken for the alignment of the dies every time. Process of making Press Form PRESS FORM AND RUBBER TECHNOLOGY

 Alignment of dies can be achieved by guide pins and dowels.  Guide pins are preferably larger in size, to avoid confusion in assembly.  Die plates are ground on the faces to keep the thickness uniform for proper profiling and grooving. Process of making Press Form PRESS FORM AND RUBBER TECHNOLOGY

 Drawing is studied and dimensions such as pitch circle diameter (PCD) and tool thickness are calculated.  Raw material for female part is held in lathe chuck, faced and turned.  Parallelism of the block is maintained by measuring at three to four places using micrometer of required range. Manufacturing of Dies PRESS FORM AND RUBBER TECHNOLOGY

 Blank is prepared by taking finishing cut on face of female part and removing from the chuck.  The male part of the press form is held in lathe chuck, faced and turned and blank is manufactured.  Remove the male blank from the machine.  Compound slide is set at an angle of 15 o and taper bore upto 8 to 10 mm length is made. Manufacturing of Dies PRESS FORM AND RUBBER TECHNOLOGY

 Female blank is held in chuck.  Its concentricity and perpendicularity are adjusted within 0.01 mm using dial test indicator.  Undercut of 7 to 8 mm depth and upto 8 mm width is made for facilitating separation of die blocks.  Compound slide is set parallel to the jobs axis. Manufacturing of Dies PRESS FORM AND RUBBER TECHNOLOGY

 Required tool of specific thickness is set to centre height using height gauge, and parallelism of tool is set with dial test indicator.  Under cut dia is measured and tool advancement is calculated as per formulae.  Tool advancement = (1/2 OD) – (1/2 PCD) + R Where, OD= Step dia of block (under cut dia) PCD=Pitch circle dia R=Half of cross sectional thickness of seal Manufacturing of Dies PRESS FORM AND RUBBER TECHNOLOGY

 Take reference of step down diameter.  Tool is advanced as per calculated amount using cross slide and cross slide is locked in position.  By advancing saddle of machine, tool is brought in contact with face of block and saddle is locked.  Groove is cut to half of ‘O’ ring thickness by using compound slide.  Measurement is taken by DTI. PRESS FORM AND RUBBER TECHNOLOGY

 Groove is polished using lapping compound.  Without disturbing the saddle and cross slide, the female part is removed.  Pre-made male part is held and trued by using DTI.  With same set up, the groove is cut using compound slide and DTI.  Extra groove on either sides of main groove is given to accommodate extra rubber. PRESS FORM AND RUBBER TECHNOLOGY

 Compound slide is set at an angle of 15 0 and taper fitment is given to suit the female part.  Further, press form number is punched.  Thermometer hole is drilled by holding press form on drilling machine.  Dispatched to rubber seal for further process. PRESS FORM AND RUBBER TECHNOLOGY

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