Patent ID: 6695996
Filing Date: 2004-02-24
Classification: B29C

Abstract:
A method for adjusting a stroke of a top die in a molding process, comprising the following steps:a. Preparing at least an apparatus for adjusting die stroke, each of said apparatus including, a plurality of supporting rods adjustably mounted between said upper and said lower stroke limiting plates, a plurality of adjustable helical springs mounted between said upper and said lower stroke limiting plates, and a central processing unit; each of said adjustable helical springs including a male case, a female case, a rotation sleeve rotatably mounted between said male and said female cases, a helical spring axially extended between said male and said female cases, a displacement sensor for measuring changes in length of said helical spring under a load and sending a signal to said central processing unit, and a rotation sleeve driver for driving said rotation sleeve to rotate an angle based on an adjusting signal from said central processing unit and thereby adjusting a modulus of elasticity of said helical spring; b. Using said central processing unit to store basic parameters for each said adjustable helical spring and setting (i) the initial force for said apparatus for adjusting die stroke, (ii) an output force of said oil-pressure cylinder and a magnitude of deformation for each said adjustable helical spring, and (iii) a load of each said adjustable helical spring based on said output force of said oil-pressure cylinder, a total number of said adjustable helical springs, and relative positions of said adjustable helical springs on said top die; c. Calculating a modulus of elasticity of each said adjustable helical spring based on load and magnitude of deformation, and employing said basic parameters to obtain through an interpolation an angle by which each said rotation sleeve should be rotated, and using said rotation sleeve driver to rotate said rotation sleeve according to said obtained angle; d. Setting said top die to an initial position, so that a predetermined distance is kept between said top die and a bottom die to facilitate injection of molten material by an injection machine from one side of said top and said bottom dies; e. Using said injection machine to inject a predetermined amount of molten material into said bottom die from one side of said top and said bottom dies, and causing said injection machine to timely move away from a moving path of said top die when the injection is completed; f. Actuating said oil-pressure cylinder to output a pressure, so that a pressing plate of said oil-pressure cylinder, said upper stroke limiting plate, said adjustable helical springs, said lower stroke limiting plate, a pressing plate of said top die, and said top die are simultaneously moved toward and onto said bottom die to apply the pressure on the molten material in said bottom die; g. Using the pressure from said oil-pressure cylinder to force said molten material in said bottom die toward points having a lower pressure and to force any remained air out of said bottom die via vents provided on said molding dies, so that said molten material fills up a closed die cavity formed between said top and said bottom dies; h. Letting said top and said bottom dies gradually cool, so that said molten material in said closed die cavity and said air vents become hardened, said apparatus applies a conservative pressure on said molding material in said die cavity, and said hardened molding material in said die cavity produces a back pressure against the pressure output by said oil-pressure cylinder; i. Keeping said oil-pressure cylinder in an unmoved state and maintaining said conservative pressure of said apparatus until said molding material in said die cavity is completely hardened, so that a molded product formed from said hardened molding material evenly shrinks during the process of hardening to provide an enhanced surface quality; j. Using said displacement sensors of said respective adjustable helical springs to send signals representing displacements of said adjustable helical springs to said central processing unit; k. Returning said top die to its initial position and release said molded product from said die cavity to complete one cycle of said molding process. l. Using said central processing unit to convert said displacement signals received from said displacement sensors and to obtain errors of said released molded product at positions corresponding to adjustable helical springs, and then calculating errors of said adjustable helical springs under a load in order to modify said magnitude of deformation and said load previously set for each said adjustable helical spring; and m. Returning for step (c) and said modified magnitude of deformation and load in the next cycle of said molding process.