Method and apparatus for adjusting die stroke

A method for adjusting a stroke of a movable die in a variable-volume mold-filling process, comprising the following steps:

• a. Preparing at least an apparatus for adjusting die stroke, each of said apparatus including an upper stroke limiting plate, a lower stroke limiting plate, 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 for 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 individual adjustable helical springs and setting (i) the initial force for said apparatus, (ii) an initial injection pressure and a subsequent injection pressure, (iii) a magnitude of deformation for each said adjustable helical spring, and (iv) a load for each said adjustable helical spring based on said subsequent injection pressure, the number of said adjustable helical springs, and relative positions of said adjustable helical springs on said movable 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 the interpolation an angle by which said rotation sleeve corresponding to said adjustable helical spring should be rotated, and using said rotation sleeve driver to rotate said rotation sleeve according to said obtained angle;
• d. Moving a plate of top die, said upper stroke limiting plate, said adjustable helical springs, said lower stroke limiting plate, and a top die toward the bottom die to perform mode-locked closing, opening vents on said dies, and then injecting a predetermined amount of molten material into a die cavity between said closed molding dies, allowing said initial injection pressure to cause said molten material to fill up a fixed-volume portion of said die cavity;
• e. Closing said vents and actuating said subsequent injection pressure to fill up a variable-volume portion of said die cavity, and allowing said movable die to stop at a point at where said load of said apparatus and a pressure of said variable-volume die cavity reach a balance point;
• f. Subjecting said molding material in said die cavity to a conservative pressure of said apparatus until a completely hardened molded product is obtained, so that said molded product evenly shrinks in the hardening process to provide an enhanced surface quality;
• g. Sending signals of displacement of all said adjustable helical springs from said displacement sensors to said central processing unit;
• h. Opening said dies and releasing said molded product from said molding dies to complete one time of variable-volume mold-filling process;
• i. Using said central processing unit to convert said displacement signals received from said displacement sensors and to obtain errors of said released product at positions corresponding to said adjustable helical springs, and then calculating errors of loads of said adjustable helical springs to modify said magnitude of deformation and said load previously set for each said adjustable helical spring;
• and
• j. Returning to step (c) and using said modified magnitude of deformation and load in the next cycle of said variable-volume mold-filling process.

An apparatus for adjusting die stroke, comprising:

• an upper stroke limiting plate having a plurality of adjustable spring seats and a plurality of adjustable supporting rod seats mounted to a bottom surface thereof;
• a lower stroke limiting plate having a plurality of fixed spring seats and a plurality of fixed supporting rod seats mounted to a top surface thereof corresponding to said adjustable spring seats and said adjustable supporting rod seats, respectively, on said upper stroke limiting plate;
• a plurality of supporting rods, each of which being mounted between one of said adjustable supporting rod seats and one of said fixed supporting rod seats aligned to each other;
• said supporting rods being used to adjust an initial distance between said upper and said lower stroke limiting plates and to support the initial force of said apparatus;
• a plurality of adjustable helical springs, each of which being mounted between one of said adjustable spring seats and one of said fixed spring seats aligned to each other;
• each said adjustable helical spring including a male case, a female case, a rotation sleeve rotatably mounted between said male and said female cases, and a helical spring axially extended between said male and said female cases to engage with said rotation sleeve;
• each said adjustable helical spring also having a displacement sensor connected thereto for measuring a change of length of said helical spring under a load and for sending out a signal representing said measured change in length, and a rotation sleeve driver connected to said rotation sleeve for rotating said rotation sleeve and thereby adjusting said adjustable helical spring to a required modulus of elasticity;
• and
• a central processing unit functioning to receive signals of actual magnitudes of deformation of said adjustable helical springs output by said displacement sensors, to obtain errors on a molded product, and to compare basic parameters set for said apparatus with said actual magnitudes of deformation of said adjustable helical springs and said errors of said molded product in order to output adjusting signals to said rotation sleeve drivers for the same to rotate said rotation sleeves and thereby adjust said adjustable helical springs to the required modulus of elasticity;
• and
• central processing unit, said displacement sensors, and said rotation sleeve drivers together providing a cyclic adjusting mode for said apparatus, enabling production of a best molded product within a lowest possible number of process cycles through a convergence method;
• and said central processing unit, when being set to automatically read errors of molded products, enabling adjustment of any accumulative error occurred in a molding process from time to time, resulted in a minimized rate of bad yield of molded products.