Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1998-03-09
2000-02-01
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 2643281, 425145, 425149, B29C 4577
Patent
active
060199172
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for controlling regulation of a hydraulic press intended for injection moulding, particularly of polymers.
BACKGROUND OF THE INVENTION
The presses used in the domain of moulding are usually actuated by a piston which moves either under the action of a hydraulic fluid under pressure, so that the pressure of injection exerted on the material to be moulded is a function of the hydraulic pressure exerted upstream of the piston of the press, or under the action of a force generated by mechanical or electrical means.
Furthermore, it is known that numerous parameters influence the value of the pressure applied to the material inside the mould. In practice, the presses of the prior state of the art comprise means for controlling the hydraulic pressure applied to the piston and means for measuring the pressure of the material inside the mould where the injection is effected. It is also known that, in stable operating conditions of the injection press, by simply regulating the pressure of the hydraulic fluid, the pressure of the material inside the mould can thus be maintained within a range, satisfactory in certain cases, despite the influence of all the technical parameters which have influence thereon, particularly the operating parameters of the machine.
Such constant and regular operating conditions of the injection press are maintained as long as no noteworthy disturbance occurs. Among the disturbances that may modify the operating conditions of the press may be retained, in particular, the stoppages thereof, whether they be necessary for normal operation of the machine or whether they be accidental, as well as the influence exerted by the variations in temperature or the irregularity of the material itself if a recycled material is used. When such disturbances occur during a cycle of injection, it is known that it is necessary to make the installation operate thereafter for a more or less long period of time, which depends on the characteristics of the press and the material to be moulded, before resuming new stable operating conditions. Moreover, the level of these new stable operating conditions may be very different from the earlier level of stability, which is translated by very different characteristics of moulded products.
During the operating time of the press under disturbed conditions, a certain number of pieces are, of course, produced which, for the majority, do not fulfill the specifications imposed, particularly concerning their mass and/or their dimensions, with the result that such pieces are discarded, which represents both a loss of time and of money.
SUMMARY OF THE INVENTION
The present invention has for its object to overcome these drawbacks by proposing a means for reducing the deviation which exists between the mass, or the dimensions, of products respectively obtained before and after a disturbance.
The present invention thus makes it possible to reduce the number of pieces discarded due to too great differences in their mass, and/or in their dimensions, with respect to the ranges of tolerances admitted. Due to the reduction of the deviation mentioned above, the moulder has the possibility of taking as reference level of a production the value corresponding to the lowest value of the range of tolerances on the mass of a product, which enables him to make substantial savings on the quantity of material used.
The present invention thus has for its object a method for controlling and regulating an injection moulding press, particularly of polymers, which is actuated by means adapted to exert on the material to be moulded a force, called injection force, which essentially comprises two phases, namely a filling phase during which the material to be moulded is introduced in the mould, which is followed by a phase of maintenance under pressure, during which a determined pressure is applied to the material, characterized in that it comprises the steps of: at least one of the dimensions, of a product moulded with at least cer
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"Viskositatsregelung beim Spritzgiessen", Kunststoffberater, vol. 23, No. 11, Nov. 1978, pp. 632-633.
Laurent Fabrice
Pabiot Jose
Ryckebusch Marc
Heitbrink Jill L.
Transvalor S.A.
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