Process for regulating the tool inner pressure curve of a cyclic

Details Process for regulating the tool inner pressure curve of a cyclic Process for regulating the tool inner pressure curve of a cyclic

1998-06-11

1999-08-31

Heitbrink, Jill L.

Plastic and nonmetallic article shaping or treating: processes

With measuring, testing, or inspecting

264 405, 264 407, 425145, 425149, B29C 4576, B29C 4577

Patent

active

059450460

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION



REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of German Patent Application 195 36 566.6, filed on Oct. 2, 1995, the disclosure contents of which is herewith also explicitly made the subject matter of the present application.


TECHNICAL FIELD

The invention relates to a method of controlling an internal tool pressure on a cyclically operating machine.
The method can preferably be used in the plastics-processing and metal-working industries, for example, in conjunction with plastics injection molding machines, blow molding machines, die-casting machines, aluminum die-casting machines, but also in conjunction with presses or welding apparatuses provided that cyclically operating processes are carried out. In so far as process curve courses are discussed in the following text, this covers not only courses that can be detected directly but also those process curve courses that can be calculated from the detected courses such as, for example, derivatives, integrals and the like.


STATE OF THE TECHNOLOGY

EP-A 233 548 discloses a method to detect the process curve courses of the hydraulic pressure in a cycle-synchronous manner. In order to attain a change-over point control between compression and holding pressure phase, specific criteria are established that are checked by way of the hydraulic pressure course. It is checked, for example, that the pressure for the change-over to holding pressure is reached only once, that the pressure course does not contain any overshooting and no pressure peak; but all of these checks are not carried out by way of the internal tool pressure. The drawback of this procedure which focuses on the hydraulic pressure, however, is that this pressure is setting-dependent and machine-dependent and is therefore difficult to evaluate. A control of the holding pressure time including corresponding criteria cannot be found in this disclosure.
DE-A 30 21 978 describes a method of controlling the internal tool pressure course on a cyclically operating machine, with the internal tool pressure course as well as the hydraulic pressure course being monitored as decision criteria for the determination of the change-over point. To accomplish a pressure shock-free change-over from the injection phase to the holding pressure phase and from the latter to the setting phase, the hydraulic pressure is controlled as soon as the actual value of the tool pressure reaches the desired starting value of the holding pressure phase, and an actual value of the pressure is predetermined at the transfer point as desired starting value of the setting phase. While this permits the transition of the internal tool pressure from one into another, it does not yet ensure a harmonic continuous pressure course.


SUMMARY OF THE INVENTION

Starting from this state of the technology, it is an object of the present invention to optimize and monitor the cycle on machines of this type so that high-quality parts are produced.
The above and other objects are accomplished according to the invention by the provision of a method of controlling a course of an internal tool pressure on a cyclically operating machine, comprising the steps of: means, of the mold cavity continues, cavity, function of time (t), which course occurs as a result of the pressure in steps a) to d), twice as a function of time (t) to determine a second order derivative, the internal tool pressure (Pwi) for presence of an extreme value (max(dPwi/dt).sup.2) of the second order derivative at least in a transition region between the regions of the internal tool pressure courses resulting from steps b) to c), and c) when an extreme value of the second order derivative occurs in step g), and show an extreme value in the transition region.
According to yet another embodiment of the invention there is provided a method of controlling a course of an internal tool pressure on a cyclically operating machine, comprising the steps of: means, of the mold cavity continues, cavity, function of a path traversed by the conveying m

REFERENCES:
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patent: 4325896 (1982-04-01), Rodgers, Jr.
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patent: 5665283 (1997-09-01), Bader et al.
Ries et al, "Druckubertragung beim Spritzgiessen durch verbessertes Umschalten aug Nachdruck", Kunststoffe, vol. 77, Dec. 1987, pp. 1232-1236.

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