Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1997-12-18
1999-06-29
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 264 407, 2643281, 425135, 425145, 425149, 36447505, 36447508, B29C 4576
Patent
active
059165014
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention concerns a process for regulating or controlling an injection molding machine for processing plastifiable materials.
PRIOR ART
A regulation of the motion of a feed screw in an injection molding machine is known-from European Patent No. 264 453. Injection speeds are set and a desired speed curve is constituted therefrom, wherein the transitions between contiguous speed steps are provided with ramps which represent either linear portions or any interpolation between the transition points. The motion of the feed screw is then tracked according to the desired curve within the scope of a regulation, wherein either speed sensors are provided or path values serving as actual values are inputted into the control by a servomotor provided with an incremental path measuring device. Both embodiments have the disadvantage that, on the one hand, the speed sensors or servomotors are expensive and, on the other hand, no direct comparison of comparable measured values is made, so that a time-intensive algorithm is necessary in order to control the machine.
European Patent No. 167 631 discloses an injection regulation in which the motor torque of a servomotor is used as a regulation variable in connection with the injection pressure. This solution too, is costly and time intensive. The same applies to the back pressure regulation according to European Patent No. 245 522 and the pressure regulation according to European Patent No. 260 328.
The prior art mentioned so far thus continuously uses servomotors for the shafts involved with the injection movement, but also for the movement of other shafts of a plastics injection molding machine. Published European Patent Application No. 576 925 too, develops the prior art in such a direction; according to that reference, electrical servomotors cooled by liquid are provided for all shafts in an injection unit. It is also suggested to assign to the drives of the different subassemblies linear potentiometers as an analog path measuring system for the regulation of the position and speed of the electrical servomotors cooled by liquid.
From German Offenlegungsschrift (application published without examination) No. 44 46 857 a process for automatically adjusting an injection speed condition is known. For this purpose a reference pressure is set as a nominal pressure curve and compared with an actual pressure in the mold cavity. If the detected pressure deviates from the nominal (desired) value, the movement of the piston of the feeding means is adjusted correspondingly. This way an over- and under-regulation relative to the nominal pressure curve results, while an adjustment of the curve to the moments at which the respective pressures are achieved is not made.
In European Patent No. 331 735 static sensors are provided for the detection of the injection forces arising during an injection cycle in the bearing area of the feeding means, for example, a feed screw. The measured values gained this way usually are applied to a force- or pressure-dependent injection control, inasmuch as measured values of the internal mold pressure cannot be detected sufficiently or due to the material used cannot be detected reliably from a determined moment in the injection cycle.
From European Patent No. 436 732 it is furthermore known to arrange a pressure sensor for the same purpose in the area of the feed screw itself.
The known devices, however, have the problem that the injection force in an injection molding machine during the injection proper varies in a range of very high magnitudes, usually several tons. During the dosing process, that is, during the material preparation, the resolution, however, should vary only in the kilogram range. Static force transducers, to be sure, can measure continuously starting from a zero point up to the high forces without losing their zero point, they do not have, precisely in the lower range, the desired resolution or, if they do, they are not suited to measure the large forces.
SUMMARY OF THE INVENTION
Based on the above-discussed
REFERENCES:
patent: 4961696 (1990-10-01), Yamamura
patent: 5154935 (1992-10-01), Kamiguchi et al.
patent: 5342559 (1994-08-01), Kamiguchi et al.
patent: 5514311 (1996-05-01), Shimizu et al.
patent: 5518671 (1996-05-01), Takizawa et al.
patent: 5585053 (1996-12-01), Arai
patent: 5595693 (1997-01-01), Fujita et al.
patent: 5611975 (1997-03-01), Kamiguchi et al.
Heitbrink Jill L.
Kelemen Gabor J.
LandOfFree
Process for regulating or controlling an injection molding machi does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for regulating or controlling an injection molding machi, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for regulating or controlling an injection molding machi will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1373505