Method of molding a plastic article including injecting based upon a pressure-dominated control algorithm after detecting an indicia of a decrease in the surface area of the melt front
US5902525A · kind A · utility
Inventor
Key dates
| Filing date | May 13, 1996 |
| Grant date | May 11, 1999 |
| Priority date | — |
| Expiry date | May 13, 2016 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C45/77
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method for injecting a plastic material into a mold cavity to precisely fill the mold cavity under low pressure and to avoid packing the mold cavity with plastic material. The plastic material is injected into the mold cavity at a rate sufficient to maintain an unbroken melt front and to avoid any spraying or splashing of the plastic material within the mold cavity. After an initial unbroken melt front is established, the rate at which the material is injected is increased in proportion to the size of the melt front. After a predetermined amount of the material has entered the mold cavity, the material is injected based upon a rate-dominated control algorithm which maintains the unbroken melt front. After detecting an indicia of a decrease in the surface area of the melt front, the material is injected based upon a pressure-dominated control algorithm where the injection rate is adjusted as needed so that an injection set limit is not exceeded in order to prevent overrunning the end point of the mold process and to eliminate splashing and associated backflow problems. The injection pressure is monitored and controlled until the mold cavity has been precisely filled, at which time…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.