Process for regulating or controlling an injection molding machine

• US 5,916,501 A
• Filed: 12/18/1997
• Issued: 06/29/1999
• Est. Priority Date: 07/11/1995
• Status: Expired due to Fees

• Current Assignee: Karl Hehl
• Original Assignee: Karl Hehl
• Inventors: Hehl, Karl
• Primary Examiner(s): HEITBRINK, JILL LYNNE
• Application Number:
  US08/981,609
• Time in Patent Office: 558 Days
• Field of Search: 264/40.1, 264/40.5, 264/40.7, 264/328.1, 425/135, 425/145, 425/149, 425/150, 364/475.05, 364/475.08
• US Class Current: 264/40.1
• CPC Class Codes: B29C 2043/5833 movement of moulds or mould parts, e.g. opening or closing, actuating
• CPC Class Codes: B29C 45/76 Measuring, controlling or regulating measuring in general G01; controlling or regulating in general G05
• CPC Class Codes: B29C 45/77 of velocity or pressure of moulding material

Abstract

In a control process speed stages are predetermined for the displacement of a movable unit and a nominal speed curve is derived therefrom. From the nominal speed curve a nominal path/time curve is calculated, from which, in turn, a position reference variable for the speed control is determined. At the time t_i determined for the modification position s_i where the speed level is to be changed for the successive speed stage, the speed of the movable unit is maintained until time t_i'"'"' which is the moment at which the movable unit actually reaches the modification position s_i. Upon this occurrence a triggering is initiated which equates the actual time t_i'"'"' with the nominal time t_i and which causes the nominal speed course to be superseded by a new nominal speed course progressing from the actual point in time t_i'"'"'. The new nominal speed course corresponds to that portion of the superseded nominal speed course which progresses forwardly from the nominal time t_i at which the movable unit should have reached the modification position s_i.

Claims

1. A method of controlling a parameter derived from motions of a movable unit displaced along a path in an injection molding machine which processes plastifiable materials;

said parameter being selected from the group consisting of speed, pressure and force;

said method comprising the following steps;

(a) setting a plurality of arbitrary magnitudes for said parameter for consecutive arbitrary length portions of said path;

(b) setting, along said path, modification positions where a parameter magnitude for one of said length portions is to change to a parameter magnitude of another, consecutive length portion during motion of the movable unit;

(c) computing a nominal parameter-course based on the magnitudes and modification positions set in steps (a) and (b), respectively, wherein said nominal parameter-course is a path/time function for setting a position reference variable to control said parameter during motion of the movable unit;

(d) determining consecutive actual positions of said movable unit during motion thereof;

(e) determining respective consecutive actual points in time at which said movable unit has reached respective said actual positions determined in step (d);

(f) comparing nominal magnitudes with actual magnitudes for determining setting magnitudes to cause the movable unit to adjust to the nominal parameter-course;

(g) determining a presence of any time discrepancy between a nominal point in time, based on said path/time function, at which a given modification position should have been reached by said movable unit and an actual point in time at which said movable unit actually reached said given modification position;

(h) maintaining a previously set setting magnitude for the motion of said movable unit throughout said time discrepancy until said movable unit reaches said given modification position;

(i) upon reaching said given modification position, the actual point in time at which said movable unit has reached said given modification position is equated with the nominal point in time at which said given modification position should have been reached;

(j) superseding said nominal parameter-course by a new nominal parameter-course progressing from said actual point in time at which said given modification position was reached;

said new nominal parameter-course corresponding to that portion of the superseded nominal parameter-course which progresses forwardly from said nominal point in time at which said given modification position should have been reached; and

(k) adapting said setting magnitudes to said new nominal parameter-course.

2. The method as defined in claim 1, wherein said movable unit is a mold closing unit of said injection molding machine and wherein steps (a) through (k) are performed on said mold closing unit.

3. The method as defined in claim 1, wherein said movable unit is an injection molding unit of said injection molding machine and wherein steps (a) through (k) are performed on said injection molding unit.

4. The method as defined in claim 1, wherein said movable unit is a feed screw of an injection molding unit of said injection molding machine and wherein steps (a) through (k) are performed on said feed screw.

5. The method as defined in claim 1, further comprising the step of comparing position values of said nominal path/time function with measured values of actual positions of said movable unit.

6. The method as defined in claim 1, wherein said parameter is speed;

further comprising the steps of performing a force-limiting regulation and superposing said force-limiting regulation on the speed regulation by performing steps (a) through (k) while selecting the force as said parameter.

7. The method as defined in claim 1, wherein at successive modification positions reached by said movable unit, repeating step (j) on the nominal parameter-course determined previously at a respective preceding modification position reached by said movable unit.

8. The method as defined in claim 7, wherein said movable unit is a mold closing unit of said injection molding machine and wherein steps (a) through (k) and said repeating step are performed on said mold closing unit.

9. The method as defined in claim 7, wherein said movable unit is an injection molding unit of said injection molding machine and wherein steps (a) through (k) and said repeating step are performed on said injection molding unit.

10. The method as defined in claim 7, wherein said movable unit is a feed screw of an injection molding unit of said injection molding machine and wherein steps (a) through (k) and said repeating step are performed on said feed screw.

11. The method as defined in claim 7, further comprising the step of comparing position values of said nominal path/time function with measured values of actual positions of said movable unit.

12. The method as defined in claim 7, wherein said parameter is speed;

further comprising the steps of performing a force-limiting regulation and superposing said force-limiting regulation on the speed regulation by performing steps (a) through (k) and said repeating step while selecting the force as said parameter.