JP3546951B2

JP3546951B2 - Inspection method for injection molding machine

Info

Publication number: JP3546951B2
Application number: JP2000272633A
Authority: JP
Inventors: 修中沢; 徳夫吉沢; 宏昌植月; 忠三清水; 政浩高橋
Original assignee: 三共化成株式会社; 住友重機械工業株式会社
Priority date: 2000-09-08
Filing date: 2000-09-08
Publication date: 2004-07-28
Anticipated expiration: 2020-09-08
Also published as: JP2002079560A

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for determining the quality of a product of an injection molding machine.
[0002]
[Prior art]
In the injection molding machine, the quality of the obtained product is determined by various methods. As an example of a pass / fail determination method, a center value is calculated from actual value data for a plurality of shots in the past for a certain actual value obtained for each shot in a driving state in which a good product is obtained, and the center value is vertically determined with respect to this central value. Set a certain monitoring width. Then, for each shot, it is determined whether or not (center value-monitoring width) ≦ actual value ≦ (center value + monitoring width) is satisfied, and if satisfied, a good product is determined, and if not satisfied, a defective product is determined. ing. Note that the actual values include a weighing time, a cushion position, a pressure-holding completion position, a filling peak pressure, an injection peak speed, a pressure-holding peak speed, and the like. Normally, the center value and the monitoring width are set for all of these actual values, and the above determination is made for all of the actual values.
[0003]
[Problems to be solved by the invention]
However, in the above method, it is necessary to set the monitoring width by examining the variation of the actual value every time the product changes, and a large amount of work is required for the operator.
[0004]
Therefore, an object of the present invention is to provide a product quality determination method that can easily perform a setting operation for product quality determination in an injection molding machine.
[0005]
Another object of the present invention is to provide a method of determining the quality of a product, which can easily apply a set value determined for a certain product (a certain mold) to another product (a different mold).
[0006]
[Means for Solving the Problems]
In the method of determining the quality of a product of an injection molding machine according to the present invention, molding conditions are determined to find molding conditions under which N (N is a positive integer) shots can be molded stably in a good condition, and at least one actual value obtained in each shot is obtained. From the (N + 1) th shot, the average value and the standard deviation are calculated for each shot from the actual value data of the past N shots counted from the immediately preceding shot, and the magnification ki is initially set with respect to the calculated standard deviation. Then, it is determined for each shot whether (average value−ki × standard deviation) ≦ actual value ≦ (average value + ki × standard deviation) is satisfied, and if satisfied, it is determined as a good product, and if not satisfied, it is determined as a defective product. , The optimum magnification ko with respect to the standard deviation is determined, and thereafter, the optimum magnification ko is set with respect to the standard deviation calculated for each shot (average value-ko × standard deviation). A determination is made as to whether or satisfies the actual value ≦ (mean + ko × standard deviation) for each shot, when satisfied good, and performs a determination that defective products to be satisfied.
[0007]
The average is a moving average.
[0008]
The actual values obtained in each shot include a weighing time, a cushion position, a pressure-holding completion position, a filling peak pressure, an injection peak speed, a pressure-holding peak speed, and the like. The average value and the standard deviation are calculated for each of the adopted actual values, and the magnification for the calculated standard deviation is set for each of the adopted actual values.
[0009]
Further, when a different product is molded and the product is similar in weight and shape to the previously molded product, the optimum magnification ko obtained at the time of molding the previously molded product is changed to the initial magnification ki. And set.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. The functions required to execute the product quality judgment method according to the present invention are as follows.
[0011]
Achievement value acquisition function: In order to determine the quality of a product, it is necessary to acquire various achievement values as in the conventional case. As described above, the actual values include the weighing time, the cushion position, the pressure-holding completion position, the filling peak pressure, the injection peak speed, the pressure-holding peak speed, and the like. These actual values are obtained once per shot. it can. The weighing time can be known from the weighing timer, and the cushion position and the pressure holding completion position are measured by the screw position sensor. The filling peak pressure can be measured by a resin pressure sensor in the mold or a resin pressure sensor near the resin outlet in the heating cylinder. The injection peak speed and the holding pressure peak speed can be measured by the speed sensor of the injection motor. it can. In any case, such a function is also provided in a conventional injection molding machine.
[0012]
Function for storing and displaying actual values: A plurality of types of actual values obtained for each shot can be stored in a storage device provided in a control device of the injection molding machine, and provided in the injection molding machine as necessary. It can be displayed on a display or printed out by a printer. Of course, not only the actual value but also various pressure waveforms and speed waveforms for each shot can be displayed. A conventional injection molding machine has such a function.
[0013]
Standard deviation calculation function: This is a function unique to the present invention, and the average value and the standard deviation are calculated for each shot from the actual value data of the past N shots counted from the shot immediately before in a certain shot. That is, when calculating the average value and the standard deviation, the actual value data for N shots is not fixed, but the actual value data is updated by one shot for each shot. It is clear that the average obtained in this way is a moving average.
[0014]
Magnification setting function for standard deviation: This is also a function unique to the present invention, and is not a standard deviation itself calculated by the above calculation function but a value obtained by multiplying a standard deviation by a magnification k to perform good product quality judgment. I'm trying to use
[0015]
Pass / fail determination function: As will be described later, pass / fail determination is performed based on determination conditions unique to the present invention.
[0016]
Next, the operation of the product quality judgment according to the present invention will be described. The procedure for making settings for product quality determination for a new product according to the present invention is as follows.
[0017]
Procedure 1: Find molding conditions under which good products can be molded regardless of whether the product is good or bad. That is, the molding conditions are determined and N shots are stably formed. N is a positive integer, for example, 30.
[0018]
Procedure 2: From the (N + 1) th shot, the average value and standard deviation are calculated for each shot from the actual value data of the past N shots counted from the shot immediately before the actual value obtained in each shot. Then, the magnification k with respect to the standard deviation is set as the initial magnification ki based on past results of the same kind of product and statistical knowledge. Further, an initial magnification ki is set for the calculated standard deviation,
(Average value-ki x standard deviation) ≤ actual value ≤ (average value + ki x standard deviation)
Is determined for each shot. If satisfied, the optimum magnification ko with respect to the standard deviation is determined while discriminating a non-defective product if not satisfied and a defective product if not satisfied. Needless to say, this initial magnification ki differs for each actual value. The number of shots in procedure 2 is, for example, 30 shots.
[0019]
Step 3: After that, the optimum magnification ko is set for the standard deviation calculated for each shot,
(Average value-ko x standard deviation) ≤ Actual value ≤ (average value + ko x standard deviation)
Is determined for each shot, and if satisfied, a non-defective product is determined, and if not satisfied, a defective product is determined. As described above, in the procedure 3, the optimum magnification ko with respect to the standard deviation is found while actually performing the molding / product quality judgment.
[0020]
FIG. 2 shows the relationship between the average value and ± ko × standard deviation σ in procedure 3. Since the average value and the standard deviation σ are always calculated from the actual value data for the past N shots from the immediately preceding shot, the vertical width relative to the average value, that is, the monitoring width always fluctuates. This means that, even if the deviation amount from the average value is the same between a certain shot and another shot, if the standard deviation of the past N shots is small, it is determined to be defective, and if it is large, it is determined to be good. means. In other words, a monitoring width corresponding to variations in the past N shots is always set.
[0021]
The products determined to be defective are separated by a shooter provided in the injection molding machine, or separated by a take-out machine.
[0022]
FIG. 1 shows a display example on a display provided in the injection molding machine. Here, in addition to the weighing time, the cushion position, the pressure holding completion position, the injection peak speed, and the filling peak pressure, the minimum holding pressure speed and the filling pressures 1, 2, and 3 are used as the actual values. The filling pressures 1, 2, and 3 are values obtained by sampling the filling pressure at different timings in the filling step. Which of these performance values is used for the pass / fail judgment can be arbitrarily selected. When selecting, the monitoring column in FIG. 1 is set to “automatic”, and when not selected, “off” (“off” is shown in the drawing). )). On the display, an average value, a standard deviation, and a magnification k are displayed for each of the above-described actual values. Of course, the average value and the standard deviation may change for each shot. Further, the magnification k is different for each actual value. Furthermore, the actual value data for each shot is also displayed below these display portions.
[0023]
【The invention's effect】
{Circle around (1)} When a product quality judgment is set for a new product, a magnification for the standard deviation is set. This is not a physical absolute value but a tendency determined by the product weight and shape (= dimensionless relative value), so that a general statistical idea can be used (for example, 99.7 within 3σ in a normal distribution). % Etc.). Further, when a different product is molded and the product is similar in weight and shape to the previously molded product, the optimal magnification ko obtained at the time of molding the previously molded product is set to the initial magnification ki and Can be set in many cases. That is, in many cases, the magnification k of a product having a similar product weight or shape can be used almost as it is.
[0024]
{Circle around (2)} The standard deviation is calculated using the actual values of the past N shots from the shot to be determined. This eliminates the need to perform a test in advance to determine the standard deviation.
[0025]
(3) As described above, the setting work for determining the quality of the product in the injection molding machine can be easily performed, and the magnification determined for one product (a certain mold) is diverted to another product (another mold). Can be made easier.
[Brief description of the drawings]
FIG. 1 is a diagram showing a display example displayed on a display in product quality determination according to the present invention.
FIG. 2 is a diagram illustrating a determination operation of a product quality determination method according to the present invention.

Claims

The molding conditions are determined, and N (N is a positive integer) shots is found to find molding conditions that can form a non-defective product stably.
For at least one performance value obtained in each shot, from the (N + 1) -th shot, an average value and a standard deviation are calculated for each shot from the performance value data of the past N shots counted from the shot immediately before the shot,
The magnification ki is initially set with respect to the calculated standard deviation, and it is determined for each shot whether or not (average-ki × standard deviation) ≦ actual value ≦ (average + ki × standard deviation) is satisfied. The optimal magnification ko with respect to the standard deviation is determined while determining that the product is good or defective if not satisfied.
Thereafter, the optimum magnification ko is set for the standard deviation calculated for each shot, and it is determined for each shot whether or not (average value-ko × standard deviation) ≦ actual value ≦ (average value + ko × standard deviation) is satisfied. And determining whether the product is good or not, if not satisfied, as a defective product.
2. The method according to claim 1, wherein the average value is a moving average value.
In the method according to claim 1 or 2, the actual value obtained in each shot includes a weighing time, a cushion position, a pressure holding completion position, a filling peak pressure, an injection peak speed, a pressure holding peak speed, and the like. When multiple results are adopted from these actual values, the average value and standard deviation are calculated for each of the adopted actual values, and the magnification for the calculated standard deviation is set for each of the adopted actual values. A method for judging the quality of a product of an injection molding machine, characterized in that:
The product quality determination method according to any one of claims 1 to 3, wherein when a different product is molded, and when the product is similar in weight and shape to a previously molded product, the previously molded product is formed. A method for determining the quality of a product of an injection molding machine, wherein an optimum magnification ko obtained at the time of molding is set as an initial magnification ki.