Eight contents of mold test
1, mold empty operation test – verify the mold action.
A. Inspection of mold opening and closing under low pressure:
1. The mold shall be opened and closed three times for fast, medium and slow respectively, and whether there is abnormal sound and blocking during opening and closing;
2. The opening and closing of the mold shall be smooth without interference.
B. Inspection of die ejection system (under low pressure)
1. The ejection action is divided into three times: fast, medium and slow, and check whether there is any abnormality;
2. Whether the thimble (cylinder) at the plane will be loosened or stuck after being ejected;
3. Whether the inclined thimble or cylinder device is equipped with positioning pin (to prevent loosening or rotation);
4. Whether there is abnormal sound and vibration when the ejector system (ejector pin or ejector block) is ejected
C. Inspection of mold reset
1. Reset the mold three times at fast, medium and slow speeds respectively to see whether it can return to the position (reset);
2. After reset, the end face of the oblique thimble shall not be higher than the mold core by 0.1mm or flush with the mold core;
3. Whether the reset limit card is in good contact;
4. Whether the ejector pin interferes with the action of the row position (whether the slider returns to the position);
5. Whether the die is equipped with thimble reset device (Mechanical).
D. Inspection of line position (slider) action
1. Open and close the mold for three times according to the speed, medium and slow respectively, and observe whether the movement of the travel position is smooth;
2. Whether the line return is normal and whether it interferes with the thimble;
3. Whether the line position is firmly positioned;
4. Action sequence of hydraulic core pulling device;
5. Check whether the line position is strained or stuck during empty operation.
2、 Test of injection balance of cavity
1. Make 5 moulds successively and weigh them;
2. Record the weight of each product in each mold;
3. Reduce the injection quantity and fill 3 molds of 20%, 50% and 90% samples in turn;
4. Weigh and record the weight of each of the above products;
5. If the difference between the maximum weight and the minimum weight of the product is less than 2%, it is acceptable – if the weight fluctuation error is within 2%, it indicates that the glue feeding into the cavity is balanced, otherwise the glue feeding is unbalanced;
6. If it is a single cavity mold, the glue feeding balance test shall also be carried out (observe the actual glue feeding situation)
3、 Test of holding time (gate freezing)
1. When the pressure holding time is first set to 1s, 3 molds of products are formed each time;
2. As shown in the table, increase the pressure holding time in turn and reduce the cooling time to keep the whole cycle unchanged (until the gate is frozen and sealed, and the product weight does not increase);
3. As shown in the figure below, set several different holding times, form three mold products each time, weigh the product weight of the specified cavity, and record the data in the table in turn;
4. Determine the best pressure holding time according to the chart.
4、 Determination of optimum clamping force
1. When the pressure holding switching position / pressure holding pressure is set to the best, the mold locking force is set to within 90% of the maximum mold locking force, three molds are formed, and the weight of each mold is recorded;
2. The mold locking force is reduced by 5ton in turn, 3 molds are formed each time, and the product weight of each mold is recorded until the product weight suddenly increases, the weight increases by about 5%, and flash begins to occur around the product.
5、 Determination method of optimal cooling time
1. When the injection molding process conditions are appropriate (after the product is filled), estimate the cooling time (select a long cooling time to completely cool the product), punch 3 mold products and measure their dimensions;
2. Record the product size in the following table and observe the deformation of rubber parts;
3. Reduce the cooling time of the product by 1 second one by one and make three molds;
4. Reduce the cooling time until the product begins to deform and the size begins to decrease;
5. The size of the injection molded products in each cooling time can only be measured after the rubber parts are fully cooled (about 15 minutes);
6. Basis for determining the optimal cooling time – considering the dimensional stability of the product.
Estimation formula of general cooling time:
1. Empirical cooling time ≥ t (1 + 3T)… Mold temperature below 60 ℃;
2. Empirical cooling time ≥ 1.5T (1 + 3T)… Mold temperature above 60 ℃;
(T represents the maximum meat thickness of the molded product).
3. Estimation formula of theoretical cooling time:
S = minimum cooling time (s)
T = thickness of plastic part (mm)
α= Thermal diffusivity of material (C ㎡ / s)
TK = demoulding temperature of plastic parts
TM = mold temperature (℃)
TC = barrel temperature (℃)
6、 Test of cooling water flow
1. Use pressure gauge and flow meter for measurement, and fill the measured data in the table;
2. Measure and record the diameter of cooling water pipe;
3. Find out the kinematic viscosity according to the cooling water temperature;
4. Calculate the Reynolds number according to the following formula; Reynolds number (RE) = 3160 × Cooling water flow / cooling water diameter × Kinematic viscosity
5. Only when the cooling water flows in the turbulent state can it have a better cooling effect (re ＜ 2000 is the laminar state; re ＞ 4000 is the turbulent (turbulent) state; Re = 2000 ~ 4000 (transition state).
7、 Test of die cooling uniformity
1. Use the mold temperature measuring instrument to measure the temperature of the core and cavity at 10 points respectively, and record it in the table below;
2. The difference between the actual temperature of each measuring point and the average value shall be less than 2 ℃. If the difference from the average value exceeds 2 ℃, it indicates that the cooling effect of the die is uneven, and the cooling system shall be improved.
8、 Viscosity analysis of solution — determining the best injection speed
1. Record the hydraulic oil temperature, dissolving temperature and mold temperature;
2. First set the sol termination position, and only use one-stage glue injection;
3. Set the holding pressure and holding time to zero, and gradually increase the injection speed after determining the starting position of glue injection;
4. Adjust the injection speed to fill 95% of the rubber parts (observe whether there is padding, and leave 5-10mm padding amount);
5. Record the maximum injection speed when filling 95% of the rubber parts;
6. Record the maximum injection speed and peak injection pressure in the “injection speed analysis data sheet”;
7. Gradually reduce the injection speed, increase the injection pressure, and observe and record the corresponding injection peak pressure when filling 95% of the rubber parts;
8. Determine the optimal injection speed from the curve.
