Professional Injection Molding Machine Adjustment Process

1. Purpose

Standardize machine operation, facilitate production, protect molds and equipment, and ensure product quality.

2. Scope of application

It is suitable for the operation and adjustment of the injection molding machine in the injection molding workshop.

3. Responsibilities

Injection technicians operate the injection molding machine safely in accordance with the regulations to ensure the normal operation of the machine, and adjust the qualified products to make the machine run efficiently.

4. Operating procedures

Before adjusting the parameters, it is necessary to clearly understand the corresponding relationship between speed, position, pressure and time.

Before adjusting the machine, refer to the injection molding process card, and input the molding parameters into the computer board. If the debugged product is completely consistent with the appearance, structure and color of the model, then it is checked by IPQC. If NG is confirmed, the pressure, speed, position, back pressure, temperature and time should be adjusted according to actual needs.

After the adjustment is confirmed by IPQC, it can be produced. Besides, the reason for the change will be recorded and signed by the process engineer or supervisor for confirmation.

4.1 Molding temperature adjustment

Before adjusting the injection molding machine, first confirm what material is used for the product. Set the heating temperature of the material tube of the machine according to the melting point of the material.

Usually, the temperature of the nozzle (first stage) is set low, the temperature of the sol (stage 2-4) is high, and the temperature of the feeding port (end stage) is low.

Injection Molding Machine Adjustment Process

4.2 Mold opening and closing setting

4.2.1 Adjustment of mold opening and closing pressure

Low pressure clamping pressure is especially important to protect the mold, the lower the pressure, the better. Adjust the low-pressure mold clamping to the minimum pressure to lock the mold. The maximum cannot exceed 20%.

The high-pressure clamping pressure depends on the size of the mold and the clamping tonnage of the machine. Adjust the high-pressure mold clamping to the minimum pressure so that the mold can lock the product without flashing. Usually the high-pressure clamping pressure is 50%-80% of the machine pressure (depending on the match between the mold and the machine).

When the product is defective, the high-pressure clamping pressure can be moderately relaxed with the consent of the superior supervisor. But the high-pressure clamping pressure should not exceed 95% of the machine pressure. Otherwise, it will affect the life of the mold and machine. The opening and closing pressure of other sections is generally 30%-60% of the machine pressure. If it is more than 60%, then it is necessary to check the mold or machine.

4.2.2 Adjustment of mold clamping position

The position of low-voltage mold clamping should be adjusted according to the size and height of the product. If the low-voltage mold clamping position is too small, then when there is a foreign object at a position greater than this, the low-voltage protection can’t work. If the low pressure clamping position is too large, it will waste time. If the high-voltage switching position is too large, then when there is a foreign object in the position smaller than this, the low-voltage protection cannot be achieved.

The high pressure switching position is too small to be unfavorable to the machine mold closing. The usual adjustment method for low-voltage protection: adjust the low-voltage position according to the size of the product, and reset the high-voltage position to zero. Clamp the mold manually until the mold cannot be completely closed (judgment method: the pressure gauge has no pressure display when the mold is clamped, and the crank arm of the machine cannot be straightened). Observe the actual value of mold clamping on the machine operation panel and then set the high pressure position. The set value should be 0.2-0.5mm larger than the actual value. (Different brands of machines have different adjustment methods).

4.2.3 Adjustment of mold opening and closing speed

The opening and closing speed should be adjusted according to the principle of slow speed. When the mold structure is complex (with sliders), the slow-speed switching mold should be used to avoid damaging the mold during the switching action. When closing the mold, the mold enters the low-pressure section, the mold should be closed at a low speed. Usually the low-pressure mold clamping speed is 10%-40%. The high-pressure mold clamping speed is 20%-50%.

4.3 Adjustment of thimble action

The ejection speed should not be too fast and the pressure should not be too large, smooth and soft is better. The ejection length should not be too long, and should be set in order from short to long during debugging. It is better to be able to eject the product and the nozzle smoothly.

4.4 Adjustment of injection molding parameters

4.4.1 Sol parameter setting

Estimate the position of the sol according to the weight of the product and the size of the machine screw. When adjusting, set a reasonable sol position from short to far according to the machine operation display screen. Do not set the melt pressure too high. Generally, it is set to 80Bar-120Bar. The melting speed setting is generally 30%-80% (depending on different materials and product appearance requirements).

4.4.2 Adjustment of injection speed

The speed of melt flowing in the mold cavity determines the depth of the fusion line of the part, the degree of gloss, and the surface defects such as burning, draping, and flow marks caused by poor exhaust. Usually the adjustment method is firstly adjusted according to the principle of slow (at the gate) – fast (in the middle of the product) – slow (at the end of the product), and then adjusted according to the surface requirements of the product.

4.4.3 Adjustment of injection pressure

The pressure from the screw injection starting position to the secondary pressure switching position. The injection pressure is responsible for converting to a holding pressure after the mold cavity is completely filled. If the pressure is too small, the parts will be uneven, the fusion line will be deep, and the gloss will be too bright. Excessive injection pressure will cause the mold to bulge and the molded product to take off. When debugging, set the injection pressure appropriately according to the requirements of the product. The maximum injection pressure should not exceed 95% of the machine system pressure.

4.4.4 Adjustment of injection position

The different speeds of injection and the conversion of different positions determine the appearance of the product. According to the appearance requirements of the product, use different speeds and pressures to match the injection conversion position, and set a reasonable injection position according to the machine display value and observation of the injected product. Usually in the machine adjustment, the position of the gate is first found, and the gate is filled at a slow speed. Then switch the second stage position to fill products with medium or fast speed. When the product is filled to about 90%, turn to low speed to the end position of injection molding (injection turning to holding pressure position or v-p switching position).

The final position is usually set as a standard for injection molded products to fill 95%-98%. It is most reasonable to observe the minimum margin of the injection molding screw (the most advanced position) 5-10MM through the control panel, that is, the last position of 5-10MM is the best. If the position of the end section is too large, the finished product is likely to be short of material. If the switching position is too small, the product is prone to flash, which has a great impact on the pressure transmission during pressure holding.

Note: The multi-cavity mold product for the first mold adjustment cannot be injected into the full mold at one time. It is necessary to control the injection position and fill it according to 30%, 50%, 80% of the product and observe whether the product is balanced.

4.4.5 Adjustment of injection time

The length of the injection time is determined by the injection position, speed, pressure and molding temperature. If the injection conversion mode is time control, the injection time should be set from short to long, until the product reaches 95%-98% of the mold hold, and then it can be switched to hold pressure. If the injection time of this method is too short, and the product is prone to material shortage. If the injection time is too long, the product is easy to stick to the mold or become white on the top. If the injection conversion mode is time + position or position control, the injection time setting should be 1-2 seconds longer than the machine display time.

4.4.6 Adjustment of release action

Loosening prevents “drooling” but allows air to enter the barrel. Generally, the set pressure is 30-50Bar, the speed is 20%-30%, and the position is 3-10MM.

4.5 Adjustment of holding pressure

The pressure from the injection pressure to the holding pressure switching position (S5) is called the holding pressure. After the proper injection pressure is adjusted, the holding pressure determines the shrinkage (lack of material), flashing, flow lines and top cracking of the product. Usually, the holding pressure is adjusted from small to large according to the requirements of the product, and the holding time is set from short to long according to needs. The holding speed is usually 5%-30%.

Note: Cancel the pressure-holding action (reset the pressure-holding pressure or pressure-holding time to zero) when searching for the injection position.

4.6 Adjustment of back pressure

The back pressure is the pressure on the molten material at the top of the screw when the screw rotates and retreats.

Increasing the back pressure will increase the melt temperature. But it will reduce the plasticizing rate, make the temperature of the melt uniform, mix the material evenly, and remove the gas in the melt. Usually the back pressure of plastic is 5Bar-30Bar. If the back pressure is too large, the screw will not move back. And if the back pressure is too small, it will not be able to compress the mixed plastic.

4.7 Adjustment of the seat part

The forward and backward of the platform usually needs to set the pressure at about 30Bar and the speed at 10%-30%. Note that the pressure of seat entry should not be too high, otherwise it will damage the nozzle of the machine and the nozzle of the mold.

4.8 Adjustment of mold temperature

Usually increasing the temperature of the mold has 3 effects.

(1) The mold temperature is related to the flow rate of the glue. The higher the temperature, the better the fluidity of the glue. While the lower the temperature, the poorer the fluidity of the glue.

(2) The smoothness of the product surface can be controlled by increasing the mold temperature. The higher the mold temperature, the smoother the product surface.

(3) The product size can be adjusted appropriately by controlling thermal expansion and contraction through the mold temperature.

4.9 Setting of Injection Monitoring in Production

Adjusting injection molding monitoring parameters in production is crucial to quality control. Injection monitoring parameters include the monitoring of injection residual amount (shooting end position), monitoring of injection time, monitoring of sol position and sol time.

After adjusting the machine and producing 50 molds normally, set the actual monitoring value by observing the machine monitoring screen. Usually the minimum position monitoring position of the injection molding screw is generally plus or minus 0.5-2MM. The sol time is plus or minus 1-3 seconds.

5. Production confirmation

After adjusting the machine to produce the finished product, we must check the sample first. If you think it is OK, you need to notify IPQC for inspection. After passing the inspection, you can notify the operator to produce. After the first piece is confirmed OK by IPQC, the first 10 molds and adjustments will be discarded as defective products to ensure that the products in production will not be mixed with defective products.

In normal production, if the continuous 3-mode product is defective, it should be withdrawn from the fort, and the reason should be checked and analyzed. After normal production, save the process parameters in time and make a process card in time.

6. Precautions

(1) When adjusting the injection molding machine, try to use the minimum pressure to make qualified products. All pressures must not exceed 95% of the system pressure without approval.

(2) When the nozzle of the machine is blocked during machine adjustment, do not increase the injection pressure to flush out the blockage.

(3) The mold must be closed when seated.

(4) When adjusting the machine, the product should not be fully molded at one time to prevent parts from sticking to the mold.

(5) When processing the mold, the seat must be withdrawn and the motor must be turned off.

(6) When dealing with machine abnormalities, two people cannot operate the machine.

(7) Do not operate the machine without training.

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