Process Setting of Abs Injection Molding Supplier

abs plastic molding manufacturers before molding, plastic must be fully dried. When materials containing water enter the mold cavity, silver ribbon-like defects will appear on the surface of the product, and even hydrolysis will occur at high temperatures, causing material degradation. Therefore, the material must be pre-treated before molding so that the material can maintain appropriate moisture.
Setting of mold temperature (i) Mold temperature affects the molding cycle and molding quality. In actual operation, it is set from the lowest appropriate mold temperature of the material used, and then adjusted appropriately according to the quality conditions. (ii) Correctly speaking, mold temperature refers to the temperature of the mold cavity surface when molding is being carried out. In mold design and molding process condition setting, it is important not only to maintain the appropriate temperature, but also to make it evenly distributed.
(iii) Uneven mold temperature distribution will lead to uneven shrinkage and internal stress, making the molding port prone to deformation and warping.
(iv) Increasing mold temperature can achieve the following effects; 1. Increase the crystallinity and more uniform structure of the molded product. 2. Make the molding shrinkage more sufficient and reduce the post-shrinkage. 3. Improve the strength and heat resistance of the molded product. 4. Reduce residual internal stress, molecular orientation and deformation. 5. Reduce flow resistance during filling and reduce pressure loss. 6. Make the appearance of the molded product more shiny and good. 7. Increase the chance of burrs on the molded product. 8. Increase the chance of depression near the gate and reduce the chance of depression far from the gate. 9. Reduce the degree of obvious bonding line 10. Increase cooling time.

Metering and plasticization (I) In the molding process, the control of injection volume (metering) and the uniform melting and plasticization of plastics. Heating barrel temperature (Barrel Temperature) Although about 60~85% of the melting of plastics is due to the heat energy generated by the rotation of the screw, the melting state of plastics is still greatly affected by the temperature of the heating barrel, especially the temperature near the front area of ​​the nozzle-when the temperature of the front area is too high, it is easy to cause dripping and threading when taking out the product.
2. Screw speed The melting of plastic is mainly due to the heat generated by the rotation of the screw. Therefore, if the screw speed is too fast, the following effects will occur: Thermal decomposition of plastic. Glass fiber (fiber-reinforced plastic) is shortened.
3) The wear of the screw or heating tube is accelerated. The setting of the speed can be measured by the size of its circumferen-tial screw speed: Circumferen-tial screw speed = n (speed) * d (diameter) * π (pi) Usually, for plastics with low viscosity and good thermal stability, the circumferential speed of the screw rod can be set to about 1m/s, but for plastics with poor thermal stability, it should be as low as about 0.1. In practical applications, we can try to lower the screw speed so that the rotary feeding can be completed before the mold is opened.
3. Back pressure (BACK PRESSURE) When the screw rotates to feed, the pressure accumulated by the molten plastic pushed to the front end of the screw is called back pressure. During injection molding, it can be adjusted by adjusting the oil withdrawal pressure of the injection hydraulic cylinder. The back pressure can have the following effects: The molten plastic is melted more evenly. The colorant and filler are dispersed more evenly. The gas is discharged from the blanking port.

4) Accurate metering of feeding. The level of back pressure is determined by the viscosity and thermal stability of the plastic. Too high back pressure delays the feeding time and easily causes the plastic to overheat due to the increase in the rotational shear force. Generally, 5~15kg/cm2 is appropriate. Suck back (SUCK BACK, DECOMPRESSION) After the rod rotates to feed, the screw is properly withdrawn to reduce the pressure of the molten plastic at the front end of the screw. This is called suck back, which can prevent dripping from the nozzle. Insufficient sprue can easily cause the main channel (SPRUE) to stick to the mold; while too much sprue can suck in air and cause air marks on the molded product. Setting the number of stable molding

(I) Pre-confirmation and preliminary setting 1. Confirm whether the material drying, mold temperature and heating tube temperature are correctly set and reach the processable state. 2. Check the action and distance setting of opening and closing the mold and ejection. 3. The injection pressure (P1) is set to 60% of the maximum value. 4. The holding pressure (PH) is set to 30% of the maximum value. 5. The injection speed (V1) is set to 40% of the maximum value. 6. The screw speed (VS) is set to about 60RPM. 7. The back pressure (PB) is set to about 10kg/cm2. 8. The sprue is set to about 3mm. 9. The position of the holding pressure switch is set to 30% of the screw diameter. For example, for a φ100mm screw, set it to 30mm. 10. The metering stroke is set slightly shorter than the calculated value. 11. The total injection time is slightly shorter, and the cooling time is slightly longer.

(II) Manual operation parameter correction 1. Lock the mold (confirm the rise of high pressure), and the injection seat moves forward. 2. Manually inject until the screw stops completely, and pay attention to the stop position. 3. The screw rotates back to feed. 4. After cooling, open the mold and take out the molded product. 5. Repeat steps ⑴~⑷, and the screw finally stops at a position of 10%~20% of the screw diameter, and the molded product has no short shot, burrs, whitening, or cracking.

(III) Correction of semi-automatic operation parameters 1. Correction of metering stroke [metering end point] Increase the injection pressure to 99%, and temporarily adjust the holding pressure to 0, adjust the metering end point S0 forward to the occurrence of short shot, and then adjust it backward to the occurrence of burrs, and use the middle point as the selected position. 2. Correction of injection speed Restore PH to the original level, adjust the injection speed up or down, find out the individual speeds that cause short shots and burrs, and select the middle point as the appropriate speed [At this stage, you can also enter the parameter setting of multi-speed corresponding to appearance problems. 3. Correction of holding pressure Adjust the holding pressure up or down, find out the individual pressures that cause surface depression and burrs, and select the middle point as the holding pressure. 4. Correction of holding time [or injection time] Gradually extend the holding time until the weight of the molded product is obviously stable. It is a clear choice. 5. Correction of cooling time Gradually reduce the cooling time and confirm that the following conditions can be met: (1) The molded product will not be whitened, convex or deformed when it is ejected, clamped, trimmed, or packaged. (2) The mold temperature can be balanced and stable. Simple calculation method for cooling time of products with a wall thickness of more than 4mm: 1) Theoretical cooling time = S (1 + 2S) …. Mold temperature is below 60 degrees. 2) Theoretical cooling time = 1.3S (1 + 2S) …. Mold above 60 degrees [S represents the maximum thickness of the molded product]. 6. Correction of plasticizing parameters (1) Confirm whether the back pressure needs to be adjusted; (2) Adjust the screw speed so that the metering time is slightly shorter than the cooling time; (3) Confirm whether the metering time is stable, and try to adjust the gradient of the heating coil temperature. (4) Confirm whether there is dripping from the nozzle, whether there is a pigtail or sticking in the main channel, and whether there are air marks on the finished product, and adjust the nozzle temperature or the release distance appropriately. 7. Utilization of stage holding pressure and multi-stage injection speed (1) Generally speaking, injection should be carried out at a high speed without affecting the appearance, but it should be carried out at a lower speed when passing through the gate and before switching to holding pressure; (2) The holding pressure should be gradually reduced to avoid excessive residual stress in the molded product, which makes the molded product easy to deform.