Control technology of injection mold and injection product size

- Mar 01, 2018-

According to the injection mold report: along with the rapid development of die industry in recent years, and the application range of new technology and new technology is expanding and improving, there has been a qualitative change from the traditional experience to the application of software development. CADCAM and CAE widely used for geometric size of mold and mold our product control technology to open up space, because of the difference of mold and mold products market in great demand, variety in shape, size, material, the structure changes, demand is high, so we a lot of problems and difficulties in the the production process of mould and product, the geometry of how to effectively control the mould and products are very visually placed in front of us. There will be different control techniques and methods for different types of moulds and products. Today I am here to talk about injection molding product size control. I will talk about injection moulds. Generally speaking, I start from the following aspects.

Control of the design of a mold


1, first, we need to know all the technical requirements of users in terms of die structure, materials, hardness and accuracy, including the correct shrinkage rate of forming plastic material, whether the product 3D size modeling is complete, and how to deal with it properly.


2, to fully consider the shrinkage of the injection products, the flow marks, the slope of the dialing die, the weld line and the cracks and so on. Injection mould


3. On the premise that the function and pattern of the injection molded parts are not obstruct, the processing method of the mould is simplified as much as possible.


4. Whether the selection of the parting surface is appropriate or not, it should be carefully chosen for the die processing, the appearance of the shape and the deburring of the forming parts.


5. Whether the pushing method is appropriate or not, the push rod, the discharge plate, the push top casing or other ways, the position of the push rod and the discharge plate is appropriate.


6. The use of the side core pulling mechanism is suitable, the action is flexible and reliable, and there should be no stagnation.


7, temperature control methods to plastic products is more appropriate, what kind of system structure of oil control, temperature control system of circulating water, cooling liquid, the number of coolant hole size, location, whether it is appropriate. Injection mould


8. The shape of gate, the size of the feed and feeding port, the proper location and size of the gate.


9. The influence of the heat treatment deformation of various modules and mold core and the suitable selection of the standard parts.


10. The injection amount of the injection molding machine, the injection pressure and the clamping force are full, the nozzle R, the gate bore diameter and so on are suitable.


And so on and so on, the comprehensive analysis preparation, from the initial stage of product parts should be strictly controlled.

Two control of process manufacturing


Although the design stage has been fully considered and arranged, there will be many problems and difficulties in actual production. We should try our best to meet the original design in production, and find out more effective, more economical and reasonable technological means in actual processing. Injection mould


1, choose the machine tool which is adapted to the economy, and make the 2D and 3D processing plan.


2, it may consider appropriate fixture for auxiliary production preparation, reasonable use of the tool, to prevent product deformation, prevent product shrinkage rate fluctuations, prevent deformation release products, improve the mould manufacturing precision, reduce errors, prevent mould accuracy changes and so on, a series of production process requirements and solving measures.


3. Here are the reasons for the size error of the forming parts of the British Plastics Association (BPF) and the distribution of their proportion:


A: the error of mold manufacturing is about 1/3, and the error caused by B wear is about 1/6C. The error caused by the imbalance of forming parts is about 1/3. The error between D predetermined shrinkage and actual shrinkage is about 1/6.


The total error is =A+B+C+D, so it can be seen that the die manufacturing tolerance should be less than 1/3 of the dimensional tolerance of the forming parts, otherwise the die can't guarantee the geometric size of the forming parts.


Three control injection moulds in general production


The fluctuation of the geometric size of the plastic parts after forming is a common problem, and it is a frequent occurrence.


1, melt temperature, mold temperature, different grades of plastics have different temperature requirements, plastic fluidity and more than two kinds of mixture use will have a different situation, should put the plastic material flow control in the best range, these are usually easy to do, but the control of the mold temperature the more complex, forming the shapes and sizes of different thickness, different proportion of a certain requirement of the cooling system, mold temperature control and cooling time to a great extent, so try to keep mold in a low temperature state can be allowed, so as to shorten the injection cycle, improve production efficiency, mold temperature change, so the shrinkage will change, mold temperature stable, precision is stable, thereby preventing the forming of the deformation, poor luster, cooling spots and other defects, make the plastic physics The performance is in the best state, of course, there is also a debugging process, especially the multi cavity die forming is more complex.


2, the adjustment and control of pressure and exhaust:


The proper injection pressure, clamping force, should be identified in the debugging of the mold, the mold cavity and the core formed by the gas air in the gap and the plastic produced must be discharged from the exhaust groove outside the mold, such as poor exhaust will be filling, produce weld lines or burn, the three for forming defects sometimes occasionally appear in the same position as a book, form part of the wall around the thick wall exists when the mold temperature is too low when there will be insufficient filling, mold temperature is too high will burn phenomenon, often appear in conjunction with the weld line in the burned area, vents are often overlooked generally, in a small state, so often as long as it does not produce the flash, exhaust shoulder deep depth as far as possible, shoulder back opening size ventilation groove is larger, so that the shoulder after the gas It can quickly discharge the mold outside. If there is a special need, if the exhaust slot is on the top rod, the same is true. First, there is no waste side, and the two is to give vent to gas, and it will do well.


3. Supplementary plastic control for the size of injection molded parts


Some plastic parts for different shapes and sizes, after stripping along with the change of temperature and pressure loss, the deformation will occur in different conditions such as warpage, then make some auxiliary fixture adjustment in forming die after promptly take remedial measures for its natural cooling after setting can achieve good correction and the adjustment effect. If strict management is guaranteed in the whole injection process, the size of the molded parts will be very ideally controlled.