The purchase of an injection molding machine pair is never a small investment, so it becomes very prudent to choose the injection molding machine. Therefore, we will give advice from 7 aspects to help those who need it to choose the right injection molding machine.
Technical parameters of the injection molding machine
Usually, the important factors that affect the selection of injection molding machine include mold, product, plastic, molding requirements, etc. Therefore, it is necessary to collect or master these information before making the selection: such as mold size (width, height, thickness), weight, special design, etc.; the type and quantity of plastic used (single raw material or multiple plastics); the appearance size (length, width, height, thickness), weight of the finished injection product, etc.; molding requirements, such as quality requirements, production speed, etc.
After obtaining the above information, you can follow the following steps to choose the right injection molding machine
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Model selection
The product and plastic will determine the machine type and series.
Since there are many types of injection molding machines, it is necessary to correctly determine which type of injection molding machine or series should be used to produce the product, such as general thermoplastic or Bakelite or PET material, single color, two-color, multi-color, sandwich or mixed color. In addition, some products need high stability (closed circuit), high precision, ultra-high injection speed, high injection pressure or fast production (multi-loop), and other conditions, you must also choose the right series to produce.
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Mold size
From the mold size to determine the machine's "large column distance", "mold thickness", "mold minimum size" and "mold tray size " is appropriate, in order to confirm whether the mold can be placed.
The width and height of the mold should be less than or at least one side should be less than the large column distance; the width and height of the mold should preferably be within the range of the mold tray size; the thickness of the mold should be between the mold thickness of the injection molding machine.
The width and height of the mold should be in accordance with the minimum mold size recommended by the injection molding machine, too small is not acceptable.
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Stroke
The mold and the finished product should determine whether the "mold opening stroke" and "mold holding stroke" are sufficient for the finished product to be removed.
The opening stroke should be at least twice the height of the finished product in the opening/closing direction, and should include the length of the vertical sprue; the holding stroke should be sufficient to eject the finished product.
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Mold clamping force
The "clamping force" tonnage is determined by the product and the plastic.
When the raw material is injected into the mold cavity at high pressure, a clamping force is generated, so the clamping unit of the injection molding machine must provide enough "clamping force" to keep the mold from opening. The clamping force requirement is calculated as follows.
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The projected area of the finished product in the direction of the mold opening and closing is derived from the finished product's external dimensions.
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The clamping force = the projected area of the finished product in the direction of the opening/closing mold (cm2) × the number of cavities × the in-mold pressure (kg/cm2).
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The pressure in the mold varies with the raw material, generally 350-400kg/cm2.
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the machine clamping force should be greater than the clamping force, and for the sake of insurance, the machine clamping force usually needs to be more than 1.17 times the clamping force.
So far the initial decision on the specifications of the clamping unit, and roughly determine the machine tonnage, then the following steps must be carried out again to confirm which injection unit screw diameter is more in line with the required.
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Injection ratio
The weight of the finished product and the number of cavities are used to determine the required "injection volume" and to select the appropriate "screw diameter".
To calculate the weight of the finished product, the number of cavities (how many cavities in a mold) should be taken into consideration; for stability, the injection volume should be more than 1.35 times the weight of the finished product, i.e., the weight of the finished product should be within 75% of the injection volume.
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Injection quality
Some engineering plastics require higher injection pressure and suitable screw compression ratio design, in order to have a better molding effect, so in order to make the finished product shot better, in the choice of screw also need to consider the need for injection pressure and compression ratio issues.
Generally speaking, a smaller diameter screw can provide higher injection pressure.
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Injection speed
In this case, it may be necessary to check whether the injection rate and injection speed of the machine are sufficient, and whether it needs to be equipped with accumulator, closed loop control, etc. In general, under the same conditions, a screw that can provide a higher injection pressure usually has a lower injection speed, and conversely, a screw that can provide a lower injection pressure usually has a higher injection speed. Therefore, when choosing the screw diameter, the injection volume, injection pressure and injection rate (injection speed) should be cross-considered and traded off.
In addition, a multi-loop design can also be used to shorten the molding time by synchronizing the compound action.
Selecting an injection molding machine manufacturer
It is best to choose an injection molding machine manufacturer with a service office nearby to purchase, because the structure of the injection molding machine is complex and it is inevitable that there will be no problems, quick after-sales service is critical. As far as possible, choose the top Chinese injection molding machine manufacturer's machine, quality is guaranteed while the price is competitive.
Human-machine dialogue capability and operability
The injection molding machine should make its operation and management more user-friendly, with easy operation and clear, easy-to-understand displays that are easy to understand at a glance. The machine should have the functions of parameter selection, product quality control, storage of mold data and automatic reproduction of all parameters, and be able to diagnose and troubleshoot faults quickly, reduce material waste in the shortest possible time, and restore the normal operation of the system.
Stability, reliability and safety
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Stability
The stability of the injection molding machine is mostly expressed in whether the mold closing mechanism and the injection system operate smoothly in each cycle, work in silence without impact, and the noise should not exceed the industry standard. These situations are related to the mechanical manufacturing and assembly precision, and also related to the reasonable design of the crank and elbow linkage and its structure.
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Reliability
Reliability and service life are mainly reflected in the system rigidity of the mold closing mechanism, which is related to the structure and size of the template, tie rod, connecting rod and its pin, as well as the material and its heat treatment process. The structure and manufacturing process of the injection molding system such as the barrel, screw, screw head, stop collar and drive spindle of the screw are the main force and wear parts of the injection molding machine, which directly affects the service life.
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Safety
The safety of injection molding machine is very important. The reliability of the low voltage protection system involves the safety of man and machine when the mold closing mechanism is opened and closed. Modern injection molding machine requires the implementation of electrical, mechanical and hydraulic joint safety protection system, this protection mainly reflects two aspects: one is the safety protection of the mold, and the other is the safety protection of the person. Before closing the mold, when the safety door is not closed properly, the mold should not be able to be closed; in the process of closing the mold, if the safety door is not closed to the correct position, the mold will stop or open automatically. If a foreign object, such as an insert, falls into the cavity by mistake due to vibration or other foreign objects, such as a hand, are mistakenly placed in the mold during mold closing, the mold should stop the closing action or open the mold automatically and alarm.
Another safety aspect of the injection molding machine is to prevent the cold start of the pre-molding screw. When the material of the screw does not reach the specified temperature and holding time, it is forbidden to start, otherwise an alarm will occur. The protection of injection molding machine nozzle splash material is necessary to prevent scalding.
High Degree of Automation
Modern injection molding machine can realize manual, semi-automatic, fully automatic operation, as long as the mold design is reasonable, it can realize fully automatic operation from injection filling to product ejection falling, and can also be equipped with robots to achieve unmanned operation. The core extraction function, the hydraulic nozzle control function and the fast heating runner probe function can be programmed into the injection molding cycle to carry out automatic cycles. High production efficiency is mainly manifested in the short molding cycle for each molded product under normal injection molding process conditions. This is a reflection of an injection molding machine mechanical, electrical, hydraulic system integrated performance indicators, therefore, must use high-quality hydraulic, electronic components, the use of precision manufacturing technology to improve the sensitivity of the injection molding machine system and the repetition accuracy, which is a reliable guarantee of efficient injection molding system work.
Energy Saving and Environmental Protection
Energy saving, mainly reflecting the injection molding machine in the power drive system, heating system, heat dissipation system to meet the normal process conditions and similar machines compared to the ability to save water and electricity. The design of modern injection molding machine should fully consider the theme of "environmental protection". The injection molding machine should prevent hydraulic oil leakage or excessive noise, and work quietly. In addition, the injection molding machine itself should also be made of more environmentally friendly materials.
Easy Machine Maintenance
The installation position of various machines such as mechanical, hydraulic, electronic and electrical components should be conducive to the maintenance and overhaul of the machine, while the degree of generalization and standardization of the injection molding machine is also very important to the user.
The above is Log for your injection molding machine purchase tips, hope you can help.
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