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How to choose vertical injection molding machine

Date:2011/12/6 17:38:12

      In general, customers in the injection molding industry for many years most have the ability to judge and select the appropriate injection molding machine to produce. However, in some cases, customers may need help manufacturers specifications in order to decide which of the injection molding machine, and even customers may only samples of the product or idea, and then ask whether the manufacturer of the machine can produce, or what kind of model comparison for. In addition, some products may require special with special devices such as accumulators, closed-loop, injection compression, can produce more efficiently. Thus, how to determine the appropriate injection molding machine to produce, is an extremely important issue. The following information is provided to the reader is referred to.
        
Usually affect the choice of injection machine molds important factors, products, plastics, molding requirements, therefore, must be collected before making a choice or have the following information: the die size (width, height, thickness), weight, special design; use the type and quantity of plastic (single or multiple plastic materials); injection finished Dimensions (length, width, height, thickness), weight, etc.; molding requirements, such as quality conditions, the production speed.
        
In obtaining the above information, you can follow these steps to select the appropriate injection molding machine:
        
1, the election of the type: the decision by the products and plastic models and series.
        
Very much due to the injection machine type, so the beginning of the right to judge this product by the first of which injection molding machine, or to produce a series which, for example, generally plastic or Bakelite thermoplastic materials such as raw materials or PET, is a single color, color, multi-color, laminated, or blending. In addition, some products require high stability (closed loop), high precision, high rate of fire, or the rapid production of high pressure injection (multi-loop) and other conditions, you must select the appropriate series to produce.
        
2, let go: the size of the mold to determine the machine's "distance between tie bars," "thick model", "Die minimum size" and "mold plate size," whether it is appropriate to confirm the mold is let go.
        
Mold width and height must be less than or at least one side is less than the distance between tie bars; mold width and height of the best in the mold plate size range; mold thickness must be between the mold thickness between the injection molding machine; mold width and height must be consistent with the injection molding machine recommended minimum die size, too small to no good.
        
3, do have: determined by the mold and finished "opening stroke" and "Ejector Stroke" is enough to make the finished product out.
        
At least greater than the opening stroke switch mode in the direction of the finished product more than twice the height, and the need to include vertical runner (sprue) in length; ejector stroke will be enough to top the finished product.
        
4, the lock is maintained: the decision by the products and plastic "clamping force" tonnage.
        
When the raw material into the mold cavity under high pressure will produce a hold mode when the power, so the injection molding machine clamping unit must provide sufficient "clamping force" so that the mold will not be softened. Clamping force requirement is calculated as follows:
        
Size obtained by the appearance of finished product in the direction of the projected area of ​​switch mode;
        
Hold-mode switch-mode power = finished in the direction of the projected area (cm2) × number × mold cavity pressure (kg/cm2);
        
Mold pressure with different raw materials, raw materials generally take 350 ~ 400kg/cm2;
        
Machine support mold clamping force must be greater than the power, and to be safe, machine clamping force is usually greater than the hold-mode power to be 1.17 times more.
        
At this point a preliminary decision has been clamping unit specifications, and generally determine the tonnage models, and then have to proceed the following steps to confirm what a screw injection unit compared to the required diameter.
        
5, the shot was full: the finished product to determine the weight and number of cavities required for "injection volume" and select the appropriate "screw diameter."
        
Calculate the weight of the finished product to be considered number of cavities (a mode a few points);
        
For stability purposes, the injection volume required is 1.35 times the weight of the finished product, that product the amount of weight required for the injection of 75% or less.
        
6, shoot it well: to determine by the plastic "screw compression ratio" and "injection pressure" conditions.
        
Some plastics require a higher injection pressure and the appropriate screw compression ratio design, have good forming effect, so in order to make the product better shot, when the screw should also be considered in the choice of injection pressure and the compression ratio of demand the problem.
        
In general, the smaller diameter screw provides higher injection pressure.
        
7, shot quickly: and "injection rate" of the confirmation.
        
Some products require a high rate of speed of injection to stabilize the injection molding, such as thin as a finish, in this case, the machine may need to confirm the adequacy of injection rate and the rate of fire, whether it be with the accumulator, closed-loop control device. In general, under the same conditions, can provide a higher injection pressure of the screw is usually a lower rate of fire, on the contrary, it may provide a lower injection pressure of the screw is usually a higher rate of fire. Therefore, choosing the screw diameter, the injection volume, injection pressure and injection rate (injection speed), considered to be cross and trade-offs.
        
In addition, multi-loop design can also be used to shorten the molding compound action synchronization time.
        
After the above steps, already decided in principle to meet the needs of injection molding machines, but there are some special problems may also be coupled to consider, including:
        
With the size of the problem:
        
In some special circumstances, the customer's mold or mold products may be small but the required large fire, or mold bulky but a small amount of radiation needed, in this case, the manufacturers of the pre-set standard may not meet customer needs, and must be so-called "size distribution" which means "big wall of a small fire" or "small big wall of fire." The so-called "big wall of a small fire" refers to the original standard clamping screw injection unit with a smaller, on the contrary, the "small big wall of fire" that is, the original standard clamping unit with a large injection screw. Of course, with the clamping and injection may also be a difference of several levels.
        
Fast machine or high-speed machine concept:
        
In practice, more and more customers will be required to buy the so-called "high-speed machine" or "fast machine." In general, the purpose in addition to the demand for the product itself, the other mostly to shorten the molding cycle, increase yield per unit of time, thereby reducing production costs and improve competitiveness. Typically, to achieve the above purpose, there are several approaches:
        
Injection speed: the electrical motor and pump to increase, or increase the pressure has (plus the best closed-loop control);
        
Feeding speed: increase the Electric motor and pump, hydraulic motor or feeding piecemeal, so that the screw speed to speed up;
        
Multi-loop system: double-loop or three-loop design, combined with synchronized movements and shorten the molding time;
        
Increase the water mold, the mold to enhance the cooling efficiency.
        
However, "there is no free lunch" performance improvement and transformation of the machine can certainly increase production efficiency, but often also increase the investment cost and operation cost, therefore, pre-investment assessment of the benefits need to be carefully measured to the most appropriate machine type have the highest benefits.

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