Generally speaking, in the injection molding industry for many years, customers have the ability to judge and the appropriate injection molding machine to produce. But in some cases, the customer may require manufacturers to assist injection molding machine which decided to adopt a specification, and even customers may only sample product or idea, and then ask whether the machine manufacturers can produce, or what kind of model is more suitable. In addition, some special products may need to match special devices such as pressure accumulator, closed loop, injection compression, etc., in order to produce more efficient. Thus, how to determine the appropriate injection molding machine to produce, is a very important issue. The following information is available to the reader.
The important factors that affect the ion of the injection machine, including the mold, the product, the plastic, the molding requirement and so on, must first collect or have the following information before ing:
The mould size (width, height, thickness, weight, special design etc.);
The number and type of using plastic (single or multiple plastic raw materials);
The molded product appearance size (length, width, height, thickness, weight etc.);
The forming requirements, such as quality and production speed.
After obtaining the above information, you can choose the appropriate injection machine according to the following steps:
1, choose the type: by products and plastic machine and a series of decisions.
Because of the injection molding machine has many types, so begin this product should correctly judge what kind of injection molding machine, or which is a series of production, such as general thermoplastic plastic or bakelite raw materials or raw materials such as PET, is a monochrome, two-color, multi-color, sandwich or mixed color. In addition, some products need high stability (closed loop), high precision, high speed, high pressure and fast production (multi loop) and other conditions, must choose the appropriate series production.
2, put down: by the mold size to determine the machine's "big column", "mold thickness", "mold minimum size" and "die plate size" is appropriate, to confirm whether the mold can be put down.
The mould width and height must be less than or at least one side than in the column spacing;
The width and height of the mold in the best mold size range;
The thickness of the mold mold thickness required between the injection molding machine;
The minimum size of die / mold width and height to comply with the recommendations of the injection molding machine, is too small.
3, we have: from the mold and product determine whether the opening stroke "and" supporting die "to take out the finished products.
The opening stroke at least larger than the finished in switching mode direction is two times the height of the above, and with the sprue length (sprue);
We need enough to support mold stroke finished top.
4, lock by plastic products and determine the "locking force" tonnage.
When the raw material with high pressure injection mold cavity will produce a supporting die strength, therefore the injection molding machine clamping unit must provide enough "locking force of the die can not be opened". The clamping force requirements are calculated as follows:
The product appearance is obtained by projection area in the direction of product switching mode;
The projection area of the supporting die strength = finished in switching mode direction (cm2) pressure * * mold cavity number (kg/cm2);
The pressure in mold with raw materials and different raw materials, generally from 350 to 400kg/cm2;
The machine clamping force required is greater than the strength of the supporting die, and to be on the safe side, the machine clamping force usually must be greater than 1.17 times the strength of the supporting die.
This has tentatively decided clamping unit specifications, and roughly determine the aircraft tonnage, then must do the following steps to confirm which one injection unit screw diameter compared with the required.
5, shot to the full: by the weight of the finished product and the number of points to determine the amount of "injection" and the appropriate "screw diameter".
The calculation of the weight of the product need to consider the cavity number (a few points);
The reasons for stability, injection amount is more than 1.35 times the weight of the product, which is required for the weight of the product within the injection volume 75%.
6, well shot: the plastic to determine the "screw compression ratio" and "injection pressure" and other conditions.
Plastic injection pressure higher some engineering and suitable screw compression ratio design, have good molding effect, so in order to make the product better shot, also need to consider the needs and problems of injection pressure, compression ratio in the choice of screw.
In general, the smaller diameter of the screw can provide a higher injection pressure.
7, shot quickly: and the "injection speed" of the confirmation.
Some products need high injection rate to fire stable molding, such as ultra-thin products, in this case, the machine may need to confirm the injection rate and rate of fire is enough, whether collocation accumulator, closed loop control device. Generally speaking, under the same conditions, can provide high speed screw injection pressure is usually low, on the contrary, the screw can provide lower injection pressure is usually high speed. Therefore, when ing the screw diameter, the amount of injection, injection pressure and injection rate (injection speed), the need to cross consideration and choice.
In addition, the multi loop design can be used to shorten the forming time of the composite action.
After the above steps, the injection molding machine can be determined in principle, but there are some special problems may also have to be considered, including:
The size distribution of the problem:
In some special conditions, customers or products may die mold small volume but required a large amount of radiation, or die size but required a small amount of radiation, in this case, the standard factory previously set may not be able to meet customer needs, and must be the so-called "size distribution", which means "great wall small shot" or "little wall big shot". The so-called "big wall small shot" refers to the original standard clamping unit with a smaller injection screw, and vice versa.