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Injection mold design drawing dimensions

update:03-01-2020
abstract:

1.3.1 General requirements for dimensioning of mold des […]

1.3.1 General requirements for dimensioning of mold design drawings
1) Units used for dimensioning: There are two types of dimensions in the mold diagram: metric and imperial. Among them, the United Kingdom, the United States, Canada, India, and Australia use the imperial system. I have used the metric system, but if the customer is from the above countries, then British system should be used. In addition, many standard parts in the mold (such as screws, push rods, etc.) are in English units, so when the mold is designed, even if other dimensions are metric, these standard parts are still dimensioned in English units.
2) Accuracy used when dimensioning.
Linear size: metric system uses two decimal places X.XXmm, inch system uses four decimal places X.XXXXin.
Angle: Use one decimal place: X.X °.
3) Dimension basis in the mold drawing.
a. Product (plastic) benchmark: The benchmark for customer product drawings. All the dimensions of the cavity and core are based on the plastic reference as the design reference. The core and cavity dimensions in the mold design diagram should correspond to the dimensions in the product diagram.
b. Mold assembly benchmark: Generally, the center of the mold base is used as the assembly benchmark. All screw holes, cooling water holes, and other dimensions related to the assembly of the mold base must be based on the design basis of the assembly.
c. Process benchmark: The benchmark determined according to the requirements of mold part processing and measurement, such as the countersink of the insert hole to the bottom surface as the benchmark.
The selection method of the die drawing size reference is as follows.
a. In the sectional view, take the parting plane as the reference and add the reference symbol at the same time, as shown in Figure 1-17. Sometimes the product engineer will require the plastic part drawing to be the benchmark. At this time, the plastic part reference coincides with the plastic part reference in the mold drawing.
b. In the plan view, the situation is more complicated and should be treated differently.
If the plastic part is symmetrical, use two center lines as the reference, and add the reference symbol at the same time.
If only one axis is symmetrical and the other axis is asymmetric, if there is a column position, the center of the column is used as the reference. If there is no column, use the longer straight line or straight edge as the reference.
If the two axes are not symmetrical, choose a column or straight edge as the reference.
Correct selection of the dimension datum is an important condition to ensure the design requirements of the part and facilitate the processing and measurement.
4) The dimensions of the same structure should be unified in different views. For example, the dimensions should be uniformly marked according to the big end. If necessary, the demolding angle should be marked together, such as 50 ± 3 °. The size of the rib (RIB) and the hole can be marked with the center size and width, depth, and diameter. The demolding angle is separately indicated.
5) The position and size of the pusher hole only need to be marked on the inner mold insert drawing, and it may not be marked on the pusher fixing plate and the template drawing, but the diameter of the pusher hole should be indicated.
6) CNC machining (CNC) parts do not need to be marked with all dimensions, only important benchmark data and inspection data can be marked.
7) The dimensions marked for moving and fixed inserts are: wire cutting; screws, cooling water holes; pusher holes; drop height of parting surface; shape matching dimensions, etc. For clarity, the above may be marked in one or more drawings.
8) The wire cutting size is only marked with the main dimensions. If the contour is complicated, the wire cutting part can be copied and printed separately, and it should be noted on the original drawing.
9) Non-standard mold bases must be marked with template-like screw holes, reset rods, guide posts, and other dimensions, as well as the NC detection size of the movable fixed mold frame, while the standard mold base is not marked. Column, reset lever and putter plate guide post).
10) When marking the processing position of the rib electrode, mark the center position of the electrode.
1.3.2 Dimension requirements for assembly drawings
1) The position chart is marked by coordinates, the center of the mold is the origin of the coordinates; the sectional view is marked by linear dimensions.
2) The assembly drawings mainly indicate the dimensions.
a. The size of the connection part of the injection molding machine;
b. The size of all parts that are not separately drawn (mainly the processing part of the mold base), but the standard hole position on the mold base may not be marked;
c. The position and size of each cavity, and try to take an integer;
d. the location of the gate and gate sleeve screws;
e. the size of the template and the size and position of the inner mold inserts;
f. The position and size of the lateral core pulling mechanism and its accessories;
g. the position and size of the positioning block;
h. Location, size and number of cooling water holes;
i.K.O hole diameter and location;
j. Length and size of the putter plate guide post and its guide sleeve;
k. the position and diameter of the props (S.P);
l. The diameter and length of the return spring, the spring hole needs to be marked with the depth and diameter, and the specifications of the spring;
m. the diameter and thickness of the stopper;
n. The position and length of the fixed parting parting mechanism in the three-plate mold and the two-plate half mold.
1.3.3 Dimensioning requirements for parts
1) Correct: Dimensioning shall comply with the basic requirements of the national standard "Mechanical Drawing".
2) Complete: Dimensioning must ensure that the production activities of the factory can be carried out smoothly.
3) Clarity: the size configuration should be unified and standardized, which is easy to look at the picture.
4) Reasonable: Dimensions should meet design and process requirements to ensure mold performance.
5) For parts with a slope, large and small should be marked next to the dimension to indicate the large and small end dimensions.
6) Basic requirements: The maximum external dimensions must be directly marked on the drawing. If a closed dimension chain is to be produced, parentheses may be placed on the largest dimensions.
7) The dimension should be marked as far as possible outside the view, so as not to intersect the dimension line and dimension figure with the outline of the view.
8) The diameter of the concentric cylinder is best marked on the non-circular view.
9) Dimensions that are parallel to each other should be sorted in order of size, with small sizes included and large sizes out, and their size numbers staggered.
10) Dimension lines should be arranged neatly, as far as possible on the same side, and related dimensions should preferably be arranged on a straight line. For densely sized areas, they should be enlarged to avoid misunderstanding.
11) The important positioning dimensions in the cavity, such as holes, ribs, slots, etc., must be marked directly from the datum.
12) All structures must have positioning and shaping dimensions. For the positioning dimensions of holes, ribs and slots, the centerline shall prevail.
13) When dimensioning the sectional view, for clarity, clarity and neatness, the internal and external dimensions shall be marked on both sides.
1.3.4 Dimension Design Example of Mold Design Drawing
1) Dimensioning example of mold assembly drawing
Due to the large dimensions to be marked in the assembly drawing, for the sake of clarity, in the actual working process, the main sectional views in the assembly drawing are not drawn with section lines.
2) Example of dimensioning of moving die B plate
The structure of the movable mold B plate includes: a mold frame, a cooling water channel, a screw hole, a push rod (push tube) hole, a reset rod hole, a hole of a fixed distance parting mechanism, and sometimes a side core pulling mechanism.
The X and Y directions are marked by coordinates, and the reference is the center line of the mold. The height dimension is linearly annotated, with the base of the template as the datum.
Different pusher vias are represented by different symbols, and their size and number are listed.
3) Example of dimensioning of fixed mold A plate
The marking method of A plate is the same as that of B plate.
4) Example of inner mold insert dimensioning
The insert diagram is usually divided into insert screw holes, cooling water circuit diagram and insert processing diagram. The shape of the insert is simple, and its screw holes, cooling water paths and processing drawings are reflected on the same drawing.
Notes on insert labeling:
a. The direction and reference angle should be accurately marked according to the side of the moving mold.
b. Use a minimum number of views to complete the drawing, and the size of a shape should be marked as clearly as possible on one view.
c. The penetrating and rubbing surfaces should be marked with text.
d. The parting surface is marked according to the position of the assembly drawing, the reference angle must be indicated, and the reference must be consistent with the assembly drawing.
e. The quenched insert should be marked with HRC value and roughing allowance.
f. In the technical requirements, indicate the mold release slope of the inner mold insert molding surface. For example, the mold release slope of the cavity is 1.5 °, and the dimension indicated is the size of the large head (end).
5) Example of slider dimensioning
The slider can be marked in the middle. The larger one can be used as a reference. The height direction is based on the bottom. The front with the plane is based on the front. The one without the front is based on the back.
All sliders need to be added on the top surface to facilitate the grinding machine to process fashion clips. The position of the process table should ensure the smooth clamping of the slider, and it should not interfere with other structures.

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