Drawing method of mold assembly drawing must have a firm foundation!

Time:2021-05-27 11:47:02 / Popularity: / Source:

Main purpose of mold assembly drawing is to reflect basic structure of mold and express mutual assembly relationship between parts, including position relationship and cooperation relationship.
For this purpose, most basic requirements that a mold assembly drawing must meet are:
First of all, each part (or component) in mold assembly drawing cannot be omitted, no matter which mold part, assembly drawing should be expressed;
Second, position of each part in mold assembly drawing and assembly relationship with other parts should be clear. In mold assembly drawing, in addition to sufficient projection diagrams explaining mold structure, necessary cross-sectional views, cross-sectional diagrams, technical requirements, title columns and detailed columns for filling in each part, there should also be other special expression requirements.
Drawing requirements of mold assembly drawing must meet national drawing standards, which are summarized as follows:

⑴ Layout and proportion of final assembly drawing.

① Relevant regulations on size and format of drawings in national standard mechanical drawings (GB/T14689-2008) shall be followed.
② Drawing can be done according to drawing method customary or specially specified in mold design.
③ Try to draw at a ratio of 1:1, if necessary, zoom according to ratio required by mechanical drawing, but size is marked according to actual size.
④ Layout method of mold assembly drawing is shown in Figure 1-72.
mold assembly drawing 
(a) Layout of general assembly drawing of stamping die (b) Layout of general assembly drawing of plastic mold
Figure 1-72 Layout method of mold assembly drawing

⑵ Mold design drawing sequence

① Main view. When drawing general assembly drawing, a stepped section or a rotating section should be used to try to make each type of mold part reflected in main view. Draw first from inside to outside, from top to bottom, that is, draw in the order of product parts drawing, punch and die. If there are too many parts, only half of drawing is allowed. When it is impossible to draw all of them, you can draw in left view or top view .
② Top view. "Open" upper (fixed) mold along punching or injection direction, and look at "opened" upper (fixed) mold or lower (moving) mold from top to bottom along punching or injection direction, and draw a top view. Main and top views should be drawn one by one.
③ Left and right view. When main and top views are not clear about assembly relationship, or when plastic mold is in horizontal position, left and right views are drawn to "open" fixed mold according to injection direction to see structure of movable mold.

⑶ Requirements for main view of mold assembly drawing

① Before drawing main view, you should first estimate approximate length and width of entire main view, and then select an appropriate ratio for drawing. After main view is drawn, there should generally be a gap of 50-60mm between its surroundings and other views or outer frame lines.
② All parts of mold should be drawn as far as possible on main view, full section view, half section view or partial view can be used. If there are parts that cannot be expressed clearly, other views can be added.
③ When cutting solid rotating parts such as round punches, guide posts, ejector blocks, bolts (screws) and pins in cross-sectional view, cross-section is not drawn; sometimes for clarity of drawing structure, punch of non-rotating body may not be drawn with hatching.
④ Drawn mold should generally be in closed state, as shown in Figure 1-75, or close to closed state, or half of it can be in closed working state and the other half in non-closed state.
⑤ Only one contour line should be drawn on contact surface or mating surface of two adjacent parts; non-contact surface or non-matching surface of two adjacent parts (different basic dimensions) should be drawn with two contour lines regardless of gap size. Indicates that there is a gap. When adjacent parts are sectioned, incline direction of section line should be opposite; when several adjacent parts are sectioned, they can be distinguished by methods such as interval (density) of section lines, oblique direction or staggering. But on same drawing, direction and interval of section line of same part in different views should be same.
⑥ Part of process structure of parts on die assembly drawing, such as chamfers, fillets, undercuts, pits, bosses, knurling, engraved lines and other details are not drawn. Line segments caused by chamfering of bolts, nuts, pins, etc. can be omitted. For connection of same component group, such as bolts, screws, and pins, it is allowed to draw only one or a few places, and the rest can be indicated by dot-dash lines.
⑦ When section thickness of part on mold assembly drawing is less than 2 mm, it is allowed to replace section line with black, such as washers in mold, stamping sheet metal parts and blanks.
⑧ How to draw spring on assembly drawing. Structure blocked by spring does not need to be drawn. Visible part of outline only needs to draw center of spring wire section or outline of spring outer diameter, as shown in Figure 1-73(a). Section of spring whose diameter is less than or equal to 2mm in the figure can be painted in black, or can be drawn with a schematic diagram, as shown in Figure 1-73(b) and (c).
mold assembly drawingmold assembly drawingmold assembly drawing 
(a) Structure blocked by spring is not drawn (b) Schematic drawing of spring (c) Spring section is painted black
Figure 1-73 Prescribed drawing method of spiral compression spring in mold assembly drawing
Spring can also be drawn in a simplified way, that is, outline of two-dot chain line, and crossed two-dot chain line in the middle, as shown in Figure 1-74.

⑷ Requirements for top view of mold assembly drawing

Top view generally only draws lower (moving) mold. For molds with symmetrical structure, half of upper (fixed) and lower (moving) molds can also be drawn. If necessary, a side view or other views can be drawn.
When drawing top view of mold structure, structure shape after removing upper mold part should be drawn. Focus is to reflect working parts installed in lower mold part. There should also be a gap of 50-60mm between top view and frame, main view, title bar or parts list.
mold assembly drawing 
Figure 1-74 Simplified drawing of spring

⑸ Drawing method of lead line of serial number

Count out number of parts in mold before drawing lead line of serial number, and then make overall planning
Task 1 Blanking progressive die
mold assembly drawing 
Figure 1-75 Assembly drawing of punching and blanking progressive die for compression spring
Serial number should generally be set in sequence with direction of clockwise rotation with main view as center. Generally, serial number is not marked on the left, position for marking closing height and tolerance is left blank. In mold assembly drawing shown in Fig. 1-75, before drawing lead line of serial number, count 27 parts in whole mold. Therefore, designer considers to arrange 9 serial numbers on the top, 9 serial numbers on the right and 9 serial numbers on the bottom. According to above arrangement, 27 short horizontal lines are drawn at equal intervals, and finally part is drawn from mold to serial number leading line between short horizontal lines.
According to drawing steps of "counting number of parts→arranging position of serial number→drawing dashes→drawing serial number lead line", all lead lines of serial number can be arranged neatly with equal spacing, and phenomenon of "overlapping and crossing" that often occurs when beginners draw lead-out lines of serial number can be avoided.
Of course, if serial number is also to be drawn on the top view (Figure 1-75), you can also draw the leading line in a clockwise order and mark the serial number. The notation requirements are as follows:
① Font size of serial number should be one or two larger than size figure on drawing. Generally, a guide line is drawn from outline of part to be injected with a thin solid line, a circle is drawn at one end of part, and a horizontal thin solid line is drawn at the other end.
② Write serial number directly on horizontal thin solid line.
③ Draw guiding lines not to cross each other or parallel to section line.

⑹ Selection of profile

As shown in Figure 1-75, selection of cross section of upper mold part of mold should focus on fixation of punch, shape of cavity of female mold, assembly relationship between mold plates (that is, installation of screws and pins), installation relationship between mold handle and upper mold seat, assembly relationship of punching system composed of punching rods, punching plates, ejector rods and push blocks. Above-mentioned key points should be used as much as possible in full section or half section, some other assembly relations can be drawn with dashed lines or omitted, and can be expressed in other views (such as top view).
Selection of section of lower part of mold should focus on installation relationship of male and female molds, shape of hole of male and female molds, installation relationship between mold plates (that is, how to install screws and pins), shape of leakage hole, etc. These places should be considered as complete as possible, and other non-critical areas should be simplified as much as possible.
In Figure 1-75, upper mold part is fully sectioned for fixing of punch, shape of hole of female mold, connection between mold handle and upper mold seat, installation of screws and pins (pins and fastening screws are arranged on the left, discharging screws and springs are arranged on the right), dashed line and partial sectional view are used to express assembly situation of initial stopper pin.

⑺ How to draw screws and pins. Pay attention to following points when drawing screws and pins.

① Size of each part of screw must be drawn correctly. Approximate drawing method of screw is: if diameter of thread part is D, diameter of screw head is drawn as 1.5D, and depth of countersunk head of hexagon socket screw should be D+1~3mm; when both pin and screw are used, pin diameter should be same as screw diameter or one size smaller (that is, if M8 screw is used, pin should be Ф8mm or Ф6mm).
② Be careful not to miss lines when drawing screw connections. Taking screw 3 in Fig. 1-75 as an example, screw is only threadedly connected with punch fixing plate 10 at tail, screw passing through backing plate 9 and upper die seat 1 should be through holes.
③ Be careful not to miss lines when drawing pin connections. Taking pin 4 in Figs. 1-75 as an example, through-hole punch fixing plate 10 and upper mold base 1 through which pin passes need to be positioned with a pin, while backing plate 9 does not need to be positioned with pin 4, so it should be a through hole.

⑻ Drawing method of workpiece diagram

① Workpiece drawing is a drawing of a stamping or plastic part obtained by stamping or molding. As shown in Figure 1-75, it is usually drawn in upper right corner of assembly drawing, name, thickness and necessary dimensions of material are stated; For products that cannot be completed in one process, process should be drawn on assembly drawing, and dimensions related to this process should also be marked.
② Scale of workpiece drawing is generally same as that on mold drawing, and it can be reduced or enlarged under special circumstances. Direction of workpiece drawing should be consistent with stamping direction or molding direction (that is, consistent with position of workpiece in mold). If it is inconsistent under special circumstances, an arrow must be used to indicate stamping or molding direction.

⑼ Layout drawing in assembly drawing of stamping die

① When using strips and strips, a layout drawing should be drawn, usually under workpiece drawing in upper right corner of assembly drawing or between top view and parts list.
② Layout drawing should include layout method, blanking process of parts, distance setting method (shape and position of side edge when side edge is used to fix distance), material utilization, step distance, overlap, material width and tolerance. Direction of material fiber should be considered in parts of bending and crimping process. Usually it can be seen from cut line of layout drawing whether it is a single process die, a compound die or a progressive die.
③ Feeding direction on layout drawing must be consistent with feeding direction on mold structure drawing to make it clear to other readers. As shown in Figure 1-75.

⑽ Technical requirements for mold assembly drawings

In final assembly drawing, requirements, precautions and technical requirements of mold should be indicated briefly. Technical requirements include type of equipment used, closing height of mold, and mold printing marks, assembly requirements, etc. Blanking die should also indicate mold gap. Sometimes drawing code marked in upper left corner is compiled by company in conjunction with product model, which is convenient for use and management of drawing.

⑾ Dimensions that should be marked on mold assembly drawing

There are mold closing height, external dimensions, characteristic dimensions (positioning dimensions matched with forming equipment), assembly dimensions (center distance of screw holes installed on forming equipment), limit dimensions (distance between starting positions of movable parts).

⑿ Title bar and detail bar

① Title bar and detail bar are in lower right corner of assembly drawing. If drawing size is not enough, you can create another page. Format of title bar and detail bar is shown in lower right corner of Figure 1-75.
② Detail column should have at least serial number, drawing number, part name, code number, quantity, material and remarks, etc.
③ When filling in part name column, first and last characters of name should be aligned, and words in the middle should be inserted evenly, or left aligned.
④ When filling in drawing number column, drawing numbers of all parts drawings should be given. Digital serial number should generally be programmed in sequence with main view screen as center and in the direction of clockwise rotation as serial number. As mold assembly drawing is generally counted as drawing number 00, part drawing number in detail column should start counting from 01. Parts without part drawings have no drawing numbers.
⑤ Remarks column mainly describes specifications, heat treatment, outsourcing or outsourcing of standard parts. Generally, no other content is noted.
⑥ Main contents in title bar include mold name, drawing scale and signature. Rest of content can be left blank.
After mold assembly drawing is completed, it is necessary to review whether relationship between closed height of mold, diameter of leakage hole, diameter and height of mold handle, height of rod, shape of lower mold base and relevant technical parameters of press is correct. This case is confirmed to meet parameter requirements of J23-16F press after review.

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