TIPOS DE DEFINICIONES

Now the designer has all the basic information about the mold to be built and can start to ®nalize the mold assembly drawing.

5.6.1 Machine Platen Layout

The platen layoutÐincluding tie bar locationsÐof the machine (or machines) the mold will be used on should be shown ®rst. This will determine the outer limits of the mold and where to place certain mold features. It will, for example, specify where coolant connections must not be located, or any planned auxiliary actuators outside the mold, latches, and so on. The mounting and ejector holes that will probably be used for the mold must also be shown.

5.6.2 Symmetry of Layout, Balancing of Clamp

For multicavity molds, it is important that the stacks are positioned such that the projected area of each cavity is as symmetrical as possible about the center of the machine, to ensure that all tie bars are loaded equally as the mold is clamped, thereby providing each cavity with the same preload to prevent ¯ashing. This can present a problem with ``family molds,'' where several different stacks or cavities with different projected areas are used in one mold. A small amount of asymmetry is often acceptable. With edge-gated, single-cavity molds, to balance the load, a pressure pad must be used opposite the stack location to simulate the force of a second cavity. In this case, the cavity itself will see only one-half of the clamping force of the machine. This is important for the selection of size of clamp, for the job. There is no such problem with center-gated, single-cavity molds.

5.6.3 The Views

Start with the signi®cant mold cross section or sections, but always work with all views at the same time; that is, both the plan views of cavity and core will ``grow'' side by side with the cross section. This prevents surprises arising when one view is far advanced and then it becomes apparent that it does not go together because another view shows some interferences. Show the selected hot runner hardware, if this is planned to be a hot runner mold. If it is a mold for which the hot runner section is purchased completely assembled by the supplier, show the interface points and dimensions only.

5.6.4 Completing the Assembly Drawing

Everything can now be shown in all views. It is not a good practice to show the complete stack in every location, even though it is easy to do with a CAD system. It would make it dif®cult to read the drawings, especially if there are many other features in the stack. To facilitate the reading of the drawing, the stack should be shown in only one location of each plan view, and just its outlines in all other locations, for example, with heavy, dotted lines. However, important information such as the centers of coolant connections, screws, alignment features, and so on should be identi®ed in all locations with small crosses and/or circles, which can then also be identi®ed with a code, such as S1, S2 for screws and D1, D2 for dowels. Such codes will make it easier to read the drawing; they will be also important when completing the cooling lines layout in the plates and the location of plate supports and large screws holding together the various mold plates, where applicable. Show now also the alignment features, the ejection system, the method of mold mounting and any connection (®xed or loose) with machine ejectors, and everything else needed by the detailers to produce the shop (detail) drawings.

At this time, show also where the outside of the mold must be marked (preferably die stamped) to identify coolant and air connections. There would be a 1 IN, 1 OUT, 2 IN, 2 OUT, and so on, and AIR 1, AIR 2, and so on. The IN and OUT can be important for cooling because in many cases it does make a difference where the cold coolant should go ®rst (IN). For example, in the core of a container mold, it should ®rst hit the area opposite the gate.

5.6.5 Bill of Materials (BoM) and ``Ballooning''

This is also the time to specify the BoM so that all materials can now be ordered and be available when required for the machining operations and the ®nal assembly. The BoM should specify not only the ®nal sizes of steels and so on, but also the hardness of the ®nished mold part. This is important not only for the buyer, but also for the detailer of the shop drawings.

``Ballooning'' is the identi®cation of each mold part on the assembly drawing. Several methods are used, but the preferred one is to show balloons (circles or ellipses about 12±15 mm in size) outside around the drawings. Each balloon contains a number identifying each mold component, but only once, from stack parts to plates to screws, and so on. This number corresponds to a line in the BoM. Each balloon has a leader (line) connecting it with the part identi®ed. Preferably, the balloons should be shown around the main cross section of the mold or near partial sections; only if these locations would not be clear enough and could cause errors should they be shown in other sections or in the appropriate plan view.

5.6.6 Finishing Touches

Finishing information of the molding surfaces should also be shownÐ preferably with standard symbolsÐon the assembly drawing, for future reference, and to be used by the detailer when making the shop drawings. Cross hatching should be used sparingly, only where it really helps to make the assembly drawing clearer. This also applies to detail drawings. This is also the time to show any notes on the drawing. (See also Section 5.2.2.4)

Usually one ``main'' title block is shown, preferably on the drawing with the main cross section; additional, smaller title blocks are on all other drawings. The title blocks identify the mold design of®ce or the mold maker, the project number and drawing numbers, the designer (by name and initials), the checker, and the detailer, if applicable. It will also show any other information pertinent to the product and will specify for which machines the mold was designed, the types of plastic, and any other information that deserves to be recorded for future use. Tolerances are not shown on the assembly drawings. They are strictly limited to the detail drawings. However, it is a good practice to show ®ts and clearances where they apply, but only if they are different from standard ®ts and clearances.