Raised Lettering

Articles of circular cross section may be made in iron paste molds. To keep the inner surface of the paste mold moist, it is coated with shellac or varnish and a mixture of charcoal and linseed oil is baked on. Hot iron molds ate used for ware of any shape, particularly for screw threading, multiple decoration, or raised lettering. 

Typically, ozone cracking initiates at sites of high stress (flaws) on the mbber surface. Thus, in general, mbber articles should be designed to rninirnize potential sites of high elongation such as raised lettering. Similarly, the use of clean molds helps to reduce the incidence of surface flaws. 

Flue-tiles, which are necessarily hollow, almost die in a low sunk relief, the raised letters being on a ... 

Many disposable glass laboratory items are made of soft glass. If a laboratory glass item does not specifically bear one of the words Pyrex , Kimax , or Duran in printed or raised letters, it is likely to be a soda-lime type of glass. 

There is no question that if the thing were reduced by 25,000 times in the form of raised letters on the pin, it would be easy for us to read it today. Furthermore there is no question that we would find it easy to make copies of the master we would just need to press the same metal plate again into plastic and we would have another copy. 

Although not really covered on the A+ exam, the first type of impact printer we re going to discuss is the daisy-wheel printer. These printers contain a wheel (called the daisy wheel because it looks like a daisy) with raised letters and symbols on each petal (see Figure 7.1). When the printer needs to print a character, it sends a signal to the mechanism that contains the wheel. This mechanism is called the printhead. The printhead rotates the daisy wheel until the required character is in place. An electromechanical hammer (called a solenoid) then strikes the back of the petal containing the character. The character pushes up against an inked ribbon that ultimately strikes the paper, making the impression of the requested character. 

Which printer contains a wheel that looks like a petal with raised letters and symbols on each petal ... 

Raised lettering is simple to cut into a metal mold or die depressed lettering will cost considerably more. 

As a closed-mold process, both surfaces of compression-molded parts can be finished. Draft for long-fiber compression-molded parts should be 3° per side, but less can be used for depths under 6 in—down to 1° per side in extreme cases. Molded-in holes are feasible in the plane of the parting line as are bosses, corrugated sections, molded-in labels, and raised lettering. Molded-in holes within a two-diameter distance from the outside edge of the part will need to be drilled as a secondary operation. The solid material thickness between two holes should not be less than one diameter (the largest). Core pulls, slides, split molds (for external undercuts), and metal inserts are recommended only for the SMC and BMC varieties. 

Reaction injection molding creates its own resin by mixing two highly reactive liquid components which react with each other by high-pressure impingement. The reaction is completed shortly after the resin is injected into the mold. This is accomplished at a pressure of 100 Ib/in, which permits the use of electro-formed and vapor-formed nickel lined epoxy, aluminum, and kirksite tools at a considerably reduced tooling cost. (Machined and plated cast steel molds can also be used.) As a closed-mold process, both sides of the part are finished and can have textures, raised numbers, and raised letters, but molded-in labels are not feasible. The finished part can be trimmed in the mold. 

A raised letter is visible only if it is at least 3 mil high. Letters that are over 30 mil high should be tapered and have fillets at the base. Raised letters can be decorated or painted by roll coating. With depressed letters, the surface of the part is spray painted and the excess wiped away, leaving paint in the recess. 

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