This article discusses technologies focused on processing plastic materials or producing direct tools used in plastics processing. The article focuses on extrusion and injection molding, covering applications, materials and their properties, equipment, processing details, part design guidelines, and special processes. It also covers the functions of the extruder, webline handling, mixing and compounding operations, and process troubleshooting. Thermoforming and mold design are covered. Various other technologies for polymer processing covered in this article are blow molding, rotational molding, compression molding, transfer molding, hand lay-up process, casting, and additive manufacturing.

This article discusses failure mechanisms in tool and die materials that are very important to nearly all manufacturing processes. It is primarily devoted to failures of tool steels used in cold working and hot working applications. The processes involved in the analysis of tool and die failures are also covered. In addition, the article focuses on a number of factors that are responsible for tool and die failures, including mechanical design, grade selection, steel quality, machining processes, heat treatment operation, and tool and die setup.

A forging die in a 250-ton press producing brass valves began to show signs of fatigue after a few thousand hits. By the time it reached 30,000 hits, the die was badly damaged and was submitted for analysis along with one of the last forgings produced. The investigation included visual and macroscopic inspection, metallographic and chemical analysis, SEM imaging, optical profilometry, mechanical property testing, and EDX analysis. The die was made of chromium hot-work tool steel and the forgings were made of CuZn39Pb3 heated to an initial working temperature 700 deg C. The entire surface of the die was covered with fatigue cracks and many fillets had been plastically deformed. Several other types of damage were also observed, including areas of oxidation, corrosion pits, voids, abrasive wear, die adhesion, and thermal fatigue. Fatigue cracking was the primary cause of failure with significant contributions from the other damage mechanisms.

Several failed dies were analyzed and the results were used to evaluate fatigue damage models that have been developed to predict die life and aid in design and process optimization. The dies used in the investigation were made of H13 steels and fractured during the hot extrusion of Al-6063 billet material. They were examined to identify critical fatigue failure locations, determine corresponding stresses and strains, and uncover correlations with process parameters, design features, and life cycle data. The fatigue damage models are based on Morrow’s stress and strain-life models for flat extrusion die and account for bearing length, fillet radius, temperature, and strain rate. They were shown to provide useful information for the analysis and prevention of die failures.

A broken cross-recessed die was examined. Examination of the unetched, polished section for impurities revealed several coarse streaks of slag. The purity did not therefore correspond to the requirements set for a high speed tool steel of the given theoretical quality DMo 5. After etching with 5% nital the polished surface exhibited a pronounced, easily-visible, fibrous structure. Microscopic examination revealed that this etch pattern was produced by marked segregation bands. The very unfavorable structure for a high speed steel tool of these dimensions and subject to such stresses together with the low purity favored the fracture of the tool.

A cross-recessed die of D5 tool steel fractured in service. The die face was found to be subjected to shear and tensile stresses as a result of the forging pressures from the material being worked. The presence of numerous slag stringers was revealed by microscopic examination of an unetched longitudinal section taken through the die. The pattern was microscopically revealed after etching with 5 % nital to be due to severe chemical segregation or banding. Considerable variation in the hardness, corresponding to the banded and non-banded regions across the face of the specimen was observed. The fracture was found to have originated near the high-stress region of the die face examination of the fracture surface. Failure of the die was concluded to have originated in an area of abnormally high hardness which is prone to microcracking during heat treatment for this grade of tool steel

This article describes the characteristics of tools and dies and the causes of their failures. It discusses the failure mechanisms in tool and die materials that are important to nearly all manufacturing processes, but is primarily devoted to failures of tool steels used in cold-working and hot-working applications. It reviews problems introduced during mechanical design, materials selection, machining, heat treating, finish grinding, and tool and die operation. The brittle fracture of rehardened high-speed steels is also considered. Finally, failures due to seams or laps, unconsolidated interiors, and carbide segregation and poor carbide morphology are reviewed with illustrations.

This article describes the six fundamental factors that decide a tool's performance. These are mechanical design, grade of tool steel, machining procedure, heat treatment, grinding, and handling. A deficiency in any one of the factors can lead to a tool and die failure. The article presents a seven-step procedure to be followed when looking for the reason for a failure. A review of the results of the seven-point investigation may lead directly to the source of failure or narrow the field of investigation to permit the use of special tests.

Two 38 mm (1.5 in.) diam threaded stud bolts that were part of a steel mold die assembly from a plastics molding operation were examined to determine their serviceability. Chemical analysis showed the material to be a plain carbon steel that approximated 1045. Visual examination revealed evidence of severe hammer blows to the clevis and boss areas and a gap between the die and the underside of the boss. Magnetic particle inspection showed cracks at the thread roots that, when examined metallographically, were found to contain MnS stringers. The cracking of the threads was attributed to a poor stud bolt design, which allowed a high stress concentration to occur at the base of the threads upon application of a lateral load. It was recommended that bolts of a new design that incorporated a stress-relieving groove be used. Threading of the bolt to eliminate the gap between the lower face of the boss and the die and an improved method of inserting or removing the bolt to avoid hammering (use of a wrench on a square or hexagonal boss) were also recommended.

Compound bow handle risers that had failed in service and during assembly along with an unassembled riser were submitted for analysis. The risers were die cast from magnesium-base alloy AM60A. Inspection of the failed risers and metallurgical investigations conducted on the stock riser revealed the presence of cold shuts at the same site in all specimens. It was recommended that all risers be thoroughly inspected and that the bow company work with their die casting shop to design a mold with acceptable filling characteristics.

A segment from a premium-quality H13 tool steel die for die casting of aluminum failed after only 700 shots. The segment was subjected to visual, macroscopic, hardness, and metallographic testing. The investigation revealed that failure occurred as a result of fatigue at an electrical-discharge-machined surface where the resulting rehardened layer had not been removed. This rehardened layer had cracked, providing a source for fatigue initiation.

An AISI D2 tool steel insert from a forming die used in the manufacture of automotive components failed prematurely during production. Results of various analyses and simulation tests indicated fatigue failure resulting from improper heat treatment. The fatigue fracture originated because of a highly stressed condition produced by a sharp corner combined with low toughness from ineffective tempering. It was recommended that 25 other inserts that belonged to the same die be double tempered.