A moldmaker (mouldmaker in British English) or molder is a skilled trades worker who makes molds for use in metalworking and other manufacturing industries. It is sometimes regarded as a variety of the trade of the toolmaker.
Moldmakers are generally employed in foundries, where molds are used to cast products from metals such as aluminium and cast iron. Moldmakers may also be employed in the plastics, rubber or ceramics industries. The process of manufacturing molds is now often highly automated.
While much of the machining processes involved in mold making use computer-controlled equipment for the actual manufacturing of molds (particularly plastic and rubber injection and transfer). Moldmaking is still a highly skilled trade requiring expertise in manual machining, CNC machining, CNC wire EDM, CNC Ram EDM, surface grinding, hand polishing and more. Because of the high skill and intense labor involved much of the mold making in the US has been outsourced to low wage countries. The majority of plastic and rubber parts that are in existence today are made using injection or transfer molds- requiring a mold to be manufactured by a moldmaker. The actual molding process is very highly automated.
Molding or moulding (see spelling differences) is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have been made using a pattern or model of the final object.
A mold or mould is a hollowed-out block that is filled with a liquid or pliable material such as plastic, glass, metal, or ceramic raw material. The liquid hardens or sets inside the mold, adopting its shape. A mold is the counterpart to a cast. The very common bi-valve molding process uses two molds, one for each half of the object. Articulated moulds have multiple pieces that come together to form the complete mold, and then disassemble to release the finished casting; they are expensive, but necessary when the casting shape has complex overhangs.Piece-molding uses a number of different molds, each creating a section of a complicated object. This is generally only used for larger and more valuable objects.
A manufacturer who makes molds is called a moldmaker. A release agent is typically used to make removal of the hardened/set substance from the mold easily. Typical uses for molded plastics include molded furniture, molded household goods, molded cases, and structural materials.
A plastic forming machine, or plastic molding machine, is developed on the basis of rubber machinery and metal die-casting machine. Since the polymer injection molding process and molding equipment in the 1870s, as an industry, plastic forming machines were rapidly developed until the 1930s, with the gradual commercialization of plastic molding equipment, injection molding and extrusion molding became the most common industrialized processing methods. Blow molding is the third-largest plastic molding method after the injection molding and extrusion blow molding method, it is also the fastest development of plastic molding method.
Forming the parison firstly, with compressed air (and tensile rod) to the radial Inflation (axial stretch) type blank, to make it close to (stretch) the blow molding cavity, then the cavity shape and size are given to the plastic products and make it cool.
Types of plastic forming machine
Plastic injection molding machine is called usually injection molding machine for short,using the injection and molding method. Plastic injection molding of thermoplastics and thermosetting plastics made from a variety of plastic products molding equipment.
To plastic extrusion machine, plastic extruder is usually called the host, and its follow-up equipments are called the plastic auxiliary equipments. With about 100 years of development, plastic extruder derived from single screw to twin-screw, multi screw or no screw and other models. Plastic extruder (the host) can match with the pipe, film, holding materials, monofilament, flat, packing tape, crowded network, plate (sheet) material, profile, granulation, cable coating and other kinds of plastic molding auxiliary equipment, composed of a variety of plastic extrusion production lines, to produce various plastic products. Therefore, either now or in the future, plastic extrusion machine are used widely in plastics processing industry.
Plastic blow molding machine is also called blow molding machine for short. The process of blow molding has two basic steps.
Plastics extrusion commonly uses plastic chips or pellets, which are usually dried, to drive out moisture, in a hopper before going to the feed screw. The polymer resin is heated to molten state by a combination of heating elements and shear heating from the extrusion screw. The screw, or screws as the case with twin screw extrusion, forces the resin through a die, forming the resin into the desired shape. The extrudate is cooled and solidified as it is pulled through the die or water tank.
A “caterpillar haul-off” (called a “puller” in the US) is used to provide tension on the extrusion line which is essential for overall quality of the extrudate. Pelletizers can also create this tension while pulling extruded strands in to be cut. The caterpillar haul-off must provide a consistent pull; otherwise, variation in cut lengths or distorted product will result. In some cases (such as fibre-reinforced tubes) the extrudate is pulled through a very long die, in a process called “pultrusion”. The configuration of the interior screws are a driving force dependent on the application.
Mixing elements or convey elements are used in various formations. Extrusion is common in the application of adding colorant to molten plastic thus creating specific custom color.
A multitude of polymers are used in the production of plastic tubing, pipes, rods, rails, seals, and sheets or films.
Type:Blown film extrusion;Sheet/film extrusion;Tubing extrusion;Over jacketing extrusion;Coextrusion;Extrusion coating
A great advantage of extrusion is that profiles such as pipes can be made to any length. If the material is sufficiently flexible, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal.
Engineering plastics are a group of plastic materials that have better mechanical and/or thermal properties than the more widely used commodity plastics (such as polystyrene, PVC, polypropylene and polyethylene).
Being more expensive, engineering plastics are produced in lower quantities and tend to be used for smaller objects or low-volume applications (such as mechanical parts), rather than for bulk and high-volume ends (like containers and packaging).
The term usually refers to thermoplastic materials rather than thermosetting ones. Examples of engineering plastics include acrylonitrile butadiene styrene (ABS), used for car bumpers, dashboard trim and Lego bricks; polycarbonates, used in motorcycle helmets; and polyamides (nylons), used for skis and ski boots.
Engineering plastics have gradually replaced traditional engineering materials such as wood or metal in many applications. Besides equalling or surpassing them in weight/strength and other properties, engineering plastics are much easier to manufacture, especially in complicated shapes.
Each engineering plastic usually has a unique combination of properties that may make it the material of choice for some application. For example, polycarbonates are highly resistant to impact, while polyamides are highly resistant to abrasion. Other properties exhibited by various grades of engineering plastics include heat resistance, mechanical strength, rigidity, chemical stability, self lubrication (specially used in manufacturing of gears & skids) and fire safety.
Screw theory is the algebra and calculus of pairs of vectors, such as forces and moments and angular and linear velocity, that arise in the kinematics and dynamics of rigid bodies. The mathematical framework was developed by Sir Robert Stawell Ball in 1876 for application in kinematics and statics of mechanisms (rigid body mechanics).
Screw theory provides a mathematical formulation for the geometry of lines which is central to rigid body dynamics, where lines form the screw axes of spatial movement and the lines of action of forces. The pair of vectors that form the Plücker coordinates of a line define a unit screw, and general screws are obtained by multiplication by a pair of real numbers and addition of vectors.
An important result of screw theory is that geometric calculations for points using vectors have parallel geometric calculations for lines obtained by replacing vectors with screws. This is termed the transfer principle.
Screw theory has become an important tool in robot mechanics, mechanical design, computational geometry and multibody dynamics. This is in part because of the relationship between screws and dual quaternions which have been used to interpolate rigid-body motions. Based on screw theory, an efficient approach has also been developed for the type synthesis of parallel mechanisms (parallel manipulators or parallel robots).
A spatial displacement of a rigid body can be defined by a rotation about a line and a translation along the same line, called a screw displacement. This is known as Chasles’ theorem. The six parameters that define a screw displacement are the four independent components of the Plücker vector that defines the screw axis, together with the rotation angle about and linear slide along this line, and form a pair of vectors called a screw. For comparison, the six parameters that define a spatial displacement can also be given by three Euler Angles that define the rotation and the three components of the translation vector.
A screw is a six-dimensional vector constructed from a pair of three-dimensional vectors, such as forces and torques and linear and angular velocity, that arise in the study of spatial rigid body movement. The components of the screw define the Plücker coordinates of a line in space and the magnitudes of the vector along the line and moment about this line.
A machinist is a person who machines using hand tools and machine tools to prototype, fabricate or make modifications to a part that is made of metal, plastics, or wood.
Related occupational titles
A traditional machinist is one who can: operate a machine tool, disassemble and repair the machine tool by building new parts such as gears, splines, and shafts from scratch using various machine tools such as mills, lathes, grinders, planers, etc. Then reassemble the machine tool and operate it.
Under the machinist title are other specialty titles that refer to specific skills that may be more highly developed to meet the needs of a particular job position, such as fitter (assembles parts), turning hand, mill hand, and grinder. Some titles reflect further development of machinist skills such as tool and die maker, patternmaker, mold maker, programmer, and operator[disambiguation needed]. Depending on the company, a machinist can be any or all of the titles listed above. A machinist is one who is called on to fix a problem with a part or to create a new one using metal working, plastic, or in some cases, wood.
Role in manufacturing
A machinist is usually called upon when a part needs to be produced from a material by cutting. Such a part may be unique or may be needed in the thousands. This could include a machinery part for a production line or anything that can be made from metal or plastic. Producing a part will often require several steps and more than one machine tool. Each machine tool plays a specific role in cutting away excess material. When large numbers of parts are needed, production planning is required to plan the most logical workflow through a series of machines. Computer numerical controlled (CNC) machines are a special computer-driven tool that can machine a large variety of shapes, and whose use in the workflow depends on the part to be machined.
CNC machines are becoming the standard due to their speed, precision, flexibility, and reduced downtime while changing jobs. Production runs consisting of large numbers of parts are more cost effective and commonly referred to as production work in the trade. Conversely, small production runs are sometimes referred to as prototype or jobbing work.
Production engineers use blueprints and engineering drawings to produce detailed specifications of the part, especially its geometry (shape), then decide on a strategy to make it. Machine tools are then configured by the machinist or toolset and production commences. The machinist works with the quality department to ensure the specifications are maintained in the finished product.
Large commercial organizations often staff machinists on site in a maintenance mode to ensure continuing operations of the production machinery. The labor cost for this role is significantly lower than costs involved with production shutdowns.
Skiving or scarfing machines cut material off in slices, usually metal, but also leather or laminates. The process is used instead of rolling the material to shape when the material must not be work hardened, or must not shed minute slivers of metal later which is common in cold rolling processes.
The skiving process, meaning “to slice”, can be applied to a variety of applications and materials. In leather, skiving knives trim the thickness of the leather, often around the edges, to thin the material and make it easier to work with. In metal working, skiving can be used to remove a thin dimension of material or to create thin slices in an existing material, such as heat sinks where a large amount of surface area is required relative to the volume of the piece of metal.
The process involves moving the strip past precision-profiled slotted tools made to an exact shape, or past plain cutting tools. The tools are all usually made of tungsten carbide-based compounds. In early machines, it was necessary to precisely position the strip relative to the cutting tools, but newer machines use a floating suspension technology which enables tools to locate by material contact. This allows mutual initial positioning differences up to approximately 12 mm (0.47 in) followed by resilient automatic engagement. Products using this technology directly are automotive seatbelt springs, large power transformer winding strip, rotogravure plates, cable and hose clamps, gas tank straps, and window counterbalance springs. Products using the process indirectly are tubes and pipe mills where the edge of the strip is accurately beveled prior to being folded into tubular form and seam welded. The finished edges enable pinhole free welds.
For lines which use low speed welding processes, such as laser welding, the skiving tools cannot normally cut – for example at speeds below metal planing speeds or about 10 meters/minute (33 feet/minute). In these cases the tools can be vibrated at high frequency to artificially increase the relative speed between the tools and strip.
Another metal skiving application is for hydraulic cylinders, where a round and smooth cylinder inside is required for proper actuation. Several skiving knives on a round tool pass through a bore to create a perfectly round hole. Often, a second operation of roller burnishing follows to cold-work the surface for mirror-finish. This process is common among manufacturers of hydraulic and pneumatic cylinders.
Skiving can be applied to gear cutting, where internal gears are skived with a rotary cutter (rather than shaped or broached) in a process analogous to the hobbing of external gears.
Skiving is also used for the manufacturing of heat sinks for PC cooling products. A PC cooler created with the use of skiving has the benefit that the heat sink base and the heat sink fins are created from one piece of material (copper or aluminum). This provides optimal dissipation and transfer of the heat from the base to the fins. Additionally, the skiving process also increases the roughness of the heat-sink’s fins. Unlike the underside of a heat-sink which needs to be smooth for maximum surface area contact with the heat-source that it cools, the fins benefit from this roughness because it increases the fins’ surface area which serves to provide more area on which to release heat into the ambient environment.