Mold Design. Note. 13. Mold Manufacturing Techniques. Bong-Kee Lee School of Mechanical Engineering Chonnam National University.

Transcription

1 13. Mold Bong-Kee Lee Chonnam National University Note

2 material removing methods machining electrical discharge machining (EDM) electro chemical machining (ECM) electro chemical and chemical etchings laser machining other methods casting rapid prototyping (or rapid tooling) hobbing heat treatment/surface treatment Machining (geometrically defined) turning, milling, drilling, sawing (geometrically undefined) grinding, honing, lapping multiaxial CNC controls and highly accurate positioning systems higher accuracy and greater efficiency three-axis milling, three-plus-two-axis milling, five-axis milling high-speed cutting (HSC): can be carried out as a complete machining without any efforts of electrode manufacturing and eroding & can achieve better surface quality, resulting in a drastic reduction in manual postmachining residual stress causing distortion annealing surface finishing

3 Machining 5-axis milling high-speed cutting ultra high-speed cutting Machining gun drill straight fluted drill which allows cutting fluid (either compressed air or a suitable liquid) to be injected through the drill s hollow body to the cutting face for deep drilling: a depth-to-diameter ratio of 300:1 or more

4 Electrical Discharge Machining (EDM) sometimes referred to as spark machining, spark eroding, burning, die sinking or wire erosion material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes (tool and workpiece), separated by a dielectric liquid subject to an electric voltage breakdown voltage Electrical Discharge Machining (EDM) wire EDM: EDM drilling, cutting sinker EDM

5 Electro Chemical Machining (ECM) metal removing method by an electrochemical process reverse electroplating most widely used (i) to produce complicated shapes such as turbine blades with good surface finish and (ii) as a deburring process drawbacks: equipment is expensive, cost- and timeconsuming fabrication of anodes only suitable for larger series of the same configuration Electro Chemical and Chemical Etchings surface texturing for cosmetic reasons, for obtaining a more scratch and wear resistant surface or a better hand based on the solubility of metals in acids, based and salt solutions for selective etching, masking techniques like screen (or silk) printing, photochemical means, and so on

6 Electro Chemical and Chemical Etchings photochemical etching dip and spray chemical etching Electro Chemical and Chemical Etchings LGP(light guide panel) in LCD BLU LED BLU LCD BLU(back light unit) glass LGP

7 Laser Machining Laser(light amplification by stimulated emission of radiation): a coherent and amplified beam of electromagnetic radiation photons of same frequency, wavelength and phase highly directional, high power density, better focusing characteristics, and so forth used for melting and vaporizing of the unwanted material from the parent material conventional laser medium: Nd:YAG, CO 2, He, Ne, etc Laser Machining

8 Casting for molds requiring extensive machining more cost-effective molds for low production runs and samples, particularly of non-ferrous metals ferrous materials: cast steel alloys, cast iron materials non-ferrous materials: aluminum, copper, zinc and tin-bismuth alloys sand casting to produce medium-to-large molds weighting several tons per mold half production of a negative pattern (wood, plastic, metal) production of the sand mold with the aid of the negative pattern casting the sand mold and removing the cooled casting Rapid Prototyping (or Rapid Tooling) Metallic Nonmetallic Commercially available In development Complexity Durability selective laser sintering High High controlled metal build-up Low High shape melting/multiphase jet solidification Medium High 3D-metal printing High High metal laminated object manufacturing Medium High laser cutting/diffuse welding Low High direct stereolithography Low Low resin casting Medium Medium metal spraying Medium Medium electroforming Medium High investment casting High High Keltool High High

9 Rapid Prototyping (or Rapid Tooling) selective laser sintering (SLS) direct fabrication of metallic molds laser beam melts powder starting materials layer by layer, with the layer thickness varying from 0.1 to 0.4mm in line with the particle size of the metal powder Rapid Prototyping (or Rapid Tooling) stereolithography (SLA) direct fabrication of nonmetallic molds laser beam traverses predetermined contours on the surface of a UV-curable photopolymer bath point by point, thereby curing the polymer 3D CAD model slicing building by SLA postcuring backing mold insert

10 Rapid Prototyping (or Rapid Tooling) metal spraying two spray wires are melted in an arc and atomized into small particles in the presence of compressed air when the particles impinge on the surface of a positive pattern, a liquid film forms that solidifies instantaneously Rapid Prototyping (or Rapid Tooling) electroforming the most accurate method of reproducing surface texture in metal coating of conductive seed layers with silver or graphite electroforming with nickel yields the best results due to such good material properties as high strength, rigidity and hardness, compatibility with the base material and good corrosion resistance electroforming, electroplating, eletroless plating

11 Rapid Prototyping (or Rapid Tooling) electroforming injection mold for CD Hobbing for producing accurate hollow molds without removing material cold hobbing hardened and polished hob is forced into a blank of softannealed steel at a low speed (0.1~10mm/min) cost-effective fabrication of hob several equal mold inserts can be made in a short time mold has a better surface quality and a long service life

12 Heat Treatment to alter the physical, and sometimes chemical, properties of a material by heating or chilling quenching tempering annealing normalizing Surface treatment to enhance the surface hardness surface hardening coating