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The molding glossary

Discover the terms, the key words, the essential technical words in this casting glossary.

B

  • Bas-relief: sculpture executed on a plane and whose volumes do not comprise projections.

C

  • Casting rod: channel through which the drawing material is poured.
  • Chapette: in the plaster hollow mold, intermediate screed intended to cover a group of parts to form a “draft” set, the chapettes are then covered with a main screed.
  • Coping: used to contain the parts of a plaster mold or the flexible membranes of an elastomer or latex mold.

D

  • Draft: a shape is said to be “drafted” when all the spoints that make up its surface are demolded in parallel along the same axis.
  • Duplicate: qualifies a single print obtained in a lost mold in the manner of a “photocopy”.

E

  • Elastomer: qualifies a flexible and elastic material.
  • Empreinte: trace left by a shape after a molding or a stamping. It is generally said of a negative. It is especially used in the moulding on nature: hand print, fingerprints, footprint, and at the dentists, teeth prints. Also used to describe the appearance of the inner surface of a mold: skin impression, orange peel impression…

H

  • High relief: said of a relief whose volumes are almost completely detached from the background and include significant projections.

M

  • Membrane: in a “cast mold” or “print under screed”, it is the regular film of flexible material directly in contact with the model. These types of molds are also sometimes called “sock molds”.

O

  • Original model: is the original shape that is used to produce a copy by molding, enlargement or reduction.

P

  • Parting line: this is the cutting line that delimits the different parts of the mold, taking into account the holdbacks. The joint planes can be very numerous and complex, they are determining in the success of a molding.
  • Positive: qualifies a shape reproduced in a negative molding.
  • Print, proof: qualifies one or more reproductions executed in the same mold.

R

  • Release agent: a film that prevents a material from adhering to a surface.
  • Reasoning a mold, a model or a print: means to conceive them mentally.
  • Reference marks or keys: these are “notches” or “studs” that are cut in the plane of the joints to facilitate the adjustment of the various parts between them.
  • Resin: translucent or opaque syrup that hardens under the action of heat or a catalyst.
  • Rigimer: describes a rigid and compact material.
  • Round-bump: is said of all shapes worked on several sides. Everything that is not a bas-relief or a low-relief is a “round-bump”.

S

  • Stamping or contact molding: operation which consists in depositing a material on a surface with a tool or by hand.

T

  • Thermosetting: is said of a material that hardens under the action of heat. Its shape is then final.
  • Thermoplastic: a material that can be worked under heat and keeps its shape after cooling.
  • Thixotropic: a liquid or paste that does not flow on a vertical wall. The thixotropic agent is generally silica powder. Example, dentrifrice. When you press the tube, it comes out of the container. And yet, it stands on the toothbrush.

U

  • Undercut: a form is in “undercut” or retentive when one or more points (retentions of its surface) oppose the axis of demolding. A ronde-bosse often presents undercuts, the different faces each being demolded along different axes. It is then necessary to make a mold in several parts, called “piece molds”, each part being delimited by joint plants

V

  • Vents: holes through which the air contained in the mold escapes during the casting process.

Extracts de “Le moulage” de Pascal Rosier – éditions dessain et tolra – 1990

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