sink mark

sink mark

[′siŋk ‚märk]
(engineering)
A shallow depression or dimple on the surface of an injection-molded plastic part due to collapsing of the surface following local internal shrinkage after the gate seals.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Worcester City, who stunned the Sky Blues in the first round, will be at home to Chesterfield if they can sink Mark Robins's Scunthorpe United at the second attempt after Saturday's 1-1 stalemate at Glanford Park.
It can be used to flu in gaps in the scan data or to repair defects from the physical originals--for example, a crack in a historic ceramic piece or a sink mark in a plastic moulding.
Unless this boss has a relatively small diameter, you will probably have a hard time eliminating an opposing sink mark on the exterior surface of the part.
However, the increased packing pressure does not provide a complete solution for overcoming sink mark problems or reducing shrinkage.
For example, the severity of sink mark was referenced by its depth, which could be measured with a surface roughness measuring machine [11] or with a micrometer [12].
A sink mark in thin sections is seen to depend on delay time, mold temperature, melt temperature and gas pressure (in order of declining importance).
In fact, the map pocket strengthening flange on the top edge of the map pocket is in excess of 1:1 (thicker than the nominal wall), which is possible only because the unsightly sink mark that would otherwise result is prevented by the gas pressure within the microcellular foam melt.
They are said to improve sink mark removal and reduce weight while preserving structural properties of ABS, LDPE, HDPE, and PP parts injection molded and extruded/coextruded.
Products improve flow, compatibilize mixed/ cycled polymers, reduce molding cycle or increase extrusion rates, and are used for sink mark elimination and improved weld-line strength.
In this case the processor had the option of changing the grade of material and I recommended as a follow-up that they switch from a nominal 13 melt-flow-rate PC to a nominal 6 MFR, since this also improves stress-crack resistance and decreases the tendency for sink marks to develop in thick walls.
An appropriate design of cooling channel reduces cooling time, increases the productivity, and minimizes undesired defects such as sink marks, differential shrinkage, thermal residual stress and warpage.