Surface-finished parts

DP is probably the fastest RP method by low material costs. Color output is also possible, but there are limitations concerning resolution, surface finish, part fragility, and available materials. 

Good surface finish parts can be made in almost any hardness, sh >e and size relatively low cost little waste most compounds suitable. 

Ultrasonic Microhardness. A new microhardness test using ultrasonic vibrations has been developed and offers some advantages over conventional microhardness tests that rely on physical measurement of the remaining indentation size (6). The ultrasonic method uses the DPH diamond indenter under a constant load of 7.8 N (800 gf) or less. The hardness number is derived from a comparison of the natural frequency of the diamond indenter when free or loaded. Knowledge of the modulus of elasticity of the material under test and a smooth surface finish is required. The technique is fast and direct-reading, making it useful for production testing of similarly shaped parts. 

Process variables also play a significant part in determination of surface finish. For example, the higher the current density, generally the smoother the finish on the workpiece surface. Tests using nickel machined in HCl solution show that the surface finish improves from an etched to a poHshed appearance when the current density is increased from ca 8 to 19 A/cm and the flow velocity is held constant. A similar effect is achieved when the electrolyte velocity is increased. Bright smooth finishes are obtained over the main machining zone using both NaCl and NaNO electrolyte solutions and current densities of 45-75 A/cm. ... 

The iavestmeat-castiag process offers extreme precisioa, exceUeat surface finishes, and part-to-part consistency. This method is the most cosdy method of produciag cast components to aear aet shape. Its value is reali2ed through the high productioa of complex castiags. 

Designers have always had to deal with the fact that parts cannot be made perfectly or if they could, they would not remain perfect for long during use. So defining the ideal component is only one aspect of the designer s job (Hopp, 1993). The designer must also decide by how much a still acceptable component can be from the ideal. A component can vary from the ideal in many ways in its geometry, its material properties, surface finish - a virtually unlimited list (Alexander, 1964). 

Production-line vibration checks are an effective method of ensuring product quality where machine tools are involved. Such checks can provide advanced warning that the surface finish on parts is nearing the rejection level. On continuous process lines such as paper machines. 

In BS 4232, Surface Finish of Blast Cleaned Steel for Painting, first quality corresponds to SA3,2nd to SA2-5 and 3rd toSA2of the much more extensive Swedish Standards Commission s SIS 055 900-1962, RusI Grades for Steel Surfaces and Preparation Grades Prior to Protective Coaling, Stockholm (1962) see also BS 7079 Part A1 (1989)... 

It should be recognized that surface finish can be more than just a cosmetic standard. It also affects product quality, mold or die cost, and delivery time of tools and/or products. The surface can be used not only to enhance clarity for the sake of appearance but to hide surface defects such as sink and parting marks. The Society of Plastics Engi-neers/Society of Plastics Industries standards range from a No. 1 mirror finish to a No. 6 grit blast finish. A mold finish comparison kit consisting of six hardened tool steel pieces and... 

Barrel finishing or tumbling is a controlled method of processing parts to remove burrs, scale, flash, and oxides as well as to improve surface finish. 

The advantage of calendering over direct sheet extrusion is that a complicated and expensive die is not required. Some additional mixing can be done as part of the calendering process, as well, and a surface finish can be applied by the final roller, if desired. Sheet up to a few millimeters thick and a meter wide can be made using calendering. 

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