Selçuk TEVRÜZ, 030070128, 5th week

Lapping

Lapping is a free abrasive machining process. An abrasive compound in a fluid suspension is applied to the lapping tool, which is called a "lap". The workpiece is placed on top of the lap and moved to cause cutting/material removal at a controlled rate. Lapping is primarily considered to be a three-body abrasive mechanism due to the fact that it uses free abrasive grains that can roll or slide betwwen the workpiece surface and the tool plate, although some grains become embedded in the lap, which would be considered two-body abrasion. A fine abrasion is applied, continuously or at specific intervals, to a work surface to form an abrasive film between the lap and the parts to be lapped or polished.

Each abrasive grain used for lapping has sharp irregular shapes, and when a relative motion is induced and pressure applied, the sharp edges of the grains are forced into the workpiece material. Each loose abrasive particle acts as a microscopic cutting tool that either makes an indentation or causes the material to cut away very small particles.

(Boljanovic V., Metal Shaping Processes: Casting and Molding, Particulate Processing, Deformation Processing, Metal Removal, 2010, pg.411)

Brazing

Brazing and soldering processes are frequently used to join copper and copper alloys. Brazing, by definition, employs filler metals having a liquidus above 450 oC (840 oF) and below the solidus of the base metal. Brazing is distinguished from soldering by the melting point of the filler metal: solders melt below 450 oC (840 oF). Brazing and soldering are used to join structural somponents, commercial and consumer products, and electrical and electronic devices.

Copper and copper alloys are among the most easily brazed metals available. A wide range of filler metals is used to join the many different copper and copper alloys, and all the conventional brazing processes can be employed. These include furnace, torch, induction, resistance, and dip brazing. The selection of the brazing process and filler metal depends on the alloy composition, the shape and dimension of the parts to be joined, and the intended application.

(Davis J.R., Copper and Copper Alloys, ASM International Handbook Commitee, pg.303)

Pultrusion

In pultrusion, resin-soaked matting or rowings (along with other fillers) are pulled through a long die heated to between 120 and 150 oC [250 to 300 oF]. The product is shaped and the resin is polymerized as it is drawn through the die. Radio frequency or microwave heating may also be used to speed production rates. The process appears to resemble extrusion. In the extrusion process, the homogeneous material is pushed through the die opening. In pultrusion, however, resin-soaked reinforcements are pulled through a heated die where the resin is cured.

(Richardson T.L., Lokensgard E., Industiral Plastics: Theory and Applications, 4th edition, pg.232)

Baka-Yoke (Fool-Proofing)

To produce quality products 100 percent of the time, innovations must be made to tools and equipments in order to install devices for the prevention of defects. This is called baka-yoke, and the following are examples of baka-yoke devices:

1. When there is a working mistake, the material will not fit the tool.

2. If there is irregularity in the material, the machine will not start.

3. If there is a working mistake, the machine will not start the machining process.

4. When there are working mistakes or a step left out, corrections are made automatically and machining continues.

5. Irregularities in the earlier process are checked in the later process to stop the defective products.

6. When some step is forgotten, the next process will not start.

(Öno T., Toyota Production System: Beyond Large-Scale Production, 1978, pg.122)