Drilling plastics

Plastics materials cover a wide range of types and applications, which are dealt with in detail in Chapter 14. 

To avoid chipping on breakthrough when drilling the more brittle materials such as Perspex, the material should be held firmly against a solid backing such as a block of hardwood. Use of hardwood prevents damage to the drill point. 

Large holes in sheet material can be produced using a trepanning tool. 

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The cationic polyelectrolytes, in particular, are versatile and useful materials with applications being found in water treatment, waste treatment, preparation of papers, textiles, oil drilling, plastics and biomedical areas (2). 

State two precautions to be taken when drilling plastics materials. 

Use cutting speeds of around 40m/min with a feed rate of 0.1 mm/ rev. Problems associated with drilling plastics materials were discussed in Section 8.7. 

Clays have layers of linked (Al, Si)04 tet-rahedra combined with layers of Mg(OH)2 or AI(0H)3- Clays are very important soil constituents and are used in pottery, ceramics, as rubber, paint, plastic and paper fillers, as adsorbents and in drilling muds. 

The first example refers to the detection of a 1mm side drilled hole at a depth of 45 mm in a polyethylene plastic material. Due to the high sound absorption in plastics, a low operating frequency is chosen. A probe having a 1 MHz element of 24 mm diameter was selected for this example. The echo pattern of a conventional probe with a PZT transducer is pre-... 

The earliest ball and stick models were exactly that wooden balls in which holes were drilled to ac commodate dowels that connected the atoms Plastic versions including relatively inexpensive student sets became available in the 1960s and proved to be a valuable learning aid Precisely scaled stainless steel framework and plastic space filling models although relatively expensive were standard equipment in most research laboratories... 

Mechanical or coil bindings ate used for notebooks and calendars. The pages ate coUated and special drilling equipment is used to punch holes in the paper. Metal or plastic cods ate insetted. This durable binding allows finished books to lay flat. 

Rheology is the science of the deformation and flow of matter. It is concerned with the response of materials to appHed stress. That response may be irreversible viscous flow, reversible elastic deformation, or a combination of the two. Control of rheology is essential for the manufacture and handling of numerous materials and products, eg, foods, cosmetics, mbber, plastics, paints, inks, and drilling muds. Before control can be achieved, there must be an understanding of rheology and an ability to measure rheological properties. 

Mixtures containing sulfated castor oil were used to increase the lubricity of water base drilling fluids (123). Sulfated castor oil is also used in dishwashing compounds as a hand softener. A typical cleaning composition contains sodium dodecylben2ene sulfonate, sulfated castor oil, ethanol, and water. A sulfated derivative of castor oil is used as a dispersant for plaster of Paris, reducing the water needed to form a plastic slurry (124). Pesticide emulsions can be stabilized using ethoxylated castor oil (125). 

One of the most cotrunon processing methods for plastics is injection moulding. Nowadays every home, every vehicle, every office, every factory contains a multitude of different types of articles which have been injection moulded. These include such things as electric drill casings, yoghurt cartons, television... 

KCl-polymer (potassium chloride-polymer) muds can be classified as low solids-polymer muds or as inhibitive muds, due to their application to drilling in water-sensitive, sloughing shales. The use of polymers and the concentration of potassium chloride provide inhibition of shales and clays for maximum hole stability. The inverted flow properties (high yield point, low plastic viscosity) achieved with polymers and prehydrated bentonite provide good hole cleaning with minimum hole erosion. 

Drilled solids include active drilled solids and inactive drilled solids. Clays and shales are considered to be active drilled solids they disperse into colloidal size readily and become detrimental to drilling by increasing the apparent viscosity and gel strength of the mud. Inactive drilled solids are sand, dolomite, limestone, etc. if they occur in colloidal size, these solids may increase plastic viscosity of the drilling mud. 

Drilling and Well Completions Bingham plastic fluid dv... 

For pipe flow of Bingham plastic type drilling fluid, the following can be used ... 

The formation may be reactive and swell. It may be unconsolidated and collapse on the tool joints or drill collars. We may have mobile formations such as gumbo shales or salt beds in a plastic condition. 

Deem, H. A., Plastic coating of drill pipe—Is it worth the added expense , World Oil, November 1964. 

Wood and metal drill bits can usually be used, but best results are obtained with commercially available bits designed for plastics. 

Plastic products must be firmly held, fixed or clamped during drilling and reaming operations to prevent dangerous grabbing and spinning of the work. 

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