Eclecticos
05-27-2007, 09:27 PM
Working With Styrene
Posted with permission By: Jim Banner http://members.shaw.ca/sask.rail/
Saskatoon Railroad Modellers Group http://members.shaw.ca/sask.rail/construction/lsbuild/workstyr.html
First of all, what IS Styrene? Styrene is a solid plastic made by polymerization of styrene gas. It is commonly sold in three forms:
1.Expanded styrene usually referred to as Styrofoam and used in the building industry as insulation.
2.Sheet styrene, with or without designs molded or pressed into one or both faces.
3.Injection molded mechanical or decorative parts, and model kits.
All three forms of styrene are useful in modeling.
A wide variety of plain and decorative styrene sheets can be purchased at hobby shops.
CUTTING STYRENE
On the list of things that make working with styrene a pleasure, ease of cutting must be close to the top. Unlike wood, styrene has no grain to worry about. And unlike metal, only two inexpensive tools are required for cutting styrene. The tools are a sharp knife, preferably with replaceable or snap-off blades.
1. Deciding where to cut. Cutting lines can be marked on styrene with a pencil. Straight cutting lines need to be marked only at the ends, but curves should be marked for the full length. Curves can be laid out free hand or with compasses or by tracing around something with the right diameter, depending on the required result.
2. Scoring the plastic. For straight cuts, position the edge of the ruler EXACTLY over the cutting line. This is easy if you put the tip of the knife exactly on one of the pencil marks and slide the ruler up to it. Then put the tip of the knife on the other pencil mark and rotate the ruler until it again touches the knife. Recheck the first end, then draw the knife along the ruler edge to score the surface of the styrene. If the knife is sharp, only a light pressure is required. Ideally, the ruler should be over top of the piece you want, so that if the knife wanders at all, it wanders into the scrap. For curved lines, it is often necessary to follow the line by eye. Try to keep the knife in contact with the styrene at all times, so that the score line is continuous. Often it is easier to turn the material than it is to turn the knife, so that you never have to cut at an awkward angle.
3. Breaking the plastic at the score. With the score towards you, bend the ends away from yourself. For straight cuts, this is a snap (pun intended). To convince yourself just how easy it is, try it a few times on a scrap piece of styrene. Also try snapping a piece that has not been scored, just to get a feel for how tough this stuff really is. Curves are a little harder to snap. Usually it helps to work in stages, first gently bending the plastic at the score line, working along from one end to the other. Then work back, bending a little more. Keep working back and forth, bending a bit more each time until the score line penetrates right through and the plastic separates.
4.Cutting holes in the center of a piece by this "score and snap" method is somewhat harder. Round holes, particularly larger ones, are not too bad if you keep working gently around them until the center breaks free. Rectangular holes, for example holes for windows, are more difficult. Often cracks will develop at the corners no matter how carefully you work. One way to avoid this is to drill a small to tiny hole at each corner. ( If you don't have a drill, use a heated pin to make the holes - just don't breath the smoke. Then connect the holes with knife scores. On the front of the sheet, use the ruler as a guide and connect the holes in the desired rectangle. On the back, connect the corners in a X. Press on the center of the rectangle from the front of the sheet to snap all the scores and pop out the scraps.
5. If required, is to remove the burr left from scoring. The fatter the knife, the duller the knife and the more pressure used, then the more material that will be pushed up on each side of the score line. See figure at left, below. This ridge can be felt by dragging a finger nail across the cut edge of the sheet (DO NOT drag your fingers along the edge, a cut edge can be sharp enough to cut you back!) In many applications, this ridge is of no consequence but in others, it does matter. It can cause enough separation between pieces that solvent welding won't work properly. The drawing in the figure below shows a vertical knife blade creating burrs as it scribes a horizontal piece of styrene. The right hand drawing shows two pieces of styrene being held apart by a burr on one of them.
http://img329.imageshack.us/img329/6537/knifescoreqm3.gif
Posted with permission By: Jim Banner http://members.shaw.ca/sask.rail/
Saskatoon Railroad Modellers Group http://members.shaw.ca/sask.rail/construction/lsbuild/workstyr.html
First of all, what IS Styrene? Styrene is a solid plastic made by polymerization of styrene gas. It is commonly sold in three forms:
1.Expanded styrene usually referred to as Styrofoam and used in the building industry as insulation.
2.Sheet styrene, with or without designs molded or pressed into one or both faces.
3.Injection molded mechanical or decorative parts, and model kits.
All three forms of styrene are useful in modeling.
A wide variety of plain and decorative styrene sheets can be purchased at hobby shops.
CUTTING STYRENE
On the list of things that make working with styrene a pleasure, ease of cutting must be close to the top. Unlike wood, styrene has no grain to worry about. And unlike metal, only two inexpensive tools are required for cutting styrene. The tools are a sharp knife, preferably with replaceable or snap-off blades.
1. Deciding where to cut. Cutting lines can be marked on styrene with a pencil. Straight cutting lines need to be marked only at the ends, but curves should be marked for the full length. Curves can be laid out free hand or with compasses or by tracing around something with the right diameter, depending on the required result.
2. Scoring the plastic. For straight cuts, position the edge of the ruler EXACTLY over the cutting line. This is easy if you put the tip of the knife exactly on one of the pencil marks and slide the ruler up to it. Then put the tip of the knife on the other pencil mark and rotate the ruler until it again touches the knife. Recheck the first end, then draw the knife along the ruler edge to score the surface of the styrene. If the knife is sharp, only a light pressure is required. Ideally, the ruler should be over top of the piece you want, so that if the knife wanders at all, it wanders into the scrap. For curved lines, it is often necessary to follow the line by eye. Try to keep the knife in contact with the styrene at all times, so that the score line is continuous. Often it is easier to turn the material than it is to turn the knife, so that you never have to cut at an awkward angle.
3. Breaking the plastic at the score. With the score towards you, bend the ends away from yourself. For straight cuts, this is a snap (pun intended). To convince yourself just how easy it is, try it a few times on a scrap piece of styrene. Also try snapping a piece that has not been scored, just to get a feel for how tough this stuff really is. Curves are a little harder to snap. Usually it helps to work in stages, first gently bending the plastic at the score line, working along from one end to the other. Then work back, bending a little more. Keep working back and forth, bending a bit more each time until the score line penetrates right through and the plastic separates.
4.Cutting holes in the center of a piece by this "score and snap" method is somewhat harder. Round holes, particularly larger ones, are not too bad if you keep working gently around them until the center breaks free. Rectangular holes, for example holes for windows, are more difficult. Often cracks will develop at the corners no matter how carefully you work. One way to avoid this is to drill a small to tiny hole at each corner. ( If you don't have a drill, use a heated pin to make the holes - just don't breath the smoke. Then connect the holes with knife scores. On the front of the sheet, use the ruler as a guide and connect the holes in the desired rectangle. On the back, connect the corners in a X. Press on the center of the rectangle from the front of the sheet to snap all the scores and pop out the scraps.
5. If required, is to remove the burr left from scoring. The fatter the knife, the duller the knife and the more pressure used, then the more material that will be pushed up on each side of the score line. See figure at left, below. This ridge can be felt by dragging a finger nail across the cut edge of the sheet (DO NOT drag your fingers along the edge, a cut edge can be sharp enough to cut you back!) In many applications, this ridge is of no consequence but in others, it does matter. It can cause enough separation between pieces that solvent welding won't work properly. The drawing in the figure below shows a vertical knife blade creating burrs as it scribes a horizontal piece of styrene. The right hand drawing shows two pieces of styrene being held apart by a burr on one of them.
http://img329.imageshack.us/img329/6537/knifescoreqm3.gif