DIY aircraft modeling. Foam Thermal Cutting Technology
- From the sandbox
- Tutorial
How many of you have already built a model of an airplane with your own hands? I’ll try to tell you about this fascinating lesson in several articles, and so I will begin the cycle on applied aircraft modeling.
In my first article I will tell you about the long-known (at least I first read about it in 1994 in one of the first books on technical topics, bought with my mother) the method of processing foam. Despite his age, he can help someone with the prototyping of a voluminous part.
Why is this needed?
In itself, styrofoam is rarely used in aircraft modeling: it is too weak. However, the forms made of it can serve as the basis for the manufacture of parts from composite materials (the simplest example is papier-mâché), the simplicity of processing makes it extremely convenient for prototyping, and its low specific gravity allows it to be left inside whole parts.
A small boring introduction about the quality of materials and innovative solutions: fate brought me to study at Hong Kong University of Science and Technology (HKUST) for a year; I didn’t guess to take the necessary tools from home (of course, and I don’t have enough different things everywhere), so I apologize for the decisions in the form of twisted-pair twisted-pair wires and the like. For example, I don’t have a single nut on hand.
For me, a linguist by education and a programmer in the last four years, aircraft modeling has become an outlet in a series of monotonous study days.
First of all, we need a blank from a piece of polystyrene foam of appropriate dimensions.
I decided to demonstrate the technology to take a thin plate and cut something flat.
It will be much more convenient to cut if there is a gap between the template and the edge of the workpiece; I chose 10 mm. The indent must match on both sides if we want to get the details with right angles. For V-shaped wings you will need to shift one plane relative to another, but more on that later. As a template for the first test, a coin with a face value of two Hong Kong dollars (2 HK $) was selected. Templates on both sides are glued to the workpiece.
Attention: glues containing acetone or toluene (“Moment”, for example) dissolve polystyrene, leaving deep holes in the workpiece. In this case, you must wait about five minutes until it is almost completely dry before gluing, otherwise there is a risk of dissolving the workpiece!
A hot wire is used as a cutter. Remembering the advice from a book from the Soviet period, I went to a music store and purchased a set of strings. For cutting, the thinnest is used, the first.
Having estimated the available power source, I measured a piece of string with a resistance of 0.7 Ohms. The length seems to be sufficient. The build quality is terrible, but nothing else was at hand. I had to take wires anyway. For power, I use a transformer from a Denon receiver shaggy (1970s, judging by the look) found in a garbage dump in the city.
After a slight adjustment of the string length, it was possible to achieve simultaneously a small cutting width (only one and a half times the string thickness. I remembered the programming past and wanted to cut “Hello, Habr”, but failed. I left it as it is. The workpiece is cut in width (~ 80 mm) like this it’s good - apparently, the temperature is optimally selected for this source.The multimeter bought here has the function of measuring temperature, but alas, the measuring bridge is not assembled correctly: when the temperature rises, its readings fall, although it initially showed about +28 degrees - the room is now slightly smaller. Based on the temperature difference, I’ll assume that the string’s temperature is 120-130 degrees. The string easily cuts polystyrene (about 3-4 cm / sec) without leaving large melted holes, practically does not burn cardboard.
Two main techniques for working with this cutter can be distinguished.
In the first case, the workpiece is fixedly fixed, the master with both hands moves the ends of the string. This method is optimal for figures with a complex profile.
In the second case, the string is pulled, and the master moves the workpiece relative to it. This method is more convenient for cutting at a strictly defined angle without a template.
As a result, I got a polyhedron in the form of a coin: In the next article I will try to talk about the production of a three-dimensional wing profile using this technology. If something was not clear - ask, I will try to highlight. See you!
In my first article I will tell you about the long-known (at least I first read about it in 1994 in one of the first books on technical topics, bought with my mother) the method of processing foam. Despite his age, he can help someone with the prototyping of a voluminous part.
Why is this needed?
In itself, styrofoam is rarely used in aircraft modeling: it is too weak. However, the forms made of it can serve as the basis for the manufacture of parts from composite materials (the simplest example is papier-mâché), the simplicity of processing makes it extremely convenient for prototyping, and its low specific gravity allows it to be left inside whole parts.
A small boring introduction about the quality of materials and innovative solutions: fate brought me to study at Hong Kong University of Science and Technology (HKUST) for a year; I didn’t guess to take the necessary tools from home (of course, and I don’t have enough different things everywhere), so I apologize for the decisions in the form of twisted-pair twisted-pair wires and the like. For example, I don’t have a single nut on hand.
For me, a linguist by education and a programmer in the last four years, aircraft modeling has become an outlet in a series of monotonous study days.
Billet
First of all, we need a blank from a piece of polystyrene foam of appropriate dimensions.
I decided to demonstrate the technology to take a thin plate and cut something flat.
It will be much more convenient to cut if there is a gap between the template and the edge of the workpiece; I chose 10 mm. The indent must match on both sides if we want to get the details with right angles. For V-shaped wings you will need to shift one plane relative to another, but more on that later. As a template for the first test, a coin with a face value of two Hong Kong dollars (2 HK $) was selected. Templates on both sides are glued to the workpiece.
Attention: glues containing acetone or toluene (“Moment”, for example) dissolve polystyrene, leaving deep holes in the workpiece. In this case, you must wait about five minutes until it is almost completely dry before gluing, otherwise there is a risk of dissolving the workpiece!
Cutter
A hot wire is used as a cutter. Remembering the advice from a book from the Soviet period, I went to a music store and purchased a set of strings. For cutting, the thinnest is used, the first.
Having estimated the available power source, I measured a piece of string with a resistance of 0.7 Ohms. The length seems to be sufficient. The build quality is terrible, but nothing else was at hand. I had to take wires anyway. For power, I use a transformer from a Denon receiver shaggy (1970s, judging by the look) found in a garbage dump in the city.
Test
After a slight adjustment of the string length, it was possible to achieve simultaneously a small cutting width (only one and a half times the string thickness. I remembered the programming past and wanted to cut “Hello, Habr”, but failed. I left it as it is. The workpiece is cut in width (~ 80 mm) like this it’s good - apparently, the temperature is optimally selected for this source.The multimeter bought here has the function of measuring temperature, but alas, the measuring bridge is not assembled correctly: when the temperature rises, its readings fall, although it initially showed about +28 degrees - the room is now slightly smaller. Based on the temperature difference, I’ll assume that the string’s temperature is 120-130 degrees. The string easily cuts polystyrene (about 3-4 cm / sec) without leaving large melted holes, practically does not burn cardboard.
Two main techniques for working with this cutter can be distinguished.
In the first case, the workpiece is fixedly fixed, the master with both hands moves the ends of the string. This method is optimal for figures with a complex profile.
In the second case, the string is pulled, and the master moves the workpiece relative to it. This method is more convenient for cutting at a strictly defined angle without a template.
As a result, I got a polyhedron in the form of a coin: In the next article I will try to talk about the production of a three-dimensional wing profile using this technology. If something was not clear - ask, I will try to highlight. See you!