Plotter
A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like vinyl or leather. In the latter case, they are sometimes known as a cutting plotter.
In the past, plotters were used in applications such as computer-aided design, as they were able to produce line drawings much faster and of a higher quality than contemporary conventional printers. Smaller desktop plotters were often used for business graphics. Printers with graphics capabilities took away some of the market by the early 1980s, and the introduction of laser printers in the mid-1980s largely eliminated the use of plotters from most roles.
Plotters retained a niche for producing very large drawings for many years, but have now largely been replaced by wide-format conventional printers. Cutting plotters remain in use in a number of industries.
Overview
Digitally controlled plotters evolved from earlier fully analog XY-writers used as output devices for measurement instruments and analog computers.Pen plotters print by moving a pen or other instrument across the surface of a piece of paper. This means that plotters are vector graphics devices, rather than raster graphics as with other printers. Pen plotters can draw complex line art, including text, but do so slowly because of the mechanical movement of the pens. They are often incapable of efficiently creating a solid region of color, but can hatch an area by drawing a number of close, regular lines.
Plotters offered the fastest way to efficiently produce very large drawings or color high-resolution vector-based artwork when computer memory was very expensive and processor power was very limited, and other types of printers had limited graphic output capabilities.
Pen plotters have essentially become obsolete, and have been replaced by large-format inkjet printers and LED toner-based printers. Such devices may still understand vector languages originally designed for plotter use, because in many uses, they offer a more efficient alternative to raster data.
Types
X–Y plotter
An X–Y plotter is a plotter that operates in two axes of motion in order to draw continuous vector graphics. The term was used to differentiate it from standard plotters which had control only of the "y" axis, the "x" axis being continuously fed to provide a plot of some variable with time. Plotters differ from inkjet and laser printers in that a plotter draws a continuous line, much like a pen on paper, while inkjet and laser printers use a very fine matrix of dots to form images, such that while a line may appear continuous to the naked eye, it in fact is a discrete set of points.X-Y plotters were categorized by two features: the format they could handle, and their architecture. The main architecture was flatbed plotters or table plotters. In this configuration the paper lays on a table and a carriage holds the pens. The whole carriage is moving on the X axis on the rail. This rail is moving on the Y axis along the structure of the table. The carriage was equipped of several type of pens depending on the manufacturers. Typically Rotring pens or Pentel pens were mostly used. Usually each carriage held several pens covering the various color needs; typically black, blue, red and green. The other system was roller plotters where the paper moved on the X axis on a large roller and the Y axis was covered by a carriage holding the pens; this carriage moved on a rail creating the Y axis. The main manufacturers of large-format plotters were Calcomp, a California-based company; and Benson, a French company especially present in Europe and the USSR. For the smaller formats Hewlett-Packard and Tectonics were the main suppliers.
Electrostatic plotters
s used a dry toner transfer process similar to that in many photocopiers. They were faster than pen plotters and were available in large formats, suitable for reproducing engineering drawings. The quality of image was often not as good as contemporary pen plotters. Electrostatic plotters were made in both flat-bed and drum types. The electrostatic plotter uses the pixel as a drawing means, like a raster graphics display device. The plotter head consists of a large number of tiny styluses embedded in it. This head traverses over the width of the paper as it rolls past the head to make a drawing. The resolutions available may be 100 to 508 dots per inch. Electrostatic plotters are very fast with plotting speed of 6 to 32 mm/s, depending on the plotter resolution.Cutting plotters
Cutting plotters use knives to cut into a piece of material that is lying on the flat surface area of the plotter. The cutting plotter is connected to a computer, which is equipped with cutting design or drawing computer software programs. Those computer software programs are responsible for sending the necessary cutting dimensions or designs in order to command the cutting knife to produce the correct project cutting needs.In recent years the use of cutting plotters has become popular with home enthusiasts of paper crafts such as cardmaking and scrapbooking. Such tools allow desired card and decal shapes to be cut out very precisely, and repeatably.
Vinyl cutter
A vinyl cutter is used to create posters, billboards, signs, T-shirt logos, and other weather-resistant graphical designs. The vinyl can also be applied to car bodies and windows for large, bright company advertising and to sailboat transoms. A similar process is used to cut tinted vinyl for automotive windows.Colors are limited by the collection of vinyl on hand. To prevent creasing of the material, it is stored in rolls. Typical vinyl roll sizes are 15-inch, 24-inch, 36-inch and 48-inch widths, and have a backing material for maintaining the relative placement of all design elements.
Vinyl cutter hardware is similar to a traditional plotter except that the ink pen is replaced by a very sharp knife to outline each shape, and may have a pressure control to adjust how hard the knife presses down into the vinyl film, preventing the cuts from also penetrating the backing material. Besides losing relative placement of separate design elements, loose pieces cut out of the backing material may fall out and jam the plotter roll feed or the cutter head. After cutting, the vinyl material outside of the design is peeled away, leaving the design on the backing material which can be applied using self-adhesion, glue, lamination, or a heat press.
The vinyl knife is usually shaped like a plotter pen and is also mounted on a swivel head so that the knife edge self-rotates to face the correct direction as the plotter head moves.
Vinyl cutters are primarily used to produce single-color line art and lettering. Multiple color designs require cutting separate sheets of vinyl, then overlaying them during application; but this process quickly becomes cumbersome for more than a couple of hues.
Sign cutting plotters are in decline in applications such as general billboard design, where wide-format inkjet printers that use solvent-based inks are employed to print directly onto a variety of materials. Cutting plotters are still relied upon for precision contour-cutting of graphics produced by wide-format inkjet printers – for example to produce window or car graphics, or shaped stickers.
Large-format inkjet printers are increasingly used to print onto heat-shrink plastic sheeting, which is then applied to cover a vehicle surface and shrunk to fit using a heat gun, known as a vehicle wrap.
Static cutting table
A static cutting table is a type of cutting plotter used a large flat vacuum table. It is used for cutting non-rigid and porous material such as textiles, foam, or leather, that may be too difficult or impossible to cut with roll-fed plotters. Static cutters can also cut much thicker and heavier materials than a typical roll-fed or sheet-fed plotter is capable of handling.The surface of the table has a series of small pinholes drilled in it. Material is placed on the table, and a coversheet of plastic or paper is overlaid onto the material to be cut. A vacuum pump is turned on, and air pressure pushes down on the coversheet to hold the material in place. The table then operates like a normal vector plotter, using various cutting tools to cut holes or slits into the fabric. The coversheet is also cut, which may lead to a slight loss of vacuum around the edges of the coversheet, but this loss is not significant.
Modern flatbed cutting table systems have evolved to integrate seamlessly with large-format digital printing workflows, incorporating vision systems, standardized cut file profiles, and sophisticated blade pressure control for both kiss cutting and through cutting with sub-millimeter precision.
Languages
A number of printer control languages were created to operate pen plotters, and transmit commands like "lift pen from paper", "place pen on paper", or "draw a line from here to here". Three common ASCII-based plotter control languages are Hewlett-Packard's HP-GL, its successor HP-GL/2, and Houston Instruments DMPL. Here is a simple HP-GL script drawing a line:
SP1;
PA500,500;
PD;
PR0,1000;
PU;
SP;
This program instructs the plotter, in order, to take the first pen, to go to coordinates X=500, Y=500 on the paper sheet, to lower the pen against the paper, to move 1000 units in the Y direction, to lift the pen and finally to put it back in its stall.
Programmers using FORTRAN or BASIC generally did not program these directly, but used software packages, such as the Calcomp library, or device independent graphics packages, such as Hewlett-Packard's AGL libraries or BASIC extensions or high end packages such as DISSPLA. These would establish scaling factors from world coordinates to device coordinates, and translate to the low level device commands. For example, to plot X*X in HP 9830 BASIC, the program would be
10 SCALE -1,1,1,1
20 FOR X = -1 to 1 STEP 0.1
30 PLOT X, X*X
40 NEXT X
50 PEN
60 END