Lecture
The plotter (from the Greek. Γράφω), the plotter is a device for automatic drawing with great accuracy of drawings, diagrams, complex drawings, maps and other graphic information on paper up to A0 or tracing paper.
Plotters draw images with a pen (writing block).
Plotters usually communicate with a computer via serial, parallel, SCSI interface and Ethernet (in the latter case, connection to a specific computer is not required, the plotter has its own IP address and, when enabled, is accessible to all machines on the local network). Some models of plotters are equipped with a built-in buffer (1 MB or more).
The first plotters (for example, Calcomp 565 of 1959) worked on the principle of paper movement using a roller, thus providing the X coordinate, and Y was provided with a pen movement. Another approach (embodied in Computervision's Interact I, the first CAD system) was a modernized pantograph controlled by a computer and having a ball-point pen as a drawing element. The disadvantage of this method was that it required space corresponding to the area to be drawn. But the advantage of this method, stemming from its disadvantage, is the easily improved pen positioning accuracy and, accordingly, the accuracy of the pattern applied to the paper. Later this device was supplemented with a special cassette holder, which could be combined with feathers of different thickness and color.
In the late 1970s, Hewlett Packard and Tektronix introduced flatbed plotters with standard desktop size. In the 1980s, the smaller and lighter HP 7470 was released, using innovative “grain wheel” technology to move paper. These small household plotters have become popular in business applications. But because of their poor performance, they were practically useless for general purpose printing. With the widespread use of high-resolution inkjet and laser printers, cheaper computer memory and the speed of processing raster color images, stylus pen virtually disappeared from everyday life.
The purpose of plotters is to provide high-quality documentation of drawing and graphic information.
Plotters can be classified as follows:
Also plotters are called wide format printers and cutters. This is not entirely correct, but de facto is already a standard.
In tablet plotters, the carrier is fixed on a flat table. The fastening is either electrostatic, or vacuum, or mechanical due to the attraction of the paper-pressing plates to (electro) magnets mounted into the table surface. No special paper required. The head moves in two perpendicular directions. The size of the media is limited by the size of the tablet.
In some small-sized devices, the head is fixed still and the table moves with the carrier fixed on it, as is done in numerical control milling machines.
There are three types of plotters with a moving carrier:
Regardless of the method of moving the carrier, the drive system of the plotters with an arbitrary scan uses either stepper motors that rotate at a fixed angle when a single pulse is applied, or an actuating system with feedback containing the drive motors and position sensors. Movements with stepper motors are usually performed 1 step in one of 8 directions.
Therefore, an approximation of the curve being drawn by the strokes of the main directions is required. Improving the accuracy of the approximation is achieved by either reducing the step, or by increasing the number of directions of movement by using additional pairs of motors or by changing the gear ratio.
Electrostatic plotters operate on the unstressed electrographic raster principle. A special dielectric paper moves under an electrostatic head containing needles with a density of 40-100 per 1 cm. Negative voltage is applied to the needles as a result of which the dielectric paper is charged and a latent image is created on it. The paper then passes through the box in which a positively charged toner is sprayed over it. Charged areas attract toner particles. In color systems, this process is repeated for each of the main subtractive colors — cyan, magenta, and yellow, as well as black.
Electrostatic plotters are faster than pen plotters, but slower than laser printers. Their speed ranges from 500 to 1000 lines applied to paper in 1 min. They work with a resolution of 200-400 dpi. Electrostatic plotters are needed if high-quality color output is required for a CAD system. Such a plotter is 10–20 times faster than a pen. Among the market leaders in these devices are Versatec, Calcomp and Benson. These plotters are very expensive, their price ranges from 30 to 150 thousand dollars.
| Tablet | Drum | |
|---|---|---|
| Drawing format | Width 210–840 mm Length 297–1188 mm | Width 210–1140 mm 297 mm length - unlimited |
| Drawing speed | 80 - 1140 mm / s | 30 - 300 mm / s |
| Accuracy | 0.8 - 0.0025 mm | 0.7 - 0.0025 mm |
| Resolution | 0.4 - 0.0025 mm | 0.1 - 0.0025 mm |
Accuracy is determined by the smallest possible value of the coordinate increment. The usual values are tens of micrometers. The resolution is determined by the actual capabilities of the executive system and the drawing head. For pen plotters, the usual values are fractions of a millimeter. For photo builders - less than 10 micrometers.
Unique high-precision plotters often have unique control protocols. Graphic plotters of wide distribution, as a rule, support the HPGL (Hewlett Packard Graphics Language) plotters protocol of the firm Hewlett-Packard. It contains a small number of graphical functions, is easily read and interpreted. Some plotters interpret the REGIS protocol, developed for VT 240 terminals (and more powerful ones).
Used in very accurate constructions, tracing of printed circuit boards. Pros: cheaper pen, faster. Disadvantages: special premises are needed (darkened photo labs).
Inkjet plotters (wide format printers) are classified into engineering, for outdoor, for internal advertising. Some of the engineering can be used for printing internal advertising, but applications such as “the plotter is intended for both exterior and interior work” are usually specs of the manufacturer and / or seller. Electrophotographic (laser) plotters are only engineering, due to the monochrome of the resulting image. The advantage of the only (as of June 2009) full-color model for printing advertisements is questioned due to the insufficient width of 914 mm for the market. As a rule, these plotters are sold with scanners (sometimes such a scanner is an integral part of a printer) under the names “engineering system”, “reprographic complex” and others, depending on the preferences of the manufacturer and the seller.
The market for inkjet engineering plotters is dominated by devices from Hewlett-Packard. Canon, Epson, Encad are also widely represented.
The inkjet interior plotter market has no visible leader and is poorly developed in the territory of the former USSR.
There are dozens of different manufacturers' equipment on the market for outdoor printing, but with very close technology, often even with compatible spare parts. In fact, the main players are the manufacturers of XAAR, Konica-Minolta and Spectra print heads, which are not equipment manufacturers.
The main producers of laser engineering technology are KIP, Ricoh, Oce, Xerox, totally occupying more than 90% of the market. Their equipment is also sold under other trademarks owned either by the manufacturer itself (for example, the Gestetner and Rex-Rotary brands are owned by Ricoh), or by a large dealer (Utax or MV, for example), or even by a direct competitor (if he has temporary problems with production).
Comments
To leave a comment
Electromechanical devices of electronic devices
Terms: Electromechanical devices of electronic devices