by Paolo Casella

 

 

  CAD and Prints  
  a complex ballet 
 
 
Squiggle

  hand-sketch simulator
 
plotter pens

 
 
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A delirium.
"Printing in color from Windows is a complex ballet
of application software, the printer driver, and even the video driver."
- PC Magazine


CAD & Prints

Printing from CAD applications under Windows, is a complex, non-stop and exhausting ballet;
to make everything going correctly you need a total compatibility among the components the Workstation, continuously running after each other: CAD Program and its last version, Operative Syistem and its version, plotter/printer model and its firmware; each one must be compatible to the others.
These compatibilities are guaranteed by the DRIVER.

In this document

Which is the difference between printer and plotter?     
First of all let's say that it is not important how the Producer named your device, if Printer or Plotter.
It has no importance if used technology for printing is by pen, ink-jet, laser or something else.
It has no importance how it is connected - serial port (COM), parallel (LPT), USB or through net.
The important is the way the Applications send data to print.

CAD programs generally have two ways for sending data to the device: PRINT and PLOT.
To “expert” users, PRINT is a raster output and PLOT a vectorial output.

Let's try an exemple:
Just take a normal straight line we want to plot on a sheet of paper.

To draw that line a CAD program commands (PLOT) to a mobile tool-pen, drill, soldering gun, engraver, etc. from an XY point to an other XY point - a simple displacement: this is a vector.

On flat bed plotter - equipped with orthogonal arms - the pen is positioned sliding them both, just the same as on a drafting table; unlike on vertical plotter, pen positioning on X axis takes place sliding a pen on horizontal bar, while for the Y axis it is caused by the up-and-down movement of the paper.

Because of this peculiar language, the vector generated a specific device able to execute such kind of orders: the plotter (with a pen or other similar tools).
To print that line, Windows generates - memorizing on computer - an image riproducing the whole sheet of paper, dot by dot, both black and white, specifying for each of them XY position, thickness and if it is black or white (or other color), then it sends it - PRINT - to the device: an enormous file (the weight which is the cause of frequently system crashes or incomplete plots and very low transmission of data to the device.

Both systems have pros and cons. To most of CAD users - and most of times - it's much better the vectorial system, PLOT (files .plt). Owing to the enormous difference in dimension and weight of files.
Evidently, dependly on the command PLOT or PRINT, you need the device able to understand the order that you will send to it.

What is a .plt file?
A .plt file is a format of file necessary to print on a prefixed printer (plotter), whether connected to the PC which has been generated from, or in other place: e.g. a Copy Centre.
This format reduces the dimension of the file to few kilobytes, rendering it even suited for e-mail.
You need to install on your PC the specific driver for the plotter that will print it, using the FILE port and the option “Plot to File.

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Modern plotters=Large Format Printers     
Modern inkjet plotters are really Large Format Printers, as HP calls them: Designjet printers, not Designjet plotters. But they work under HPGL protocol, the standard language for CAD programs.

The HP 500 Designjet Printer: slow plot generation.
Born as a normal printer with PCL 3 language (PCL 5 and higher are HPGL-2 compatible, instead), to work in CAD needs an optional HPGL card; this is already installed on all other models.
Without this card you'll practically generate, load and print an A0 size in PDF!!
If we think the time we need, very often, for few A4 PDF pages.....
Slow plot generation, output data size up to ~10x larger than drawing size, incomplete plot; system crash or a need of more memory, Print Server or Buffer.
To say the truth, this may happen even with an HPGL equipped device; there are many reasons: Autocad itself that creates enormous files, the System Operative version, an old driver not updated, Windows itself.

It's possible to get rid of these inconveniences providing with a more powerful, up-to-date driver - a Third Party Product that we can supply - even suggested by HP, Autodesk and many Others.
You may forget all these problems by installing a good driver and cut down - 50/70% - the weight of files and time for printing.

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HPGL: a Standard Language        
Every plotter has its own protocol (language) to comunicate with CAD programs:

PCI for Calcomp, Summagraphic;
BGL for Benson-Océ;
GPGL for Graphtec;
DM-PL for Houston;
HPGL for Hewlett-Packard;
MH-GL for Mutoh;
RD-RTL, CAMM-GL for Roland
SRL for Selex
ENCAD RTL for earlier ENCAD
and others.

In the course of the years, for CAD programs, the HPGL protocol rapidly imposed itself as a standard, leaving the place to the following HPGL-2, with more performances.
Just like first MS-DOS and the following Windows.
All plotter manufacturers, pointing to a larger market, joined it to theyr own protocol.
Or as Encad, Numonics, Neolt, Regma, Selex, Ioline and many others did in following years, installed the only HPGL - with some little adaptations - grown by this time as the standard de facto: however an endless number of dialects.

HPGL (Hewlett-Packard Grafic Language)
The HPGL plotter driver which is distributed with Windows 95/98/Me wasn't written by Microsoft or Hewlett Packard.
It was originally developed by a Company in Texas for an earlier version of Windows, and was only designed in the first place to work with one particular application, with an HP A0 plotter - single sheet.

HPGL-2
Hewlett-Packard successively developed HPGL-2, a high performance protocol; but it is his own, all the others are emulators (dialects). Many dialects, since each Manifacturer joins such protocol the firmware of every his device.

Which difference between them?
Basically, HPGL is a language for pen plotters: transmits a pen number to the plotter, the corrisponding pen is taken from the carrousel; the thickness of the pen draws the thickness of the line on the paper.
To produce a wanted different thickness, the user must set it on the PLOTTER.
HPGL files are also very large and, after being imported, result in a profusion of polylines or individual elements which can only be reduced to normal proportions again by specific optimization.

HPGL-2 transmits to the plotter all informations for colours and thickness: only the plotters with HPGL-2 protocoll can understand these istructions; the thickness of the lines are definited by the CAD program.
By HPGL-2 you can also get a long plot, longer than cm 111,8 - A0 size - normally cm 160 and much longer on roll feed plotter; it is also able to offer considerably better graphics capabilities.
Performances and more advanced instructions in this protocol allow fast transmission of data to the device and fastest plot generation returns CPU to the application quicker.
If you convert files HPGL-2 in HPGL, you'll lose all these capabilities.
Every time you make a plotter working in emulation of an other model, you make it work with capabilities of this last one

Some modern ink-jet plotters, missing a good driver, are even forced to work as an old pen plotter*:

From ENCAD, technical:support pages

  • I have an early model NovaJet 3 and need drivers to operate the machine under Windows XP Professional. I can't find any on your driver download page.

    "ENCAD is not developing a Windows XP driver for the early model ENCADs (NovaJet     II, NovaJet II, NovaJet III and the CADJET).
    Install an HP-GL, HP-GL/2 (if available), *HP 7475, HP 7550, HP 758X, or HP 759X, and set the emulation on the early model ENCAD to match the driver that you installed".
  • Does ENCAD have a Windows 2000 driver for the NovaCut series"

"ENCAD does not have a driver labeled as Windows 2000. You can use the Windows NT 4.0 driver for Windows 2000 and it seems to work well".

Therefore, every time that, in order to print, you set a modern inkjet or laser plotter in emulation of an old one, you make it work with features and limits of a primordial machine.

from the Official site ENCAD.com

  • "... going to set up the plotter, the display says that the sheet is not supported ...or, with a right format - type " 914*1700 - it only prints up to the A0"

HP-RTL: practically a standard
Mixed protocol raster/vectorial that HP developed for his "inkjet large format printers".
It is already the standard for many Producers and also here with many dialects..
The HP DesignJet Windows drivers don't provide an interface for controling colors and line widths, or for optimising output for vector mode applications: and very heavy as well.

PCL-5 (and higher)
Hewlett-Packard Page Control Language. The protocol PCL-5 is the standard for many modern HP laserjet and HP compatible printers.
Developed since 15 years is a more economic, simple and quick alternative to Postscript.
It is normally used on laser and inkjet desk printers.
PCL-5 allows the use of HPGL files on these peripherals, which might be used when the plotter is missing or for quick prints in small size (A4 e A3); or print preview.

Even inferior to Postscript and to its descendant PDF, it is used in almost all printers in the world: more than 70 milions installed.

The reason is that the overwhelming majority of documents doesn't need the potency of a Postscript.

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WINDOWS and HPGL/HPGL-2 Protocol         
Microsoft doesn’t include support for HP-GL/2 devices with Windows 95/98/Me, but does provide an HP-GL/2 driver with Windows NT4/2000/XP/VISTA, but gives a lot of errors and malfunctions, in addition to output data size up to ~10x larger than drawing size

WinLINE makes even pen plotters work efficiently with popular Windows programs by translating the printed page into efficient vector graphics statements that pen plotters can understand.

From an Autodesk Thecnical Support page:
"Because the Microsoft Windows driver has several limitations............; the HPGL-2 driver that is installed with Windows NT4/2000 and XP, is a Micorosoft version; does not support custom sizes and cannot be used to create long plots.
There are several reasons for not using the Windows driver provided by Microsoft, these include:

  • General Protection failure
  • Out of paper pen movements
  • Incorrect lines style and line width
  • Incomplete plots
  • Low resolutions affecting curve smoothness
  • Incorrect text sizing, positioning, and/or rotation
  • drawing does not fit on the sheet
  • Spurious lines crossing the drawing and others more".

Windows is a raster language: a grid of dots
For this reason Windows doesn't transmits the simple order to pick up a pen and move it on XY axis, drawing a line on the paper but it reproduces all the image on his grid of dots: to make that line it puts thousands of dots one beside the other, from the beginning to the end, giving the idea of a line: they are an infinity of graphic entities, each one with its instructions for XY position, color and thickness: cause of the heaviness of files, even if they are few lines or few polygons, needing long time for printing, incomplete plots, system crash.

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Compatibilities                 
All Producers declare theyr product compatible to.....
A lot of times this is a bit hazardous declaration

from a CAD discussion Forum:
"I have just installed Autocad 2005 and with 630 ENCAD plotter can not print formats above A0; I premise that I downloaded the specific DRIVER

All Forums are full of messages like this one here above

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CAD and small Desk Printers
margins - centering - fonts - colors
(the following remarks are the same for plotters too)

Very often, with no apparent reason, you may obtain different, contrasting results;
Causes of this usually are:

  • the same CAD Program version sending files to different printer models;
  • different versions of CAD program sending files to the same printers;
  • the same CAD program version, the same printer model but different Windows version.

    • We read - PC PROFESSIONAL Magazine - CANON giving an answer to a customer that was complaining about the lack of an XP driver for his printer:
    "Every producer provides his product with a driver for most popular Operative Systems, the moment of first issue giving all informations about it.
    .............Updating Windows 2000 to Windows XP, for instance, Microsoft modified substantially instructions for dyalog between O.S.s, drivers and printing peripherals..."

We have good prints from all Programs, not from CAD
Why we usually have good prints from programs such Word, Excell, Corel Draw, Paint etc. whilst it's not like that printing from CAD?
As told before, the CAD language creates a vector, a .plt file, for the standard plotter protocoll HPGL: almost all desk Printers do not have HPGL protocol.
A table Printer doesn't act, then, like a plotter being its logic and mechanics not generated for this: therefore it is not able to correctly understand the order coming from a CAD, and prints if and what it interprets.
And each Printer model executes the work according to its firmware version.
Some may print correctly, without any error: they have full compatibility between the firmware, the Program version, the Operative System version: it's a lucky coincidence.

Margins & Centering
The CAD (vectorial language), sends in succession instructions to the plotter and develops the drawing starting from the lower left of the page. Windows is a raster language and creates the full page, reproducing the image on its grid of dots. The origin of this page is the center of it; this is the reason why we find so many problems in getting correct margins.

Roll feed Printers - Epson and others
why on these printers, Epson 1520 & 3000, even if they declare a 5/6 meters long plotting they stop at cm 118?
The reason of a maximum lenght at 1118 is because the printer, receiving CAD instruction (vectors), starts automatically Epson Plot (no more supported by Epson), an emulator of primordial HPGL A0 plotter: and the A0 size is mm 1118.
This protocol is also missing the interface for controlling line widths: a vector has not a width.

Fonts do not match
fonts on display are not corresponding to those on paper

Reasons are different :

  • A small difference is normal: the characters are adapted to the grid of pixels on the monitor and the print resolution is different.
  • Most CAD programs do not know the peripheral (do not have the specific driver).
  • Many Fonts are described in the logic of the printer/plotter; the definition may be different:
    for example, on HP Fonts are much smaller than those on Roland plotter.
    A big difference, already visible on the layout, may result from the reduction in scale for printing. The size of the texts is played according to set: 3 mm set on the draft will be 3 mm on paper.
  • Some CAD programs do not give the possibility to set the height of the character in the design other than in print.
  • Some CAD programs have many more problems in generating correctly True Type Fonts

Colors - CMYK vs RGB
colors on display are not corresponding to those on paper

Short for Cyan-Magenta-Yellow-BlacK, and pronounced as separate letters, CMYK is a color model in which all colors are described as a mixture of these four process colors. CMYK is the standard color model used in offset printing for full-color documents. Because such printing uses inks of these four basic colors, it is often called four-color printing.

vs

In contrast, display devices generally use a different color model called RGB, which stands for Red-Green-Blue. One of the most difficult aspects of desktop publishing in color is color matching - properly converting the RGB colors into CMYK colors so that what gets printed looks the same as what appears on the monitor. A very good driver may reduce this effect.

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Windows and long plots      
Why, even our printing device declares long plot up to 5/10/15 meters, we can't obtain prints that long?
Printing by the Windows Printer Manager, you can not exceed cm 327.

From an Autodesk Thecnical Support page:
"According to HP, due to a Windows limitation, the plots cannot exceed cm 327...."

You may obtain them only if your CAD Program has the specific driver for that specific printing device, able to talk to it bypassing the Windows Printer Manager.
You'll find such limits with every driver within Windows: Microsoft, HP, OCE, EPSON, ENCAD, KODAK, KIP, CANON etc.
NOT in Winline.

Why in AutoCAD (sometime) you may have longer plots?
When you obtain that, i'ts because that AutoCAD version drives directly that plotter and/or printer recognizing its firmware, bypassing/forcing the Windows Printer Manager.

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What is a driver?            
A driver is a piece of software used by your computer to communicate with a particular peripheral.
There are drivers for printers, video, sound, modems, and many other peripherals. Drivers are regularly updated and new versions can help fix problems and bring significant performance improvements.

Driver: why do we need them?
Every printing peripheral is piloted by the Application; therefore the program must know the protocol (language) of the printer to send instructions wich; so we say that the Program is compatible, has the driver for that specific peripheral*.
Other case is that the peripheral may declare to have itself the driver for that specific Program as it knows the language that will send it printing instructions.
Tipical: my HP printer has driver for Autocad (and maybe, sometime, it says for which Autocad version).

*From an Autodesk Thecnical Support page:
"Other important considerations when finding a driver, is to consider the type of printer you
have, the AutoCAD version and the Operating System version.
For example, you would need a specific driver for an HP DesignJet 200 plotter for AutoCAD 14 in Windows NT.
In Other words, this particular driver would probably not work for an other HP DesignJet plotter model running in AutoCAD 2000 in other Windows version".

Why upgrade drivers?
There are two main reasons to upgrade drivers:

  • Problem fixing
  • Support of a new technology

Problem fixing
Compatibility problems are the most frequent problems solved by a new driver release. For instance, certain software may not run correctly due to the way they display information on the screen. The problem can be solved either by a new video driver or with a new release of the software.

Support of a new technology
Some peripherals rely on the processor computing power (for instance, most inkjet printers). Others peripherals integrate dedicated, specialized chips (for instance, graphics accelerator cards). New drivers optimize the communications speed and task sharing between the processor and the peripheral. A new driver can bring as much as 50% performance increase for certain tasks.

We must realize that this is the only way to talk two entities speaking different languages in Windows.
Missing such possibilities, we rely on a Third which acts as translator between the two: "Windows Printer Manager", that is a generic printer driver.

Let's make the example of two people of different nationality and idioms, an Italian and a German, that must operate in England (Windows) and that they must exchange precise instructions of job. Because these two entities can be understood, it needs that at least one of them knows to the perfection the language (dictionary, grammar, and sintax) with which the other speaks. Not understanding one the language of the other, entrust the english who both declare to know well. Results are different, depending on how much perfectly these two individuals know and speak english. Finding itself in difficulty they are entrusted to an interpreter who asserts to know perfectly theirs two mother languages.
The problem is that our “multilingual interpreter”- the Printer Manager in Windows - many times is a liar:
it is not true that it knows perfectly those languages, consequently ........

DRIVERS and theyr develop
Developing drivers needs a very long time and substantial amounts; not always Producers find advantage, after the first draft, in developing more performanting drivers*, or compatible with new versions of Operating System, since the quick obsolescence of theyr peripherals.
And when and if they develop them, they do it discontinuously and with very long period of time and not allways with good results.

*From PC PROFESSIONAL magazine
Responding to an User complaining about missed develop of a new driver in Windows XP for old printers 1520 e 3000 under Win95/98, Epson gives this answer:

".....in this case it's not just a simple update ..... but a totally new develop, costing very important human, economic and financial resources, same as those necessary to introduce a new, modern product that the market is uninterruptedly asking......................".

For these reasons Manufacturers prefer join to Windows, even with all problems and limits that is possible to experience when you print (plot) from a CAD program.
Missing some specific drivers the assignment is submitted to a generic driver, the "Printer Manager" in Windows, that is an independent application, autonomous from the Operating System, just as any other printer driver.

Fortunately for consumers, a Third Party is specialized in the production, development and updating of the drivers for many peripherals.
Same HP (as Autodesk and many others), recommends the use of it, when those of his printers and of his new plotters are not satisfactory.

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How may you get these DRIVERS?          
we have these drivers: we are the distributors for Italy, East Europe and some other Countries: please ask.
On our webpages you can read the characteristics.

Contacts

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The WinLINE Drivers are by download only.
So you'll get them the day you order, with no shipping charges.
As soon as we get a document as confirmation, the license server sends you a download URL, User Name and Password.
All copies of WinLINE include exaustive Technical Support by the Help On Line

This page is Paolo Casella & C. product - 2008 - all rights reserved.

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