Re: What is Cad, CAM, Controller for Sheet cutting

>
>Sorry, I'm being dense. Isn't the translator the piece of software
>that converts dxf to g code?
>

Burning and many table machines are very simplistic when you first look at what you want to do. It sounds very convenient to draw a shape or 2 in Corel Draw, save the file as a DXF or an HPGL and feed that to the controller. This is a realistic method to make parts for many people. However if you want to control the size with any precision, if you want to create approaches, or tabs, if you want to arrange multiple shapes onto the same sheet, the process becomes more complex. Most people quickly tire of the attempt to do this with any kind of efficiency in a drawing program and switch to a CAD drawing program, OR they already know Autocad or ABC cad and decide that it is the "best" way to make designs and start from that point. Unfortunately most CAD programs are not designed to produce tool paths. They are designed to produce drawings of buildings, hydraulic and electrical diagrams, or maybe mechanical components. The tools to make a useful toolpath are usually found in Cad-Cam systems. These are programs that combine electronic drawing capabilities with specialized functions that help to develop tool paths which can produce a part that is exactly what is wanted, from the first cut.

For example, nearly any 2 axis cutting process, whether plasma, laser, router, mill or water jet, has a width of cut. A Cad-Cam program will allow you to develop a tool path that accounts for this width of cut. Many systems call this an offset curve, and it must have a look ahead capability so that as the cutting progresses, the tool does not cut into an adjacent contour from another direction. Few Cad programs can properly handle this & will have no problem producing offset curves that slice right through the corner of the next letter in a text string.

Many cutting processes need to start their cutting, off of the outline of the part and finish at some distance away so that the cut is uniform and doesn't have a blow hole, burn mark, or divot at the start and end points. With a Cad program you can draw a teardrop shaped approach and depart with overlapping cuts. It will be a time consuming process. With a decent Cad-Cam program you can select many shapes and automatically add approach and departs to them all.

Some sheet cutting, depends on the part remaining attached to the board. Small parts that break loose on a router will quickly be chewed to bits if they get between the cutter and the sidewall. They can also snap a cutter turning at 30,000 RPM. To control this loose part and cutter interaction, some manufacturers will leave small attachments between the part and the sheet. This is called tabbing. It is very similar to the injection molded plastic models of cars and airplanes. Everything is still attached after the cuts, but a fairly simple razor cut or a twist will break it free. Since wood and plastic parts often require sanding before finishing, a little sanding easily removes the mark from the tab, and involves very little extra cost.

Sheet layout and nesting are important to those that want to make several parts and utilize the material with very little waste. Few CAD programs do this well and for that matter few Cad-Cam programs either. However there are some high end systems that do a good job. Look for some sheet layout tools in a Cad-Cam program.

Lastly a 2d cad program cannot help you to control the order and Z pickups of your cutting. It will also probably not let you control the direction of cut either, whether a circle is cut clockwise or counterclockwise. 3D CAM programs do this very well.

These are the reasons that you may want to consider learning a new CAD program and why you may want to also consider a CAM program. If you get into the process and find that things are difficult, there is a low cost program that provides nearly all the above features. Which one you ask? Why Vector cam of course. ;-)

The choice of controller software is actually a minor detail once it is running. They nearly all understand G-code. Few can handle DXF or HPGL with any real finesse. Windows doesn't buy you any advantage in a controller. What are you after a pretty computer, or a system that makes the part correctly and quickly? The real analysis, as anyone that has made a part will tell you is not to be done from a computer and with remote observations, but from the actual parts produced.

As far as the recent evaluation of "free" software on the internet, I was surprised that Ability System's Indexer LPT for Windows was not mentioned. They have a direct HPGL read and I believe I heard that they have a nice lookahead in their Windows version too. I can't vouch for the program, but I know many people have used it for many years.



Best Regards, Fred Smith- IMService
Listserve Special discounts and offers are at: http://209.69.202.197/cadcamedmdro.html

imserv@... Voice:248-486-3600 or 800-386-1670 Fax: 248-486-3698