Volume 3 No.4, Spring 2000
CNC Workshop is a multi-media CD-ROM and workbook packaged for your students as an affordable textbook purchase, providing an opportunity for increased CNC visualization and student labwork productivity. It's major components include:
My sophomore-level CNC students and I tried out CNC Workshop this past semester (Spring, 2000), focusing on the workbook and the simulation modules.
CNCez SIMULATION SOFTWARE
The simulation software is the heart of The CNC Workshop package. It essentially performs a graphical NC verification of Fanuc-compatible CNC programs. The simulation is considered interactive, since it will display some of the programming steps as they are keyed into the editing interface. Sometimes it doesn't quite display all the tool motion when you would expect it to, but that can be overcome by selecting the appropriate display settings, as will be discussed later.
The editing interface is fairly intuitive; most students managed to learn to enter, edit and simulate their programs by simply trial and error. The CBT module and the workbook do provide instruction on the use of the simulation software interface.
The CNC programs created in CNCez are saved in text format, and programs created in a text editor can be brought into the simulator if they are formatted correctly. We were able to bring student part programs created in the simulator to our Haas Vertical Machining Center (VMC) simply by changing the program file name to a Haas program number and exchanging the ":" value for the program number with the letter "O," which Haas recognizes.
CNCez comes with copies of the example problems which are located throughout the workbook, especially in conjunction with the presentations of new G- and M-codes. This allows the simulator to demonstrate particular programming techniques and strategies. Figure 1 is a still graphic captured in the middle of a demonstration program on cutter radius compensation. The first (smaller diameter) toolpath is has already been machined along the coordinate path specified. The second toolpath is being compensated to the left of the coordinate path.
Figure 1. CNCez Mill demonstration of
cutter radius compensation.
There is a CNCez Mill and CNCez Lathe program as part of this package. Our students worked with the CNCez Mill software. Some of the helpful features which offered us some programming flexibility included the ability to select from common tool diameters, to set rectangular part sizes and select work coordinate systems.
THE CNC WORKSHOP WORKBOOK
What is called a "workbook" in this case is really a combination mini-text with an added G- and M-code guide and sections on the use of CNCez Mill, CNCez Lathe, and EdgeCAM.
Content of the workbook includes an introduction to the history and process of CNC, fundamentals of CNC (such as coordinate systems and directions), and some basic programming procedures and documentation. A fairly thorough G- and M-code section provides an explanation of each code and usually a sample program which can be called up from the CD-ROM and simulated. These explanations are a little more understandable to students than the explanations found in the CNC machine tool manual, but they are ordered chronologically for reference rather than in some sort of logical order of introduction. Therefore, it is up to the instructor to introduce and assign readings and simulations of these codes in a meaningful order.
The initial sections the workbook includes some occasional exercises as well as lists of "lab exercises" (which are really reading questions) at the end of each section. Because the answers to all of the exercises and problems, including programming problems, are provided in the back of the workbook, these cannot be used to evalute student effort.
Chapter 8 provides a section of "workbook exercises" which are program problems. These jump from very simple introductory problems to two "advanced" exercises. Again, suggested programs solutions for all these exercises are provided in Appendix A, so these really only serve as example problems for students.
CNC WORKSHOP COMPUTER-BASED TRAINING
The text content provided by the workbook is somewhat light, but the computer-based training modules contain amplifications on all the workbook content, including a very large collection of figures, with color graphics, animations, and videos, as well as audio descriptions. The introduction section contains an outstanding presentation of film footage and photos describing the history of CNC. Color graphics, unavailable in the workbook, are used in the CBT module to differentiate directions and illustrate concepts, as shown in Figure 2. A collection of animations and videos of actual machining are used in the presentation and explanation of new concepts. Figures 3 and 4 are examples of video clips used to demonstrate the application of linear interpolation motion.
Figure 2. CNC Workshop CBT Color
Demonstration of Axes for Horizontal Milling
Figure 3. Snapshot of CBT Animation of Linear
Figure 4. Snapshot of CBT Animation of Linear
Other strengths of the CBT system include galleries of images of CNC machine tools, milling tools, and turning tools. There are also some interactive exercises in the CBT modules on fundamentals and programming concepts.
One current glitch, at least with our installation, is the inability to access the contents pages for each separate CBT module (except for the introduction to the interactive simulator). Instead of clicking on a specific topic for the particular day's lesson, the user must page through the tutorials in a linear manner.
INSTALLATION AND USABILITY ISSUES
Installation and Entry
CNC Workshop's CD-ROM software does require installation before operation. An updated workshop.exe file is available for download from Torcomp's CNC Workshop support page, http://www.torcomp.com/cnc/workshopfaq.htm, which resolves some of the Windows 98 (and apparently also Windows NT) bugs. However, we still ran into a great deal of difficulty getting the software to run properly on our Windows NT laboratory computers. Most students installing the software on their home computers (Windows 95 or 98) had no problems after downloading the file fix. A few had additional issues related to the Internet Explorer interface required to run CNC Workshop's CBT module.
Our biggest problem was simply launching the program and its various modules. Once we eventually discovered that some of the roadblocks we were facing were simple bugs with backdoor solutions, we were able to enter the program and get down to business. We get only the top menu line of the program with the rest of the window not appearing. (Torcomp calls this a "blank screen") if we enter the simulation straight from the desktop; but simulation launched just fine from the CBT menu (which, by the way, wouldn't launch automatically from the CD; we could only seem to launch by manually opening the CD files until we reached the workshop.htm file). Finally we read through enough of torcomp's FAQ's to discover that simply minimizing the window which showed only the menu line would allow the entire window to display properly when restored.
Other Usability Issues
Our experience with the software concentrated on the CNCez Mill simulation package. We noticed the following annoyances:
In February, Torcomp released a beta version of CNCez Pro. This is a completely re-written program designed for professional programmers. For those who can afford professional software, this may be an alternative to CNC Workshop's CNCez software, providing the advanced functionality currently missed.
At the end of the semester, I asked the students what they thought of the software and workbook and specifically, did they think it was worth the price. Almost all students stated that in spite of the hassles and headaches of getting the program to work properly, they thought the program and workbook were worth the price, which was the same as or less than the price of a normal textbook (about $55 or $60). They appreciated being able to use the simulation as a verification tool before moving their programming assignments to the VMC. (Their conclusion assumes that the laboratory does not already have a good NC verification package available.) Another advantage the simulation software provides is the ability for the student to have access to the simulation on his or her own home computer.
From an instructor's standpoint, the ability to simulate simple programs opened up a wealth of opportunity for "demonstrating" sample programming techniques and for allowing the students to practice some smaller programs or program examples before concentrating on the larger programing assignment.
The workbook is somewhat light on content, but contains a good G-code and M-code guide. It is probably also necessary for providing an organizational bridge to the richer multimedia CBT modules.
The apparent inability for the simulation software to handle subprograms may be a drawback as students advance in programming skill, but in spite of the many snags we experienced with the software, the workbook has been a positive introductory CNC experience for my students. I am looking forward to building a stronger organization of these tools into my class and lab activities.
|||Nanfara, F., Uccello, T., & Murphy, D. (1999). The CNC Workshop: A Multimedia Introduction to Computer Numerical Control. Reading, MA: Addison Wesley Longman, Inc.|
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