Due to the fact that these three aspects are generally achieved hand in hand with each other they have been brought all under the same heading. Let us consider an operations sheet. The operations sheet, for a CNC programme, denotes a list of operation numbers, the tool used for those operations, their speeds and feeds and a brief description of what each operation does.
The calculations for the speeds and feeds are based loosely on the formula
where, rpm = rotations per minute
S = cutting speed of material
D = diameter of tool
The values have been slightly adjusted based on the author’s experience in this field as he performs the tasks in this assignment for his living.
Using Cad/Cad To Produce The Program
The software can now be used to create the program. This is performed by first either creating the drawing within the Cad/Cam package or by importing the drawing from a suitable Cad package such as AutoCAD® or Catia®. See Fig. 1. The next step is to define tool paths that need to be cut. These vary from package to package. Some Cad/Cam packages deal specifically with tool paths whilst others create groups and curves (such as CamTech Peps®) and then generate their tool paths from these. See Fig. 2.
Next, it is necessary to define the tools that are going to be used and then apply them to the tool paths or curves and state what process is required to operate. E.g. Pocket mill; finish profile; drill etc. When this stage is reached it is possible to view the cutting process on the PC to observe how the tools are going to run. See Figs. 3-8. This provides a clear (assuming a quality Cad/Cam package is used) indication of any problems that may exist. It is related specifically to the component that is required to be created within this project. Any alterations may be achieved by entering the Cad/Cam’s code window. An example of the code generated in Camtech Peps® is shown below with a description of what the code means.
3D Graphical View
Program created
The program can now be “post processed”. This involves, as described on page 1, placing the code generated in the code window through a language translator. This translated code is now in the language form the CNC machine can now understand. It has just been “post processed”. The translator is known as a post processor and each different type on CNC control system has its own post processor. Whilst this would, at first glance, appear cumbersome it does allow for great flexibility within any company that has a wide range of CNC machines with different controls. The code generated in the code window by the Cad/Cam is specific to the Cad/Cam package but generic to the job. This generic code can be accessed and then post processed by many different post processors allowing the job to be passed to many production machines within a company.
There are two examples of post-processed code listed here. One is in the ISO format that is often called FANUC® (as FANUC® closely follows the ISO standard). The other is in the language Heidenhain®. This language is often used of CNC mills and machine centres due to its ease of reading and writing. It can almost always be found on CNC mills manufactured by Bridgeport® who have a partnership with Heidenhain®.
The ISO Format
The Heidenhain® Format
Either of these two programs are now ready to be uploaded to the CNC machines control system ready for manufacture.
Macro’s
A macro is a text body into which textual substitutions may be made possible at assembly or run time. Once defined it looks like the code that would be present if typed/written long hand. Macro’s are used to simplify the use of an operating system or program. In some system’s macro’s can be nested so that in their expansion a macro definition can contain other macro’s.
Example
With an operating system such as Windows 9x/NT/Me/2000 there is a desktop which the computer automatically boots to. On the desktop are a group of shortcuts to various programs or areas of the operating system. When the user clicks on one of the shortcuts a program/sub-program opens ready for use. This shortcut is a macro that saves the user from independently locating the appropriate executable file for the program desired and loading and running the program.
In individual programs macro’s can also be written (often in the language Visual Basic) to allow a certain function to occur. Macro’s can take the form of either -:
- A sequence of keys that need to typed by the operator to achieve a certain function within the basic program
- A functionality that the user finds useful but is not available as standard in the basic program.
Each of the buttons in the figure (Fig. 9) below represents a macro which performs an individual task within the Cad/Cam program. All Windows® based programs have macros incorporated within them in some manner.
Fig. 9 – Example of macro buttons.
Databases
Databases are widely used in the computing industry. They are a means of collating data and then retrieving that data at a specific point in time either directly or by using search criteria.
First a history lesson. By the 1970s, the advent of new technologies for the transmission, storage, and distribution of data, once the prerogative of book publishing, had become a problem for the industry; television screens and databases became symbols of the challenges to editors and publishers alike. The increasing use of sophisticated copying machines posed new problems to the need of publishers and authors to protect their property by copyright, and in 1976 the U.S. Congress passed a major revision to their Federal Copyright Law that attempted to define to what extent published material could be reproduced without payment of royalties. In the late 20th century, computers and such related innovations as the CD-ROM and the Internet allowed publishing to expand, making readily updated texts available on-line and on disk and fostering multimedia presentations and interactive uses. The easy access to and copying of electronically published material created additional copyright issues, and in 1998 U.S. Congress passed legislation that extended copyright protection to on-line material. In addition, the wide availability of computer-driven desktop publishing technology to small presses and individuals gave impetus to the production of a wide variety of self-published books. Technology also led to the development of the “electronic book,” which combines the storage, search capabilities, and adaptability of a computer with the simulated page format of a traditional book; early versions appeared in the late 1990s and were called databases.
Most Investigators are conditioned to think of a database as a source for obtaining record searches such as Civil, Criminal, Fictitious Business Names, Corporations, etc. They are databases that may be searched in order to obtain the necessary background information needed on a specific subject.
The reason to use a database is because information needs to be managed. Information can be analysed using printed summary reports or lists for cases due today, next week, or next month.
A database is a collection of data that you can sort, search, add to, edit and print when needed. Imagine the database as the container that holds your information, and as such, being able to organise and manipulate it.
A database such as Microsoft Access®, called a Database System, contains numerous tables or files, which store information about related topics. Due to the relational design of Microsoft Access®, information can be joined between files, therefore, eliminating duplicate data entry. For example, picture the client file: a user can see all the related records to his/her client such as the case, contacts, invoices, other cases, transactions and so forth. With Microsoft Access®, a user can access data from other files to use in the current file. A relational database allows data from another file to be displayed, edited, and used in the current file. Each occurrence of data is stored in only one file at a time, but a user can access and work with that data from any file. Because data from a related file is displayed in, and not copied into the master file, you always see the data in its current state. An exception to this is when you need the data in its original state, then Microsoft Access® is designed to look-up the data. One example would be if a Subject had a change of address. The user would not want the address to change in the original case. He/she may want to know the address at the time the case was created.
A relational database is used to set up and manage data efficiently and with flexibility. Instead of creating many database files that together store multiple occurrences of data, a user can store single occurrences of values in smaller files. A user can then work with the data in many ways. A user can make any changes to data in only one place, which promotes data accuracy. An important factor in all of this, is that it saves disk space because the data is stored in only one place.
In the event a user is using a network or there is more than one person using the database, an administrator will want to set up access privileges and passwords. This promotes file security by controlling who can use a file and particular fields and layouts, and which tasks they can perform.
With regards to Cad/Cam programs, databases can be used -:
-
To collate tool libraries
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To collate material libraries
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To collate speeds and feeds
- Create BOM’s (Bills of Material)
- Job management sheets
A database consists of four main aspects. These are the -:
- File – a container that houses lots of different categorised areas or records,
- Record – a collections of fields,
- Field – Independent pieces of information common across a set of records, and
- Real Data – data that is put in fields.
A database’s core construction can be represented visually as in Fig. 10. It can be seen that the database is made up of several layers. The Interface is where the user and applications can access and interact with the database. The Database Manager manages the flow of data around the database and between the database and the user/applications. The database is the confines within which the raw data is stored and handled. The raw data is the data that is input by the user/applications for use for indexing/retrieval later.
Fig. 10. – Visual Representation of a Database
Conclusion
It appears clear that by the purchase of CAD/CAM not, only could the production rate be increased dramatically but the overall image of a company could be improved by being able to promote an advanced, competitive machine shop that would be capable of producing almost any item that could physically fit on the machines the Company owns. Savings could be obtained from other areas such as reducing the required skill level actually at the machine, which consequently means that these operators could be paid less. Skill levels will need to be maintained to allow the machines to be programmed and set to work but this will involve the use of fewer skilled people (and therefore reduced higher rates of pay). These men would already be conversant with Cad/Cam, as there would often be an allowance in the cost of the software for the programmer/setter(s) to go on a training course on the operation of most Cad/Cam programs.
An independent quality control system would need to be implemented but, as already stated, could be performed by the programmer/setter as he won’t be at the machine front. There would be no significant cost involved for setting this up as all measuring equipment would already be in place for inspection since the current operators would be maintaining their own quality control. Also the programmer/setter(s) should be able to identify the best process to achieve the finished product. The only cost attributable to setting this up would be the requirement to log the inspections for future quality referrals (be that on a PC or by a paper method).
Databases allow the rapid development of a Cad/Cam program to be constructed as repetitive figures would not need to be constantly re-entered. These figures could be given as drop down menus, which can be swiftly accessed by the programmer. Macro’s also enable a programmer to reduce his program production time by reducing the number of repetitive keystrokes down to just one to perform the same sequence of actions.
It is proposed that a company embrace the purchase Cad/Cam and support its implementation.
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