characters max.| Reader / Puncher Interface | RS-232 interface |
| Memory card interface | Standard |
| External part number search | 9999 |
Only some software options are listed in the table:
| Additional work coordinate systems | 48 sets or 300 sets |
| Extra custom macro common variables | up to 999 |
| Tool life management | |
| Additional tool life management sets | 512 |
| Automatic corner override | |
| Automatic corner deceleration | |
| Coordinate system rotation | |
| Feedrate clamp by arc radius | |
| Hypothetical axis interpolation | |
| Custom macro interruption | |
| Jerk control | |
| Polar coordinate interpolation | |
| Program restart | |
| Increment system multiplied by 1/10 | 0.0001 mm 0.00001 inch |
| Scaling function | G50, G51 |
| Small diameter peck drilling cycle | |
| Smooth interpolation | |
| Circular threading | |
| 3D coordinate conversion | |
| 3D cutter radius offset | |
| Load monitoring | |
| Position compensation (for backward compatibility only) | G45-G48 |
| Tool retract and recover |
| 3 | PROGRAM INTERPRETATION |
When working with CNC machining centers or CNC lathes programs, the machine operator monitors not only the numerous tool motions, but also the actual program flow. This is especially true - and a very important observation - for the beginning of the actual production run. During full production, the CNC operator will frequently check the program as it is displayed on the control monitor (screen), to keep an eye on the machining process. This initial evaluation usually takes place at the control system of the machine during part setup. Many machine shops also issue a printed copy of the part program to make the monitoring a bit easier, particularly for programs that are only a page or two.
Regardless of the extent a CNC operator is involved with a particular part program (on screen or on paper), it is important that he or she fully understands its contents - what exact information does the program really provide? There is a lot more information provided even in a short program than a brief simple look can absorb. The first step in the process of understanding the program itself is to understand the way it was written - to understand the program structure.
A CNC program can be written in so many different ways that is makes it impossible to find any degree of consistency between individual part programmers, even within the same company. Operators can greatly influence any programming style, based on their experience of using many programs to machine various parts. Operators can also communicate their preferences to the CNC programmer, who should use such information in the best way to improve program structure.
Every part program has a single and very specific purpose that will always be the same - to machine a part. The way it is written has to be logical in many ways, some of them quite obvious. For example, the order of tools in the program is the order of tools for actual machining. If coolant is required for a certain operation or for the whole part, it is logical to include coolant ON function (usually M08) in the program. Machining order must also be logical - roughing will always be done before finishing, heavy operations before light operations, etc. All these structural features are generally followed by all CNC programmers, otherwise their programs would not work.
The area of the ‘not-so-obvious’ program structure flaws can be quite large. Poor program structure will increase lead time and also can make a life of the operator a bit unpleasant or even difficult. These flaws of structure belong to the logical program features and mainly relate to G-codes and M-functions, particularly to their application within a program.
One very common break of logical structure is using the right G-codes in the wrong place. Typical example are G-codes used before tool change, for example:
N1 G21 G17 G40 G80 G90 G54 G00 G49
N2 T01 M06
N3 . . .
Although technically correct, this structure has several potential problems. One is having G21 (or G20) in the same block with other G-codes, which is not allowed on some controls, especially those that can convert metric and imperial mode between each other. That may not be important for one machine, but for another, it may be very important. Placing G20/G21 in a block by itself will make the program available to more similar machines and prevents problems on those machines that require it.
Is G20/G21 Really Needed ?
Some programmers do not use G20 or G21 unit selection in the program at all. They often based their reasoning on the fact that only metric jobs or only jobs in imperial units are ever done on that machine. While that may be true today, it may not be true tomorrow. Programmers who do not use the proper G-code for units selection count on the following control feature:
Units set before machine shut-off remain in effect after machine power-on
In absolute terms, command G20
