Level-Two Programming
A fixed (canned) cycle begins with a code such as G81, which starts the drilling cycle. The code is followed by several variable entries called parameters.
Bolt circle. A pattern of holes or other features distributed about a central datum.
Canned cycle. A second common name for a fixed cycle.
Departure point. The initial position from which a given routine is started. Often designated with the letter I in programming manuals.
Parameter. A blank requiring an entry to customize a fixed cycle.
Shape address numbers (shape definition). The line numbers often defined by P and Q parameters in canned cycles.
Tiled routines. Overlapping and connecting mill routines to machine away a given area of complex shape.
Threading Cycles
On a manual lathe, when the half nut lever is engaged, a geared connection between spindle rotation and tool lead is locked in. But on a CNC lathe, there is no mechanical connection. The spindle has its drive motor and the tool turret has one drive motor for X and one for the Z axis.
On a few older machines with less responsive drive systems (Fig. 14.1), there is also a deceleration distance at the end of the thread as well but it is always shorter than the acceleration zone.
Figure 14.1 The thread cycle requires a departure point outside both the X and z positions relative to the finished thread.
Branching Logic—Loops and Subroutines
Branch. A departure from a linear format whereby the program flow jumps to a designated address to create a loop or to find and operate a subroutine, then return to the origin of the callout.
Logic diagram. A graphic tool used to visualize the syntax of branching logic.
Nesting. The use of a loop or subroutine within a loop or sub routine.
Smart loop. A programming tool that turns the program flow back upon itself a given number of times.
Special CNC Programming Tools
Mirroring. A program code or draw utility whereby geometry is reversed.
Obverse (shape). The counterpart shape required to mold a correct feature.
Scaling. A program factor (or draw utility) whereby dimensions are expanded or contracted by a percentage.
Shrink factor. The amount of percentage change of part geometry.
References: Gen [1-3].
Assessing questions:
1. What kind of programming languages exist?
2. What do you know about the Code Words and commands?
3. What is the Level-two programming?
4. Loops and Subroutines?
5. Special CNC programming tools.
Lecture 15. Advanced and advancing technology. Design for CNC manufacturing. CAM mill programming.
The Solid model advantage
Assigning a given material to the design (aluminum in this exercise), a finished solid part or assembly can be weighed and stressed to see how it will perform. A visual display tells the designer locations where forces concentrate; thus it might need more material or a redesign of the shape.
There are numerous software, which can help to simulate machining processes, such as SolidWorks or CATIA. Depending on the simplicity of using it can be chosen the first one. However, it does not meant that this software is the best one. More information about application of this software you can read in official web sites.
References: Gen [1-3].
Assessing questions:
1. What kind of advantages in CNC machining?
2. How to create model of a part?
3. What is a solid model?
4. Advantages of SolidWorks?
5. Additional application for created part model?
References
Machining and CNC Technology, Michael Fitzpatrick, update edition, 2005, ISBN 0-07-337374-5
Machining and CNC Technology, Michael Fitzpatrick, third edition, 2014, ISBN 0-07-337378-8
Manufacturing Automation: Metal Cutting Mechanics, Machine Tool Vibrations and CNC Design, Y.Altintas, Cambridge University Press, 2012
Computer Control of Manufacturing Systems, Y.Koren, McGraw-Hill, 1983
Pythagorean-Hodograph Curves, R.T.Farouki, chap.29, springer 2008
Introduction to Computer Numerical Control, James V.Valentino, Joseph Goldenberg. - 5th edition, 2013, ISBN – 13: 978-0-13-217603-3
CNC Machining Handbook, industrial press Inc., Madison James G., 1st edition, 1996, ISBN 0-8311-3064-4.
Computer Numerical Control of Machine Tools, G.E.Thyer, 2nd edition, ISBN 0 7506 0119 1.
CNC programming handbook: comprehensive guide to practical CNC programming, Peter Smid, 2000, ISBN 0-8311-3136-5
Manufacturing Engineering and Technology, 6th edition, S.Kalpakjian.