Ibrahim a, S. Sulaiman a, A. Jusoh b, A. Macro programming technique comprises of a main program and Macro subprograms. NC program for a basic type of machining feature namely pocket was first generated using macro and CAM system. Macro program utilizes very fewer blocks than CAM generated program.
The different between both programming methods are discussed. Finally, an integrated feature based machining system is proposed. All rights reserved. Introduction Machining feature is the remnant volume after subtracting the designed feature from the raw material [1, 2, 3, 4].
Rough machining feature is the volume after roughing is subtracted from the raw material. The machining feature should include the topological and geometric information of the machining region to offer preliminary data for generating the machining strategy. Examples of machining features include faces, pockets, holes, and slots. Razak et al. There are many alternative definitions of machining features. To machine a part, both the machining features and the machining operations must be defined, and the operations must be sequenced.
A feature-based machining system strengthening the function of material removal machine to work in more intelligent and helps the user to shorten the pre-machining setup time [6]. While a generative process planner enables a computer numerical control CNC machine to automatically define the operations for cutting the designed features [5].
Without machining feature, program is input manually and the cutting path will based on the coordinate given. Programming will take longer time and the machining efficiency will not achieve as good as feature-based.
Design by feature [8] is a technique by which the designer can document and communicate the design intent. For instance to define a hole, designer can specify radius, depth and location parameters. The second approach is by means of pattern recognition. This method is largely used in computer-aided manufacturing CAM software. However generating NC program by commercial CAM software will result in longer part program besides utilizing a large memory space in CNC machine controller [9].
And the last approach is by human assisted recognition. Based on human-assisted recognition, this paper aimed in evaluates the feasibility of using parametric programming in the implementation of feature-based machining.
Parametric Programming by Macro Parametric programming [10] is applied to CNC operations in generating a single CNC program for parts with similar design, inventing macros for machining custom design features, and developing subprograms for a group of parts that are not similar in design but require similar machining operations.
Parametric programming can significantly reduce the part programming time and these applications particularly fit group technology manufacturing in which similar parts are grouped into part families and then processed by a number of machine tools within a cell or by a single multi- tasking machining center.
Macro is very similar to subroutine. The different is that macro enables user to specify arguments and control the variables [11]. With macros, repetitive cycle can be defined.
It may be considered as the highest level of NC programming [12]. This technique is more powerful and flexible. Designed in separated programs, macros can be called by the main program or other macros using macro number. Macro program will not go through the normal executor.
Macro executor interprets and executes macro commands included in an NC part program. Methodology Fig. The most commonly machining feature in tool and die making; pocket was used in this study.
NC programs are also generated by manual programming using macros. Machining simulation was then performed on a CNC milling machine controller to prove its functionality. Different sizes of pockets width, length and depth were studied. Machining parameters such as spindle speeds and feedrates were kept constant. High speed steel HSS straight end mill of 10mm diameter was used for this purpose. For instance, 1 is representing the pocket length and 2 refers to pocket width.
To generate a new program for different design, the user needs only to redefine the variables in the macro. As there is no new program added, the memory used in the controller remains more or less constant. There are main program and macro program in macro approach. The main program prompts user to select the type of feature required. Once selected, user is requested to key in details of the feature.
These include its center location, pocket length, depth, corner radius, depth and width of each cut, tool number, cutting feedrate and spindle speed. Results and Discussion N G1 Z N Y N X5. N Z N X2. Y[ [ 23]] N Y X N Z For example, modal G codes such as G1, G2 and G3 are for linear interpolation, clockwise interpolation and counter- clockwise interpolation respectively while the canned cycle like G81 is for drilling a hole.
The same codes may be used repeatedly in order to create or to cut a given machining feature. With CAM, the part program can be thousands of blocks in size. It happened because of CAM generates the program based on cutting path coordinate. The larger the machining part, the longer the part program.
Also the deeper the cutting depth, the larger the program sizes. To perform accurate taper thread milling taper threads , for example, your control must have the ability to form a spiraling motion in XY while forming a linear motion in Z helical motion will not suffice in this case. Unfortunately, most CNC controls do not have spiral interpolation. But, believe it or not, with custom macro you can generate this desired motion.
In essence, custom macro allow you to can create your own forms of interpolation. Driving accessory devices: Probes, post process gauging systems, and many other sophisticated devices require a higher level of programming than can be found in standard G code level programming. Custom macro is the most popular parametric programming language used to drive these devices. In fact, if you have a probe on one or more of your machines, you probably have custom macro! Utilities: There is a world of things you can do with custom macro that you would never consider doing without it.
Custom macro can help reduce setup time, cycle time, program transfer time, and in general, facilitate the use of your equipment. A few example applications that fit into this category include part counters, tool life managers, jaw boring for turning centers, using standard edge finders as probing devices, and facilitating the assignment of program zero.
Example: To stress what can be done with parametric programming, we show a simple example written in custom macro B for a machining center application. It will machine a mill a hole of any size at any location. Notice how similar this program is to a program written in computer programming languages. O Program number. Diameter of end mill. Tool length offset number. G90 G54 S M03 Select abs mode, coordinate system, start spindle. G00 X Y Rapid to hole center.
G43 H Z. G01 Y G00 Z. Mike Lynch. Quick Intro to Parametric Programming. Recent Posts See All. Post not marked as liked 1. Post not marked as liked 2.
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