Machining and CNC Technology Level 1 Programming Machining and CNC Technology

Machining and CNC Technology Overview “Since so few programs are written by hand today, why take the time to learn such a method?” It’s a valid question with four very good answers. YCC = Yellow code compiler, a pencil Machining and CNC Technology

Valid Skills for Trade Masters The complete machinist needs to trouble shoot program codes to solve error messages. Then they edit out bugs or edit in improvements to make programs safer or more efficient. Third, during setups, commands are punched in at the controller, to make or modify tooling, and to move the machine by manual data input. All these key tasks require code reading-writing mastery. Shop Talk – Programming The final reason is advancement. Many machinists aspire to programming after running the machines for a time. Obviously a good command of commands is a must in that job! Machining and CNC Technology

Machining and CNC Technology Goals Code Words and Program Conventions. > Name Six Word Prefix Letters > Explain Groupings of Codes > Begin a Vocabulary of Alphanumeric Words > Compare Command Lines to Code Words Outer Program Structure > Start Programs with Safety Modes > Cancel Unwanted Modes > End Programs with Safe Tool Movements Machining and CNC Technology

Machining and CNC Technology Goals Continued Compensated, Linear Cutter Paths > Calculate Coordinates for the Tool Path > Write a Manually Compensated Mill Program Writing Arc Commands > Write Arc Commands using the Radius Method > Write IJK Arc Commands Center ID Method Writing Compensated Programs > Use the G41/42 Compensation Codes in a Program > Write On-Ramps for the Cutting Tool. > Write Off-Ramp commands   Machining and CNC Technology

Trade Tip on Memorizing Codes and Conventions Trade Tip on Memorizing The main objective is not to memorize codes, although doing so will accelerate mastery. The goal is to learn the possibilities. First, we'll examine a short code word vocabulary. Then we'll investigate data conventions, how to make entries the control can accept. Next we look at a set of command words to begin programs safely and how to end them too. Lastly, we'll learn program structure and how to join the code words together into complete command blocks. Machining and CNC Technology

Machining and CNC Technology Terms Needed When you begin study, don’t bypass the terms. Knowing their meaning will speed mastery, Alpha-Numeric Code Command (Command Line) Command Word (Word) Code Groups Prepatory Codes (G Codes) M Code words Modular Command Terms found on Page 824 Machining and CNC Technology

Machining and CNC Technology Codes to Commands A command line in a program is a complete set of instructions to be acted upon by the control. It is composed of alphanumeric code words, coordinates and numbers. Machining and CNC Technology

Machining and CNC Technology Universal (Almost) Those code words come from a set that was written before machines had micro-processors with RAM. They could read code and act upon it but not use variables on the fly, such as offsets. As such the 50 core G words and 50 M words survived from those early codes. They cause simple motions such as feed rate linear or two axis circular motion. They are standard codes everywhere. Machining and CNC Technology

Machining and CNC Technology But, the EIA originators that invented them could foresee their set would need space for expansion. So they left 50 of the first 100 words blank in both the G and M categories. Today, all of those words have been filled too. Some have become nearly universal CNC code, due to their use on Fanuc controls, an early leader in CNC. But, today we have gone far beyond 100 words in both the Miscelaneous and the G codes. EIA-RS274-D (Electronic Industries Assoc. Recommended Standard ) Machining and CNC Technology

Machining and CNC Technology Program Structure Programs divide into three portions: Start, Body and End Commands Even CAM generated programs need beginning commands that set conditions or cancel unwanted conditions left over from the previous program. And they require final codes to close certain modular modes and actions Machining and CNC Technology

Communication and File Names Some controls require specific codes and labels at their beginning. Others do not. To find out, simply read a program from that machine or read the programming manual. Machining and CNC Technology

Generic Startup Commands As a suggestion only, here’s a typical startup command set: G80 G40 Cancel cycles & compensation G20/21 Inch or metric values G90 Absolute values (G91 incremental) G94/G95 Feed IPM or IPR FXXX Sets feed rate for first cut SXXXX First RPM G17/18/19 Sets active mill plane for interpolation and comp RPM and feed rates might also be placed later in the program, but must be entered on or before the line where they are used in a command. However, there is no harm in placing them in the header of the program also . Your instructor will have a specific set of safety and startup codes required for your controller and situation Machining and CNC Technology

Machining and CNC Technology Retract Distances This is another area where your instructor will set a policy as to how close to the work, new programmers can rapid their cutting tools! A half inch is a good distance but may be too close especially for larger turning centers where crashes are spectacular. A safe distance to rapid travel to and from Machining and CNC Technology

Compensating Programs Break out your calculators for this unit! Calculating compensated significant points can be a challenge. It was in finding a better way to solve this kind of math that Mastercam software was born! Machining and CNC Technology

Coordinate shifts for uncompensated programs To profile mill this shape, using a cutter path program, each significant point must be calculated as a distance off the geometry. Machining and CNC Technology

Machining and CNC Technology Points A and I are simple, their program coordinates A’ and I’ are the radius distance away from the geometry, at 90º All remaining points require triangle solutions. Machining and CNC Technology

Machining and CNC Technology For Example To find Point B’ based on Point B. Machining and CNC Technology

Unit 4 Writing Arc Commands Don’t put your calculator away just yet! The next toolpath challenge is calculating arc commands. Depending on the part shape, they can be simple or require a bit of computation. Machining and CNC Technology

Machining and CNC Technology Arc Parameters Writing an arc command is not unlike drawing an arc with a compass. You must have five parameters You may need to define “Parameters” Machining and CNC Technology

Machining and CNC Technology Three Command Methods There are three different ways to program an arc. Each begins knowing by default, the start point since it’s the current cutter position – it’s automatically known. Then by identifying other key information, more parameters are automatically known as well. Machining and CNC Technology

Machining and CNC Technology For Example: If the center point is identified as a coordinate, then the radius is automatically the distance from the start to the center. Each of the three methods supplies a combination of key parameters such that the others are automatically known. You may need to sketch this on the board. Machining and CNC Technology

Machining and CNC Technology One command identifies the center of the arc, the end point, and the curvature. Another identifies the radius distance, curvature and end point. These two are the ones we’ll study in the text, the Radius Arc Command and the Center ID Command A third method, not discussed in the text, is the polar method where the key parameters are the radius, degree of arc and which direction, clock-wise or CCW. Machining and CNC Technology

Writing Compensated Programs OK – put your calculators away. After the last two units, you will have an appreciation for letting the computer do the calculating using cutter comp commands! For compensated programs, we use the part path geometry, not the calculated tool path. Machining and CNC Technology

Machining and CNC Technology Cutter Left or Right? The first item to define, after writing the part path coordinates, is to which side of the geometry line is the cuter to go? Think of it this way: if you are mowing along a fence, to which side of the fence are you? You (the tool) are either to the right or left of the fence (workpiece) looking in the direction you are walking. Machining and CNC Technology

Here’s what it looks like: Fence You and the Mower G42 G41 Machining and CNC Technology

Machining and CNC Technology In addition to the compensation code G41 (cutter left) or G42 (Cutter right), You’ll need to write a ramp-on path that brings the cutter to the work in such a way to begin compensating and not leave marks where it begins cutting. You’ll also need to refer to the tool radius compensation memory for distance offset from the geometry. Then with your program properly written, watch the magic happen as the cutter traces around the work shape! Machining and CNC Technology

Machining and CNC Technology Conclusion After working the problems of hand program compilation, you can see what a time and math saver CAM software can be. It does it all for you based on a part drawing! Still, you wouldn’t want to leave training unable to write programs by hand. It’s not often the PC goes down these days, but if it does, it’s the code literate machinist that saves the day! Machining and CNC Technology