Vertical Machining Center (VMC) Motion .. 4-‐5. CNC CNC Machine Coordinates. would fill volumes and is beyond the scope of any one book or course. The goal of this . Read the Reading Assignment for each lesson (PDF). PDF Drive is your search engine for PDF files. 9/Series CNC Mill Operation and Programming Manual G and M Programming for CNC Milling Machines. Results 1 - 10 G Codes - Program Example Using Canned Cycles 1) A part program is written, using G and M G and M Programming for.
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Looking for CNC Programming, CNC Machine Programming, CNC G-Codes, or Examples in pdf form to download and study? As great as the world wide web is, . This book is not intended for sale under any circumstances. INDUSTRIAL machine tools in CNC have enabled industry to consistently produce parts to. Computer Numerical Control (CNC) Machine. Page 4. Advantages and Disadvantages of CNC Complex contours/surfaces can be easily machined.
The safety contract makes clear the obligations and operating regulations of the facility. Failure to abide by the terms of the contract is cause for dismissal from the shop. Never operate a machine that you have not been properly trained to use by a qualified person. Read the machine operator manuals and follow all safety instructions. You must follow proper operating procedures when using any machinery.
Do not use hand tools from any personal toolbox without permission of the owner. You must never remove the guards or disable the safety equipment from machinery. Inappropriate footwear includes: Watch for slippery conditions and clean up any spills immediately. Name Printed: You must immediately report ANY injury to the instructor. Do not lift objects heavier than can be easily manage without the aid of a lifting device or help.
Start Date: You are not authorized to work in the shop area until you attend the Safety Orientation. Do not engage in disruptive conversation.
I certify that I have read and agree to comply with all of the above shop regulations. I realize that I may be asked to leave the shop area for non-compliance with any of the above rules. Proper Attire. Shoes must be fully enclosed. You will wear ankle-length pants. Failure to follow safety guidelines is cause for dismissal from class. You must not enter the shop area under the influence of drugs or alcohol.
You must tuck in your shirt. If I am asked to leave. You must be courteous to others in the shop. You must wear safety goggles over prescription glasses unless your glasses have side shields and are ANSI safety approved. By signing this contract. If the machine makes an unusual noise or acts in any suspicious manner. I will do so immediately and willingly. By my signature below. You will only operate equipment accompanied by an instructor. Return of Tools and Parts-You will return any tools.
Use Hearing Protection — You will wear hearing protection when and if asked to do so by the instructor. You must not use any equipment alone. You must clean any spilled liquids immediately. You may not use equipment without supervision available and without receiving instruction in its use.
Your actions must not interfere with others or their work area. If an injury requires medical attention. Loose hair and clothing are extremely dangerous. This includes prescription or over- the-counter drugs that include warnings against operating machinery.
No Jewelry — You will remove all rings. You must not consume alcohol within 8 hours of entering the shop area. Four flute mills are more rigid. Ball nose mills are used for 3D milling. Because they are sturdier than an end mill they are also sometimes used for roughing operations. They are used to create a fillet on the bottom of a wall. Center cutting mills can plunge straight down into material. Any tool supply catalog will list many others. Discussing every type.
End Mills Milling tools include flat. This chapter introduces the most commonly used tools for prototype and short run production machining. Two flute cutters provide more chip clearance when milling in close areas.
Center-Cutting End Mills Milling tools are either center cutting or non-center cutting. Chamfer mills have an angled nose used to create a chamfer or to de-burr parts. Bull nose end mills have a radius corner. Number of Flutes Milling tools usually have either two or four cutting flutes. They are rigid. They are often used for the first machining operation to quickly create a flat finished face on the part. Non-center cutting end mills require a pilot hole.
The center of the other has a small hole at the center. Carbide Insert Figure 3: Notice that the cutting edges of the center cutting end mill continues to the center of the tool. Face Mill A face mill has cutting inserts that are replaced when worn. Countersink drills are used to create the conical face for a machine screw. Corner Radius Tool Corner radius also called Corner Round tools are used to place a fillet on the outside corner of a part.
Slitting saws and side milling cutters are installed on a special arbor. The conic helps prevent the subsequent drill from wobbling and ensure the drill is located precisely and drills straight down.
Slot Tools 3. Combined spotting-countersinks are used to create a screw clearance hole and countersink in one operation.
Because they come to a sharp point and resist bending. Figure 4: Corner Round Tool 3. Woodruff cutters are single piece tools used for creating slots and undercuts that can be held in a standard tool holder. Form taps roll taps form the thread by forming the metal to shape. Spotting Drill Countersink Combined Figure 6: Tip Angle Twist Drill Figure 7: Twist Drill Taps Cutting taps form threads by shearing material away. The tip angle of most twist drills is degrees. Be sure the tip angle of the countersink matches the included angle of the machine screw.
Usually made of high speed steel. Form taps produce no chips and are used for soft materials including aluminum. Remove too little or too much material and the hole will not be the correct size. Taps Bottoming taps are used to tap blind holes.
The spindle then stops. Taps require a hole drilled to the correct size to ensure the thread is formed properly. Reamer Figure 9: Reamers require a specific size hole be drilled before use. Spiral point taps push the chip ahead and out the bottom of a through hole. Most CNC Machines support rigid tapping.
The tap is advanced at a feed rate that matches the thread lead into the hole. Machines without rigid tapping require special tapping attachments. Reamed holes are usually accurate within.
Refer to the drill chart in Appendix A to find the correct drill size for a specified thread size and fit. Reamer Use reamers to create holes of precise shape and excellent surface finish. Cutting speeds and feeds are also important. This saves having to download and stock counterbore tools and pilots. As the tool advances into the material it causes a small amount of the material to shear away.
Counterboring is not necessary when using a CNC machine. Clockwise Tool Rotation Chip Formation Cutting tools remove metal by shearing action as illustrated in Figure 11 below. It is used to spot face holes. This is called Conventional Milling. Conventional milling causes the tool to rub against the cutting surface. Cutting in the opposite direction causes the tool to scoop up the material. This is not a problem on CNC machines because they use ball screws.
Chips should be curled and may change color due to heating. As the chip is ejected from the work area it carries with it some of the heat generated by the shearing process. Raking chips across the finished surface also produces a poorer surface finish. Chip Load A methodology for calculating cutting speeds and feeds is presented later in this chapter. Unless specifically recommended by the tool manufacturer for the material being milled. Conventional Milling Milling tools can advance through the material so that the cutting flutes engage the material at maximum thickness and then decreases to zero.
Conventional milling is used often on manual machines because backlash in the machine lead screws causes the tool to lurch when climb cutting. Climb milling produces far less cutting pressure and heat. This is called Climb Milling. Climb vs. One of the best ways to validate cutting speeds and feeds is to observe the chips created by the machining process.
After gaining some experience machinists are able to adjust cutting speeds and feeds based in part on the size. These speeds and feeds can. Speeds and feeds require adjustment due to many factors including the maximum spindle speed or horsepower of the machine.
This selection is actually more difficult on a CNC than a manual mill because. Tool sales representatives can be a valuable resource. The best source of data about cutting speeds and feeds for a specific tool.
These have become increasingly sophisticated and often provide good cutting data. Probably the most vexing problem for the beginning CNC machinist is selecting proper cutting speeds and feeds. The following pages provide cutting data for the most commonly machined materials and a methodology for calculating speeds and feeds.
Yet even the best speed and feed data is just a starting point.
If the part is held by double sided tape. CNC mills require calculating speeds and feeds in advance. Conventional Milling 3. As always. If the tool is very long and thin. SFM Surface Feet per Minute is the speed at which the material moves past the cutting edge outside diameter of the tool in feet per minute. SFM values depend on the tool type. How Speed Formula is Derived Because cutting tools are defined by their diameter in inches. Circumference is the circumference of the cutting tool in feet.
NumFlutes is the number of cutting flutes. TPI is the threads per inch of the tap. Feed Formula Feed is the linear feed of the tool through the material in inches per minute. Tap Feed Formula For tapping operations. CL is the chip load. Tap Feed Formula Feed is the linear feed of the tool through the material in inches per minute. For a twist drill.
Speed is the result of the previous formula in revolutions per minute. Speed is the result of the speed formula Figure 15 in revolutions per minute. Round off milling speeds and feeds to the nearest integer. Calculate the cutting speed and feed for a milling operation given the following values: Parameter Value Tool Diameter.
Step 1: Calculate RPM 3. Round off drilling feeds to the first decimal point. Calculate the cutting speed and feed for a drill operation given the following values: Round off tapping feeds to three decimal points or the maximum number the machine allows.
Maximum Spindle Speed Example Solution: Never use tools that have been used to machine metal to cut plastic. Carbide cutters work better for aluminum and other metals. A good practice is to keep two sets of tools: High speed steel cutters work best for plastics. The sharp edge of the tool will be compromised and cutting performance and finish will suffer.
Milling Aluminum. Drill Peck Increment. The values are relatively conservative and work well for materials and tool types listed on the previous pages. New York. Production machining is obsessed with minimizing run time and maximizing tool life because even small improvements per part can result in significant cost savings.
Prototype and short run production seeks to maximize reliability. For materials or tools not listed. Be methodical. When a problem occurs. Milling XY. This book is an essential reference for anyone using machine tools.
Analyze what is happening. Tables 8 and 9 on the following pages list recommended machining parameters for prototypes. Sometimes that is the worst thing to do and decreasing speed and increasing feed may be a better option.
A CNC machine cannot be successfully operated without an understanding of the how coordinate systems are defined in CAM and CNC machine and how the systems work together.
Number Line The basis of this system is the number line marked at equal intervals. Length offsets are required to account for different tool lengths how far a particular tool extends out of the holder. X-Axis Number Line. It also describes how the machine work coordinate system WCS is set on the CNC machine so the machine knows where the part is located within the work space. One point on the line is designated as the Origin. It concludes with a discussion of tool length and diameter offsets.
The labels. The origin. This lesson begins with a review of the Cartesian coordinate system and then explains in detail how the coordinate systems between CAM and the CNC machine are related to each other. The axis is labeled X. Diameter offsets are the key to highly precise machining where part tolerances can be maintained to an accuracy of.
Y and Z. Numbers on one side of the line are marked as positive and those to the other side marked negative.
A plane can be divided into four quadrants. Figure 3 shows the XY plane. Planes are named by the axes that define them. III and IV with axes designations as shown in the illustration below. Figure 4 shows a typical VMC with the sheet metal covers removed to expose the movable parts. The Y-Axis moves the table forward-backward. Table 1 lists the units and maximum precision for inch and metric data used by CNC machines.
This table moves in the XY-Plane. Material to be machined is fastened to the machine table. The machine column grips and spins the tool. The machine can be switched with a single code to accept either. The column controls the Z-axis and moves up-down. Even if the part is designed in metric. Units and Precision 4. In the United States. As the operator faces the machine. The machine control sends a motion signal. Ball screws have almost no backlash. Table Motion 2. The Origin point for the machine coordinate system is called Machine Home.
This causes the servomotor to rotate a ball screw attached to the table or column. This is the postion of the center- face of the machine spindle when the Z-axis is fully retracted and the table is moved to its limits near the back- left corner. Position Feedback Figure 5: Command to Servomotor 3. CNC controls employ electronic compensation to adjust for any minor backlash that may exist. The control point for the Machine Coordinate System is defined as the center-face of the machine spindle.
The actual position of the axis is continuously monitored and compared to the commanded position with feedback from a servo transmitter attached to the ball screw. This accuracy is achieved in part by the use of a closed-loop servo mechanism. Rotate Ball Screw 4. Machine coordinates are thereafter in relation to this home position.
The Power On Restart sequence simply drives all three axes slowly towards their extreme limits -X. Once all three axes have stopped moving. This signals to the control that the home position for that axis is reached. Home position is found by the Power On Restart sequence initiated by the operator by pushing a button on the machine control after turning on the control power.
As each axis reaches its mechanical limit. This is one of the most common ways to hold a part. Jaw pockets. Top View Left View For example.
Pay particular attention how the part is rotated between jobs. The outside dimensions of the part have already been milled to size on a manual machine before being set on the CNC machine. Figure 7 shows a part gripped in a vise. To make programming and setting up the CNC easier. While it can be located anywhere in the machine envelope.
The home position is far away from the table. Job The term. Figure 7: As new parts are loaded into the vise. The outside shape of this part was machined to size on a manual mill before being set on the CNC machine. If the datum shifts for any reason. Notice that. Because the location of the moving jaw varies depending how much force the operator uses. The vise has two jaws. This ensures all parts are loaded into the exact same position each time.
Because the edges of the block are already milled. Set Fixture Offset XY or part probe.
The left face of the part rests against a Vise Stop. In other words. The concept of repeatability is essential to precision machining. When using a vise. The Vise Stop establishes the X-axis origin. The fixed jaw position is not significantly affected by clamping force. The CNC is used to create the holes. Parallels precision ground rails are used to support the part.
Vise force can even significantly deform thin parts if excessive force is applied. This variability is so large that it is common practice to mark the closed position of the handle with a black marker or use a torque wrench to ensure the clamping pressure is consistent between parts.
As mentioned earlier. Fixture Offset G54 can be used to machine both sides. Whether a new WCS must be defined. As shown in Figure Since this position does change based on clamping force. The best practice is to maintain as many reference surfaces as possible whenever the part is rotated. Notice that the WCS used in Job 1 and 2 cannot be used because the part standing on end is much taller. This helps ensure the hole will be located precisely on the part side. It is also worth noticing that.
The vise stop has also been lowered so the stylus contacts the face of the part. A new Fixture Offset is defined G55 to shift the datum to the point shown. By turning the part as shown in Figure If making many parts without a second vise.
Maintaining close machining tolerances requires being fastidious and consistency of work. Small chips or even excess coolant under a part or vise can cause problems. As a practical matter. Machine set up is best done after the program is completely written. As long as the part is positioned where the tool can reach all machining operations it can be located anywhere in the machine envelope.
They make setups easier because the exact location of the part in the machine envelop does not need to be known before the CNC program is written. In conjunction with Tool Offsets. If the tool wears or breaks and must be replaced. There are many offsets available on CNC machines. To complicate matters further. Understanding how they work and to correctly use them together is essential for successful CNC machining. Figure 8: This is done using machine Tool and Fixture Offsets.
When this method is used. This method is fast. A method for doing this is included in Lesson 6. Follow the procedure in use at your facility or refer to your machine tool documentation to determine which method to use. All tools are set to a known Z-position. This value is entered in the TLO register for that tool. In fact. All tools must be reset whenever a new job is set up. The CNC machine needs some way of knowing how far each tool extends from the spindle to the tip.
This makes it very easy to reset tools if worn or broken. Fixture Offset Z may or may not be used. In its simplest use. Problems with this method include the need to face mill the part to the correct depth before setting tools. The tool is jogged to the part datum Z and the distance travelled is measured.
Both the 2nd and 3rd methods also require the distance from the tool setting position the top of the block or tool probe to the part datum to be found and entered in the Fixture Offset Z. The method shown in the center is much better and used in this book. The machine adds the two values together to determine the total tool length offset. A tool probe is very similar to the block method. It does this slowly lowering the tool until the tip touches the probe and then updates the TLO register. These thirty or so words are best memorized because they appear in almost every CNC program and knowing them helps you work more efficiently.
The official name of this language is RSD. They read like a book. Table 1 and Table 2 on the next pages show the most common G and M codes that should be memorized if possible. Most machines have a vocabulary of at least a hundred words. The G-code language was developed when machine controls had very little memory. Programs that use multiple tools repeat steps two through nine for each.
This is due in part to machines having different configurations and options. It was therefore designed to be as compact as possible. Each sentence in a CNC program is written on a separate line. While at first this language may seem arcane. Always refer to the machine documentation for the exact words and syntax for your CNC machine.
Blocks are arranged in a specific sequence that promotes safety. While many of the words used by different CNC machines are the same. John Parsons. Rapid above hole. Depth Z-. Drill N26 G80 Cancel drill cycle. Position N7 G43 Z1. N8 Z0. H2 Rapid to safe plane. Hole N27 Z1. Lead in line. N9 G01 Z To N23 G43 Z1. Machine N11 Y2.
N32 G90 Reset to absolute positioning mode for safety. Rapid to safe plane. Tool T2 0. End N29 M9 Coolant Off. N10 G41 Y0. Line move to cutting depth at 18 IPM. Move N22 X1. N25 G98 G81 Z Position N24 Z0. N14 X N19 T2 M6 Load Tool 2. N2 T1 M6 Load Tool 1. Change N18 M9 Coolant Off. H1 Rapid to safe plane. N33 M30 Reset program to beginning. N16 G00 Z1. While these rules are covered in this chapter. On CW.
N21 M8 Coolant On. Program Format The program in Figure 1 below machines a square contour and drills a hole.
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N28 M5 Spindle Off. Contour N12 X2. N15 G40 X To N6 G00 X Figure 1: Simple CNC Program 5. Move N5 M8 Coolant On. N13 Y Program T1 0. Some codes have different meanings depending on how and where there are used. Offset 1. N17 M5 Spindle Off. Drill hole canned cycle. CDC Left. Table 3: Code Meaning A Rotation about X-axis.
Q Used in drill cycles. X X-coordinate. N Block Number. It is always used in conjunction with G41 or G42 and a XY move never an arc. B Rotation about Y-axis. Z Z-coordinate. R Arc radius. S Spindle speed in RPM. The angle is in degrees and up to three decimal places precision. G G-Code preparatory code. When called. O Program Number. The table below lists the most common address codes. G1 A D Cutter diameter compensation CDC offset address. Codes are either modal.
F Feed rate. J Arc center Y-vector. C Rotation about Z-axis. I Arc center X-vector. Most modern machines use these codes. D Tool Diameter Register Used to compensate for tool diameter wear and deflection. G-M Code Reference. P Dwell time. K Arc center Z-vector. A complete list is included in Appendix B. Y Y-coordinate. Y or Z-axis respectively. D is accompanied by an integer that is the same as the tool number T1 uses D1. T Tool number. H Tool length offset TLO.
G1 G41 X1. No decimal point is used. M M-Code miscellaneous code. Expanded definitions of G- codes appear in the next section of this chapter. G43 H1 Z1. Certain drill cycles also use I as an optional parameter. Block numbers are integers up to five characters long with no decimal point. Because they take up control memory most 3D programs do not use block numbers.
Feed rates can be up to three decimal places accuracy for tap cycles and require a decimal point. G1 X1. G18 G3 X. Certain drill cycles also use J as an optional parameter. This is an integer that is preceded by the letter O and has no decimal places.
G Preparatory Code Always accompanied by an integer that determines its meaning. Accompanied by G4 unless used within certain drill cycles. Most G-codes are modal. It is always accompanied by an integer H1.
In the G17 plane. Expanded definitions of M-codes appear later in this chapter. Only one M-code is allowed in each block of code. G2 X1. The maximum length of a comment is 40 characters and all characters are capitalized.
S M3 T Tool number Selects tool. G1 Z-. This code is called tape rewind character a holdover from the days when programs were loaded using paper tapes. Coordinates are modal. Comments Comments to the operator must be all caps and enclosed within brackets. R is also used by drill cycles as the return plane Z value. Up to four places after the decimal are allowed and trailing zeros are not used. G83 Z-. It is an integer value with no decimal. It is an integer value always accompanied by M6 tool change code.
Z Z-Coordinate Coordinate data for the Z-axis. G83 X1. G1 Y1. K vectors. G2 Clockwise arc. G80 Cancel drill cycle.
G81 Simple drill cycle. G-Codes Codes that begin with G are called preparatory words because they prepare the machine for a certain type of motion. G1 Line motion at a specified feed rate. G90 Absolute coordinate programming mode. G98 Drill cycle return to Initial point R.
End of Block This character is not visible when the CNC program is read in a text editor carriage return. Code Meaning G0 Rapid motion.
The most common G-codes are shown in Table 1 and a complete list and their meaning is included in Appendix B. G59 Fixture Offset 6. G43 Tool length offset TLO. The definition of each class of code and specific meanings of the most important codes are covered next. G3 Counterclockwise arc. G83 Peck drill cycle. G84 Tap cycle. G91 Incremental coordinate programming mode. Most machines now allow the leading zero to be omitted. Used to position the machine for non-milling moves. G28 Return to machine home position.
G54 Fixture Offset 1. G4 Dwell. G82 Simple drill cycle with dwell. G56 Fixture Offset 3. G57 Fixture Offset 4. G58 Fixture Offset 5. G55 Fixture Offset 2. Older controls required G-codes to be written with a leading zero. A complete list of M-codes is included in Appendix B. A incorrect offset or coordinate move can crash the machine faster than the operator can hit the emergency stop.
G0 X0. Code Meaning M0 Program stop. M9 Coolant off. The table below lists the most common M codes and their meaning. Only one M-code can appear in each block of code. M2 End of program. It is always used with a coordinate position and is modal. M6 Change tool. M5 Spindle stop. They control machine auxiliary options like coolant and spindle direction. M8 Coolant on. G0 Dogleg Motion Caution: The rapid speed of some machines can exceed 1. Press Cycle Start button to continue.
M30 End program and press Cycle Start to run it again. M4 Spindle on Counterclockwise. G0 does not coordinate the axes to move in a straight line. M3 Spindle on Clockwise. Unlike G1. M1 Optional stop. Use the rapid feed override on the machine when running a program for the first time.
Table 2: Common M-Codes 5. Tool Diameter Offset Value D1 0. G17 is the machine default. The wear register can be thought of like a table that the control refers to with every move. G40 cancels cutter compensation. The amount of offset is entered in a CNC control D-register. Figure 3: G3 commands counterclockwise arcs. It is always accompanied by an H-code and Z-move. These offsets can be thought of like a table on the control: If there is no deviation. G43 Tool Length Compensation G43 activates tool length compensation.
Work Offsets Tip: G54 is usually used for the first machining setup. Additional offsets are used to machine other sides of the part.
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G1 G41 D1 X1. G54 X0. The process for finding the TLO detailed in Lesson 6. CNC Operation. The TLO can be thought of like a table on the control: Tool Length Resister Z H1 The X and Y values represent the distance from the machine home to part datum XY. The Z value is the distance from the tool reference point for example. Work Offsets The TLO is combined with the active fixture offset on the control so the machine knows where the tip of the tool is in relation to the part datum.
Helmut is now retired. Practical CNC design, construction, and operation techniques are provided, leading to a thorough understanding of computer-based numerical control systems, components, and technologies. Featuring hundreds of color images and schematic diagrams, the handbook explains machining fundamentals and shows you how to build and safely operate fully automated, technically sophisticated mechatronic equipment.
The latest CNC programming languages, flexible manufacturing systems, and troubleshooting methods are also discussed in this hands-on guide. Kief, Helmut A.
Roschiwal Abstract: Full details. Table of Contents A. Preface B. About the Authors A. Part 1: Introduction to CNC Technology 1. Historical Development of Numerical Control Production 2. Milestones in the Development of NC 3.
Part 2: Functions of Numerical Control Systems 1. Implementation of Dimensional Data 2. Implementation of Switching Information 3. Functions of Numerical Control Systems 4. Programmable Logic Controllers 5. Part 3: Types of Numerically Controlled Machines 1.Preface B. G81 Simple drill cycle. Transfer G-code program to CNC machine. The tool holder and block used depend on the type of tool and mount direction.
Chamfer mills are of various tip angles are in high speed steel.
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