Machining Flashcards
State the function of code:
G00
Point to Point positioning (rapid transverse)
This command moves the tool at the machines maximum travel speed to coordinates specified after the command. This code is primarily used to the position before beginning a new cut instead of cutting.
State the function of code:
G01
Linear interpolation (Cutting Feed) This command moves the tool along a straight line to the coordinates that follow it. Additionally, with the G1 code, you apply a feed rate for the cut.
State the function of code:
G02
Clockwise Circular Interpolation/Helical
This command moves the tool along a clockwise curve to coordinated specified after the code
State the function of code:
G03
Counter-Clockwise Interpolation/HelThis command moves the tool along a counterclockwise curve to coordinated specified after the codeical
State the function of code:
G40-G42
Tool Diameter Compensation
G40 - Cutter compensation cancel - Cancels cutter radius compensation utilised in codes G41 and G42.
G41 - Cutter compensation left - This command is used to activate cutter radius compensation (used to ensure the diameter of the tool is compensated for within the coordinates of the cut) and to set the tool to a geometry left of the stock. This method is used for climb milling.
G42 - Cutter compensation right - This command is used to activate cutter radius compensation (used to ensure the diameter of the tool is compensated for within the coordinates of the cut) and to set the tool to a geometry right of the stock. This method is used for conventional milling.
State the function of code:
G70
input units set to inchs
State the function of code:
G71
Input units set to metric (mm)
State the function of codes:
G80-G89
Canned or Fixed Cycles for Drilling
State the function of code:
G90
Absolute Programming Mode
Absolute command
State the function of code:
G91
Incremental Programming Mode
Incremental command
State the function of the following codes: G00 G01 G02/G03 G40/G41/G42
G00 - Point to Point positioning (rapid transverse)
G01 - Linear interpolation (Cutting Feed)
G02/G03 - Clockwise Circular Interpolation/Helical and Counter-Clockwise Interpolation/Helical
G40/G41/G42 - Tool Diameter Compensation
G40 - Cutter compensation cancel
G41 - Cutter compensation left
G42 - Cutter compensation right
State the function of code:
M00
Program Stop:
Cancels the spindle and Coolant functions; stops part program execution
State the function of code:
M01
Optional Stop
Program stop often used when the operator want to re-fixture the part
State the function of code:
M02
Program End
Marks the end of the program; stops the spindle, coolant and axes feed
State the function of codes:
M03
M04
Spindle on CW
M03 - Starts clockwise rotation of the spindle
M04 - Starts counterclockwise rotation of the spindle
State the function of code:
M05
Switches the spindle off
State the function of code:
M06
Tool Change
Requests an automatic tool change
State the function of codes:
M07-M09
Coolant Toggles
M07 - Switches on the secondary coolant systems
M08 - Switches on primary coolant systems
M09 - Switches off both the primary and secondary coolant
State the function of code:
M30
Indicates the end of the main program
What are three parts of the CNC program
- Program Setup
- Material Removal
- System Shutdown
Example:
% Program start Flag
: 1001 Four digit program number
N5 G90 G20 Use absolute units and inch programming
N10 M06 T2 Stop for tool change, use tool#2
N15 M03 S1200 Turn the Spindle on CW to 1200 rpm
N20 G00 X1 Y1 Rapid to (X1,Y1) from origin point
N25 Z0.125 Rapid down to z0.125
N30 G01 Z-0.125 F5 Feed down to Z-0.125 at 5 ipm
N35 G01 X2 Y2 Feed diagonally to X2,Y2
N40 G00 Z1 Rapid up to Z1
N45 X0 Y0 Rapid to X0,Y0
N50 M05 Turn the spindle off
N55 M30 End of Program
State the equation for calculating spindle speed
Vc = π×D×S
Surface Cutting speed (m/min) =
Pi x Diameter x spindle speed
Rearranged as:
Vc/ (π×D) = S
State the equation for calculating feedrate
F = z×fz×S Cutting Feedrate (mm/min) = Number of cutting edges x Feedrate per cutting edge x spindle speed
Describe the operational instructions and the CNC code to enable the operator to machine the outside profile of the component leaving 0.15mm stock for a final finish pass.
When producing a part using a manufacturing machine, you may wish to leave stock remaining for a finishing pass. In order to do this, we must utilise the cutter radius compensation utilised within commands G40, G41 and G42. When establishing the cutter compensation of the tool, the operator will select the tool being used and the program with compensation for its radius when cutting the part to meet its specification, but if we want to leave additional material on the stock, the operator must simply go into the tools settings and override the current radius and increasing it by 0.15mm. Now when the operator begins the cut, the machine will function as if it is removing an additional 0.15mm, when it is not removing that stock.
Describe the major benefits of CNC manufacturing
- Repeatability and Quality of Manufactured Components
- Production of Profiled 2 and 3 Dimensional Components
- The speed of Production: Safe Utilisation of High Cutting Surface Speeds and Feedrates
- Amalgamation of Production Operations :
Reduction of Number of Set-Up Operations
Reduction of Tooling and Fixture Inventories
Increased Quality - Manufacture From Minimum Number of Datum Locations - The utilisation of Lower Cost Standard Tooling
- Flexibility of Manufacture
- Reduction in number of Machine Tools required and consequently Floor Space
- Dynamic Manufacture - Lower Work In Progress
- Reduced Lead Time Implying the Potential for JIT Manufacturing
Identify significant manufacturing management/system task necessary to ensure the effective operation of CNC machines
Manufacturing Systems MUST Ensure :
- Quality / Optimised / Verified CNC Programs
- Full Potential of the CNC Resource Being Used
- Procedures for Updating and Maintenance of ALL Programs
- Kiazen Methodology to Continually Improve Programming Techniques
- Economic Batch Quantities ( EBQ ) Approaching Unity
- Efficient and Effective Implementation of Tooling and
Fixture Management Systems - Quality Products
Define the following terms:
Set-up time
Cycle time
Setup time: the entire time a machine is down between production runs
Cycle time: the time it takes to complete a production run divided by the number of good workpieces produced
State the three ways to reduce set-up time
Eliminate (especially on-line) tasks
You save the amount of time it was taking to perform the task
Move on-line tasks off line
At least the machine is not down during the performance of the task
Many tasks can be done while the machine is running production
Assumes you have adequate lot sizes, cycle times, and available personnel
Often requires duplications (especially tooling)
Facilitate tasks
Make it as quick & easy as possible to perform the task
The easier a task is to perform, the faster it can be done!
Task simplification makes it possible for people with the lower skill to perform well
Often the easiest alternative to justify
Describe the concept of single minute exchange of dies (SMED) and the crucial requirement to incorporate this into the manufacturing process
SMED - Single minute exchange of dies
Reducing SET-UP times towards zero implies making a manufacturing facility more flexible. Within the SMED concept flexibility is the organizations capability to react to change, rather than resource flexibility.
Two aspects of flexibility most concern manufacturing companies:
- Variety of products, processes and activities
-Uncertainty of the system to predict demand.
Crucial Steps for Set-Up Reduction
- Select: Selection criteria for machines with highest set-up times, bottleneck operations and most likely to yield savings.
- Record: establish accurate records of current practice.
- Analysis e.g.. clamp/unclamp, load/unload, adjustment, cleaning, inspection etc.
- Eliminate: attempt to simplify and eliminate wasteful activities.
- Simplify :- Attempt to simplify all remaining activities eg. material handling, pre-set tooling etc.
- Classify :-
internal operations - work that must take place when the machine is stopped
External: work that must be done before the machine is stopped.
The challenge is to convert as much internal work to
external work implying the resource is stopped for the
minimum time between operations.
Develop a method and equipment. These
developments will support the new set-up
activities for both internal and external work.
Implement revised procedures. New methods
will become standard practice. New method
studied for training purposes and as further
projects for improvements.
For the programming of a CNC machine tool discuss:
- Interactive graphical programming
- Off-line (CAD/CAM) programming
Interactive Programming at the Machine Tool:
• Simple and Complex Geometric Programming
• Skilled Operator Function
• Lack of Data Integration
• Difficult to Ensure Executive Control
• Repeatable Cost per Machine Tool
• May Contribute to non-productive time
• The utilisation of 3D CAD solid models has
enabled the CNC machine tool programmer to
generate toolpaths by attaching appropriate
tooling strategies directly to the geometrical
feature of the solid model.
• In a similar way, software exists to enable the
CMM programmer to manipulate the probing
system around an imported 3D CAD model
thereby developing off-line programming
capabilities.
This has the potential to substantially
reduce the time required to develop and
approve programs and enables:
– full graphical simulation,
– eliminates the possibility of a probe crash,
– optimises probe positional movements,
– increases the productive utilisation of the CMM resource.
Off-Line Programming Systems:
- Simple and Complex Multi-Axis Programming Capability
- Skilled Operator Function
- Graphical Simulation to Verify Programming Data
- Executive Control
- No Alternative for Complex Geometrical Profiles
- Potential for Minimum Non-Productive Time at the CNC, M/c Tool
- Overheads - Hardware / Software / Programmers etc
- Off-Line Programming Systems Aids the Maintenance
of CNC Programs.
- Component Parts Filed Within the CAD/ CAM
Processing System Database Configuration
n When Required by the CNC Machine Tool these Files
are Processed Using An Independent Master Tooling
File to Generate the CNC Code
- Comparison against all mainstream CAD formats
- Rapid alignment even for complex freeform shapes
- Inspection of user-defined sections
- The ability to inspect along the edge of a part
- Full Geometric Inspection capabilities.
- Automatic creation of inspection features from CAD
- A step by step Geometric Dimensioning & Tolerancing (GD&T) Wizard
- Point, wireframe and surface export for measured entities.
- CAD manipulation - including surface offsetting (e.g. reverse side for sheet metal, spark gap for electrodes)
