131.2.4 - CAD/CAM/CNC Mills

CNC Mill Operation

Loading Programs onto a CNC Mill

There are several ways programs can be loaded & ran by CNC machines, which can be divided into the following categories:
- Local Memory/Access Methods:
  - Manual Data Input (MDI): This involves manually entering the G-code program into the CNC machine's control panel. This method is time-consuming and error-prone, as the operator must enter each line of code accurately. However, it is useful for small, one-off jobs where programming time is not a concern.
  - Removable Storage Device: Some CNC machines have a built-in removable storage device, such as an SD card or CompactFlash card. The G-code program can be saved to the removable storage device and inserted into the CNC machine's control panel. This method is similar to USB storage, but uses a different type of storage device.
- Remote Memory/Access Methods:
  - Direct Numerical Control (DNC): In this method, the G-code program is stored on a computer or server and transferred to the CNC machine via a wired or wireless connection. This is more efficient than manual data input as the program can be easily updated or modified, and the operator can avoid errors in manual data entry. However, this method can be slower if the network or transfer speed is slow, and there is a risk of data loss if the network connection is lost.
  - Ethernet: This method involves connecting the CNC machine to a network via Ethernet cable. The G-code program can be transferred from a computer on the network to the CNC machine over the network. This method is similar to DNC, but uses a wired connection instead of wireless.
  - Cloud-based storage: In this method, the G-code program is stored on a cloud server and accessed by the CNC machine over the internet. This method is similar to DNC, but uses a cloud-based server instead of a local server.
- Obsolete Memory/Access Methods:
  - Drip Feed: Drip feed is a method of sending the G-code program to the CNC machine one block at a time, rather than sending the entire program all at once. This is useful when the program is too large to fit in the CNC machine's memory all at once. The CNC machine receives each block of code and executes it before requesting the next block. This method can be slower than other methods, but is useful when the CNC machine's memory is limited or when a large program needs to be run on a machine with limited memory.
  - Tape-Read: Tape-read is an older method of loading G-code programs onto CNC machines, which uses magnetic tape. The G-code program is stored on a magnetic tape, which is read by a tape reader attached to the CNC machine. This method was commonly used in the early days of CNC machining, but has largely been replaced by newer, more efficient methods.
The choice of method depends on factors such as the complexity and length of the program, the available technology, and the operator's preferences. In general:
- Local Memory/Access methods are more suitable for smaller or simpler programs, especially ones that are ran on specific machines repeatedly without change
- Remote Memory/Access methods are preferred for larger or more complex programs, and ones that vary and are updated/changed regularly
- Obsolete Memory/Access methods are now less commonly used due to advances in technology and the availability of more efficient and reliable methods, but may still be used for older machines in some production environments

Graphics Run & Dry Run

Both graphics runs and dry runs are important because they help to reduce the risk of errors and ensure that the G-code program will run correctly on the CNC machine. By using these testing methods, operators can catch potential problems before they occur, reducing the risk of damage to the machine or the part being machined. This can save time and money, as errors can be corrected before any actual cutting takes place. Additionally, these testing methods can help to increase efficiency and reduce downtime, as operators can quickly identify and address any issues before running the program on the machine.

Graphics Run

- A graphics run is a digital test run / visual simulation of the G-code program on a computer screen/control panel. This allows the operator to see a 3D representation of the part being machined and how the tool path will be executed, without the machine physically moving. Graphics runs can be used to check for potential problems such as tool collisions, over-travel, and other issues that could cause damage to the machine or the part. The operator can make any necessary adjustments to the program before running it on the machine, reducing the risk of errors and increasing efficiency.
  - The primary benefit of a Graphics Run is to test your program's G-Code for machine alarms/errors due to code and/or setup.

Dry Run

- A dry run is a physical test run of the G-code program on the CNC machine, but without the cutting tool engaged in the material. In a dry run, the machine will move through the program's tool path as if it were cutting, but without actually making any cuts. This allows the operator to test the program for potential problems, such as incorrect tool paths, improper feed rates, or other issues that could cause damage to the machine or the part. A dry run can help to reduce the risk of errors and increase efficiency, as any issues can be addressed before actual cutting begins.
  - To perform a Dry-Run on a Haas machine, you can apply temporary, additional offsets to raise either the Tool Height Offsets (not recommended) or the Work Z Offset (recommended) high enough that the tools will no longer contact the part
    - This tells the machine that the program is actually above where the part really is, and therefore the tools will perform the same X & Y movements, just hovering up above the part and "cut air"

Safely Running a Program

When running a CNC program for the first time - called "Proving Out" a program - there are some active tools you can use & steps you can take during operation of the machine to avoid crashes and improve the performance of the program:
1. - Overrides: Overrides are used to adjust the machine's feed rate, spindle speed, or other parameters during the cutting process. Overrides can be used to increase or decrease the cutting speed, or to change the spindle speed for different types of cutting tools. This allows the operator to optimize the cutting process for the material being machined, or to make adjustments if issues arise during the cutting process.
    - On programs that are unproven, it is recommended to run at reduced Rapid speed, to give yourself more time to react
  - Distance-to-Go: Distance-to-go is a feature that displays the remaining distance the machine needs to travel to complete the currently-highlighted/running line of the program.
    - This feature can be used to predict whether or not a crash will occur
      - For example, if the tip of a tool is hovering roughly 3" above a part, yet the Z-Axis Distance to Go says -10", then the tool will attempt to travel 7" past the surface of the part, resulting in a serious crash.

Feed Hold: Feed Hold allows the operator to temporarily pause the machine's movement during execution of the program. Whenever in doubt, press Feed Hold & contact a supervisor as needed. To resume the program after activating Feed Hold, an operator must press Cycle Start.
- Feed hold can be used to immediately stop the machine if the operator notices any potential safety issues, such as tool breakage, material binding, or other problems that could cause damage to the machine or the part being machined, allowing the operator to identify and correct the issue.
- Feed hold can be used to make adjustments to the machine during the cutting process, such as adjusting the tool or the cutting speed, or checking for cut quality/finish/location. The operator can make the necessary adjustments and then resume the cutting process.

Single-Block: Single-block is a mode that allows the operator to run the program one line of G-code at a time. This is useful for testing and verifying the program, as well as for troubleshooting any issues that may arise. When single-block mode is enabled, the machine will execute each line of code and then pause, allowing the operator to verify the position and movement of the machine before continuing to the next line.

By using all these features, operators can have greater control over the machining process, and can adjust or modify the program as needed to optimize the process for the material being machined. These features can also help operators to troubleshoot and identify any issues that may arise during the machining process, helping to improve efficiency and reduce downtime.

2.4✔ CHECKPOINT

Cut Soft Jaws

- For this Checkpoint, you will be running a program to make a 4" vise soft jaw:
  - Using the instructions given in the comments of the program below, ensure your setup from the previous checkpoints is correct to run the program:
    - O04100 (4 IN SOFT JAW).nc
  - Before cutting your parts, do both of the following:
    - Perform a Graphics Run, to check for code alarms/errors
    - Perform a Dry Run, to check for setup errors
    - Have your instructor verify proper setup
  - Run the program to cut out the 4" Mill Vise Soft Jaw, & inspect according to the blueprint shown below
- Once done, add documentation of your progress to your previously-created "CNC Mill Operation" Project page on your portfolio website, including:
  - Pictures(s)/Gif(s)/Video(s) and/or Summaries/Descriptions of:
    - Your full setup before running OP1 of the program
    - The part after OP1
    - Your OP2 setup
    - The finished part after OP2
    - Possible improvements
    - Descriptions/summaries of what you did/learned, including any mistakes/learning moments during this task

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