CNC Machining Basics

If You Don't Know the Structure, You Can't Read the Alarm Messages

There are dozens of buttons in front of a CNC machine. The most common thing new employees hear in their first month is "Don't touch that," but no one explains why it's not allowed.

In the end, the machine consists of four parts: the place where the material is held, the place where the tool is held, the axis that moves both, and the controller that gives instructions. If you can distinguish these four, you'll understand half of the alarm messages and what senior workers are saying.

1. Start by Distinguishing the Two Types

> "Is the rotating part the material or the tool?" This one question is the key difference between the two machines. The risk factors also come from here.

2. CNC Lathe Structure

      [Spindle Head]                            [Tailstock]
   ┌───────────┐                       ┌─────────┐
   │  Spindle   ├─[Chuck]═══Material═══        │ Center     │
   └───────────┘                       └─────────┘
        │                 ┌────────┐
      Spindle Motor        │  Turret   │  ← 8~12 Tools
                          └────────┘

   Z-axis: Parallel to the spindle (length direction)
   X-axis: Perpendicular to the spindle (diameter direction)

3. Machining Center Structure

        ┌───────────┐
        │ ATC Magazine │  ← 20~40 Tools
        └─────┬─────┘
        ┌─────┴─────┐
        │   Spindle   │   Z-axis (up and down)
        └─────┬─────┘
   ══════════════════════
   │  Table + Vise     │   X-axis (left and right) / Y-axis (front and back)
   └─────────────────────┘

ATC (Automatic Tool Changer) automatically changes the tools in the magazine to the spindle. If the tool number and the magazine port number don't match, the wrong tool will be used. This is a common cause of collisions.

Adding a 4-axis (rotary table) allows the addition of an A-axis or B-axis, enabling machining of multiple sides in one setup.

4. Controller (Controller)

> Changing companies may change the controller. The basic G-code is mostly the same, but M-code and screen operations differ. Trying to operate based on "this is how it was at the previous company" can lead to accidents.

5. Buttons You Must Know on the Control Panel

6. Safety — This Is Where People Get Injured

Confirm Material Clamping

• Make sure the chuck wrench (handle) is removed. If it's left in place and the machine is started, it will fly out like a bullet. This is a typical type of accident with manual chucks.
• Check that the chuck jaw has clamped sufficiently. If the clamping is too short, the material may be ejected due to cutting force.
• If the protruding length of the bar is more than three times the diameter of the clamping part, support it with the tailstock or steady rest.
• For hydraulic chucks, check if the chuck pressure (clamp pressure) is within the specified range. If it's too low, the material may scatter; if it's too high, thin parts may deform.
• For vises, ensure that the parallel (parallel bar) is tightly pressed so that it cannot be moved by hand. If it's loose, the material may sink during machining.
• After tightening the clamp screws and bolts, visually check that the tools do not get caught in the path.

Prohibit Opening the Door While Rotating

• The door interlock is a safety device that stops the spindle when the door is opened. Disabling this with tape or magnets is considered unauthorized dismantling of safety measures, which is prohibited under Article 80 of the Industrial Safety and Health Act and Article 99 of the Enforcement Rules of the same Act. If dismantling is absolutely necessary, you must obtain permission from the employer and immediately restore it once the reason no longer exists.
• The moment you open the door to "just quickly check the dimensions" is the most dangerous. Confirm that the spindle has stopped before opening.
• Never wear gloves while rotating. If a cotton glove brushes against a rotating part, the entire hand can be pulled in. Also, keep long sleeves, necklaces, and long hair tied back.

Remove Chips After Stopping

• Chips are like a razor blade. Accidents are common when removing them with bare hands, as they can cut tendons.
• Stop the spindle → use a chip hook (hook) or brush. Do not pull them by hand.
• Blowing chips with compressed air is dangerous because they can fly into the eyes or into the slide cover. Follow the company's regulations.
• Areas where aluminum or magnesium chips accumulate pose a metal fire (Class D) risk. ABC powder extinguishers cannot put it out.

> Many BULLGANG machining companies operate with one person operating multiple machines. If you're distracted by the machine next to you, you might end up operating this machine with the door open. Developing the habit of finishing one machine before moving to the next ensures safety.

7. Working with Foreign Workers

Many colleagues who entered on an E-9 visa are assigned to operate CNC machines. The problem is that alarm messages only appear in Korean and English.

• When an alarm appears, do not reset it. Take a photo of the screen and show it to the team leader — the alarm number indicates the cause
• Instructions related to emergency stop, doors, and chucks should be confirmed once more with pictures or actual objects
• Don't just rely on the answer "I understand." Make sure they actually do it before confirming

First Week Checklist

• Three locations of the emergency stop button on your machine (control panel, side, remote)
• Check if the door interlock actually works (does the spindle stop when the door is opened)
• Designated storage location for the chuck wrench and vise handle
• Location of chip hook and brush
• Location of fire extinguisher and applicable fire class (confirm D-class for areas where chips accumulate)
• Order of ZRN (Return to Origin) operation
• How to reduce rapid override to 25%