Activity 001: MIG Welding β First Beads on Flat Plate¶
Activity ID: U6M2-ACT-001 Duration: 45 minutes Objective: Students will run their first MIG weld beads on flat mild steel plate, practicing consistent travel speed, CTWD, and torch angle. Group Size: 2 students (one welds, one observes and provides feedback, then swap)
Overview¶
This foundational activity introduces students to the physical experience of MIG welding. Starting with straight-line stringer beads on flat plate, students will develop the basic motor skills needed for all subsequent welding activities.
Materials & Equipment Needed¶
- MIG welder set for mild steel (ER70S-6 wire, C25 gas, 0.030" wire)
- 4 mild steel plates: ΒΌ" Γ 4" Γ 8" (2 per student)
- Soapstone or welding marker
- Wire brush and chipping hammer
- Welding table with work clamp
- Angle grinder with flap disc (for surface prep)
- Full PPE: welding helmet (shade 10-12), FR jacket, leather gloves, boots, hearing protection, respirator, welding cap
- Practice bead evaluation ruler/guide
- Fire extinguisher within 15 feet
Instructions & Procedure¶
Phase 1: Setup & Machine Settings (8 minutes) 1. Prepare plates: grind one surface of each plate to bright metal 2. Mark 6 parallel lines lengthwise on each plate, spaced Β½" apart (soapstone) 3. Set MIG welder parameters for ΒΌ" mild steel: - Wire feed speed: 350 IPM (approximately 130-150A) - Voltage: 20V - Gas flow: 22 CFH 4. Clip the work clamp directly to the welding table 5. Verify all PPE is on β instructor checks both students
Phase 2: Student A β Stringer Beads (15 minutes)
Bead 1: Slow and steady 1. Position comfortably β feet flat, arms braced on the table 2. Hold the gun at 90Β° work angle, 10Β° push travel angle 3. Place the wire tip at the start of line 1, lower your helmet 4. Press the trigger β wait 1 second for the arc to establish 5. Travel at a steady speed (approximately 10-12 inches per minute) 6. Maintain β " CTWD (stickout) 7. Complete the 8" bead, release the trigger, hold still for 1 second (post-flow)
Beads 2-3: Speed variation 8. Bead 2: Travel slightly faster than Bead 1 9. Bead 3: Travel slightly slower than Bead 1 10. After all three, compare: which has the best width consistency?
Beads 4-6: Parameter adjustment 11. Bead 4: Increase voltage by 2V (keep WFS the same) β observe bead shape change 12. Bead 5: Return voltage to original, increase WFS by 50 IPM β observe penetration change 13. Bead 6: Return to original settings β run the best bead you can with everything you learned
Phase 3: Student B β Stringer Beads (15 minutes) Repeat Phase 2 with roles swapped. Student A observes and provides feedback on: - Consistent bead width (mark any width changes) - Consistent ripple spacing - Start and stop quality - CTWD consistency
Phase 4: Evaluation & Discussion (7 minutes) 1. Wire brush all beads to remove slag/spatter 2. For each bead, evaluate and record: - Width consistency (Β±): ___mm - Height consistency: even / uneven - Ripple spacing: even / uneven - Spatter amount: none / light / moderate / heavy 3. Identify your best bead and explain why it was the best 4. Instructor reviews selected beads and provides technical feedback
Discussion Points¶
- How did changing voltage affect the bead shape?
- How did changing wire feed speed affect the sound and penetration?
- What was the hardest part of maintaining a consistent bead? (most students say travel speed)
- How did the observer's feedback help the welder improve?
Expected Outcomes¶
- Students can start and stop a MIG arc safely and consistently
- Students produce at least one bead with Β±1/16" width consistency over 6" of travel
- Students understand the relationship between voltage, WFS, and bead characteristics
Assessment Rubric¶
| Criteria | Excellent (4) | Proficient (3) | Developing (2) | Beginning (1) |
|---|---|---|---|---|
| Bead Consistency | Width varies <1/16" over 6" | Width varies <β " | Width varies <ΒΌ" | Highly inconsistent |
| Arc Control | Smooth start/stop, stable arc | Minor arc issues | Frequent arc instability | Cannot maintain arc |
| Parameter Understanding | Correctly predicts effect of changes | Observes effects with prompting | Limited understanding | No connection between parameters and results |
| Safety Compliance | Full PPE, proper technique throughout | Minor reminders needed | Multiple corrections | Significant safety issues |
Safety Considerations¶
- Full welding PPE is mandatory β no exposed skin near the arc
- Observer must wear welding helmet or be behind a welding screen β reflected UV causes arc eye
- Hot plates must be marked "HOT" and handled with pliers only
- Keep the gun trigger pointed away from your body and others when not welding
- If the wire fuses to the contact tip, turn off the machine before attempting to clear it
- Fire watch: 30 minutes after the last weld
Last Updated: 2026-03-19