Identify cause of contact tip burn-back and failure of wire to feed; make necessary adjustments.

Lesson Plan for

CRT 130-3

NON-STRUCTURAL ANALYSIS AND DAMAGE REPAIR SECTION III

Course HS Title: / Non-Structural Analysis and Damage Repair / Program:
KCTCS Courses included in HS Title: (Lesson is prepared for course highlighted.)
KCTCS Course No. / KCTCS Course Title
Introduction/Context / This lesson will instruct the student on how to identify the cause of contact tip burn-back and failure of wire to feed, and make necessary adjustments. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in a Collision Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Prepared By / School / Date:
Grade Level / No. Students / No.IEP's: / Lesson Length:
Task
Identify cause of contact tip burn-back and failure of wire to feed; make necessary adjustments.
No. / Objective
1 / Given the proper tools and instruction, the student will be able to identify the cause of contact tip burn-back and failure of wire to feed, make necessary adjustments, and pass a written test covering the task with 100% accuracy.

Connections:

New Common Core:
RST 11-12-2
RST 11-12-3
New Common Core Technical
TD-SYS-1
TD-OPS-3
New Science Standards
HS-PS2-3.
Skills Standards:
AA001
EG011

INSTRUCTIONAL MATERIALS/TECHNOLOGY

Teacher Designed Materials and Other Handouts


Textbooks and Workbooks

Author / Title/ISBN No. / Edition / Publisher / Pages
Duffy / I-Car Professional Automotive Collision Repair / Second / Delmar / 171-172


Equipment

Quantity / Item / Source
As Needed / Welder / Various


Content/Presentation/Demonstration Outline

Instruct students that many MIG welders have a burnback setting to control the amount of time that the electrode is energized after releasing the trigger. Tell them that burnback occurs when the electrode wire melting rate is faster than the wire speed. Explain that the electrode wire melts back inside the contact tip and melts to the tip. When this happens, tell them the wire cannot feed and the tip will need replacing.
Tell students that they should adjust the burnback setting while doing test welds. Let them know that they should always perform test welds on a piece of scrap similar to the piece being worked on. Explain that there also might be a mode setting for switching the welder to stitch, spot, or continuous mode.
Instruct students that settings are different based on the type of metal being welded. Let them know that the recommended settings on the welder will usually be for uncoated steel. Let them know that coated steel, compared to uncoated steel, requires heat (voltage) and wire speed (amperage) settings for next higher gauge metal. Also, tell them to use a slightly slower travel speed and more vertical gun angle.
Explain to students that MIG wire speed is how fast the rollers feed the wire into the weld puddle. Tell them that an even, high-pitched buzzing sound indicates the correct wire-to-heat ratio producing a temperature in the 9,000°F (4,982°C) range. Let them know that a steady, reflected light is desirable, and that it will start to fade in intensity as the arc is shortened and wire speed is increased.
Inform them that if the wire speed is too slow, a hissing and plopping sound will be heard as the wire melts away from the puddle and deposits the molten glob. There will be a much brighter reflected light.
Explain that too much wire speed will choke the arc. This is because more wire is being deposited than the head and puddle can absorb. Let them know that the result is the wire melts into tiny balls of molten metal that fly away from the weld, creating a strobe light arc effect.


Applications/Practice

1 / Refer to content


Evaluation and feedback Prior to Testing or Lab Work

1 / Objective 1. / Formative assessment / Instructor will observe students as they practice the procedure to assure correct procedure and safety practices are being followed. A checklist will be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.


STUDENT ASSESSMENT:(Assess student progress with performance criteria.)

1 / Objective 1 / Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)