The evidence guide provides advice on assessment and must be read in conjunction with the performance criteria required skills and knowledge range statement and the Assessment Guidelines for the Training Package.

Overview of assessment

A person who demonstrates competency in this unit must be able to take a systematic approach to the identification of the cause of faults in aluminium extrusions and to determine the appropriate action to remedy the fault.

Critical aspects for assessment and evidence required to demonstrate competency in this unit

Assessors must be satisfied that the candidate can competently and consistently:

comply with WHS, regulatory requirements and risk management procedures

correctly identify bearings, apertures,components, and critical measurements and tolerances on die drawing

liaise with extruder operators, die designers and die makers to obtain information to assist in the identification of causes of faults

identify root cause of faults in both hollow and solid die extrusions

identify die, die support, process and temperature-related shape and surface faults

identify appropriate action to take to remedy extrusion faults

access, analyse and add to die history records.

Context of and specific resources for assessment

This unit may be assessed on the job or a combination of both on and off the job. Access to the extruder and die producing the faulty extrusions and to die and extrusion records must be possible.

Assessment must cover extrusions produced by both solid and hollow dies and across a range of extrusion shapes and faults.

The competencies covered by this unit would be demonstrated by an individual working alone or as part of a team. The assessment environment should not disadvantage the candidate.

This unit may be assessed in conjunction with any other units addressing the safety, quality, communication, hand tools, machine operation, recording and reporting associated with die correcting.

Method of assessment

Assessment must satisfy the endorsed Assessment Guidelines of the MEM05 Metal and Engineering Training Package.

Assessment methods must confirm consistency and accuracy of performance (over time and in a range of workplace relevant contexts) together with application of underpinning knowledge.

Assessment methods must be by direct observation of tasks and include questioning on underpinning knowledge to ensure correct interpretation and application.

Assessment may be applied under project-related conditions (real or simulated) and require evidence of process.

Assessment must confirm a reasonable inference that competency is not only able to be satisfied under the particular circumstance, but is able to be transferred to other circumstances.

Assessment may be in conjunction with assessment of other units of competency where required.

Guidance information for assessment

Assessment processes and techniques must be culturally appropriate and appropriate to the language and literacy capacity of the candidate and the work being performed.

Required skills

Required skills include:

interpreting die maintenance requests for information on likely fault causes

liaising with extruder operators, die designers and die makers, and maintenance department

interpreting die drawings

interpreting production records and die maintenance records

evaluating solid die extrusion faults, including:

loss of shape

incorrect extrusion length, width or thickness

surface faults

evaluating hollow die extrusion faults, including:

loss of shape

incorrect extrusion length, width or thickness

surface defects

unbalanced flow through ports

speed differences through die

collapse of extrusion or extrusion features

evaluation of die support system for:

slide alignment

coining (impression) of bolster

faults and incorrect tolerances and alignment of backers, feeder plates and bolsters

Required knowledge

Required knowledge includes:

aluminium extrusion process, including:

die heating

billet heating

loading of dies and billets

breakthrough control

flow speed

rolling

quenching

stretching

aluminium extrusion alloys and their extrusion performance

extruder components and controls

requirements of AS/NZS 1866:1997 Aluminium and aluminium alloys – Extruded rod, bar, solid and hollow shapes for extruded products

causes of die deformation, including:

damaged or die

poor or incorrect die support due to:

poor manufacture

wear

incorrect component placement/selection

die and die support design and die manufacturing related faults, such as

tolerances and clearances too tight and beyond range of realistic correction by die corrector

tolerances and clearances too great causing components to move out of position during extrusion leading to flow blockage

reasons for die blockage, including:

die damage

over polishing or incorrect die polishing

tongue bending

bearing clearances too tight

overheating of billet

indicators of die support faults, including:

deflecting mandrels

die dishing

die movement during extrusion

check for metal extruding inwards or outwards

effects of nitriding and re-nitriding on die performance

billet composition and billet heating procedures

changes in billet composition caused by reheating

process related faults:

incorrect temperature settings for pre-heating of billet

bad breakthrough control by operator (setting too fast or too high a pressure):

poor extruder settings

speed through die too fast/slow

fouling of section on relief

unsuitable support of extrusion after exiting die

poor/incorrect quenching

faults not subject to action by die corrector

poor quality billet

mechanical/electrical fault with extruder

types of extrusion faults and their relationship to die correction techniques and die correction limitations, including:

shape distortion:

during extrusion

on exit from die

loss during quenching

length overruns

section collapse

surface faults, such as:

breakdown

pickup

tearing

streaking

die lines

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation, needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Die support

Die support is the specified toolstack dimensions that will support dies, according to the force the extruder can exert.

Container

The container is the part of the extruder that holds the billet and billet support components.

Support tooling

Support tooling is the name given to the various pieces of tooling (e.g. bolsters that provide stiffness to the die during extrusion).

Die holder

Die holders accommodate the diesets (feeder plate, die plate and backer). Die holders are the first components in toolstacks.

Bolster

Bolsters are deep discs of steel that provide stiffness in the toolstack to allow the die to remain flat and thus do its work properly. The term bolster includes any inserts designed to cut the cost of support tooling.

Die slide

The die slide is the part of the extruder that accommodates the dies and other tooling that makes up the toolstack.

Toolstack

The toolstack is the assembly of die, feeder plate and backer, holder and support tooling that fits into the die slide.

Die

The die is the part of the tooling that creates the extrusion shape as the metal is forced through it.

Bearing

The die contains bearings of various lengths. Bearings are lands that act as frictional controls on metal flow. The bearing is an outline of the extrusion shape cut through the die to the highest precision possible.

Feeder plate

The feeder plate precedes the die and provides an additional degree of flow control. It is also described as a control plate. It is bolted to the die and backer, forming the dieset.

Faults

Faults expected to be considered by a die corrector include faults in:

dies

die support systems

billet and die heating

billet composition

extruder settings

extruder operation

Backer

The die must be given support against the force needed to make metal flow. The first item of support is the backer. Backer profiles are usually slightly larger than die apertures (precision cut) and are not high precision items.

Platen plate

The platen plate or pressure ring is set into the front wall of the press as a replaceable feature. Platen plates take up the forces applied to the toolstack and transmit them to the extruder structure.

Primary and secondary bolsters

Some larger press operate with a combination of single, one piece bolsters for special shapes and a split system of primary and secondary bolsters.

The primary bolster is usually deeper than the secondary and provides the main support. It is cut closer to the die aperture than the secondary bolster which closely follows the primary aperture so as to back it up.

Secondary bolsters are likely to be shared by several primary bolsters