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 correcting solid and hollow dies and their die support systems, including conducting trial extrusions to verify corrections. Proper use of hand and power tools and workshop machines is required in undertaking corrections.

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 associated with extruder operation and die handling

relate intended changes to bearings, apertures, other die components, and toolstack components to particular extrusion faults

adjust metal flow using workshop machines, hand tools and handheld power tools to correct bearings

maintain bearings and other die components to specification

identify situations where die or other components must be either scrapped or returned to die manufacturer

supervise or conduct trial extrusions to verify corrections

report and document results of corrections.

Context of and specific resources for assessment

This unit must be assessed on the job with access to the extruder for which the die has been designed and relevant die and extrusion records. Access to hand and machine tools, including a milling machine, surface grinder and relevant hand and power tools, are also required.

The competencies covered by this unit would usually be demonstrated by an individual working in a team environment that includes extruder operators, die designers and die makers. 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:

shortening of bearings through milling, grinding, hand or machine polishing as appropriate to speed up flow or increase feed

techniques to choke bearings to achieve slowing of flow, including:

opening of angle of bearing on inner web

hand filing

machining and dressing of bearings to remove roughness and rags

peening of bearings

surface grinding of die face

chiselling ends of blunt bridges in hollow dies

undercutting of mandrels to relieve blockages

increasing pocket clearances

performing precision measurement

adjusting bolster and die support, including:

selection of different size backers

polishing or surfaces to overcome dishing

identifying simple die design changes (e.g. layout, orientation, number of holes, and so on) to increase productivity and recovery

recording corrections on die history cards and providing feedback to die designers

Required knowledge

Required knowledge includes:

die technology:

construction:

solid dies

hollow dies

die support components

composition and characteristics of various die steels

die manufacturing process

nitriding process and purpose

extrusion design process and behaviour of typical shapes during extrusion

bearings:

shape and definition

bearing deflections

bearing wash

bearing choke where entrance to die aperture is wider than the exit angle

negative bearing (entrance is narrower than the exit angle) increases speed of flow

die support technology and common faults:

bolsters:

matching of dies to bolsters

typical faults in extrusions related to poor bolster selection or fit

backers:

softening

dishing

feeder plates:

tolerances too close can cause heat related surface defects on extrusions

tolerances not matched to bearings in die can cause shape loss

extrusion process:

shape behaviour of typical extrusion products

channel shapes and tongue movement faults and typical distortions and corrections

runout length variations and possible causes:

recycled and unevenly cooled billets

out of alignment die slides

bearings worn or polished unevenly

operator variables:

incorrect heat settings

incorrect selection of bolster for die

poor breakthrough management

principles of flow:

variation of flow speed through local details and thicknesses

variation across container diameter

variation due to length of bearing

speed of metal through die along with temperature determines how metal flow fills die

source and purpose of heating of:

billet

die

extrusion and extrusion created heat

surface defects and their causes:

die lines caused by roughness at surface edges, damaged bearing edges, bearing wash or flaking of nitriding

pick up (surface tearing)

streaking

blisters

inclusions in billets

nitriding flaking off die face

effects of incorrect heat:

collapsing of thin walled sections due to over heating

blocking of the die

surface breakdown and faults:

roughness

streaking

tearing

dangers of welding extrusion dies

die efficiency considerations:

monitor die performance over time using examine die and extrusion records

balance die correction against tonnage, speed and recovery rates

recommend new die or major re-work by die manufacturer where required

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 pressed 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.

Backer

The die must be given support against the force needed to make metal flow. The first item of this 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.