The process of developing your new shape is a joint effort by you, the customer, and Fletcher Aluminium. The objective being to design a shape which best meets the customer’s functional and economic requirements while optimising the many benefits and few constraints of the aluminium extrusion process.

This section introduces you to extrusion terminology and definitions, extrusion manufacturing limits, extrusion tolerances and extrusion design limits.  It also concludes with essential reading on the range of alloys and tempers available and their typical applications, mechanical properties and surface finish criteria.

Extrusion Manufacturing Limits:
The general and significant constraints on extrusion manufacture are;

• The overall size of the profile.
• The minimum wall thickness that can be extruded.
• The extrusion tolerances that apply, and the complexity of the shape itself.

Size
The size of a profile is generally described in terms of circumscribing circle diameter, which is the diameter of the circle which can be drawn to contain the profile cross section.

Maximum Circumscribing Circle Diameter (mm):
Solids: 180mm
Hollows: 160mm

Note:
Larger circumscribing circles up to 200mm diameter can be accommodated on certain solid sections subject to special enquiry.

The maximum extrudable wall thickness of any section is determined mainly by the section size, i.e., the smaller the profile or CCD, the thinner the possible wall thickness.  A significant factor limiting wall thickness is the alloy of the extrusion, hard alloys require heavier wall thicknesses.  The remaining key factor affecting wall thickness is shape complexity.   As a result, wall thicknesses for complex shapes should be based on the following guidelines but discussed in detail with Fletcher Aluminium Technical and Sales staff.

Recommended Minimum General Wall Thickness
Circumscribing Circle Diameter (mm)	Solids		Hollows
	6060	6261	6060	6261
Up to 50	1.2	1.5	1.5	2.0
Over 50, Up to 100	1.6	2.0	1.8	2.5
Over 100	2.0	2.3	2.0	3.0

Note:
The above table of minimum wall thickness is a guide only.  Wall thickness is finally determined by a section size and shape.  Requirements outside the above table are subject to special enquiry.

Length:
Dependent on section weight and shape, maximum cut length is 13 meters.

Standard lengths for extrusions are between 2.5 and 6 meter lengths, less than 2 meters or over 6 meters are subject to special enquiry due to handling and transport limitations.

Extrusion Tolerances:
The manufacturing extrusion dimensional tolerances which apply are those presently set down by the Aluminium Development Council of Australia (A.D.C.) in Aluminium Standards and Data “Wrought Products” (Third Edition 1978).

Invariably, tolerances for an individual geometric shape are subject to negotiation and agreement between extruder and customer, under this provision the function of the shape is given priority.

All Manufacturing tolerances are subject to review from time to time.

An example of solid metal dimension tolerance from the ADC source follows:

Dimensional Tolerances (Rounded Down)
Cross-Sectional *Metal Dimension	A.D.C	Fletcher
Up to 3mm	0.15mm	0.15mm
3.0-6.0	0.18	0.15
6.0-12.0	0.20	0.20
12.0-20.0	0.23	0.20
20.0-25.0	0.25	0.25
40.0-50.0	0.36	0.35
50.0-100.0	0.61	0.60
100.0-150.0	0.86	0.85
150.0-200.0	1.12	1.10
200.0-250.0	1.37	1.35

Notes:

1. Dimensional tolerances have been rounded down to the nearest 0.05mm, because dial callipers used to measure metal dimensions are almost universally graduated at intervals of 0.05mm.
2. *Metal dimensions refer to solid metal dimensions or any measurement unbroken by a gap or void.  For tolerances across gaps or voids refer to the A.D.C. standard.