Aluminium training

Extrusion press alignment: tools and techniques

(Cm. Reconciliation also press – General principles)

Alignment Principles

The proper extrusion press alignment is required for maximum production quality and minimum downtime. The srict geometric relationships of the components of an extrusion press are fundamental to proper press alignment [1, 2] (Fig. 1-3).

These relationships must be correct when the press is at operational working temperature to allow for thermal growth effects. They also implies to the major press components during the various operational load and event conditions of ram and container pressure and extrusion [1, 2].

Fig. 1-1 – Identification of press components [1]


Fig. 1-2 – Extrusion press diagram [4]

Fig. 2 – Illustration of press components (RL Best) [1]

1 – hydraulic power unit; 2 – tie rods; 3 – butt shear; 4 – extrusion platen;
5 – container shifting cylinders; 6 – operator’s console; 7 – die slide; 8 – container;
9 – container housing; 10 – billet loader; 11 – press base; 12 – billet loader cylinders;
13 – pressing stem; 14 – crosshead; 15 – side cylinders; 16 – cylinder platen;
17 – main cylinder
Fig. 3 – Typical direct drive hydraulic extrusion press [3]

The geometric relationships of the static components:

  • The press base should be level with respect to gravity. The relevant contact points should lie in a flat plane.
  • The back platen and the front platen should be located perpendicular to the base.
  • The pressure ring bushing should have its hole centered in the front platen. Its front surface should be flat and parallel to the front platen.
  • The press center line is the line joining the platen centers, and all the platen-centered components should lie on this line.
  • The guide ways for the crosshead and container should be straight and parallel to the base. They should be symmetrically spaced about the press center line.
  • The main cylinder, bearing bushing, flange, and ram piston should be concentric and centerd on and perpendicular to the back platen.
  • The crosshead should be center-mounted on the ram and fitted with a straight and centered extrusion stem perpendicular to the back platen.
  • The geometric center lines of each of the four machined tie rods or columns should be parallel to and symmetrically located about the press center line.

The geometric relationships of the moving components:

  • The ram piston and the extrusion stem move along the press centerline over their full stroke.
  • The center line of the container bore is coincident as it moves along the press center line from its open to closed position.
  • The centerline of the tooling stack is coincident with the press center line loads.
  • The billet loader positions the billet so that its centerline matches the centerline of the container and stem before it is loaded into the container.

Traditional and modern press alignment methods

Press alignment methods and measuring instruments can be divided into traditional and modern. The use of various traditional press alignment tools are, essentially, linear one-dimensional step measurements of components, which together can give the complete geometric state of the machine. Full alignment of the press by traditional methods requires a very long time (several days), because some parts need to be measured disassembled, and others can only be done on a cold press. Nonetheless, some simple tasks of setting up the press and checking individual components can be more practical and economical using traditional methods.

Modern 3D coordinate measuring systems provide a 3D global approach. Full press alignment is faster, more accurate and reliable, and also has a number of other advantages compared to traditional methods. Below is an overview of traditional methods and tools for extrusion press alignment..

Tradition Alignment Methods and Tools

Machinist’s Level

Accuracy 0,004 mm / m. Do not apply on hot surfaces.

Surveyer’s Presision Optical Level

Accuracy 0,001 mm / m.

Laser Level

Usually used instead of Surveyer's Presision Optical Level (Figure 4).

Fig. 4 – Three-plane laser level (See www.hamarlaser.com) [1]

Trammel Rod

It is made to order. Used to measure distances between cross members (or between column bushings). Steel or aluminum tube is equipped at one end with a micrometer, and on the other - a spherical tip (figure 5). In order to ensure the necessary accuracy, these rods have a special supporting device for preventing their deflection under its own weight, as well as thermal insulation to prevent heat from the thermal expansion of the container.


Fig. 5 – Trammel Rod device [1]

Taper Gauges

Fig. 6 – Container Taper Gauge [1]

Adapter Block for Angled Guide

for presses, in which the guide frame is not horizontal, and oblique ones use special adapters (figure 7), which allow the use of normal base points in horizontal alignment frame press.

Fig. 7 – Adapter Block for Angled Guide Ways [1]

Piano Wire

The diameter of the strings 0,4 to 0,5 mm, strength from 1700 to 3400 N / mm2 (Figure 8).

Fig. 8 – Alignment with piano wire [1]

Fixtures for Piano Wire Tensioning

The determination of the center line of the press with the help of a "piano" string is carried out by pulling it between the centers of the hole of the front cross member and the ram (figure 9).

Fig. 9 – Fixtures for alignment with piano wire [1]

Precision Tube Fixture

Instead of strings used for leveling the appliance from the finely crafted pipe with special patients with plugs, and special devices to center as shown in Figure 10.

Fig. 10 – Precision Tube Fixture [1]

Base Centerline Fixtures

Alignment of the press center line of the frame, which is determined by special precise holes (figure 11).

Fig. 11 – Fixture for Base Centerline Method [1]

Dummy Dies and Tooling Stack

It is used for the rapid control of the alignment die assembly relative to the container.

Standard Measurement Tools:

  • compasses;
  • calibers;
  • squares;
  • rulers (usually 2,5 m);
  • a set of shims.

Sources:

  1. Extrusion Press Maintenance Manual, ed. Al Kennedy
  2. Extrusion Press Alignment with Modern Technology /J. E.V. Mulder and G.J. Smith – Aluminium Extrusion Seminar
  3. Aluminum and Aluminum Alloys /ASM Speciality Handbook – 1996
  4. Influence of Al Microstructure on Hard Anodising Quality – Profile Material / Tom Hauge, Hydro Aluminium, Norway – 2014