The Modig Universal Holding Fixture for Chord Trimming is used to clamp pre-formed aluminum extrusions while the extrusion is machined in a gantry milling machine.

The UHF for Chords consists of a number of sections which can be placed on the work table of the machine in many different ways. Most common is to set up two fixtures on the machine work table with 15 sections in a 180° fan shape for each fixture.

The picture above shows 30 sections placed in a 360° circle during the test run in the Modig factory.

The fixture is operated from a CNC control which handles 30 axes moving independently of each other. The result is a fixture with a setup time of a few seconds. The fixture is available in three different sizes: small, medium, and large.

Each pedestal has two CNC controlled movements; one longitudinal running in and out from the fixture centerpoint and one for rotation of the head. The two movements have top precision by means of the transmission and measuring devices.

The clamping units on one head consists of the following equipment:

• One reference stud to locate the reference corner of the workpiece.

• One arm which swings up from underneath and clamps the workpiece against the reference stud from the side.

• Two fixed supports in the same vertical plane as the reference stud.

• Two movable pads which comes out from the head horizontally then clamps the workpiece downward against the fixed supports. The down movement is set by a cam.

All of the clamps, as described previously, can easily be exchanged to fit a new extrusion profile. Setup time is very short.

The head of each pedestal can rotate ±180° which makes it possible to clamp a wide variety of parts, from extrusions which are more or less straight to parts with a very small radius.

The clamping devices have been designed to have very quick movements. Machining is not delayed or interrupted since the clamps on each pedestal can be retracted from the workpiece as the cutting tool passes.

The clamps retract and re-clamp fast enough to allow machining at feed rates up to 600"/min. (15 m/min.) and maintain rigidity since adjacent clamps remain in place.

The whole fixture is designed for low maintenance. For example:

• Each pedestal can easily be lifted away and replaced with a spare unit when needed.

• The lower part of the fixture is covered by sheetmetal for walking, providing a flat surface for operator access to the fixture.

• The head of the pedestals are very clean without cables, hoses, or connection terminals. The chips fall to the floor away from the parts and clamps.

• The small number of moving and fixed parts in each pedestal reduces the risk of breakdowns.