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above: shows a clear view of the mandrel which contains the dies.
These have a radius top to match the inside of the tube. The stripper sleeves and the punches are concave shaped to match the diameter of the outside of the 110mm diameter tube. The scraps drop into the
hollow bored mandrel and every four blows these are ‘stoked’ out by a long stroke air cylinder fitted with a ‘drain rod’ end. The signal to the air cylinder is via a PLC control unit in the electrical
cabinet. (all designed and manufactured by Parsell Minni-Die ).
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On this page we have the extremes of punching tubes using a mandrel. The illustrations above and to the right show a special purpose machine to punch the various holes required in traffic
light mounting poles.
The tubes were previously drilled which was both time consuming, slow, and created messy swarf. Our solution was for a machine to punch the tube in a number of blows by rotating the tube
through the quadrants and locating previous holes with an indexer.
For other holes, the tube could slide and roll in cradles so that movement and location was easy for the operator.
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above: This machine is punching small copper tubes which
have spun closed ends. Due to the nature of the component it could not be loaded onto a normally designed mandrel. Instead, our engineers created the unique approach of making the mandrel a portable
loader device. The tube is slotted onto the mandrel and then the whole is located in a precision body that contains the hydraulic punches. The punches pierce the tube and push the scraps through into the
mandrel. When the mandrel is withdrawn and the punched component is removed, the slugs can be tipped out by tapping the mandrel gently on the bed.
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Sometimes components of a ‘tubular’ form need holes for various applications and a recent machine shown to the right hand side was designed and manufactured for punching parts in a boiler
condenser assembly.
Here, a series of rectangular holes were punched in pairs and further holes were punched by indexing the component via a rotating holder and quadrant indexer. The operator loads the
component onto the die holder which matches the inside diameter. A previously punched hole was used as a locator to position the component for the first slotting blow.
A lever handle not visible in the photograph was then used to index the assembly via a series of equi-pitched indexing pin holes just visible on the quadrant table.
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Because the bore of tubes can vary significantly for mandrel location, it is important from the beginning to assess the quality and manufacturing tolerances of the tube, because this will
lead to loading problems.
Tubes must also be straight and true because material with dinks or bows will be difficult to load onto mandrels
The traffic light pole shown in the photographs left/below has a total of 26 holes from 7mm diameter to 32mm diameter in 4 metre tubes of 110mm diameter x 4mm wall thickness. Production time
allowed is between 2 and 2,5 minutes.
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above: The tube has just been punched at the top end in six blows
using the first two tools on the bed. The tube has been extracted to this position for the photograph and the indexer with a spring plunger - actually locates holes punch further down the tube at the
same time as those at the top of the tube.
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above:The machine will produce three different components using
three different mandrel loaders. The mandrel is itself the die and some components have five holes and some have three holes. Because the component is part of a boiler manifold, it was important to have
burr free holes for the next operation. Originally all these components were drilled by one man taking 40 hours per week in continuous production. The machine reduced production time to 2 days per week.
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above: A component punched with a series of ventilation holes in ten simple indexes. Floor to floor time is about 25-30 seconds
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