Product category:
Machinery and Production Equipment
News Release from: Mollart | Subject: Subcontract component manufacture
Edited by the Engineeringtalk Editorial
Team on 19 October 2000
New production method developed for
pneumatic part
Mollart Engineering has completely re-engineered the manufacture of a complex pneumatic hammer barrel component following investment in the UK's first Mazak Integrex 300Y mill-turn centre
Mollart Engineering, the Chessington-based sub-contract machining operation of the Mollart Group, has completely re-engineered the manufacture of a complex pneumatic hammer barrel component for its customer following investment in the first Mazak Integrex 300Y mill-turn centre installed in the UK Not only did the in-house machine setter/operator develop the method, by switching from a previous casting requiring seven separate machine tools with complex fixturing, to a solid SG iron billet and four operations, Mollart' new concept significantly reduced the level of subsequent scrap components found at the customer's works
This article was originally published on Engineeringtalk on 20 Jul 2000 at 8.00am (UK)
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With the change away from castings, Mollart now supplies the component complete.
This includes the billet material sourced from its TM Steels stockholding operation in Chesterfield.
Says Guy Mollart, Chairman: "We are increasingly providing total supply with 'added value' to sub-contract components involving deep hole drilling.
Our philosophy is that we are prepared to purchase the latest machine tool technology to maintain quality and achieve competitive cycle times against competitors.
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Proof of this includes investment over the last two years in machines such as the Mazak, an Hitachi Seiki HiCELL, Studer grinding machines and a digital technology-based Delapena E3000 honing machine.
"We have also recently installed pressure test equipment and large capacity, six metre bed electronic lathes, machining centres and sliding head CNC lathes for various components," adds Guy Mollart.
This strategy has led to a wide range of contracts, many long running and to produce continuous production components for telecoms, nuclear, automotive, defence, medical and off-road vehicles, for which the hammer barrel is a typical component.
In fact, the original hammer barrel component would be regarded by many sub-contractors as a production engineering nightmare being a difficult shape to hold and having so many deep holes combined with tight positional and geometric tolerances.
The part has two oval flanges at each end with a central portion of the body waisted.
This feature makes it very difficult to hold.
Following Mollart's re-engineering, it is now produced from a SG iron sawn billet 112 mm diameter by 240 mm long.
The hammer barrel has a central bore 33 mm diameter with 10 micron tolerance and has to be concentric, within five micron, to counterbores of 42 mm and 50 mm diameter.
The two end faces must also be parallel and flat within five microns.
A whole series of grooves are specified in the central bore, some of which are to tight positions as break-outs from deep hole drilled feed holes.
There are three main deep holes of 6 mm diameter by 205 mm, 138 mm and 82 mm deep and a 2 mm diameter deep hole by 20 mm deep running at an angle of 25o to the centre line.
In addition, various milled features, drilled and tapped holes and counterbores are included on the part drawing.
Previous methods involved setting up initial datums on the casting, gundrilling and honing the main bore as a process size for further location.
CNC machining centres produced various holes, the end faces had to be ground and a special purpose lathe operation used to drill the angled deep holes followed by Mollart gundrills to produce various other hole features.
The final finishing operation involved CNC honing the main bore.
With the mill-turn capability of the Integrex 300Y, Mollart's setter/operator Jason Taylor was able to draw upon the tooling expertise of the Mollart Botek team as well as Mollart's deep hole drilling machine application engineering to put together the new method.
This is explained by Guy Mollart: "We have machine tool build, deep hole process development, the Mollart Botek tooling engineers all on the same site and can draw on our TM steels material supply operation in Chesterfield.
I don't know of any other company being able to offer this level of expertise and support for a sub-contracting operation," he says.
The new method involves the billet for the hammer drill body being first loaded to a three-jaw chuck on the Mazak for the OD to be turned and the end flange profile milled.
The main bores are roughed part way to within 1 mm of finished size and two holes in the flange drilled and chamfered using C and Y-axes and a process location tooling hole machined.
The part is then turned around and reloaded to jaws with a probe location of the tooling hole for datum position.
The OD is turned to blend and the end of the flange profile milled.
The main bore is drilled to breakthrough and three holes gundrilled, using 70 bar coolant pressure, 6 mm diameter by 205 mm deep, 138 mm deep and 82 mm deep at 4,000 revs/min and 138 mm/rev feed rate.
Two conventional holes are then drilled and using C and Y-axes, side holes drilled and tapped offset from the centre line of the part.
The component is then loaded to a mandrel and the sides milled, the waist diameter turned and undercuts produced using combinations of C and Y-axes.
The final operation involves loading to a fixture with a floating steady to finish out the counterbores to a 10 micron tolerance.
The main diameter is single point bored and finally reamed to size, in order to maintain the 10 micron tolerance and a series of grooves machined down the main bore.
Then, using the machine B-axis with spindle C-axis, a 2 mm hole is gundrilled at 250 to the centre line using a 6,000 revs/min driven Mollart Botek gundrill at 24 m/min feed rate to break into one of the internal grooves.
Maintains Guy Mollart: "The process we have developed is highly cost-effective but it only works because we have been brave enough to commit to investment in the right plant.
Our recommendations to our customer to change material and process has shown considerable savings especially on final tests for leaks while making us so much more confident on the consistency of product we can deliver.".
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