Mollart’s Microdrilling technology leads to £1.5 million installation success in USA
2 mins read
The capability of Chessington, Surrey based Mollart Engineering to develop a high precision, micro-deep hole drilling solution for oxyacetylene gas cutting torch nozzles has enabled its US customer to reduce a 35 machine installation to just five Mollart four spindle Microdrill VDMs. As a result, components are now produced at a rate of almost 1,000 per hour from the new installations, regenerating the output capacity by 25 per cent. Further advantages from the gundrilling process have been achieved with up to 100 per cent improvement and greater consistency in the burn pattern of the nozzles.
The machine build contract, worth in excess of £1.5 million to Mollart combines, in a single cycle, the deep hole drilling of a 2.3 mm dia central stepped bore for gas feed by 75 mm deep in the Terillium copper material. This bore is then counterbored to 3 mm dia by 50 mm deep with a further six, 2 mm dia through holes created for air feed.
These 2 mm dia holes are set on a 12.4 mm pitch circle (PCD) but inclined in a converging fan pattern towards the central bore at an angle of 6° 20' to break out at the nozzle end on a 6.8 mm PCD.
In the Mollart solution, developed around its four spindle Microdrill VDM, three additional axis movements giving tilt, PCD positioning and a rotary indexing motion have been integrated to the special control software that also incorporates independent tool monitoring. There is also a programmable function that enables the hole pattern to be quickly calculated when setting a new part.
The special fixturing, that enables 224 parts to be held on the table at the same time under the four spindles, also enables the drilling of the different hole diameters in the same part without reclamping. The spindles are each run at 25,000 revs/min and at a feed rate of 450 m/min.
The vertical spindle Mollart Microdrill VDM has four high speed, 25,000 revs/min spindles that power the micro-diameter solid carbide gundrills, with through coolant feed, upwards into the components. This technique maximises control over swarf evacuation with each spindle being driven at a penetration feed rate of 450 m/min.
Following machining trials, all components were tested for burn pattern and were found to demonstrate an improved performance of up to 100 per cent over the previous method of production. This was attributed to the high quality of the gundrilled hole generated by the Botek tooling that created a burnished surface from its precision ground carbide guide pads giving improved flows of both gas and air.
Once installed, the customer was able to reset the machines to accommodate the 75 different types of part in record times of between five and 15 mins. Cycle times were proven at 19 secs for the six 2 mm holes and just 6 secs for the central hole creating a further saving of 25 per cent on the cycle time originally calculated at quotation stage. As a result each machine is able to produce parts at a rate of 189 per hour.
