Product category:
Tooling services
News Release from: Horn Cutting Tools | Subject: Grooving tooling and applications engineering
Edited by the Manufacturingtalk Editorial
Team on 30 May 2003
Grooving tooling speeds up machining
cycle times
Grooving tooling and applications engineering has helped a transmissions manufacturer to make considerable savings in machining times, tool life and solve swarf management problems.
Grooving tooling and applications engineering provided by Horn UK, Ringwood, has helped JCB Transmissions to make considerable savings at its Wrexham factories In one case, the move to Horn groove milling tools has shaved 1.72 minutes from the machining cycle for hub swivels, significantly reducing the cycle time
This article was originally published on Manufacturingtalk on 27 Apr 2004 at 8.00am (UK)
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The success of these and other applications have led to Horn being appointed as preferred supplier for grooving and thread milling applications at the factories.
A JCB spokesman commented.
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"We're committed to a process of continuous methods improvement as part of JCB's lean manufacturing program.
From a tooling perspective that means identifying the suppliers who are most capable within specific areas and having them develop solutions to identified problems.
However, logic suggests that if a supplier like Horn can make a difference on a problem job there might also be a benefit to be gained from applying their tooling to regular tasks.
In fact this is what we've found as the Horn range is so wide that in some cases - such as beam axle end circlip grooves - we have been able to replace a third party's specially ground grooving inserts with standard items from Horn." The 'breakthrough' job for Horn was on machining of SGI cast iron hub swivels.
These comprise a family of 40 components used on all JCB wheeled vehicles, and are produced in tens of thousands per annum.
A feature of all of the swivels is a stub axle spigot which carries a bearing for the hub assembly.
In all cases the spigot needs to have a radiused undercut machined where it joins the casting to allow the bearing to seat properly.
In many cases, though not all, a circlip groove is machined closer to the nose of the spigot.
The components are machined in a single set-up on horizontal machining centres, using over-turning tooling to machine the basic spigot diameter.
Machining practice is to use circular interpolation to groove mill the undercut radius and the circlip groove.
The solution put forward by Horn for the undercut replaced an existing four-tooth tool, using twin edge inserts, with a 5-tooth cutter using triple edged inserts.
The insert grade is Horn TI25, a TiCN coated grade suitable for grooving and finishing at lower cutting speeds.
Custom ground R314 triangular inserts provide the form For JCB's application, the cutting data was adjusted as follows.
Spindle speed was reduced from 1100 rev/min to 1010 rev/min but the feed rate more than doubled from 430 mm/min to 959 mm/min.
This reduced the cycle time for the operation from 2.52 minutes to 1.13 minutes.
In addition cutting edge life trebled from 50 minutes to 150 minutes, providing much longer intervals between tool replacement.
The Horn solution reduced the overall cycle time by 1.39 minutes, while tool life increased from 20 components per edge to well over 100.
Overall cost of the operation reduced by over 80 per cent.
Likewise the Horn solution for the top groove comprises a standard Type 328 triple edge groove milling insert carried on a standard Horn shank.
This saves a further 0.33 minutes per component compared with the previous tool.
The cost savings for all hub swivels produced in a year comes to a very significant sum.
A similar application involves machining of circlip grooves on a planetary hub component.
This is essentially a cast iron dish form with three spigots cast into the base.
JCB had been using a special purpose tool to over-turn the grooves but this has now been replaced by interpolative groove milling using a standard Horn tool.
The most recent application to be solved using Horn tooling, however, is one where no productivity gain was sought, as the JCB spokesman explains.
"The swarf problem on annulus ring production is one that other tooling suppliers had been trying to solve for some years, without success.
The incentive to have Horn take a fresh look at the problem arose from the improvement that they made on hub swivel machining.
Once again they proved more than equal to the task and it became obvious to us that Horn's expertise in grooving meant that we should make them first choice for this type of application." The annulus ring forms part of the braking system used on a variety of JCB wheeled vehicles.
The component is machined from a rolled heat treatable steel ring using an automated production cell.
This comprises a twin spindle turning machine, a broaching machine and a robot loaded induction hardening station.
Among other features, the turning operations include machining of three circumferential grooves on the inner diameter of the ring, each of which has chamfered edges.
"We had a real problem with swarf accumulation on this operation," says the JCB spokesman.
"The old tooling was good for about 50 components per edge.
However its performance was marginal and towards the end of that period it was regularly the case that we would start to get an accumulation of strong stringy swarf.
This would foul follow-on tooling and occasionally it would get into the turret index mechanism, preventing the turret from seating properly.
We then had to shut down the cell while the problem was cleared manually, which interrupted production.
In addition, because the cell is designed for automatic operation it isn't very user friendly and we considered that manual clearance presented a hazard which we wanted to eliminate." Horn was asked to put forward a solution.
One constraint was the need to work with the existing cutting data.
This made success highly dependent on the effectiveness of the tool geometry.
In the event three alternative Horn inserts were trialled before the ultimate solution was arrived at.
This utilises a TF 42 grade S229 insert with the impressed type.A.
chipbreaker geometry.
The inserts are specially form ground with break edges to combine the grooving and chamfering operations into one, and are used with a Horn Type 213 holder.
To maximise effectiveness of the tool, cutting speed was reduced slightly but this adjustment was kept within the limits affecting the balance of the production cycle.
Ultimately the solution that Horn provided not only solved the swarf problem but it also doubled tool life compared with the previous tooling.
In addition the Horn inserts have two cutting edges whereas the previous tooling was single edged.
Tip changeover interval has doubled from 50 components to 100 but the number of inserts required reduced by a factor of four.
This has saved 5p per component on a family of parts produced at the rate of around 450 per day.
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