productivity on themachine is enhanced.

Boosting Productivity of Machining Centers: Some Tips

VMC Jvith Rotary Table and Cradle Type Fixture

In today's competitive manufacturing scenario,production equipment and processes playa criticalrole in determining productivity. The challenge is tomaximise the output with given resources.

Making 100 parts in an hour on a machine costingRs 10 million need not be as productive as making60 parts on a machine costing Rs. 4 million, theoperator being the same, though the latter machinecould be slower.

In achieving higher productivity, it is necessary toimprove the ratio of the output earnings to the totalinput cost, covering men, machines, tools,depreciation, rent, power, etc. The challenge is tofind ways to get the best out of a machine.

Any production process, metal-working included,involves several aspects, each of which has to beanalysed thoroughly.

The only activity that earns revenue is machining orcutting while everything else, though absolutelynecessary for the process, is a drag. By reducing thenon-cutting activities to an absolute minimum, the

Pneumatic Clamping Fixture

Let us consider the non-revenue-earning activities,which cannot be totallyeliminated.

Loading and unloadingconstitute one such

Mr. P. Venkataramanoperation, when the5 r. Vice President, Marketing

machine is virtually idle. Itis like an aircraft before take off, waiting indefinitelyfor its passengers to get on board. No fly,no money.

Some more of the necessary but unproductiveactivities include: changing tools for differentoperations, positioning the machine table to therequired position, retracting a tool after cutting isdone, clamping and unclamping the job in itsfixture.

It may be surpnslllg, but true, that in a CNCmachining center the cutting activity accounts forno more than 25% of the total available machinetime! It is like having a cup of coffee in a five starrestaurant at Rs.l00. This is made up of 20 bucks

Hydraulic Clamping Fixture

for the coffee and 80 for the place. Whatever thecoffee may be, the setting does not add value to thedrink as such, unless something really big ishappening over coffee.

So all productivity improvement measures need tofocus at the 75% untapped goldmine ofopportunities. What can be done? Some or all ofthe following can help.

Choose an appropriate fixture with power clamping(hydraulic or pneumatic) over a manual fixture.typically, a power clamping fixture can do clamping

and unclamping in 10 to 12 seconds, in contrast toalmost a minute with manual bolts and nuts. Evenwith quick clamping devices, the number ofelements to be worked one after another consumestime, unlike the simultaneous action in a multi-element power clamp.

Reduction in operator fatigue is an added bonusadding to productivity. Situations in which theoperator forgets to tighten are also avoided.

Where possible, plan multiple pieces in one load,again with power clamps. This has the effect ofdistributing idle machine times during tool change,

Linear Pallet Changer

spindle start and stop, ete., over a number of partsinstead of on just one. In a typical case, where theratio of cutting time to idle time is almost one toone in the machine cycle time of 100 seconds(excluding load/unload operations), loading fourcomponents in one load would result in reductionof machine cycle time to about 70 seconds percomponent. This alone amounts to a gain of 30%.

Opt for a pallet changer selectively where time forloading/ unloading is considerable as with heavyjobs. This totally masks out the load/unload timesfrom the cycle time, leading to a big jump inproductivity. This is because the activity is carried

VMC with Index Table

Rotary Pallet Changer

out outside the machine while cutting is going oninside. One can imagine what a 2-minute job-handling activity that is outsourced to a palletchanger can do to boost productivity. An addedadvantage could be that manual clamping can bedone, since enough time is available in most suchcases, thereby reducing the investment and uppingproductivi ty.

It is also wise to go in for a pallet changer, whenplanning the production of multiple pieces.

Efforts must be made to reduce the number of set-ups wherever feasible. This results in the directbenefit of avoiding the multiple handling involvedif done in too many set-ups. However, this calls foradditional features like indexing arrangements

Rotary Tilting Table

(index table, rotary table) on the machine, withfurther investment.

This option needs to be weighed carefully againstthe lost time in changing set-ups on the machine andthe multiple loading times charged to thecomponent's production cost, whether done onone machine or on multiple machines.

The hidden benefit is superior component accuracy,as inter-related dimensions of different set-ups are

The use of the new generation cutting tools, suchas solid carbides, PCD and cermets, permits amanifold increase in the cutting parameters andlower cycle times. This is achieved without aproportionate load on the tool cost. A PCDreamer, for example, working on an alloycomponent can take speeds up to 200m Imin andlive to deliver one hundred thousand holes ascompared to a carbide reamer working at 60ml minand not more than 20,000 holes.

achieved without any disturbance in between. Thiscontributes to productivity, as it eliminates scrapand non-conformances.

Rationalization of tooling, combining toolswherever possible like step drills, step reamers,drill-cum-chamfer, etc. minimize tool changes.

Choice of tools with a coolant-through facility anda high pressure CTS system on the machine hasproved highly productive in many cases.

VMC Jvitha Gantry System

At AMS, a sustained effort is on to develop cost-effective, high performance machines that cut idletime, permit faster tool changes, high accelerationof machine movements, faster rapids, swifterspindles, and quicker pallet changes. The objectiveis to achieve productivity jumps, while maintainingand improving quality levels.

High Speed Machining Centers from AMS

Coolant Through Spindle

MCV-400XL

A planned pre-determined tool replacementprotocol based on past performance data on toollife, avoids unexpected breakage, damagedcomponents and scrap. If economical, toolmonitoring systems can be installed to warn againstimpending wear-out.

Where manpower costs are high as in Europe orJapin1 the right solution for machine tending in highvolume manufacture is flexible automation. Thisinvolves the installation of robots and gantrysystems linking machines for totally unmannedmachining cells. Such systems are gainingacceptance in India too, in the auto industry. Anumber of them have been operating successfullyin leading companies, resulting in significantproductivity gains in spite of considerable initialinvestment.

CHALLENGER+ SUPER DART

110

Spindle speedRapid traverse X/Y /Z

80-8000/100-1000040/40/40

80-8000/100-1000050/50/40

100-10000/120-12000/150-1500050/50/40

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