Combating Tool Decay

Author K.V. Rangaswamy
Published
March 01,2009 - 11:00am

A parts manufacturer finds that brushing the cutting edges of tools with nylon bristles extends tool life, improves part quality and reduces manufacturing costs.

As parts manufacturers continue to boost productivity, customers typically demand a reduction in the price of machined parts every year, feeling they deserve a “productivity discount.” However, profitability is dangerously eroded. To survive and hopefully thrive, a manufacturer’s input costs must be reduced.

Some areas for improvement include employee productivity gains, longer tool life, better management of consumables and a reduction in energy consumption. A team at ABI Showatech (India) conducted work in those four areas and found tool life improvement provided significant advantages.

Courtesy of ABI Showatech

Tool life and the quality of the threaded aluminum component improved after ABI Showatech started brushing the tap’s cutting edges.

An initial breakthrough came when tapping was studied for thread quality. This was prompted by a customer complaint about fine metal particles sticking to thread walls.

We tried various methods, such as increasing the coolant pressure from 3 to 10 bar (44 to 145 psi) when tapping, applying taps with wear-resistant coatings and enhancing lubricating properties. Unfortunately, the improvements were minimal and not satisfactory.

Examining a tap’s cutting edges under magnification revealed minute particles adhering to the edges. We concluded that these metal particles were from the aluminum workpiece material and created a barrier. Although minute, this barrier prevented the tap from effectively cutting the threads. Our assumption that increased coolant pressure would remove the metal particles proved incorrect.

Then the idea of cleaning taps with a brush—a mechanical operation—was proposed, which has to be done for every tapping cycle. To prevent the time-consuming interruption of the tapping cycle for brushing in a machining center, a brush with nylon bristles was mounted to the fixture, and the machine was programmed to swipe a tap against the stationary brush before commencement of the tapping cycle.

As a result, the machine operator reported improved quality of the threaded component after gaging it. The threads were clean and free of loose, tiny burrs. The thread quality was maintained even after exceeding the prescribed tool life, which we determine for every tool applied to help manage tool inventory. New tool life parameters for the taps were then established (Table 1).

Table 1: Tap life before and after brushing.

No. Tool no. Brushing introduction date Tool life to date Tool life before brushing

1

M10 tap

Oct. 25, 2004

n 13,242 tap 1 life

n 11,894 tap 2 currently running

6,000 holes/tool

Before and after brushing was introduced, the M10 X 1-6H tap from Emuge (India) was run at a 600-rpm spindle speed and a 1-mm/rev. feed. The tool cost savings from brushing was about $650 per year.

Brushing began with taps and was extended across the board for all cutting tools. The extension of tool life was not uniform for every tool, but the results were encouraging. Tool life improved from 200 to 400 percent by brushing the cutting edges at the beginning or end of each machining cycle. Tests were conducted for more than 6 months on ceramic indexable milling inserts.

Table 2: Tool life comparison of drills applied for machining aluminum master cylinders before and after brushing.

Equipment Tool name Tool material Tool no. Tool life (holes/tool) Tool life increase
        Before brushing After brushing  

1. VMC

Drill

Carbide

11DF5238

8,000

20,000

2.5×

2. VMC

Drill

Carbide

11DV5237

700

1,500

2.1×

3. VMC

Drill

Carbide

704473

8,000

20,000

2.5×

4. VMC

Drill

Carbide

11DF5227

7,000

20,000

2.9×

5. VMC

Form drill

PCD

11DF5274

20,000

55,000

2.8×

6. VMC

T/FIX drill

Carbide

11DF5224

8,000

12,000

1.5×

The advantages of tool brushing includes improved part quality, longer tool life, lower tool inventory and an increase in machine uptime because of a reduction in the frequency of tool changes. The total cost savings for brushing all tools in our operation is about $12,600 per year.

We tried to extend tool life further by using brushes impregnated with abrasives, such as aluminum oxide or silicon carbide. However, tool life was reduced by using abrasive-impregnated brushes in all cases.

Work is being performed to fix a rotary ring brush in a tool’s home position in an automatic toolchanger, which should improve cycle time. CTE

About the Author: K.V. Rangaswamy is executive director for ABI Showatech (India) Ltd., a high-volume manufacturer of automotive parts, including master cylinders, turbochargers and camshafts. He can be reached via e-mail at rangakv1933@yahoo.co.in or balaji.r@turboenergy.co.in.

Related Glossary Terms

  • aluminum oxide

    aluminum oxide

    Aluminum oxide, also known as corundum, is used in grinding wheels. The chemical formula is Al2O3. Aluminum oxide is the base for ceramics, which are used in cutting tools for high-speed machining with light chip removal. Aluminum oxide is widely used as coating material applied to carbide substrates by chemical vapor deposition. Coated carbide inserts with Al2O3 layers withstand high cutting speeds, as well as abrasive and crater wear.

  • automatic toolchanger

    automatic toolchanger

    Mechanism typically included in a machining center that, on the appropriate command, removes one cutting tool from the spindle nose and replaces it with another. The changer restores the used tool to the magazine and selects and withdraws the next desired tool from the storage magazine. The changer is controlled by a set of prerecorded/predetermined instructions associated with the part(s) to be produced.

  • brushing

    brushing

    Generic term for a curve whose shape is controlled by a combination of its control points and knots (parameter values). The placement of the control points is controlled by an application-specific combination of order, tangency constraints and curvature requirements. See NURBS, nonuniform rational B-splines.

  • coolant

    coolant

    Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

  • feed

    feed

    Rate of change of position of the tool as a whole, relative to the workpiece while cutting.

  • fixture

    fixture

    Device, often made in-house, that holds a specific workpiece. See jig; modular fixturing.

  • gang cutting ( milling)

    gang cutting ( milling)

    Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.

  • machining center

    machining center

    CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

  • milling

    milling

    Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

  • polycrystalline diamond ( PCD)

    polycrystalline diamond ( PCD)

    Cutting tool material consisting of natural or synthetic diamond crystals bonded together under high pressure at elevated temperatures. PCD is available as a tip brazed to a carbide insert carrier. Used for machining nonferrous alloys and nonmetallic materials at high cutting speeds.

  • tap

    tap

    Cylindrical tool that cuts internal threads and has flutes to remove chips and carry tapping fluid to the point of cut. Normally used on a drill press or tapping machine but also may be operated manually. See tapping.

  • tapping

    tapping

    Machining operation in which a tap, with teeth on its periphery, cuts internal threads in a predrilled hole having a smaller diameter than the tap diameter. Threads are formed by a combined rotary and axial-relative motion between tap and workpiece. See tap.

  • toolchanger

    toolchanger

    Carriage or drum attached to a machining center that holds tools until needed; when a tool is needed, the toolchanger inserts the tool into the machine spindle. See automatic toolchanger.

Author

Executive Director

K.V. Rangaswamy is executive director for ABI Showatech (India) Ltd., a high-volume manufacturer of automotive parts, including master cylinders, turbochargers and camshafts. He can be reached via e-mail at rangakv1933@yahoo.co.in or balaji.r@turboenergy.co.in.