Modern Mirror Cutting Machine – Mechanical Project 2017

Modern Mirror Cutting Machine – Mechanical Project 2017

SYNOPSIS

Our project work, mirror
cutting Machining (MCM) presents the working of abrasive jet
machining and removing materials from the brittle and heat
sensitive materials by the application of high speed stream of
abrasive particles carried by a gas medium through the nozzle.
In particular drilling of holes of minimum diameter and maximum
depth is also possible in MCM with greater accuracy and surface
finish.  Since no heat is induced while machining the
surface, the workplace is not subjected to thermalshocks.

Mirror cutting machining
apparatus can be used for determining the material removal rate
(MRR) for materials like glass, ceramics and aluminium sheet by
varying the parameters like pressure, nozzle tip distance (NTD)
and size of abrasive flow rate. In this project we have
designed and fabricated the Abrasive jet machining apparatus
for drilling holes and cutting glass, ceramic plates and
aluminium sheet.

INTRODUCTION

Rapid technology development
in the field of new materials and alloys with increasing
strength, hardness, toughness, heat resistance and wear
resistance have imposed many problems and difficulties during
the machining by conventional means.

Machining intricate and
complicated shapes of this and fragile components and accurate
and economical forming of very hard, high strength materials
which are being extensively used in Aeroplane and nuclear
industries have forced the scientist, engineers and
technologists to search for new techniques of machining which
can readily provide an effective solution to these problems.

As a research and development for the last forty years several
new methods of machining have emerged.  Among the new
methods we are going to deal with the Abrasive Jet Machining.
The conventional techniques like turning, drilling, milling
etc., are well known and involves the use of mechanical power
between the workpiece and the tool whereas in this method need
not be the case with unconventional on advanced machining
techniques.

Modern Mirror Cutting Machine
Modern Mirror Cutting Machine

WORKING PRINCIPLE

Mirror cutting machining
(MCM) removes material through the action of a focussed stream
of abrasive-ladden gas.  Micro-abrasive particles are
propelled by inert gas at velocities of upto 300 m/sec.
When directed at a workpiecs, the result in erosion can be used
for cutting, etching, cleaning, deburring, polishing, and
drilling.

Material removal occurs through a chipping action, which is
especially effective on hard, brittle materials such as glass,
silicon, tungsten, and ceramics.  Soft, resilient
materials, such as rubber and some plastics resist the chipping
action and thus are not effectively processed by
MCM.

No work piece chatter or vibration occurs with this process
because the large enables MCM to produce fine, intricate detail
extremely brittle objects.  The MCM processed eggshell
provides a graphic example of the delicate nature of the
process.  In addition because heat carried away by the
abrasive propellant gas, workpieces experience no thermal
damage.

APPLICATIONS

The manufacturer prepares a reusable rubber stencil for each
model panel.  The rubber stencil is then placed on the
surface of the panel and the abrasive jet is used to etch the
exposed areas providing permanent marking.  In this
particular use, the Abrasive Jet Machining (MCM) costs only 1/3
of cost required for label method of production.

1. Variety of diverse jobs has been successfully performed by
MCM.  These include cutting threads into glass rods,
deflashing small castings, die and mound touch up, cutting
titanium fink and drilling glass wafers.

2. The MCM has been successfully employed to manufacture small
electronic devices consisting of a 0.38 tungsten disk.
After the two materials were were brazed together.  The
silicon wafer must be trimmed and beveled without harming the
tungsten disk.  To accomplish the task an MCM nozzle is
mounted at the desired angle and directed at slowly rotating
part with this technique the unwanted silicon is trimmed off
each part in less than one minute.

3. An example of debburing plastic parts with MCM is cited by
Lacourte (1979) in an application involving the manufacture of
small biomedical analysis packages.  Small plastic cubes
are cross drilled with two 0.34mm diameter holes.  Tiny
burrs are created internally at the intersection of the two
holes must be removed without providing scratches.  It is
not only able to meet this difficult quality requirement, but
it also was able to reduce deburring time by 80% when compared
with the old method of deburring.

ADVANTAGES

1. MCM provides cool cutting action, no heat damage occurs to
the delicate work materials.

2. Cutting action is shockless.

3. Ability to cut fragile and heat sensitive materials without
damage.

4. Ability to cut intricate hole shapes in materials of any
hardness and brittleness.

5. No variation due to surface irregularities and tool wear as
in conventional machining.

6. Low capital cost.

7. MCM units are easy to operate and maintain.

DISADVANTAGES

1. Stray cutting is unavoidable if not properly controlled.

2. MCM yields low material removal rates.

3. Nozzle life is limited.

4. Replacement of rubber hoses which carry abrasives may be
necessary.

5. A suitable dust collection system is required to prevent
pollution.

6. Embedding of the abrasive in the workpiece surface may occur
while machining softer materials.

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