A fundamental investigation of recycled glass as a media for vibratory mass finishing
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A FUNDAMENTAL INVESTIGATION OF RECYCLED GLASS AS A MEDIA FOR VIBRATORY MASS FINISHING. Mr. Pitipong Benjarungroj. Supervisor: Dr M Morgan 11 th February 2011. Content. Introduction Aims / Objectives Problem Outline Experimental programme Results. Introduction.

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A FUNDAMENTAL INVESTIGATION OF RECYCLED GLASS AS A MEDIA FOR VIBRATORY MASS FINISHING

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A fundamental investigation of recycled glass as a media for vibratory mass finishing

A FUNDAMENTAL INVESTIGATION OF RECYCLED GLASS AS A MEDIA FOR VIBRATORY MASS FINISHING

Mr. PitipongBenjarungroj

Supervisor: Dr M Morgan

11thFebruary 2011


Content

Content

  • Introduction

  • Aims / Objectives

  • Problem Outline

  • Experimental programme

  • Results


Introduction

Introduction

  • Mass finishing refers to the process technologies for generating edge and surface finishes on a wide range of metallic and non-metallic materials

  • Common edge and surface finish requirements include: deburring, descaling, surface smoothing, edge-break, radius formation, removal of surface contaminants from heat treatment and other processes, bright finishing, pre-plate or coating surface preparation.


Introduction1

Introduction

  • Mass finishing is an increasingly important operation found adjacent to conventional operations eg. laser cutting, water jet and EDM operations.

  • Applications are wide ranging and varied in material eg: coinage, domestic artefacts/ utensils, musical instruments, automotive and aerospace components


Introduction mass finishing process

IntroductionMass finishing process

  • Energy is imparted to the abrasive media mass via a vibratory or rotary means to impart motion to it and to cause it to act on the surfaces. [process control parameters: vibration amplitude, frequency, (rotational speed)]

  • Common mass finishing processes include: vibratory bowl and linear; barrel, centrifugal barrel and centrifugal disk, and rotating barrel

  • Fluid (compound solutions) required for lubrication (-lower frictional forces and reduce wear), aid swarf removal, cleaning, ease handling


Introduction mass finishing process1

IntroductionMass finishing process

Vibratory Bowl

Linear Vibratory

Centrifugal disk

Centrifugal barrel


Introduction mass finishing process2

IntroductionMass finishing process

Centrifugal barrel - Vid

http://www.youtube.com/watch?v=pQAJCCBP-gw

Bowl - Vid

http://www.youtube.com/watch?v=rHzik_z-1C8

Linear tumbler- Vid

http://www.youtube.com/watch?v=DvECh0f6lEs

:Flow is amenable to CFD –velocity profiles through 2-D planes


Introduction mass finishing process3

IntroductionMass finishing process

  • Conventional media wear – used media and debris (including bond, swarf!) sent to landfill

  • Frequently significant loss in media volume bond plus abrasive

  • Performance over time deteriorates (reduced number of cutting edges)


Introduction mass finishing media

IntroductionMass finishing media

  • “Media” refers to the abrasive consumable elements used in mass finishing process.

  • The common media types include natural abrasives, synthetic random media, preformed ceramic and resin-bonded media, and metallic media.

  • The composition of a media determines whether it is a cutting or finishing type of media.


Introduction mass finishing media1

IntroductionMass finishing media

  • Preforms are generated from the abrasive media (eg. Al2O3, SiC) held in a bond

  • Resin bonds: polyester or urea-formaldehyde (generally unpleasant to work with)

  • Ceramic bonds – vitreous based, includes glass frit

  • Preforms are typically cylindrical, conical or tetrahedral in shape

  • Common processing stages: base materials processing; mixing; compaction; heat treatment; cleaning


Introduction mass finishing media2

IntroductionMass finishing media

  • Geometry largely depends on application


Vibratory finishing

Vibratory Finishing

Recycled Glass Media

:-Innovation from Vibraglaz (UK)Ltd.


Introduction2

Introduction

  • The media under investigation is produced wholly from recycled glass [V-Cut]. In its raw state it is in cullet form. The cullet is cleaned of contaminants and crushed. The cullet is then sieved and subsequently graded in a manner similar to that for abrasive grains. The source of glass is varied but is in general glass scheduled for landfill and most recently is predominantly window glass.


Introduction3

Introduction

  • The production process is greatly simplified:

    - materials pre-processing is minimal

    - moderate mixing [media possessing varied grain size]

    - moderate compaction

    - heat treatment


Introduction4

Introduction

  • Production control requirements:

    - mould technology (and release agents)

    - heating rate, critical temperature (Tmax), duration at Tmax, cooling rate / quenching

Each have a strong effect on media quality

Secret recipe!


Introduction5

Introduction

Sample V-Cut media


V cut benefits

V-Cut Benefits

6 key features that distinguish it from other media:

  • No binder required

  • Significantly higher percentage of abrasive

  • Density: plastic media < V-Cut < ceramic media

  • Strong green credentials and low environmental impact

  • Recyclable

  • Lower cost


Media comparision

Media Comparision

200x magnification (CAMApp - desktop equipment)

V-Cut

Ceramic

Plastic

Note Cutting edge density


Media comparision1

Media Comparision

  • In preliminary studies V-Cut has been shown to achieve a comparable

  • performance to conventional media

  • common metals

  • standard vibratory machine / process conditions

  • typical processing times

  • Performance w.r.t. :target criteria (Ra, brightness)


Aim objectives

Aim / Objectives

HOW?


Aim objectives1

Aim / Objectives

  • To acquire fundamental understanding of the material characteristics of the media

  • To obtain machining data over a range of machining conditions

  • Establish and compare performance of V-Cut with conventional media


Problems challenges

Problems / Challenges

  • V-Cut Preparation Challenges

    • Cullet quality

    • Sourcing availability

    • Size consistency within a stated grain size (grade)

    • Mixture -various grades


Problems challenges1

Problems / Challenges

  • V-Cut Production Challenges

    • Mould material (influences temperature gradients and release)

    • Rate of heating temperature

    • Critical temperature Tmax– duration at Tmax

    • Rate of cooling

    • Release agents


Project objectives

Project objectives

  • Materials characterisation

    - Hardness

    - Fracture strength

    - Cutting edge density (undertaken at intervals tests –test the validity of piranha vs shark analogy)

- Crystallographic structure (influence of grain size on crystal size? Growth?)

- Crystal growth mechanism (temp – time dependency)

Is it like water crystals freezing?

Effect of second or multiple cookings!


Project objectives1

Project objectives

+

=

After

Before


Early studies

Early Studies


Materials characterisation

Materials characterisation

  • Why we need to know these properties?

    • Glass is different from others material - the mechanical properties of glass depend strongly on temperature.

    • In most materials the modulus increases with increasing pressure and decreases with increasing temperature. In glass the modulus increases with increasing temperature


Preliminary bend test

Preliminary Bend Test

  • The results suggest an experimental error. The Modulus of elasticity values vary widely. The principle reason for the disparity in results was reasoned to be the high surface roughness of the specimens. Further tests designed to reduce these errors.


Preliminary bend test1

Preliminary Bend Test

  • The strength of glass strongly depends upon its surface condition. Tiny flaws(cracks) in the surface lead to weakening and failure by brittle fracture. It also becomes weaker with time under stress (fatigue).

  • The theoretical strength of glass is relatively high (~2.4×1010 Pa for vitreous silica and ~1.6×1010 Pa for commercial soda-lime glass), but these strengths are rarely approached in practice because of the surface flaws.


Preliminary hardness test

Preliminary Hardness Test

  • Due to the brittleness of the glass, it is not readily amenable to conventional mechanical testing methods; there is a tendency to spontaneous failure before any deformation mode can manifest itself in the stress/strain response.

  • Therefore, techniques which involve large components of hydrostatic compression to restrain fracture are required. Hence, the indentation test is currently considered the most suitable method in the study of brittle materials

HV = F/A;

A = d2/1.854;

Therefore, HV = 1.854F/d2

Where; F =applied load

D = arithmetic mean of the two diagonal d1 and d2


Preliminary hardness test1

Preliminary Hardness Test

  • The results show a promising hardness value, with the average value of 2.23 GPa. However the inconsistency of the obtained data means that there may have been some error during the experiment. The reason behind this may be due to wide variation in the grain size. Further tests are scheduled to be completed.


Materials characterisation1

Materials characterisation

  • Replication methods for surface topography assessment

  • -identification of cutting edge density

  • -insight into wear mechanism

Cannot use stylus methods –stylus wear and lack of information on surface features


Production process early studies

Production Process –Early studies

The oven used for production of media (-premarket media)

was of a general type used for ceramic components and had

controlled travelling rack (determined cycle time) and

temperature.

Assessment of this system was undertaken with / without

stacking of moulds.

It was found that media quality varied widely when stacked.

Thermal images where obtained of the production oven and

laboratory ovens.


Thermal imaging

Thermal Imaging

-wide variation in temperature occurs within

different regions of the oven

(a)

(b)

Direct View of Laboratory Oven interior

2-D (a) and 3-D (b) Plots of Oven interior


Thermal imaging1

Thermal Imaging

It was established that stacking was problematic and the

company have chosen to design an envelope(conveyor) type oven system to

accommodate single layer moulds.


Performance assessment

Performance Assessment

  • Volumetric removal

  • Media Wear rate

  • Surface roughness , Ra (principal parameter measured)

  • Brightness observation

  • Burr removal (visual assessment)

  • Cycle times


Performance assessment1

Performance Assessment

V-Cut media used in studies

Liner

Mass Finisher (vibratory tumbler) used in studies


Surface roughness representative results

Surface Roughness - Representative Results

Region of interest for industry


Surface roughness representative results1

Surface Roughness - Representative Results

***

It can be noticed from the results that the Ra for Aluminium and Brass is higher than

that at which the tests commenced.

This is due in part to the roughing effect of the abrasive and in part to the burnished

condition at which they came to machining (shown later).

Furthermore, most operations with these two materials would primarily be associated

with deburring and/or rounding, not surface roughness.

Polishing would be undertaken with a much less aggressive media.


Surface roughness

Surface Roughness

Discussion

media 780 is medium grade cutter / polisher

Results are consistent with published data for conventional media

(in-house comparative data being prepared)

Limiting values indicate boundary of performance on particular material

For example: If lower Ra is required with material = aluminium,

then different grade (i.e. polisher) would be needed, though this

would be achieved at the cost of lower material removal rate


Surface roughness1

Surface Roughness


Surface roughness2

Surface Roughness

Discussion

media 790 performs more as a polisher than media 780

The abrasive action of the media is evident in the early part of the graph –

i.e. the cutting edges initially dig into and hence roughen the surface

before finishing occurs

This is not so evident with a harder material eg. MS or SS


Surface roughness3

Surface Roughness

  • Further tests are in progress on this front.

  • Conventional media is now available for the tests

  • Material range is being widened – we have a Titanium based alloy

  • being prepared (coupons) -Aerospace turbine blade for

  • comparative studies.

These laboratory based tests are preparatory tests prior to scheduled

in-situ company (Rolls Royce) confirmation tests


Brightness observation

Brightness observation

Brass before and after 10 minute of machining

Brass before machining

Brass after machining


On going and further studies

On-going and Further Studies


Thank you for your kind attention

THANK YOU FOR YOUR KIND ATTENTION


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