Cost Reduction Through Wax Reclamation

EICF Best Practice WorkshopBilbao

24th May 2005

Richard Hirst

Agenda• Wax Costs• Wax Reclamation

– Reclamation options• ‘Reclaim’• ‘Reconstituted’

– Processing route– Controls– Performance– Uses

• Cost benefits

Wax Costs

• Investment casting waxes are heavily dependent on petrochemical industry derivatives

• Oil price drives the cost base• Oil companies increases are non-negotiable• ‘Super-spike’ could see oil reaching US$105

resulting from strong global demand, especially USA and China (source Goldman Sachs)

•

Oil Price 2004 to DateBrent Crude

Oil Price 2004 to DateWest Texas Crude

Cost Factors

• Wax manufacturers actively challenge raw material cost increases and minimise them where possible

• Supply shortages in some materials exacerbating the situation e.g. filler (styrene monomer), EVA, Carnauba wax

• Supply chains are reviewed, alternative suppliers sought

• Increased costs absorbed wherever possible through improved efficiency of manufacture

• Wax cost reductions are unlikely•

Wax Reclamation• Has existed for a long time often with simple

reclamation carried out on-site– dewatering, sometimes basic filtration

• In western markets reclamation has largely moved to specialist wax companies– with specialised recycling equipment– who have local authority approval for movement

and processing of recyclable material• Reclamation has obvious environmental and

economic benefits• The development of advanced recycling

techniques has allowed the wider usage of recycled wax

•

Wax Reclamation - Processing

• Two routes are available for the reclamation of used (ex autoclave) wax1. Simple recycling techniques allow

reclamation for use as runner wax –‘Reclaim’

2. Advanced recycling techniques allow reclamation for use as pattern wax –‘Reconstituted’

• Both allow investment casting foundries to make significant savings to their wax costs without detriment to casting quality

•

Reclaim Wax

• Used almost exclusively for runner production• Products can range from simple ‘reclaim’

wax, or with additions to meet an agreed specification

• Used wax is cleaned and filtered• Blayson usually recommends retaining filler

material in the final product. This gives the following advantages to the runner wax :– improved injection performance– quicker setting– a more stable wax with less distortion– reduced cavitation/sinkage

•

Reconstituted Wax• Customers returned wax is marked, kept separate

and Reconstituted for their use only • Using advanced reclamation techniques used wax is

cleaned and filtered• Virgin materials are then added to adjust properties

and ‘Reconstitute’ the wax to within the parameters of the original specification

• The results of reconstitution are very good with properties in line with those of the virgin material

• A complete range of wax patterns can be produced with reconstituted wax

• Significant cost savings are achievable, with no loss of performance or quality

•

Wax Reclamation Processing Route Wax Reclamation Processing Route -- Major OptionsMajor Options

From autoclave

5000Kg

To wax manufacturerfor Recycling

Option 1 Option 2 Option 3

Reclaim

Filler, water, extraneous materials removed

< 2500Kg

ReclaimCleaned as

option 1% filler retainedPossibly some

additions

< 4000Kg

ReconstitutedAdvanced Cleaning

Raw materials blended in to

restore to pattern wax specification

< 5000Kg

Recycled Wax Usage - Runners

• Reclaim runner wax is used by the majority of foundries across all market sectors

• The use of a good quality reclaimed runner wax can significantly contribute to lower process costs– less scrap– greater throughput– improved runners = improved casting quality

•

Recycled Wax Usage - Patterns

• Over recent years many foundries in the cost driven ‘Commercial’ sectors in Western markets have switched to the use of reconstituted pattern wax either:– reconstituted 100%– or containing a percentage of reconstituted

material•

‘Aerospace’ Sector• The aerospace sector has so far resisted

reconstituted pattern wax• Due to the relative disparity between wax

costs and value of castings produced. – the need for costly re-approvals is also a

significant factor– as are concerns regarding possible trace elements– however reclaim wax is widely used for runners

• Technically we believe that Reconstituted wax, produced through a ‘closed loop’ system, could be used for pattern production without detriment to casting quality

Quality Comparison : Reconstituted v Virgin Wax

• No detriment to chemistry with Reconstituted wax– No significant (measurable) increase in key

elements– No significant increase in Ash content

• Dimensions – SPC indicates a close match between the dimensional capabilities of Reconstituted and Virgin wax

•

Dimensional Capability

1

Ash Content - Virgin Wax

Ash Content – Reconstituted WaxIn

divi

dual

Val

ue

21191715131197531

0.09

0.06

0.03

_X=0.05410

UCL=0.09279

LCL=0.01540

Mov

ing

Ran

ge

21191715131197531

0.04

0.02

0.00

__MR=0.01455

UCL=0.04754

LCL=0

Observation

Valu

es

2015105

0.08

0.06

0.04

0.080.060.040.02-0.00

LSL USL

S pecificationsLS L 0.00U S L 0.08

0.100.050.00

Within

O v erall

S pecs

WithinS tD ev 0.0128989C p 1.03C pk 0.67

O v erallS tD ev 0.0136224P p 0.98P pk 0.63C pm *

1

Process Capability Sixpack of Reconstituted Wax Ash contentI C har t

M ov ing Range C har t

L ast 2 1 O bser v ations

C apability H istogr am

Nor m al P r ob P lotA D : 0.962, P : 0.012

C apability P lot

Viscosity Comparison

60 65 70 75 80 85T [°C]

0

1

2

3

4

5

6

7

8

9

10

11

ƒ [P

as]

L0053ƒ = f (T)

K0524ƒ = f (T)

K0624ƒ = f (T)

Rheology Comparison

40 45 50 55 60 65 70 75 80 85T [°C]

-1 10

0 10

1 10

2 10

3 10

4 10

5 10

6 10

7 10

ƒ' [

Pas]

20

40

60

80

100

Ì [°

]

L0053 OSCƒ' = f (T)Ì = f (T)

K0524 OSCƒ' = f (T)Ì = f (T)

K0624 OSCƒ' = f (T)Ì = f (T)

Oscillation

Critical points for Reconstitution

• Foundries must use a wax that contains suitable materials for reconstitution

• Imperative to start with a virgin wax that will resist oxidation

• The use of a non-sticky virgin wax will help reduce the use of silicone release agent– less chance of ash levels increasing from silicone entering

the system• Ideally only one base wax should be used in the

foundry’s wax system– easier to monitor and control

• Prudent to occasionally replenish system with some virgin wax addition

•

Quality ControlQuality Control• It is extremely important that the wax manufacturer

maintains total quality control over the process • The incoming material from a foundry is :

– marked and kept separately so customers receive back their own material (to ensure exclusion of undesirable constituents)

– tested for :• Ash content• Melting and Congealing point• Viscosity• Filler content• Water content

• From these results, dependent on the requirement, additions are made in order to reclaim or reconstitute the wax to within agreed limits

Controls on Wax for Reclamation• Used wax must be clean, i.e. without foundry floor

waste, boots, gloves, bottles, cans, broken shell etc• The amount of silicone used in the process should be

minimised• Water mixed with the wax during dewax should be

minimised• A filter cloth placed over the autoclave tray can help

prevent ceramic sand entering the wax during dewax• Autoclaved wax should be made into blocks on

pallets and suitable for transportation– blocks should be strapped and wrapped to further reduce the

chance of contamination during transportation/storage– ‘big bags’ offer a cost effective option

Wax Reclamation - Cost Benefits

• The use of reclaim and reconstituted wax offers significant cost savings to investment casting foundries

• Using a fully reconstituted pattern wax can generate savings of approximately 20%

• Wax disposal costs are avoided– in the UK currently £600/t (900 Euros) landfill cost– not always available/possible

• The discipline of good process control will itself be a major benefit and reduce costs

•

Summary

• Wax reclamation is not new and recycling has always taken place

• The latest techniques allow full reconstitution to virgin wax specification

• This can generate savings of up to 20%– on top of saving disposal costs

and finally• As disposal costs and raw material prices

continue to increase, Reclamation is likely to become a necessity for all materials