Cost Reduction Through Wax Reclamation - Blayson · 2020. 5. 12. · • Used wax must be clean,...
Transcript of Cost Reduction Through Wax Reclamation - Blayson · 2020. 5. 12. · • Used wax must be clean,...
Cost Reduction Through Wax Reclamation
Agenda• Wax Reclamation
– Reclamation options• ‘Reclaim’• ‘Reconstituted’
– Processing route– Controls– Performance– Uses
• Cost benefits
Wax Reclamation• Has existed for a long time often with simple
reclamation carried out on-site– dewatering, sometimes basic filtration
• In most 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
ReconstitutedAdvanced Cleaning
Raw materials blended in to
restore to pattern wax specification
< 5000Kg
ReclaimCleaned as
option 1% filler retainedPossibly some
additions
< 4000Kg
Option 3Option 1
Reclaim
Filler, water, extraneous materials removed
< 2500Kg
Option 2
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’ sector 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
149.65149.55149.45149.35149.25149.15149.05
16
12
8
4
0
LSL USL
WithinCp 1.011CPL 1.012CPU 1.010Cpk 1.010
Overall
Cpm *
Pp 0.808PPL 0.808PPU 0.807Ppk 0.807
WithinOverall
149.65149.55149.45149.35149.25149.15149.05
20
15
10
5
0
LSL USL
WithinCp 1.057CPL 1.011CPU 1.104Cpk 1.011
Overall
Cpm *
Pp 0.746PPL 0.713PPU 0.779Ppk 0.713
WithinOverall
Capability Histograms of Test Block Virgin and Reconstituted A7-FR/60
Virgin Wax
Reconstituted Wax
Indi
vidu
al V
alue
28252219161310741
0.04
0.02
0.00
_X=0.01677
UCL=0.04254
LCL=-0.00900
Mov
ing
Ran
ge
28252219161310741
0.030
0.015
0.000
__MR=0.00969
UCL=0.03166
LCL=0
Observation
Valu
es
3025201510
0.03
0.02
0.01
0.0480.0400.0320.0240.0160.0080.000
LSL USL
S pecificationsLS L 0.00U SL 0.05
0.0450.0300.0150.000
Within
Overall
Specs
WithinS tD ev 0.00859012C p 0.97C pk 0.65
O v erallS tD ev 0.00784744P p 1.06P pk 0.71C pm *
Process Capability Sixpack of Virgin Wax Ash contentI C har t
M oving Range C har t
Last 2 5 O bser vations
C apability H istogr am
Nor mal P r ob P lotA D : 0.257, P : 0.699
C apability P lot
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– becoming even more expensive– 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