SlideTalk Video: V-Process Casting (Vacuum Process Casting)

SlideTalk Video: V-Process Casting (Vacuum Process Casting)

Lost Foam Casting (LFC) and Vacuum Process Casting (VPC, V-Process) -their Need Acceptance and Limitations for Foundry Modernization in India

Lost Foam Casting (LFC) and Vacuum Process Casting (VPC, V-Process) -their Need Acceptance and Limitations for Foundry Modernization in India
GD Mishra1, steel@gdmtechnics.com CEO, General Dynamic Multi Technical Consultancy LLP 1A Mechanical Engineer and MBA having 30 years of diversified experience in Product Application and implementing new Concepts and Project in India. Liquid Helium, Brewpubs, Lost Foam Castings(v-LFC) and V-Process (VPC) are few of the Products and Processes introduced in India by his efforts.

The foundry which can use all its resources efficiently, with minimal wastage and pollution to environment, would be an ideal foundry today.  Other than Power/Energy the most important input in any of the sand casting foundries is “Sand”.What would be an ideal foundry today?

In conventional sand foundries, be it Green Sand Process, Resin Sand Process or Shell Sand, sand needs binders to serve our needs to make various types of moulds. The sand from these moulds after use is to be reclaimed. Most of the smaller resin sand foundries do not have Sand Reclamation units because of Capital Investment and its Operational & Maintenance Costs. Of Course, these binders are also Pollutants to some degree in the Shop Floor as well as when thrown out as waste. The process of reclamation is prone to breakage of sand grains which lead to suspension of fine fibrous silica dust in the air, leading to life threatening disease called Silicosis to the manpower exposed to it and often wrongly diagnosed by Doctors as Tuberculosis. All these adds to cost to the foundry owner and the society at large. But world over now Sand is being considered as a perishable natural resource and various Governments have started putting restrictions to its use and after use studies are being conducted.

LFC, VPC, HPML and other such Highly Energy Efficient Modern Moulding Lines are the answer these above issues.

LFC & VPC needs no sand binders. The Mould strength is achieved by vacuuming in specially designed flasks or boxes. Adequately designed vacuum arrangement guarantees equal mould hardness in horizontal as well as vertical walls of the mould. In both LFC and VPC system after pouring and cooling of casting, there is no vigorous effort & time consuming Knockout Process, just topple the flask, the free-flowing sand goes into the sand cooler and back to hopper for moulding.

Lost Foam Casting

Today Vacuum Assisted Lost Foam Casting (v-LFC) Process is finding a great acceptance in foundries in China which have more than 3500 LFC foundries with different variants as shown in Fig.1. Recently foundrymen in India have generated interest into this process which is quite economical and reduces the

variants to about 40%. v-LFC uses Free-flowing sand without any binders and sand is re-used after cooling and removal of dust if any. The cost production by v-LFC is also reduced between 18- 35% depending upon the casting its profile, need of cores and metallurgy.

How, most Economical Moulding Process today

1. Most economical moulding process for 20 kg to 350 kg castings. Any size any shape and weight possible may be even 10-12 tons.
2. A kg of EPS (Expanded Polystyrene)/STMMA (styrene methyl-methacrylate) can produce 250-300 kg of casting.
3. Intricate parts can be cast
4. No Core, so no Core cost
5. No Rejections due to Core Shifting
6. No Fins so almost nil fettling
7. Faster Delivery, Satisfied Customers, More Orders
8. Very good Surface Finish upto 200 RMS can be achieved, without big efforts, better surface finish upto 150 RMS can achieved.
9. Machining work minimized
10. Sand reused with only 2% wastage
11. Steel, Ductile Iron & Grey Iron all can be cast very successfully
12. Environmentally friendly and Pollution Free workshop.

v-LFC Process Diagram

Acceptance of v-LFC

v-LFC Process has been successfully adopted for Grey Iron, Ductile Iron, Mn-Steel, Carbon Steel and recently expertise is being developed in special Alloy Steels too. Quite a few successful Aluminium Foundries by LFC are operating in China. Castings of Magnesium & Titanium Alloy castings is being practiced in Europe.

Generally, when we work out the viability for adoption of this process we ask for present yield, casting weight, moulding sand weight, core-weight, the higher it is higher is the margins for savings. But the most important aspect is the technical viability in all cases and the acceptable levels of rejections under various test condition. If similar castings have not been successfully achieved elsewhere in the world by v-LFC we should refrain in the earlier stages of adaptation of the LFC process in your foundry.




Energy Savings in LFC Process

1. Sand reclamation, the primary attrition and the secondary attrition to achieve 75% reclamation level and the thermal attrition to achieve total 95% reclamation level needs lots electrical and gas; while the Lost Foam Technology only needs sand cooling and re-circulation.
2. Because the LFC process sand does not stick to the casting surface and there are no fins, so no energy by way of hammering, grinding and chipping is needed for knockout and fettling of castings. Save time too.
3. Machining allowances of 1-1.5 mm at tool point so less machining needed, saves Energy and Time.
4. The overall weight of the casting is reduced needing less molten metal, so Energy is saved.

****

V-Process (VPC) or Vacuum Process Casting

This is yet another moulding process which doesn’t need any chemical or organic binders in the sand for moulding. One of the foundry which adopted VPC in India could envisage to double its moulding capacity in 2 years’ time, after all his process cost has become economical by 20-25%.

Foundries which are into Railway Castings in India making Side Frames, Bolsters for Casnub Bogies, Coupler etc and CMS Crossings should immediately target to reduce sand cost and shop-floor related pollution in their foundries. Foundries making large wear resistant Mn-Steel castings like Jaw Plates, Blow-Bars, Cone and Mantel should reduce their cost of resin sand usage and cost of Primary, Secondary Attrition and Thermal Reclamation and related manpower and maintenance costs.

V-Process Steps:

Step 1:      The pattern (with vent holes) is placed on a hollow carrier plate.

Step 2:      A heater softens the 0.07 to .0.2 mm EVA (ethylene-vinyl acetate) plastic film. EVA Plastic has good elasticity and a high deformation ratio.

Step 3:      Softened film drapes over the pattern with 0.03 to 0.05 MPa vacuum acting through the pattern vents to draw it tightly around the pattern.

Step 4:      The flask is placed on the film-coated pattern. Flask walls are also a vacuum chamber with the outlet shown at right.

Step 5:      The flask is filled with dry, un-bonded sand. A slight vibration compacts sand to maximum bulk density.

Step 6:      A sprue cup is formed and the mould surface levelled. The back of the mould is covered with unheated plastic film.

Step 7:      Vacuum is applied to the flask. Atmospheric pressure then hardens the sand. The vacuum is released, pressurized air is introduced into the carrier and the mould is stripped.

Step 8:      The cope and drag assembly form a plastic-lined cavity. During pouring, moulds are kept under vacuum.

Step 9:      After cooling, the vacuum is released and free-flowing sand drops away leaving a clean casting, with no sand lumps. The sand is cooled for re-use.

Benefits of V-Process

1.          Reduction in Sand Consumption 98%

2.          No water, no binder and no additives in Sand

3.          Cost reduction by about 20%

4.          Very Smooth Surface Finish 120 RMS

5.          Excellent Dimensional Accuracy

6.          Zero Draft

7.          Thin Wall Sections Possible

8.          Excellent Reproduction of Details

9.          Increased Pattern Life (no wear of pattern)

10.        Very Easy Knock-out, within no time.

11.        No sand sticking or inclusion

12.        No toxic fumes from burning the binders

13.        Excellent sand permeability

14.        Moisture related casting defects is zero.

15.        Yield increases

Examples by V-Process

Thus, both LFC & VPC today have very promising future in Indian foundries, where because of various types of pollutions now young capable engineers refrain to join. These options are win-win situation for Foundry Owners and Executives. Sooner the better Foundries should do an audit towards adaptation of these modern moulding technologies.

Control Pollution in your Foundry, Make more Profits:

Modernize your Foundry by adopting LFC / VPC:

Where Micro Crystalline Silica is generated in a Foundry? 

1. Knockout: In LFC & VPC the sand is free flowing, only bound by vacuum which is released after casting, so no vibration or hammering is needed to release the casting from the sand.
2. Fettling: In LFC & VPC with proper SOPs there is no sand sticking on the cast surface hence no surface grinding. Hence no crystalline suspended silica dust is generated.
3. Sand Reclamation: The Sand processing plant of LFC & VPC is essentially sand cooling, no primary secondary attrition is required; Any dust generated is also sucked into dust collector. 

GD Mishra CEO

steel@gdmtechnics.com +919200258915
General Dynamic Multi Technical Consultancy LLP

Silicosis & Crystalline Silica -by Mr Paul Cochrane