Vacuum Lost Foam from China (V-LFC) Versus foamcast Lost Foam Metal Casting Technology
| Sr | Parameter | Foamcast | Vacuum Lost Foam from China (V-LFC) | Impact on Foundry that proposes or plans to use the V-LFC Process |
|---|---|---|---|---|
| 1 | Availability of Raw Beads required for molding patterns | EPS (Expandable Polystyrene) is abundantly available in India. Supreme Petrochemicals Ltd. offers foamcast grade EPS specifically for the Lost Foam Process. EPS can be purchased locally in 25Kgs. Bags with a MOQ of 100Kgs. | STMMA copolymer resin has to be imported from China. Shipment is done in part loads, is very expensive and a feasible MOQ is 1000kgs. Shelf life of STMMA is 3months in an airconditioned environment. | Involves hassles of regular import since STMMA is classified as hazardous cargo hence part shipment is expensive. Price is prone to fluctuating foreign exchange rates and customs duties. Storage is expensive. |
| 2 | Availability of coating materials | Coating materials consist of Zircon, Molochite & Colloidal Silica which are common foundry materials avaliable across India. | Coating materials are branded and have to be sourced/imported from Foseco or ASK Chemicals | Coating cost are high and there is no scope for developing alternate cost effective coating materials. Eg. In foamcast fused silica can be used instead of zircon for some metals. |
| 3 | Aluminium Tooling/Die | Aluminium Dies are not fixed on the molding machine. The molding machine is vertical hence cores can be fixed on all five sides of the mold/die. Most importantly the tool/die cost is less since the cores are manually operated | Aluminium Dies are fixed on the molding machine. The molding machine is horizontal hence cores cannot be fixed all sides of the mold/die. Tool/die cost is very HIGH as the cores are automatically operated | Developing tools/dies is expensive hence only castings with a large quantity requirement are feasible, ideally in excess of 1000nos/month. Whereas in fomcast you can use the tool/die for a few tens or few hundreds of castings. |
| 4 | Foam Pattern Sections | Due to the modular vertical molding machine there is ease of mold/die design hence the patterns are molded as far as possible in a single piece or else with minimum sections. | Mold/Die design is rigid since the molds/dies are fixed on the machine. Due to the rigidly designed molds the foam patterns have to be molded in multiple sections. | More the number of joints more are the chances of rejection during assembly of the pattern. Ideally the pattern should be molded as single piece. |
| 5 | Assembly & gluing of foam patterns | A polymer hot melt glue is used which is burned-off before metal is poured, hence the residue from the glue does not interfere with the metallurgy of the casting | Minimum glue is applied between joints otherwise the metal burning the glue will absorb the fumes. Further Each joint has to be glued & then taped with a self adhesive tape so that the joint does not open up. | Process is very laborious and is prone to in-process rejection since the taped joints have a tendency to open up under the pouring pressure of the liquid metal. In foamcast this situation simply does not exist! |
| 6 | Strength of pattern and detailing on the surface | Density of molded EPS foam is 40kgs/cu.mt. which gives the pattern fantastic dimensional accuracy & strength. High density allows the use of finer beads so the details like lettering on the pattern is prominent and well formed. | Density of molded STMMA foam is 18kgs/cu.mt. which makes the foam pattern weak and delicate. Low density means bigger beads so the detailing on the pattern is poor. | Foam patterns have to be dipped in the coating. Light STMMA foam patterns are delicate and difficult to coat & are prone to breaking during the dipping process. The STMMA patterns have to be light to reduce carbon pick up. |
| 7 | Size of Casting | There is no Limitation of size of the casting. Since the patterns are molded for High Density EPS foam large patterns are strong & stable. | Large castings are difficult to cast since the patterns are not always strong and have a tendency to break due to its brittleness. | Lot of parameters have to be considered before a decision is taken to mold the patterns. Large castings are a risky affair. |
| 8 | Backing Media | Free flowing unbonded 45AFS coarse silica sand is required as a backing media to strengthen the shell during pouring | To reduce pouring defects expensive INCAST olivine sands are required for the production of large grey and ductile iron castings. | Olivine Sands have to be imported and if locally available sands are used the chances of in process rejection due to foam inclusion and gas entrapment increase. |
| 9 | Process Equipment | All critical & ancillary equipment required for the entire process are indigenously developed & are available in India/Worldwide. | Critical equipment has to be purchased from China. Additional cost has to be paid to stock spares of such equipment. | Equipment has to be checked & tried before it is sent to India. In the event of failure there is difficulty in communication due to the language. |