When to Use Complete equipment for lost foam casting？

Lost foam casting

Tubular Lost Foam

This is a condensed version of a four-month odyssey which is chronicled in its entirety here.

http://www.alloyavenue.com/vb/showthread.php?-Gating-Tubular-Lost-Foam-Part

Much of the above was learned from the contributions of others in that thread all of whom I hope to see here in the near future.

If you are looking for more details, kindly visit Lost foam casting equipment.

I started this project on a lark that turned out to be a great learning experience, very useful tool in casting practice, and surprisingly (shockingly) effective. This was the first in a series of experiments in lost foam casting that I tried only because I had built a furnace but had no molding sand, prep equipment, nor flasks and wanted to cast something. Lost foam was the fastest path to a casting.

The concept test piece was a water neck for an automotive intake manifold, 1 1/2" OD, 1/4" wall. I made a few jigs for my over arm router which made reproducing the foam patterns practical.

I decided to detail the parts with wax fillet. While I was at it, I had a silicone mold of an embossed logo from a previous project so decided what the heck and used it to make a wax embossment for the castings to see if it would work.

I had solicited opinions on how to gate the part on the AA forum. This orientation was the winner.

The blue foam was a Dow product that was leftover packing from items shipped to me. I researched the various foams and found two basic types; Expanded Polystyrene (EPS) and Extruded Polystyrene (EXPS or XPS). EPS is typical lower density beads that is expanded with steam in molded shapes. It's typically white, low(er) density which is good, hot wires well, and though it cuts easily, it does not machine nor sand to good surface finishes particularly well. XPS on the other hand does machine and finish well with abrasives. I found six densities commercially available from Owens Corning which is the pink trade named as 'Foamular'. The big box stores typically carry the Foamular 150 and 250. I found the Foamular 150 to be the best trade of low density, strength, machinability, and ability to achieve fine surface finishes with common abrasive paper'..amazingly so in fact. Foamular 150 is 1.3 lbs/ft3. EPS is usually 1lb/ft3 or less and many use it as sprue and gating material to take advantage of its very low density.

For a mold, I just started out with a plastic 5-gallon bucket and to pack the loose sand after it was poured in place I had a vibration platform on springs left over from casting refractory for my furnace.

Pattern Coatings

I also received quite a bit of advice and experimented with a number of coatings for improved surface finish. About everything worked great but thinned drywall mud achieved as good of result as any, was the least expensive, easiest to apply, fastest drying, and just fell off the castings during quench. The above may only hold for aluminum as bronze, iron and higher temp alloys may require coatings with better refractory properties.

Glues and Adhesives

For gluing pieces together, you need to make sure the glue doesn't have solvent that attacks polystyrene. Many do. Hot melt is da-bomb for smaller pieces but tends to set up too fast if you need longer working time, but it does burn out very cleanly. I initially used shellac for glue by applying several coats and drying with a heat gun. Shellac is reduced with alcohol which does not attack polystyrene. When you add the second or third coat, it reactivates the first coats and behaves like contact cement. It makes a good thin joint but doesn't burn out as clean as hot melt. The happy medium for longer working time was wood glue, sometimes slightly thinned. It also burned out very clean but doesn't stick on contact like coated shellac so small pieces of packing tape work well to hold parts in place. You can wipe away the excess with a damp cloth or cotton swab. A very thin joint is important if you need to sand the seam. All adhesives will make sanding the glued joints evenly very difficult and load up power abrasive sanding. Hot melt is terrible in this regard. Shellac , best, thinned wood glue a good compromise.

I had some leftover pieces so I made a couple of similar test parts from the scraps. Here they are sprued up and coated along with a couple of test coupons of the wax logo.

Here they are after being vibrated in loose sand. Keep in mind this is just loose sand, no binder of any kind. I also added a pouring cup to make it easier to hit and feed the sprue during pouring. Some folks call these Kush cups, I believe from the fella that popularized it.

'I fluxed, did not de-gas, and poured at F and here was the result. Wow, I didn't expect it to turn out that well.

I was dumbstruck by how well the loose sand tubular core remained stable and the quality of the surface finish''.both way exceeded expectations. Now the hook was now firmly set.

Though the results were very good, upon closer inspection, I found some casting flaws. Though opinions varied, 'fold' flaws are common to the process. So I embarked on a series of refinements and process control improvements.

Best,
Kelly

 

Lost foam casting

Lost foam casting is often used to cast small to medium complex products from some metal alloy materials. The final products maintain high precision and good surface finish.

Continue series blog of casting technology of Vietnam Cast Iron, this article will bring a brief and concise summary about the lost foam technology which often used to cast high detailed products.

The author will provide a detailed explanation including definition, advantage & disadvantage, and application of the lost foam process so that everyone could be easy to have a clear idea about this metal casting technology either you are an expert or freshman to this mechanical industry.

Lost foam technology

 

What is Lost Foam Casting?

Lost foam casting is a type of evaporative pattern casting. This method is quite similar to investment casting which uses wax instead of foam in the pattern making process.

The foam pattern was first used in metalworking in . Although this mold casting technique is not as popular as other methods such as sand mold casting or permanent casting, it maintains outstanding advantages, especially in casting complicated and precise molds.

Unlike traditional methods which include the pattern withdrawn process before casting and require skillfulness in the pattern removal step, with respect to the lost foam method, the pattern is evaporated when the molten metal is poured into helping to reduce these considerations.

The lost foam casting process

Lost foam process

The lost foam casting technology included 5 steps: designing the pattern; applying insulation painting; placing the pattern into the sand flask; pouring the molten metal; and collecting the castings.

How a lost foam pattern is made?

Firstly, a pattern is designed from polystyrene foam. This type of foam plays an important role in this casting method. It is a good thermal insulator and chemical resistance, enable working normally at the temperature below 75 oC.

Depending on difficulty and details of the product, the foam pattern can be made from different manners.

Making the pattern for lost foam process

For highly detailed casting patterns, the foam pattern is partly made and glued together. For the small volume, foundries often make patterns by hand-cut or machined from a solid foam block. If the pattern is simple enough, a hot wire foam cutter can be applied.

In case the volume is large, the pattern can be mass-produced by a process similar to injection molding.

Polystyrene beads are injected in a pre-heated aluminum mold at low pressure. After that steam is applied leading to polystyrene expands more to fill the empty cavity and then form the pattern or a section. The final pattern is approximately 97.5% air and 2.5% polystyrene.

Casting process

Once the pattern is formed, it is coated with insulation paint, placed in a flask and surrounded in un-bonded sand and compacted.

the pattern is coated with insulation paint in lost foam process

The covering paint works to increase the durability of the mold surface, protect from erosion, and broken. Whereas, the flask is designed suitably for this method so that when the molten metal is poured into the mold, the gas generated by foam burning is withdrawn completely.

After molten metal is poured into the foam pattern, the foam pattern is burned out and the casting is formed.

Lost foam method is apllied to cast steel product

What are the advantages of the lost foam casting process?

Lost foam casting maintains excellent advantages in comparison with other metal casting methods.

1. It is able to cast very complicated castings.
2. It is advantageous for guaranteeing high precision and smooth surface finish.
3. Casting by the lost foam technique guarantees nearly no errors or defects.
4. Generally, this method is also more economic than investment casting because it involves a few steps. Applying the lost foam process, the foundries can save a lot of labor and production costs.

What could be disadvantages of the lost foam casting process?

Except from numerous advantages, there are two main limitations of the lost foam casting technology.

1. Firstly, the pattern costs can be high for low volume applications.
2. Another disadvantage is the patterns are damaged or distorted easily because of its low strength. 

Application of Lost Foam Casting

Lost foam technique can apply in various materials ranging from alloy steel, carbon steel, alloy cast iron, ferrous alloy to alloy aluminum.

Ignore a few limitations, there are various advantages found in the lost foam method. Because of its precise casting ability, this process is often preferable to cast complicated and detailed products.

It is applied in a variety of industries ranging from the arts, computer technology, agriculture, national defense, automotive, to civil areas.

For many cast products cylinder heads, cylinder blocks, pipe fittings, valves, fire hydrants, motor starters, 3D models, gearbox details and more the lost foam casting process is the perfect match.

High detailed and complex lamp posts, gas burners, fences, pump housing, aluminum castings, pan support, etc. are also often processed by the lost foam casting.

Lost foam casting in Vietnam

• Lost foam workshop
• Foam pattern in lost foam casting

Together with sand casting, the lost foam technology is most widely and popular applied in metalworking foundries in Vietnam because of its economic effectiveness and good quality.

Vietnam Cast Iron is the leading company in metalworking. We supply custom-designed products meeting international standards within fields as following:

• Urban Decoration
• Agriculture Machinery
• Construction Industry
• Transportation
• Marine
• Water Supply and Drainage

Our productions are mainly made from cast iron, ductile iron, carbon steel, and aluminum; and processed by three main innovative technologies including Green Sand, Lost Foam, and Furan Sand.

With respect to the lost foam technique, we often recommend this method for high-detailed products. The outcome delivers tight tolerances, good surface finish, and save cost for the buyers.

Lost foam technology is an efficient and economic process. At Vietnam Cast Iron, with numbers of high skillful and expert labors and high-tech machinery, we could manufacture almost any products by the lost foam process, from a lamppost, manhole cover, pump housing to trash bin, fence, gas burner, etc.

We work with our customers to decide the best casting processes resulting best quality for final products and minimizing the buying cost.

Request a quote to get more information on how our casting service can match your project requirements.

Contact information

• Company: Vietnam Cast Iron Co.Ltd
• Address: Lai Xuan, Thuy Nguyen District, Hai Phong city, Vietnam
• : [ protected]

Tubular Lost Foam

This is a condensed version of a four-month odyssey which is chronicled in its entirety here.

http://www.alloyavenue.com/vb/showthread.php?-Gating-Tubular-Lost-Foam-Part

Much of the above was learned from the contributions of others in that thread all of whom I hope to see here in the near future.

I started this project on a lark that turned out to be a great learning experience, very useful tool in casting practice, and surprisingly (shockingly) effective. This was the first in a series of experiments in lost foam casting that I tried only because I had built a furnace but had no molding sand, prep equipment, nor flasks and wanted to cast something. Lost foam was the fastest path to a casting.

The concept test piece was a water neck for an automotive intake manifold, 1 1/2" OD, 1/4" wall. I made a few jigs for my over arm router which made reproducing the foam patterns practical.

I decided to detail the parts with wax fillet. While I was at it, I had a silicone mold of an embossed logo from a previous project so decided what the heck and used it to make a wax embossment for the castings to see if it would work.

I had solicited opinions on how to gate the part on the AA forum. This orientation was the winner.

The blue foam was a Dow product that was leftover packing from items shipped to me. I researched the various foams and found two basic types; Expanded Polystyrene (EPS) and Extruded Polystyrene (EXPS or XPS). EPS is typical lower density beads that is expanded with steam in molded shapes. It's typically white, low(er) density which is good, hot wires well, and though it cuts easily, it does not machine nor sand to good surface finishes particularly well. XPS on the other hand does machine and finish well with abrasives. I found six densities commercially available from Owens Corning which is the pink trade named as 'Foamular'. The big box stores typically carry the Foamular 150 and 250. I found the Foamular 150 to be the best trade of low density, strength, machinability, and ability to achieve fine surface finishes with common abrasive paper'..amazingly so in fact. Foamular 150 is 1.3 lbs/ft3. EPS is usually 1lb/ft3 or less and many use it as sprue and gating material to take advantage of its very low density.

For a mold, I just started out with a plastic 5-gallon bucket and to pack the loose sand after it was poured in place I had a vibration platform on springs left over from casting refractory for my furnace.

Pattern Coatings

I also received quite a bit of advice and experimented with a number of coatings for improved surface finish. About everything worked great but thinned drywall mud achieved as good of result as any, was the least expensive, easiest to apply, fastest drying, and just fell off the castings during quench. The above may only hold for aluminum as bronze, iron and higher temp alloys may require coatings with better refractory properties.

Glues and Adhesives

For gluing pieces together, you need to make sure the glue doesn't have solvent that attacks polystyrene. Many do. Hot melt is da-bomb for smaller pieces but tends to set up too fast if you need longer working time, but it does burn out very cleanly. I initially used shellac for glue by applying several coats and drying with a heat gun. Shellac is reduced with alcohol which does not attack polystyrene. When you add the second or third coat, it reactivates the first coats and behaves like contact cement. It makes a good thin joint but doesn't burn out as clean as hot melt. The happy medium for longer working time was wood glue, sometimes slightly thinned. It also burned out very clean but doesn't stick on contact like coated shellac so small pieces of packing tape work well to hold parts in place. You can wipe away the excess with a damp cloth or cotton swab. A very thin joint is important if you need to sand the seam. All adhesives will make sanding the glued joints evenly very difficult and load up power abrasive sanding. Hot melt is terrible in this regard. Shellac , best, thinned wood glue a good compromise.

I had some leftover pieces so I made a couple of similar test parts from the scraps. Here they are sprued up and coated along with a couple of test coupons of the wax logo.

Here they are after being vibrated in loose sand. Keep in mind this is just loose sand, no binder of any kind. I also added a pouring cup to make it easier to hit and feed the sprue during pouring. Some folks call these Kush cups, I believe from the fella that popularized it.

'I fluxed, did not de-gas, and poured at F and here was the result. Wow, I didn't expect it to turn out that well.

I was dumbstruck by how well the loose sand tubular core remained stable and the quality of the surface finish''.both way exceeded expectations. Now the hook was now firmly set.

Though the results were very good, upon closer inspection, I found some casting flaws. Though opinions varied, 'fold' flaws are common to the process. So I embarked on a series of refinements and process control improvements.

Best,
Kelly