HTSmith
Silver $$ Contributor
Say what?
Forged or Investment Cast - Does it Matter in Guns?
- Thread starter Phil3
- Start date
?????
Raythemanroe
Bullet Whisperer
The 700 Rem receiver is not an investment casting. It starts out as a piece of bar stock or cold drawn tubing which is milled to finish it.
Castings are usually used because a precision casting is a near net shape process. When the casting is precise enough and well enough designed it is often possible to produce a cheaper product because many machining operations may be avoided. Unfortunately many as cast surfaces do not have a surface texture as nice as produced by machining. Such a rough finish can look cheap and objectional even though perfectly serviceable.
All this assumes the casting is properly designed. Poor design casting is not a fault of the process it is a fault of the designers.
Castings are usually used because a precision casting is a near net shape process. When the casting is precise enough and well enough designed it is often possible to produce a cheaper product because many machining operations may be avoided. Unfortunately many as cast surfaces do not have a surface texture as nice as produced by machining. Such a rough finish can look cheap and objectional even though perfectly serviceable.
All this assumes the casting is properly designed. Poor design casting is not a fault of the process it is a fault of the designers.
mensajd
Quod Erat Demonstrandum
On one of the Outdoor Channel shows, they showed an episode regarding the Ruger factory wherein a very skilled craftsman had to mechanically true up the investment cast receivers as part of their manufacturing process. Didn't give me a warm and fuzzy feeling about the efficacy of the process.
I started working with investment cast aerospace parts back in the late 1970s. I have been to many of the US foundries and I have developed the tooling and processes to machine many different castings.
You need to be aware of how the process works to appreciate how dependent on design it is.
1. A mold is used to create a wax pattern. Hot wax is injected into the mold and is removed while still warm. The cooling wax part shrinks and warps unevenly as it cools.
2. The wax part often wax welded to other parts to make more complex parts.
3. The completed wax is dipped into a number of liquid ceramic slurries. When these layers harden the shell is heated to melt out the wax.
4. While the hollow shell is still red hot it is pulled out of the furnace and is poured full of molten metal. Remember the shell was originally formed around wax parts that shrank and distorted while cooling. Now that cavity is filled with hot metal which also shrinks and warps as it cools. When cooled the ceramic shell is broken and is knocked free of the metal. So you have metal parts with 2 sets of shrinkage and warpage.
There is 1 way to minimize this shrinkage and warpage. That is to perfect the mold when possible and then place the warm wax parts in special cooling racks. There is extra time, tooling and handling required.
The way most foundries deal with the warp and twist is violence.
You will find 5 lb dead blow hammers labeled BFH they use to beat the castings into submission. Skilled and semi skilled workers use hammers and presses to "straighten" castings. Sometimes it is the most economical way to get parts made. But some times they crack or break the parts. This often requires liquid penetrant inspection and X rays to detect.
If the casting is then machined all over you can still have a nice looking part. If many areas are left as cast they are often ugly. That is ok for some products that are out of site. But you would not want as cast on a double barreled shotgun at least not on the exposed surfaces.
You need to be aware of how the process works to appreciate how dependent on design it is.
1. A mold is used to create a wax pattern. Hot wax is injected into the mold and is removed while still warm. The cooling wax part shrinks and warps unevenly as it cools.
2. The wax part often wax welded to other parts to make more complex parts.
3. The completed wax is dipped into a number of liquid ceramic slurries. When these layers harden the shell is heated to melt out the wax.
4. While the hollow shell is still red hot it is pulled out of the furnace and is poured full of molten metal. Remember the shell was originally formed around wax parts that shrank and distorted while cooling. Now that cavity is filled with hot metal which also shrinks and warps as it cools. When cooled the ceramic shell is broken and is knocked free of the metal. So you have metal parts with 2 sets of shrinkage and warpage.
There is 1 way to minimize this shrinkage and warpage. That is to perfect the mold when possible and then place the warm wax parts in special cooling racks. There is extra time, tooling and handling required.
The way most foundries deal with the warp and twist is violence.
You will find 5 lb dead blow hammers labeled BFH they use to beat the castings into submission. Skilled and semi skilled workers use hammers and presses to "straighten" castings. Sometimes it is the most economical way to get parts made. But some times they crack or break the parts. This often requires liquid penetrant inspection and X rays to detect.
If the casting is then machined all over you can still have a nice looking part. If many areas are left as cast they are often ugly. That is ok for some products that are out of site. But you would not want as cast on a double barreled shotgun at least not on the exposed surfaces.
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