Our Design and Manufacturing Process
The following walk through provides a general overview of the design process for both sand and permanent mold castings. For more information about each step in the manufacturing process, please see the descriptions of each step below.
The design process starts with an idea or a need. As the customer it is your job to figure this one out. Once we have defined what it is we want our casting to achieve we further define the idea with a prototype or parametric model.
The purpose of the prototype/parametric model is to further quantify what we want in the final casting. With current modeling software such as SolidWorks, the prototype may only exist as a digital rendition (parametric model) but it still provides us with all of the physical dimensions that would exist with the real thing. Now that we know what we want to cast it is time to design the tooling.
Tooling consists of all of the required fixtures and elements that are needed to provide us with the internal and external geometry of our finished casting. Tooling for a casting can consist of but is not limited to the core box, a loose pattern, a match plate, or a permanent mold.
With loose patterns, or match plates the tooling serves as the slug that the sand is packed around to create our desired geometry. Permanent molds and core boxes are in them selves molds that provide the external geometry of the casting or the core.
Given the demand of the customer each piece of tooling has a point at which it becomes the most economical way to produce a casting. For example, single part production or prototyping would require no more then a loose pattern while a production run of 5000 castings would demand the use of a match plate or permanent mold.
Now that we have our tooling and our cores it is time to create the mold/s. Our sand system consists of two hunters, three squeezers and one rollover. The hunters are automated molding machines that use match plates to generate molds. Sand is fed into repositories above and below the match plate and then hydraulically compressed to create the mold halves complete with all of the required gating. Each half of the mold is indexed into one another and the mold is complete. The squeezer and the rollover work much in the same way but the process is not automated.
Permanent molds on the other hand are another ball game. To produce a permanent mold a drafter works with a parametric modeling program such as SolidWorks to create a solid model of the part. The model is then imported into a CAM program such as SurfCam or MasterCam to generate the tool paths. Once the paths are created a CNC uses the data to mill the desired geometry out of a piece of iron. Once made a permanent mold provides an improved surface finish and generates castings faster then the sand casting process.
With everything in place we move onto the casting. Molds generated on our automated molding machines (hunters) are fed into a carousel where they are indexed into place and housed for pouring. As each mold is filled the carousel rotates the next mold into position for pouring, drops a previously poured mold off for shake out, and grabs a new mold from the hunter line. The process operates continuously until the desired number of castings are produced.
To facilitate permanent mold castings multiple furnaces are located through out the plant. Each furnace serve as work stations for multiple molds. Once a mold is filled an automated timer starts to count down the optimal time it takes for the casting to solidify. As the worker is waiting for the aluminum to cool he is busy tending another mold. The entire process is choreographed to minimize down time and maximize output.
Shake out is the process that de-sands the casting. After the part is cast it needs to be removed from the mold. This is done by placing the filled mold onto a agitated table that basically sifts the casting out of the sand. Once the aluminum is exposed and the remaining sand is removed the castings are placed into a cart where they await the next step. The sand that was used for the mold is routed back into out sand system where it will be used again to provide the mold for another part.
To de-core a permanent mold casting the part is fixed into a machine known as a rattler. The rattler vibrates the casting in order to break the core sand loose. The frequency of vibration must be tailored to the specific casting to achieve the optimal effect.
As a casting comes out of its mold it consists of a little more then just the desired part. Additional strands of material known as gates, risers, and runners were incorporated into the original mold to account for variables that come with the casting process. Now that we have our casting the additional material is of no use to us so a sawyer removes it. Everything removed from the casting is collected and brought to our smelter where it is melted down and reused.
To clean up any flashing or burrs left over from removing excess material our castings are brought to the grinding line. Here castings are carefully inspected and touched up.
Once the casting reaches a point at which all of the unwanted material is removed, parts are batched together and brought to heat treat. Here we have 7 heat treat ovens, 4 quench tanks and 6 ageing ovens that are utilized to create our desired tempered designation. Having a complete heat treat department in house allows for faster turn around times and optimal control over the process.
Unless an as-cast finish is desired we place our castings into a machine called a wheelabrator. The wheelabrator is basically an automated sand blasting machine that cleans the surface of a casting with steel or glass shot. Castings that are produced with a permanent mold do not regularly go through this process.
Our Vacuum Pressure Impregnation System (VPI) is used to seal the porosity that can naturally occur with in a casting. The castings are placed into a the VPI where the air is removed and sodium silicate is introduced. The drop in pressure forces the sodium silicate into any fishers or voids creating a sealed pressure vessel. Once impregnated the castings are subjected to a pressure vessel analysis to verify their integrity.
At this point if the as cast dimensions don't hold the tolerance required, or features need to be added to a part the casting will be brought to our production machining department. Here we address all of the critical areas of the casting that could not be incorporated into the mold. Tapped holes, face finishes, hole patterns, anything that needs to be held to with in .005" tolerance is managed by computer numeric control (CNC).
Finishing is a broad term that encompass the last process that a casting encounters. The finish of a casting is completely dependant on the demands of the application. For some an as cast finish will suffice, others will require such processes as galvanizing, powder coating, or tin plating. Not all finishing processes are done in house but if we can facilitate the need we will.
To provide a superlative product for such a large array of industries demands a level of performance that exceeds customer expectations. To accomplish this we have implemented quality assessment procedures into the manufacturing processes from conception to completion. Common practices include; first article reports (physical measurements and properties), digital go-no go fixtures, X-ray analysis, and three stage alloy analysis (spectrograph).
Once the castings have made it through all of the required processes they are boxed and brought to the shipping department. From here the boxes are loaded on to trucks and shipped to the appropriate destination.