Fit Form Function FAQs
Part design is crucial to the success of your component. It is important for the overall success of your project to stay on target when it comes to timelines and deliverables. To you, a supplier asking for a design for manufacturing review has the potential to hinder your progress—but an initial design review at the beginning of a project could save costs to the fit, form, and function of the part with design experts’ input. Below are a few frequently asked questions regarding the investment casting process and how our team of highly trained engineers can improve your part.
Is my part too heavy for investment casting?
Just like any other manufacturing process, there are limitations with investment casting. In multiple steps throughout the investment casting process, the molds must meet certain weight requirements. Molds themselves have weight restrictions based on the type of alloy poured, maxing out at 100 to 120 pounds and meeting the industry weight standard. At other stages, molds are handled manually, or even automatically by Signicast’s state-of-the-art automation and robotics systems, requiring strict weight and safety restrictions.
Does surface area cause limitations?
There are three areas in which surface area has limitations—dip cells for our ceramic shell-building process, dewaxing where we’re using that steam pressure to remove the wax from the shell, and then our burnout ovens.
The more surface area the part has, the more viscous slurry sticks, increasing the weight of the sprue and causing weight limitations for the robot.
Now that we have a fully injected and dipped mold, we have the weight of the wax and the added weight of the ceramic shell weight. In this stage, there are personnel safety weight limitations to safely transport the molds in the plant.
The molds are fired to 1800℉, and once the temperature is reached, we must ensure that the molds are still handled safely.
How do I take full advantage of the investment casting process?
As previously mentioned, almost every design will face a geometry, pour weight, or shell weight limitation during the initial mold design phase.
But it is through a Design for Manufacturing (DFM) meeting that the Signicast Engineering team will work with you to broach potential limitations, increasing the value of the part right out of the gate. Your part is “renting” space on a mold, so whatever changes made, or features added to the design are essentially free—so long as you don’t increase the footprint of the mold.
For example, holes or bosses can be added to the design without the overall footprint of the part increasing. The number of pieces on the mold will stay the same, as well as the piece part price. Small price implications could be added to the tool cost.
In a recent project, the Signicast Engineering team brought a customer’s piece part price down from $23 to $18—a cost reduction of almost 30%. The price reduction was not caused by the alloy cost, but rather a design change that allowed more pieces per mold. The initial customer DFM session also utilized the full benefits of the investment casting process by adding lettering, lot codes, part numbers, and logos on the parts—for no additional cost.
When should I consider alloy and heat treatment selection?
Very often, alloy selection and heat treatment are thought of very early on in the design process and never revisited.
Some of our customers use cutting and grinding tools. A knife blade design came to our team designed in 420 steel because it was originally machined from solid. After talking about the function of the part and doing a DFM call, our in-house metallurgist suggested a D2 tool steel. The end result—seven times the original wear resistance, therefore extending the life of the part in service.
It is also important to think about heat treatment. If you want a part that is going to be heavily machined, you definitely want to heat treat and homogenize the material before machining to limit hard spots or broken tools. However, if you aren’t doing extensive machining, you may be able to eliminate heat treat altogether.
How can I eliminate machining and ultimately cut costs?
By simply designing an investment casting to have certain features, your part can avoid having to be machined and eliminate a large cost of the part.
Our engineering team often sees prints with surface finish callouts. This is often adding cost where it’s not needed. Many of the features that we machine on the casting are for size, position, or flatness. A surface finish only needs to be called out if it’s for a sealing surface, O-ring groove, or a press fit. Very often, the DFM process can help you eliminate one or two machine passes, or even reduce the cycle time for machining altogether.
How long does a DFM meeting take?
Typically, it depends on the complexity of the part and where our engineering team can find room for improvement. On average, the meeting could take between 15 minutes and 1 hour. In that time, our team will be able to have a full DFM call and leave with action items and be able to update the quote or RFQ.
To learn more about the design for manufacturing process and how Signicast can add value into your component without adding cost or production lead time, download our FREE webinar, Saving Cost: Fit, Form, Function.