How DFM Can Cut Product Costs and Increase Quality
What is DFM? Why is manufacturability important, and how does it save cost? Design for manufacture explained, with real-world examples.
What is DFM?
DFM is the practice of designing a product so that is able to be efficiently manufactured. The acronym DFM is short for “Design for Manufacturing”. It is set apart from traditional functional engineering which seeks to achieve a desired mechanical or visual design.
Functional engineering focuses on performance, or how well a design achieves its desired function. However, DFM design for manufacturing aims to reduce overall product cost. DFM also ensures that a product is able to be manufactured efficiently, or in other words have good manufacturability. It does this through knowledge of the manufacturing process, and design principles and improvements. Good DFM achieves these cost minimizations while maintaining function and visual design.
When answering “what does design for manufacturing mean?” you can consider it a process to make manufacturing easier and more efficient.
In other words, DFM is a process to discover how to reduce production cost in manufacturing. DFM can reduce costs in several ways. One way is by reducing the amount of and complexity of required steps in the process. If operations can be eliminated through small design changes, time and cost savings are achieved.
Alternatively, optimizing the design for the type of manufacturing also brings cost reduction. For example, injection molded plastics are susceptible to breakage if ejected on shear from the mold. Ejection pins placed in strategic locations can save on material costs.
What is manufacturability?
Manufacturability is the ability for a part to be manufactured efficiently and at the lowest possible cost. When a part is poorly designed for its manufacturing process, it can result in an overly large loss of material or time. When this loss happens, the part is not considered manufacturable. In other words, it has a low manufacturability.
How DFM Affects Cost
The design phase is the area of product development that has the greatest affect on cost. Changes made in the design phase are much less expensive than the production phase. Therefore, DFM should occur as early as possible, ideally before tooling has begun. Here are ways in which costs can be lowered by DFM:
Reduced Total Number of Operations
DFM seeks to optimize production by eliminating unnecessary steps. With each additional step in the process, more potential for error is introduced. Therefore, overhead and labor costs reduce by examining and reducing complexity.
Optimized Process Tolerance
Certain manufacturing processes such as injection molding are susceptible to various types of failures. For example, the way the material is ejected from the mold could become problematic if the mold doesn’t have significant enough tapering, or draft to ease the release from the tool.
Failures such as this increase the time of production as well as material waste. This results in increased costs.
Optimized Material Tolerance
In the same way that designing for the manufacturing process can decrease costs, so can designing for the material tolerance. Continuing with our injection molding example, plastic materials with walls that are too thick cool much slower and run the possibility of causing sink.
Conversely, areas of the design that are too thin are fragile. An engineer will identify these areas and address with ribbing or other design changes in accordance with the material type. This increases the product quality and viability, also decreasing costs.
Standardization of Parts
Part of the DFM work includes examining the potential for combining similar parts into a global standardized part. This is done by either adopting the same material across parts, or by adopting the same part design.
As a result, this approach accomplishes a total reduction in number of parts which eliminates the tooling and overall product cost.
How Much Can DFM Save?
Because there are so many variables involved, it is impossible to say how much DFM can save you without a proper DFM analysis. At AMS, we have gained our customers savings up to 50% on manufacturing costs. Not all customers see returns as great as these, but savings are still significant especially on high volume production.
Probably more significant, however, is the cost of quality. Product costs are not simply accounted for in total waste, remakes, and time. DFM is considered a type of “prevention cost” which includes the cost of things that improve product quality. Luckily, at AMS it’s a service we include for free, so technically it’s not even a cost.
Regardless, implementing proper DFM early on in the development process can eliminate much of the risk of returns, recalls, warranty claims, replacements, and lost customers. This is a type of hidden cost that is intangible to the company, but can easily snowball out of control and kill profitability.
DFM proves that increasing quality doesn’t have to be expensive.
At AMS, we follow a production part approval process (PPAP) which is common in the automotive industry. This provides a clear understanding for ourselves and our customers on tolerances during the manufacturing process. High tolerance production is not good, as it results in lower yield and higher costs.
This is a design phase process, but also present during the tooling and prototype phases. Therefore, designers and engineers must work together to ease tolerances. This results in increasing manufacturing yields and lower costs. Additionally, quality increases because of a reduction in potential defects.
Design for Manufacturing Examples
Now that you have a handle on the answer to “what is design for manufacturing” let’s look at some examples. These are just a few DFM examples from AMS projects. There are many methods in addition to these examples that the design process can apply to product manufacturing.
LiPo Battery Door DFM Improvements
AMS was engaged to participate in turn-key supply chain services for an up and coming toy blaster brand. As a part of the process, our engineering team identified many areas of attention in order to increase the product’s manufacturability.
In this example, the plastic parts on the hinge could have caused sink marks due to the amount of material present. This is caused because thicker parts of the plastic cool at slower rates which causes the sink marks to form. Additionally, we suggested that the customer reduce the thickness of the clasping mechanism. Therefore, this change will help add strength and avoid sink marks in the hook.
DFM in manufacturing is critical for parts like this. This is because a well implemented DFM process can reduce or eliminate flaws before they become manufacturing issues.
DFM Manufacturing Draft Angles
In this design for manufacturability example, the original design lacked the proper draft angles. Draft angles ensure that the plastic part can be easily ejected out of the plastic injection machine.
This is because injection molding machines work by injecting liquid plastic into a mold form of two halves pressed together. That liquid plastic cools and hardens after which ejects from the separate mold halves. Most mold designs use a push pin in order to forcibly eject parts out of the mold cavity.
If a part does not eject properly from the injection molding machine, it can cause delays, limit production capacity, and often break apart. In fact, it can even reduce the life span of a mold by adding undue stress. This results in an increase in raw material and labor cost, and a reduction in supply. Therefore, taking proper design for manufacturing steps prior to mass production is not only necessary but economical.
Bending Tolerances and Features
This example shows the potential pitfalls of not performing a manufacturability design review on metal parts. Bending processes have tolerances and this part design has features in close proximity to the bend. If this product design process did not include a review of these critical features, it would have failed in production. DFM reviews must take place in the design stage for maximum effectiveness.
The above diagram shows the math involved when determining bending tolerances in metal manufacturing.
Hopefully this article has not only answered the question of “what is DFM” but also informed you about the process and why it is so crucial. Remember, the earlier in the manufacturing process that issues are caught, the cheaper it is to correct them. When outsourcing, it’s important to partner with trustworthy and capable company that has your back through the entire process.
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