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DFMandFMEAmodule2A.pptxDesign for Manufacturing (DFM) occurs early in product development, before tooling and assembly process, when the product is being designed.
This will make manufacture less time-consuming, which will reduce cost and increase ease of manufacturing basis principles.
Introduction to DFM
THE DFM METHOD
DFM involves simultaneously considering design goals and manufacturing constraints in order to identify manufacturing problems while parts are being designed; thereby reducing the lead time for product development and improving product quality can be concluded that the design stage is very important in product development. Often an otherwise good design is difficult or impossible to produce.
Typically a design engineer will create a model or design and send it to manufacturing for review and invite feedback.
This process is called as design review.
If this process is not followed diligently, the product may fail at manufacturing stage.
If the DFM guidelines are not followed, it will result in iterative design, loss of manufacturing time leading to longer time to market.
Hence the present work aims to apply the DFM approach for the process and product improvement of medical equipment
Several DFM/DFA guidelines have been developed to assist the designer. Consequently product competitiveness has been improved by applying these DFM techniques. Nevertheless, the decision- making process and the expertise of the designer continue to be the key aspects to ensure the success of DFM, due in part to the availability of DFM information [6, 7, 10].
The DFM method is illustrated in the following figure. It consists of five steps plus iteration [7]:
i. Estimate the manufacturing cost.
ii. Reduce the costs of components.
iii. Reduce the costs of assembly.
iv. Reduce the costs of supporting production.
v. Consider the impact of DFM decisions on other factors.
Elements of the manufacturing cost of a product. From “Product Design and Development”, by K. Ulrich, 2003, p. 258.
DFM method begins with the estimation of manufacturing cost of the proposed design. This helps the team to determine at a general level which aspects of design- components, assembly or support- are.
DFM approach was applied for the productivity improvement of one of the Electrocardiograph (ECG) model called as ―CARDIART 108T DIGI‖, manufactured by one of the leading medical equipment company in India.
The following problems were identified in its production:
1. Low productivity. The model was initially designed by the company for a low volume of production around 50 to 60 units per month. But presently the production volume is insufficient to meet the demand.
2. Obsolete tools and related quality issues. 3. High manufacturing cost.
The Figure shows the various causes for low productivity of the model:
The average monthly production of the model was around 200 units. The production capacity has to be increased to meet varying demands from 250 to 1000 units per month. So in order to achieve this target, re-engineering of the product is necessary.
The major objectives of re-engineering are to improve the volume and reduce the cost of production. Various parts in top panel, bottom panel and the final assembly of CARDIART 108T DIGI are shown in figures 3, 4 &5 and the BOM is shown in Table1.
Manufacturing Cost Analysis of Present Model
Reducing the Cost of Components and Cost of Assembly:
Redesign components to eliminate processing steps
Integrate Parts
Standardize Components
Evaluation of Assembly Efficiency
Before the design modification
After the design modification
Manufacturing Cost Analysis of Present Model Manufacturing cost is a key determinant of the economic success of a product. International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 4, April 2014) 82 In simple terms, economic success depends on the profit margin earned on each sale of the product and on how many units of the product the firm can sell. The number of units sold and the sales price are to a large degree determined by the overall quality of the product. Economically successful design is therefore about ensuring high product quality while minimizing manufacturing cost. DFM is one method for achieving this goal; effective DFM practice leads to low manufacturing costs without sacrificing product quality. Component Cost The table below shows the list of major mechanical components of the ECG 108T- DIGI along with the Part code, quantity required per unit and their individual rates.
Reducing the Cost of Components and Cost of Assembly The following DFM strategies are followed to modify the design and to reduce the component cost of CARDIART 108T DIGI:
1. Redesign components to eliminate processing steps:2. Integrate Parts:
3. Standardize Components: 4. Evaluation of Assembly Efficiency
The assembly efficiency of the product is measured as an index which is the ratio of the theoretical minimum assembly time to an estimate of the actual assembly time for the product.
This concept is useful in developing an intuition for what drives the cost of assembly.
To determine the theoretical minimum number of parts, the following three questions are asked in the assembly for each part. Only parts satisfying one or more of these conditions must ―theoretically‖ be separate:
The part need to move relative to the rest of the assembly. Small motions that can be accomplished using compliance (e.g., elastic hinges or springs) do not count.
The part is to be made of a different material from the rest of the assembly for fundamental physical reasons.
The part has to be separated from the assembly for assembly access, replacement or repair.
The 3 seconds‖ in the numerator reflects the theoretical minimum time required to handle and insert a part that is perfectly suited for assembly. It can be taken as the average time (sustainable over a whole work shift) required to assemble a small part that is easy to grasp, requires no particular orientation, and demands no special insertion effort.
The results of the case study emphasize the relevance of DFM methodologies in product design and manufacturing.
It also gives idea regarding how manufacturing complexity and costs can be reduced in early design stages.
The application of DFM principles resulted in improvements in three major areas; Product Quality, Cost and Delivery.
With the help of improved design, the company attained the ability to execute mass orders of 1000 to 1500 units per month without any extra investment in assembly line.
Also, the return of investment (cost of new die) was possible within a year.
The major quality issues like breakages in castings and noise disturbance in ECG due to aluminum components were averted.
With this improved design and processes, the production lead time was reduced from 2 weeks to 1 week.
The total production cost and time were also reduced considerably.
Although further iterations in the DFM process are not presented, it is recommended that the results of the process should then be fed back into the design process to provide further DFM iterations and improvements through modifications that optimize detailed manufacturability issues.
Conclusions
Example
CUBO PACE
https:// www.youtube.com/watch?v=tEEHFt9uACI
https :// www.youtube.com/watch?v=C31RPvtFw6k
Activities for DFM:
Watch the following video and respond the following questions:
What is the most important consideration when eliminating product components?
In addition, identify a simple product you are very familiar with, use the video as a hint to apply DFM into your product
Apply DFM methodology following the example from the video. Follow the steps: conceptualization, analysis, redesign, and conclusion.
Construct the Assembly diagram by hand or a software
Create a list of questions to help you decide what components are necessary and what components you may need to eliminate without the lost of functionality
Provide sketch (made by a software or by hand) to indicate the original design and the redesigned product
Lean Six Sigma-Tools
Project Selection, NPV, SIPOC Diagram, VOC, CTQ, Pareto Chart, Process Mapping
C&E Analysis, Process Capability Analysis, Sampling, Basic Statistics
Hypothesis Test, Correlation, Regression, Multi-Vari, CI’s, ANOVA
DOE, Poka-Yoke, FMEA, RSM
Control Plans, SPC, SOP’s
Agenda
What is FMEA?
Why is an FMEA important?
History of FMEA
Benefits of FMEA
Limitations of FMEA
How to conduct an FMEA?
What is FMEA?
Failure Mode and Effect Analysis
A systemized group of activities designed to:
recognize and evaluate the potential failure of a product/process and its effects
identify actions which could eliminate or reduce the chance of potential failure
document the process
FMEA is a process that identifies all the possible types of failures that could happen to a product and potential consequences of those failures.
The Failure Mode is what could go wrong
The Effect Analysis is how it would happen; how likely is it to go wrong; how bad would it be
https:// www.systems2win.com/solutions/FMEA.htm
Failure mode - the way in which something might fail
Effects analysis – studying the consequences of the various failure modes to determine their severity to the customer
FMEA Terms
FMEA Terms
Effects analysis – studying the consequences of the various failure modes to determine their severity to the customer.
The blowout of a tire is likely to have the most serious consequence, since when a tire suddenly explodes, the car might go out of control.
On the other hand, a puncture problem usually allows the tire pressure to decrease gradually, allowing the driver time to sense the problem before he looses control.
Neither failure mode is something the driver wants but of the two the puncture is preferred.
Preventing problems is cheaper and easier than cleaning them up.
Some things are too risky or costly to incur mistakes.
Healthcare is a good example of this because we have very costly and risky procedures. An FMEA is critical for healthcare procedures because preventative medicine is less costly than curative medicine. We want to prevent problems before they happen and that is exactly what an FMEA does.
Why do an FMEA?
The Reasons for FMEA
Get it right the first time
Identifies any inadequacies in the development of the product and to get it right the first time so that there are no costly mistakes later.
Tests and trials may be limited to a few products
Regulatory reasons
Continuous improvement
Preventive approach
Team building
Required procedures
FMEA Provides the Potential to:
Reduce the likelihood of customer complaints
Reduce the likelihood of campaign changes
Reduce maintenance and warranty costs
Reduce the possibility of safety failures
Reduce the possibility of extended life or reliability failures
Reduce the likelihood of product liability claims
Identify potential and known failures
Reduce the number of engineering changes
Reduce product development time
Lower start-up costs
Greater customer satisfaction
Increased cooperation and teamwork between various functions
Continuous improvement
Benefits
FMEA was proposed by ARMY about 60 years ago. It was used as a reliability evaluation technique to determine the effect of failures.
Failures were classified according to their impact on mission success and personnel/equipment safety.
Formally developed and applied by NASA in the 1960’s to improve and verify reliability of space program hardware.
History
Used to analyze concepts at the early stages before hardware is defined (most often at system and subsystem)
Focuses on potential failure modes associated with the proposed functions of a concept proposal
Includes the interaction of multiple systems and interaction between the elements of a system at the concept stages.
Concept FMEA
Design FMEA
A design FMEA is used to evaluate design requirements and design alternatives.
It aids in the initial design and provides additional information to aid in the planning process for manufacturing and assembly
Increases the probability that potential failure modes have been considered
Provide additional information to aid in the planning of efficient design testing
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Process FMEA
Identify potential product related process failure modes
Assess the potential customer effects of the failures
Identify the potential manufacturing causes on which to focus on
Develop a ranked list of potential failure modes
Document the results of the manufacturing of a product
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Types of FMEA
The main difference between the two is that:
A Design FMEA is done during the design phase of a product to ensure failure modes have been addressed
A Process FMEA is done to a process to ensure failure modes have been addressed.
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Resources Needed
Commitment of top management
Knowledgeable individuals with expertise in: Design Manufacturing, Assembly, Service, Quality, Reliability
Individuals who want to identify failure modes before a design or process failure mode happened
People resources. They may be internal or external to the business or a combination of both
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FMEA Timing
FMEA should be updated:
at the conceptual stage
when changes are made to the design
when new regulations are instituted
when customer feedback indicates a problem
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Advantages
Enhance design and manufacturing efficiencies
Alleviate late change crises
Minimize exposure to product failures
Augment business records
Improve “bottom line” results
Add to customer satisfaction
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Limitations
Employee training requirements
Initial impact on product and manufacturing schedules
Financial impact required to upgrade design, manufacturing, and process equipment and tools
These limitations should be recognized and treated as short term to minimize interruptions to a business.
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Risk Assessment Factors
Severity (S): A number from 1 to 5, depending on the severity of the potential failure mode’s effect
1 = no effect
5 = maximum severity
Probability of occurrence (O): A number from 1 to 5, depending on the likelihood of the failure mode’s occurrence
1 = very unlikely to occur
5 = almost certain to occur
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Risk Assessment Factors
Probability of detection (D): A number from 1 to 5, depending on how unlikely it is that the fault will be detected by the system responsible (design control process, quality testing, etc.)
1 = nearly certain detention
5 = impossible to detect
Risk Priority Number (RPN): The failure mode’s risk is found by the formula RPN = S x O x D.
RPN = Severity x Probability of Occurrence x Probability of Detection.
The probability of detection is a rating on how likely it is to detect the failure
And the risk priority number is found by multiplying the severity rating by the probability of occurrence by the probability of detection.
The auto industry says that a risk priority number of 75 is acceptable. Anything more than that is unacceptable.
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Risk Priority Number
The risk priority number is found by multiplying the severity rating by the probability of occurrence by the probability of detection.
How to conduct an FMEA?
-find severity rating
-find probability of occurrence
-find probability of detection
-find the risk priority number. It is found by multiplying the severity rating by the probability of occurrence by the probability of detection.
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Process Steps:
1: Identify modes of failure (e.g.: car won’t stop)
2: Identify consequences & related systems for each mode
3: Rate the Severity (S) of each effect
4: Identify potential root causes for each failure mode
5: Rate the Probability of Occurrence (O) of each root cause
6: Identify process controls and indicators (e.g.: brake squeal)
7: Rate Detectability (D) of each mode/root cause (we cannot detect it)
8: Calculate risk priority (S*O*D) and criticality (S*O)
9: Use design to mitigate high-risk or highly critical failures, and re-assess to ensure goals have been achieved
Example:
Battery
Headlight
Switch
Possible Failure Modes:
Light doesn’t turn on
Light doesn’t turn off
Possible Consequences:
Light doesn’t turn on
Driver can’t see obstacles
Car inoperable at night (8)
Light doesn’t turn off
Battery died
Car won’t start (10)
Possible Root Causes:
Light doesn’t turn on
Battery dead (8)
Broken wire (3)
Headlight out (10)
Switch corroded (2)
Switch broken (3)
Example:
Battery
Headlight
Switch
Possible Failure Modes:
Light doesn’t turn on
Light doesn’t turn off
Possible Consequences:
Light doesn’t turn on
Driver can’t see obstacles
Car inoperable at night (8)
Light doesn’t turn off
Battery dies
Car won’t start (10)
Possible Root Causes:
Light doesn’t turn off
Short circuit in switch (2)
Operator error (left on) (8)
Example:
Battery
Headlight
Switch
Controls/indicators:
Light doesn’t turn on
User notices lights on in dark
Light doesn’t turn off
User notices lights on in dark
Detectability:
Light doesn’t turn on (6)
User notices lights on in dark
User doesn’t notice lights not on during day
Light doesn’t turn off (6)
User notices lights on in dark
User doesn’t notice lights not on during day
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Example:
| Possible Effect | Root Cause | S | O | D | RPN | Crit. |
| Car inoperable at night | Battery dead | 10 | 8 | 6 | 480 | 80 |
| Broken wire | 8 | 3 | 144 | 24 | ||
| Headlight out | 8 | 10 | 6 | 480 | 80 | |
| Switch corroded | 8 | 2 | 96 | 16 | ||
| Switch broken | 8 | 3 | 144 | 24 |
Failure Mode: Light doesn’t turn on
Risk Priority Number (RPN)
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Example:
| Possible Effect | Root Cause | S | O | D | RPN | Crit. |
| Car inoperable at night | Battery dead | 10 | 8 | 2 | 160 | 80 |
| Broken wire | 8 | 3 | 60 | 30 | ||
| Headlight out | 6 | 10 | 2 | 120 | 60 | |
| Switch corroded | 8 | 2 | 40 | 20 | ||
| Switch broken | 8 | 3 | 60 | 30 |
Failure Mode: Light doesn’t turn on
Redesign: Use two headlights instead of one, add visual lights-on display in console.
Risk Priority Number (RPN)
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Example:
| Possible Effect | Root Cause | S | O | D | RPN | Crit. |
| Car won’t start | Short circuit in switch | 10 | 2 | 7 | 140 | 20 |
| Operator error | 10 | 8 | 7 | 560 | 80 |
Failure Mode: Light doesn’t turn off
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Example:
| Possible Effect | Root Cause | S | O | D | RPN | Crit. |
| Car won’t start | Short circuit in switch | 10 | 2 | 2 | 40 | 20 |
| Operator error | 10 | 8 | 2 | 160 | 80 |
Failure Mode: Light doesn’t turn off
Redesign: Add audible indicator when driver’s door is opened while lights are on, add visual lights-on display in console.
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References
Lean Six Sigma - http://www.leansixsigma.com/
Stunell Technology - http://www.stunell.com/images/fmea.jpg
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Thank you!!!
