Product Functional Testing Before China Production – Part 9

Once you have built a prototype, it is a good idea to subject it to functional tests. This is what we cover in this part of our series on new product development.

functional_testing

Wikipedia defines a physical test as: ‘a qualitative or quantitative procedure that consists of determination of one or more characteristics of a given product, process or service according to a specified procedure. Often this is part of an experiment’.

Basically, once you have produced your working prototype you need to test it against the product specification in order to verify that the design meets and can deliver against the project expectations of the business goal.

Functional testing should be carried out at a sub-system level that tests the functionality of small ‘bits’ of the design, as well as a full system test which covers the entire product functionality.

Types of Functional Testing

There are two types of functional test, positive tests and negative tests.

Positive Functional Testing

This testing is carried out by applying input functions or instances that would be expected in ‘real life use’ and the output is monitored, measured, checked and verified to be correct.  Part of this testing can include verifying what the operating window for certain conditions is (this is verifying the operating tolerances of different functions).

An example of testing for operating window could be the drive rollers in a printer where the test being carried out is to verify the nip force required between the two rollers that move the paper through the printer in a precision and control way. If the springs that apply the force are too ‘light’ then the rollers will not be able to move the paper with accuracy and there could be paper slipping or uneven drive resulting in skewed paper and multiple sheet feed. If the springs are too ‘heavy’ then the paper might become damaged and a curl may appear once the paper has passed through the printer. Finding the top and bottom limits for this function is referred to as the optimum operating window or the tolerance band for the specification.

Negative Functional Testing

This involves testing the product with input values that are known to be out of specification or invalid inputs. The product should be designed to cope with incorrect input, this testing is where the results of bad inputs are observed, measured, recorded and verified.

Use the printer again as an example, if multiple sheets were forced into the printer, the rollers may try and move them through the printer, but if the number of sheets were in excess of what the specification states the printer should STOP and an error message be displayed showing a ‘paper jam’ or whatever the designer has specified as the error message. If there is a miss-feed (no paper being transported through the printer), again the printer should stop and an error message displayed.

Operating Window

By carrying out these tests you will be able to establish the limits of the system or sub-system as well as determining the optimum operating conditions. Once the limits have been established, they can be used as part of the test criteria for any production line testing that needs to be conducted within the manufacturing plant.

We have witnessed some very successful methods of testing which include limit or threshold testing within Chinese factories. A simple example of a graph showing limits and an operating window is shown below.

Limits_testing

In this case, products would be tested on the production line to determine of the operated within the operating window, closer to the optimal operating window is better.

The Importance of Prototype Build before Production – Part 8

One key milestone in a new product development cycle is making a prototype.

Prototype_Build

What is a prototype?

A prototype is a representation of a design produced before the final solution exists. It allows you and potentially your future customers to understand the product. Prototype models are often used for photo shoots, trade shows and exhibitions, customer feedback, and design verification purposes.

What are the benefits of making a prototype (for your company and your customers)?

One of the crucial stages that remain part of the product development cycle involves the development of a working model which allows you to:

  • Test various design features
  • Verify design functionality
  • Review initial product shapes or branding images
  • Elicit feedback from customers or early adopters
  • Use the prototype as a test-bed for developing additional features
  • Identify issues as early as possible within the development stage and before going to production
  • Provides a physical model for company stakeholders to review and obtain a greater understanding of the product

What are the benefits of making a prototype (for your Chinese supplier)?

The three major benefits I see are:

  • Ensuring communication is clear (have they understood what you wanted?)
  • Ensuring they are capable of making the prototype (sourcing the parts, putting them together, etc.) — Note that often this is possible when making a few pieces but impossible in mass production.
  • Providing samples that can be used for further approvals — for example by quality inspectors when checking production before shipment in China.

Engineering and Design Benefits

From a designer’s point of view, the goal is to make a product that is not only fit for purpose within the market, but also to design the product so that it can be manufactured as easily and as cost effectively as possible.

Having a prototype produced will allow the Engineering and the Design teams to review best practice techniques such as Design for Manufacture (DFM), Design for Assembly (DFA), as well as providing an excellent opportunity to carry out tests for Failure Modes and Effects Analysis (FMEA).

(Failure Modes and Effects Analysis is a step-by-step approach for identifying all possible failures in a design, a manufacturing or assembly process, or a product or service. Failures are any errors or defects, especially ones that affect the customer, and can be potential or actual.)

The Bottom Line

You almost always need to show a working model of your product idea to someone at some point. Whether it’s to potential investors to get funding, possible distribution and retail partners, or for pre-sale promotion on your website, you will invariably need some sort of physical representation of your product idea that will show viewers how it works.

When preparing for production in China, it is extremely important to get prototypes as early as possible. If the development of a new product takes too long, the manufacturer will lose interest in your project and switch his attention to the next hot product.

Designing Physical Mechanical Parts for China Production – Part 7

When it comes to developing hard goods, there are often mechanical parts. They need to be designed before prototypes start to be made.

Pysical parts design

Mechanical parts can refer to internal mechanisms to drive trains and cases, and everything in between. In other words, all the components of a product that have a physical presence and are not part of the electronics design.

Design is generally carried out using computer aided design (CAD) software that allows individual physical components to be designed and developed in a three-dimensional space. As individual components are developed, they can be built into an assembly using the same 3D CAD software.

Some of the advantages of using 3D CAD software to design and develop products are:

  • Short product design time
  • More effective communication with suppliers — factories in China are used to 3D designs
  • Visualization of parts and assemblies
  • Change from solid to transparent to wire frame, for review and analysis purposes
  • Quick and easy to change the design
  • Automatic Bill of Materials generation
  • Part parameters can be added to calculate weight and part costs
  • Part error detection and assembly clash analysis
  • Standard part library for ease of adding screws, nuts, bearings and other standard hardware
  • 3D data files can be used directly to make products, both prototypes and production
  • Data can be emailed to suppliers and customers with ease
  • Implementation of data management process

3D_design_of_physical_part

The image above is a screen shot of a product designed using 3D CAD software. In this view you can see the green top section has been made transparent thus allowing the viewer to see inside the design. The red sections indicate problems from a clash point of view within the assembly itself.

These issues can be fixed before data is released to a supplier who would produce prototype parts. Without the 3D CAD, drawings may have been sent to the supplier, prototype parts made and only when the assembly was put together the clash issues would have been found. This would result in rework and additional parts being made for checking again.

Developing the PCB for a Product Made in China – Part 6

Let’s keep going with the series of articles on new product development. This sub-step is dedicated to products that contain electronics.

PCB design

If your product requires a printed circuit board (PCB), this falls under the ‘hardware design’ element of this phase. We will not go into too much detail of how to design a PCB, but will however go over the basic steps behind best practices (Source: National Instruments tutorial 6894).

Step 1 of the PCB design starts with the understanding of what it is required to do and then goes onto researching each of the individual physical components (such as resistors, capacitors, transistors, diodes, ICs and other components). Part research and selection requires trial and error and a structured methodology to understand how each component works within the overall design of the PCB.

Step 2 is all about generating a schematic of the PCB design, also known as capture. The schematic capture uses a CAD design interface specifically for PCBs which have all the required product symbols of the circuit components. The schematic is a design representation in the form of symbols connected together by lines which is known as a net, an example of a schematic diagram is shown below:

PCB schematic

Step 2 also includes simulation. Once the schematic has been completed, simulation of the design can be run which can predict the behavior of a circuit and analyze the effects of various components and signals upon the design. This is an important step in the modern design process because it allows one to emulate the performance of a device before it is even physically built. A design topology can be tested immediately to see if it needs to be modified. Simulation can therefore save both time and money. Simulation can help uncover the most uncommon flaws quicker, and prior to costly prototyping.

Step 3 is where the PCB layout is completed. During the layout stage the actual integrated circuits (ICs) and components are placed onto the board, and connected via a current carrying conduit called a copper route (or copper trace). The final necessary step is creating a board outline which defines the form factor of the PCB (the form factor is important as it will ensure that the board fits the chassis, system or physical environment in which it will be eventually placed and operated from).

Step 4 is the final step in the validation of a PCB — prototype test. It is important in validating if the design meets the original specifications, while manufacturing test is important in making sure each device shipped to a customer meets the appropriate testing standards.

The prototype test analyzes the real-world behavior of a PCB and compares it to design specifications to benchmark these results. From a high-level perspective this stage requires a test engineer to take design specs from the designer and evaluate the PCB performance (thereby commenting on the success of the design). Based on this analysis the test engineer needs to either communicate to the designer if some form of design modifications are necessary on the board, or if it is ready for manufacturing.

How to Understand Quotations from Chinese Suppliers

Here areBest Quality & Sourcing Articles some interesting or useful articles that I found recently.

NOTE: A FEW DAYS AGO I HIT THE “PUBLISH” BUTTON INSTEAD OF THE “SAVE” BUTTON SO THIS MESSAGE WAS POSTED TWICE. SORRY ABOUT THAT.

Question your Quotes from China

Jacob Yount gives excellent advice about the way to understand and respond to quotations from Chinese suppliers. Good read, especially for purchasers with limited experience in China.

Restricted Substances: 5 Challenges when Buying from China

Fredrik Gronkvist has a knack for taking a complicated and boring issue and simplifying it. If you are curious about safety requirements such as REACH, ROHS, Cal Prop 65, and so on, this is a good article.

Retail Global Sourcing Report

CBX Software produces a report every quarter that includes many interesting data (labor rates, freight costs, currency moves, etc.) as well as some analysis of the latest trends.

Minimum Wages in China for the year 2014-15

Interesting database about minimum wages in China, with details per city.

‘Made in China’ Is Increasingly Becoming ‘Made in USA’

The American press keeps relating examples of a revitalization of American manufacturing. But the so-called vast “re-shoring” movement hasn’t happened.

What if 3D printing was 25 times faster?  

It seems like a new technology is going to allow 3D printing to become much, much faster. If this promise becomes true, it might impact the global manufacturing industry in a major way — especially in product lines where China is currently competitive (injection molding, metal machining).

Plastimake

I just discovered this fun product. Look into it if you need to make prototypes for certain types of hard goods.

Quality Issues in China: Planning for the Worst Case Scenario

I responded to this Q&A about the types of quality issues, what to do in case of minor issues, what to do in case of major issues, and what steps small buyers should take to avoid those problems in the first place.