Build Of Pre-Production Tooling – Part 11

In many cases, manufacturing a new product necessitates the preparation of custom tooling. This is an important step.

Pre-production_tooling

The output from the design reviews should include a data pack with 3D CAD files and the relevant technical information for each part so that the Chinese supplier can produce tooling that will be able to produce production intent parts.

For example, if we consider a product that has injection molded components, there are a number of different approaches to achieving pre-production parts; the direction you opt for will partly be driven by your budget. If you are looking to launch your product on a limited budget, then full production tooling may be cost prohibitive, and therefore ‘soft tools’ would be ideal in this case.

These ‘soft tools’ are not actually soft — they are generally made from steel referenced as P20. Tools produced from this steel can normally produce quantities from 10,000 up to 100,000 or more. In some cases the toolmaker may state a P20 tool is good for 500,000 shots (a shot being a single injection cycle where the tool closes, plastic is injected into the tool, the tool opens and the parts are ejected and the cycle starts again).

Another option is to produce tools from aluminum, but fewer toolmakers provide this service. The most common is the P20 steel option.

Full production tooling, on the other hand, would be manufactured from a different grade steel, typically H13 steel. It is able to produce in the region of 1,000,000 shots. Using this harder steel physically takes longer to produce tools, which is why tools produced from P20 or aluminum are often referred to as ‘Rapid Tooling’.

Benefits of Rapid Tooling/Soft Tooling

  • The rapid tooling process produces tools in a much shorter time frame than that of conventional tooling (in the region of one quarter the time to first tool trial).
  • Getting parts quicker allows testing to start earlier and consequently any issues found that require changes can be introduced earlier in the development process.
  • The cost of producing these tools is lower than the conventional tools.
  • These tools can be used for limited production runs (generally up to 100,000 shots), which means the product can be introduced to market and start to generate revenue which could be used for replacement by fully hardened production tooling.
  • Getting product to market faster with tooling being produced quicker than conventional tooling allows for a product to be introduced to market that much quicker.

Design for Manufacture (DFM) Analysis

During the pre-production tooling stage, DFM analysis should be carried out. This process ensures the product and each of the parts has been designed in such a way that they can be manufactured with ease.

Some DFM general guidelines are:

  • Standardize parts wherever possible
  • Reduce the overall number of components (can two parts be design as one, for example)
  • Reduce the number and types of parts
  • Design in mistake-proofing features
  • Design parts for best handling and orientation
  • Design for ease of assembly
  • Design for assembly direction (during assembly the parts should be added from the top without having to keep turning the assembly all the time)
  • Minimise flexible parts and too may connections

Some DFM guidelines specific to molded parts:

  • Ensure correct draft angle has been applied so that part ejects from tool cleanly
  • Design the tool taking into consideration the correct shrinkage rate for the polymer specified
  • Slides should be designed and optimized for minimum wear and maximum accuracy
  • Parting lines should be positioned to allow for best separation of cavities which allow for clean part ejection
  • Ejection points should be positioned so that they eject the part with even pressure and without damaging the part
  • Wall thickness optimization is very important when designing a part (incorrect wall thickness can result in sink marks and poor part integrity)
  • Mold structure is a review of the gate type and position, venting, cooling, and lifter designs
  • Pressure optimization of the injection process
  • Temperature of the tool and the injection process, to ensure parts are molded correctly
  • Tolerance analysis of the part to ensure in mass production the process can reliably and repeatably produce parts within specification

Design Review Iterations (New Product Development) – Part 10

After building a prototype and subjecting it to functional tests, you will likely need to make revisions from both a functional stand point in order to ensure the product actually meets the business goals as well as from a product specification stand point, which could include cosmetic changes like shape, size, color, and finish.

Design_Review_Iterations

An iterative cycle would include a design review where all the test data are presented and analyzed so that changes can be suggested and planned, another prototype built (which could just be a sub-section or the whole product, depending on the change required), further testing of the product to gather data, and then that data needs to be defined ready for the next design review meeting.

These design reviews are not only a method to help verify the design of the product, but also a means to reduce the risk associated with the new product.

Operating Window

The test data presented during the design reviews should include limit testing, to understand what the operating limits are; this should include failure thresholds as well as optimal operating conditions. These data should provide information on the tolerances within the system and sub-systems of the product, a simple example of this is shown the figure below.  In the ideal situation the system operating window should be a large as possible thus provide a more robust and stable product. A small operating window means the system is sensitive to change which could ultimately create problems when the product is in the market place, which would result in great warranty claims and returned products.

Optimal_Operating_Window

Other test data presented should include result from Highly Accelerated Life Testing commonly referred to as HALT.

Highly Accelerated Life Testing (HALT)

HALT is intended to identify weaknesses within the design during the development stage of the product so that they can be fixed or designed out before the product gets to production. Highly Accelerated Life Testing includes vibration, high & low temperatures, rapid temperature cycling, and humidity, combined stress, on/off cycling, voltage limits and frequency limits. The HALT process is shown in the figure below.

HALT_process

The Review Cycle

Design reviews are conducted with a design review team composed of experienced, senior-level personnel who understand the technology involved in the product or system and its associated technical risks. Ideally, these personnel should not be directly involved in the program in order to provide an objective perspective on the design.

Design review team members are chosen to match their skills and expertise to the requirements of the project. The team is multi-functional to address all the subject matter and issues covered during the review. The team may stay in place for the project or new personnel may be added and existing design review team members dropped as the project evolves in its development cycle (source: NPD – solutions DRM Associates).

This cycle continues until no changes are required and the product gets signed off as pre-production ready. At which stage a technical data file needs to be generated in order to send to suppliers. The Design Review Iteration Cycle is shown in the figure below.

Design_Review_Iteration_Cycle

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.