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This month we cover the topic “design for manufacturing” – DFX is particularly relevant in plastic part design as it will impact part quality as well as costs (both tools & parts). Enjoy the content.

1.0 Introduction:

Product design is driven by trends, new materials, visual aspects and costs. The problem is that industrial designers, product designers etc. often lack manufacturing & process experience as they rely on 3D software tools to create models that look good but are difficult to manufacture.

We illustrate problems in the case of plastic parts as they play an important role in most of today’s products, be it a car, a coffee machine or a laser printer.

Similar examples could be tabled for die-casting, investment casting and to a lesser degree for stamped and CNC machined parts.

To be at the tail end of product designs (= manufacturing) is often not enviable – it will require resourcefulness, flexibility to find ways to make parts via process, material and tool adjustments.

2.0 Interplay Part Design – Tool Design:

Plastic part manufacturers and customers know that the successful production of high- quality parts depends on optimum design of parts and tools.

Here we highlight the key drivers that influence the results:

a) Design for injection molding:

The culprit for problems with molding parts is often the neglect of basic part design rules. Here we summarize a few essential guidelines:

· Uniform wall thickness

The fundamental issue with tick & thin wall sections is that they cool at different rates. Temperature differences associated with differential shrinkages can result in distortions, deformations/warpage. If uniform wall thicknesses are not possible, ensure that the material flow is from thick to thin. Better is to keep a uniform wall thickness and add ribs to provide strength.

· Rib design

Ribs should be ~ 70% of the wall thickness – spacing and height must be considered carefully. If ribs are too thick, sink marks will be visible on the opposite side of the rib.

· Boss design

Bosses are used for fixing plates, printed circuit board assemblies etc.; bosses on ribs generally use two 90deg gussets; free standing bosses four gussets and corner bosses three. Gusset thickness is approx.. 70% of the part wall thickness. Use of sufficient draft angles will help to reduce part ejection forces.

· Part corner design

Sharp corners in product design violate part manufacturing criteria. The price for gaining extra interior volume, achieving better mating between 2 components or for aesthetic reasons is disproportionate with the molding disadvantages (stress concentration, lack of torsional stiffness, restriction of heat flow (inside  outside of the tool). Guidelines for corner designs (radii, chamfers) can be found in many text books.

· Part draft angles

Draft angles on a part are needed to assist the ejection of parts from the mold. Product designers frequently avoid the incorporation of draft angles in their designs as they alter part appearance and impact internal part volumes. Adding sufficient draft angles is important, in particular in parts with surface texturing and fiber glass filled materials. Draft angles generally range between 1.5 – 5 degrees.

· Avoid undercuts

It may not be possible to avoid undercuts but the designer should be mindful if the added complexity undercuts cause in the tool design (sliders, lifters, …). Such mold components not only increase tool costs but impact tool life, reliability and tool maintenance.

b) Tool design for manufacturing:

Good tool design is equally important to achieving optimal part molding results. It is far outside this article to cover details of good tool design.

In all our customer tool projects, we outline the basic tool concept in our quotation and refine details once the project is implemented. During the DFM process details of the tool layout are addressed:

  • Gate design

  • Venting

  • Cooling system design

  • Ejection system design

  • Shrinkage & warpage considerations

Mold type, mold cavities, tool material materials and runner types are selected based on part size & complexity, tool life, molding process and material, surface finish requirements etc.

3.0 Product Design and Manufacturability Cases

In this section we show you examples that cover early project phases as well as issues that needed to be solved once we had molded parts in our hands …

3.1 Moldflow analysis and part design optimization

Figure 3.1 shows the assembly of a frame and cover. The example highlights risk points and how they have been addressed


There are 4 risk points in the frame and cover that will impact function and aesthetics

a) Cover:

Risk(1): The 2 side ribs of the cover are prone to warpage which will affect the part assembly and function

Fix: We design separate cooling circuits for the ribs such that we can improve the warpage by cooling temperature adjustment

b) Frame:

Risk(2): The design of the side walls have a high chance of deformation

Fix: We design separate cooling circuits for the ribs such that we can improve the warpage by cooling temperature adjustment

Risk(3): Part walls are visible and flow/weld lines are not allowed

Fix: Using Moldflow analysis allows us to optimize the position and size of the gate to move weld lines into the part corners

Risk(4): There is a high risk that the part will stick to the cavity side

Fix: We use moving inserts to release the ribs first before opening the tool

3.2 Tool cost reduction through smart part re-design

Figure 3.2 shows a filter housing part and is an example of how tool costs can be reduced by “design for injection molding”

Issue: The geometry of the grill ribs required costly angles sliders

Fix: By redesigning the shape and structure of the grill ribs, sliders could be eliminated without compromising the function of the part

3.3 Fix of poor part sealing problem after initial mold trials

Figure 3.3 shows the housing of a wireless leak detector; we illustrate how we overcame a detector sealing problem in a 2k housing design

Issues: The sealing of 2 housing parts failed to pass IP65 testing conditions.

Parts & materials are:

  • The lower housing (ABS) is a 2k part with a TPE sealing strip

  • The upper housing and battery cover are in ABS

  • There are gaps in the TPE sealing strip in the vicinity of 2 connectors

Fix: Change the geometry of the lower/upper housing parts in the area of the connectors to get continuous sealing and hence an improvement of the gasket function

3.4 Solve part warpage problem by changing the molding material

As suppliers of injection molding tools, our project managers focus on the tool design aspects and generally take part data from our customers as provided. Even if a tool has been designed well and the correct material shrinkage has been used, there can be surprises one you mold the parts.

Figure 3.4 shows an adapter (approx.. 200mm long) where the molded part was bent like a banana!

Issue: Significant part warpage occurred (up to 7.5mm) over the length of 200mm rendering the part useless.

We embarked upon a series of experiments to find a pragmatic way to solve the problem.

a) Experiment 1: Adjusting molding parameters

  • Holding pressure adjustments: no effect

  • Cooling time adjustments: no effect

  • Cooling temperature adjustments: no effect

b) Experiment 2: Simulation of wall thickness change

Simulation of top wall thickness reduction by placing thin copper sheets into the mold

  • 0.5mm reduction: 25% improvement

  • 1.0mm reduction: small negative warpage

c) Experiment 3: Manufacture part with different molding materials

  • ABS: 90% improvement (warpage < 1mm)

  • PP (higher hardness): 60% improvement but still NG

  • PP+30GF: 95% improvement (warpage acceptable ~ 0.5mm)

4.0 Conclusions:

We have been involved in the production of > 500 injection molding tools and understand the complexities and finesses of manufacturing high quality tools.

Our project managers are experts – they can judge good tool design but also know the art of optimizing molding conditions to produce excellent parts.

However, if the part/product design is poor – no matter what you do, you may never be able to produce a good part. It all starts with design! Good design not only impacts the process results (part function, visual aspects) but cost (tool cost, fill time, cooling time, tool life, etc.).

Design for manufacturing is maximizing part and tool design for the benefit of long-lasting tools capable of producing excellent parts.

We play an important role in the interplay between these 2 elements. We use the expertise and knowledge to iron out problems, correct mistakes and find ways to reduce tool complexity and cost.

The simpler a tool – the lower the chance of problems in production.

Inspecting products after manufacturing is an essential step to ensure that you get what you paid for. As you cannot judge your own work, it is important to have an independent specialist (with a good nose and sharp eyes) checking everything, from a metal part to a household appliance.

We have incorporated the final inspection step into our order fulfillment process. This is why customers have confidence and trust working with us. I hope that the cross-section of examples are of value – enjoy the August 2022 edition - Roland Schmid

1.0 Introduction:

With close to 20 years manufacturing experience in China, we have learnt the importance of inspecting products prior to release and shipment to customers.

We have paid the price of assuming process stability and repeatability.

To get consistent quality is absolutely not a given – you can never relax or remove your attention to what is being done and how.

I assume that this is the reason why many foreign companies use inspection services of reputable international companies such as SGS, TUV, DEKRA, etc. to check goods.

Whether it is a valve, a die-cast AL-housing, a cable assembly or an injection molding tool, it is essential to have the products inspected.

The following sections outline the inspection processes for different commodities and how the results are reported.

2.0 Inspection of Customer Repeat orders:

The readers of our newsletter understand our core business segments and the range of products/parts that we supply. Here we show you examples of how we handle repeat orders and the extent of the inspection work.

Inspections are typically done on a sample basis with defined sample levels and accept/reject quantities for different defect classifications.

Inspections for repeat orders cover the following:

  • Visual mechanical checks

  • Dimensional checks

  • Functional checks

  • Critical component checks

  • Packaging checks

2.1 Metal Ring

In high precision metal parts, focus is on dimensions, tolerances and surface quality. We also verify that the correct raw material has been used (authenticity of material certification document!).

Figure 2.1 provides excerpts of the typical inspection steps carried out in a metal ring.

2.2 Wireless Leak Detector

Inspection of electronic products (at the finished goods level) focus on function, cosmetic aspects, packaging, including content and printing of user manuals etc.;

In the case of the wireless leak detector, checks covered the following:

  • Correct LED function (different colors for specific warning states)

  • Transmission tests

  • External device connection tests

  • Assembly quality and packaging

2.3. Battery Holder

This is a very simple product. Nevertheless it is important to check the following:

  • Key Dimensions

  • Holding of the batteries (clamping force)

  • Battery contacts

  • Soldering quality (use of correct solder to ensure good bond between wires and contacts)

3.0 Inspection of Injection Molding Tools

Injection molding tools are complex and part/design specific and in many cases must meet certain “house standards” of the end customer (molding company).

We have established a comprehensive final tool inspection procedure that covers the following:

  • Overall tool checklist (see Figure 3.1)

  • Tool details

  • Tool frame

  • Core & cavity side details

  • Tool components

  • Steel hardness

  • Cooling channel sealing

  • Packaging & documentation

Figure 3.2 shows extracts of the tool inspection report

  • Steel heat treatment certificate

  • Cooling system layout

  • Tool drawings

  • BOM

  • Packaging & Documentation

Figure 3.3 shows tool packaging & documentation

4.0 Inspection of 3rd party Products

Our services cover inspection of 3rd party products, typically in the appliance sector.

We have significant experience with products such as fans, humidifiers, toasters, water kettles, aroma diffusors – just to name a few.

The emphasis on checking 3rd party products is on the following:

  • Product function

  • Product safety

  • Product visual aspects (cosmetics)

  • Product packaging, labeling, user manuals etc.

Figure 4.1 shows extracts of an inspection report of a humidifier. The results underline how important it is to comprehensively check appliances in the factory. In this case, the WiFi function (setting of different humidity levels & continuous mode) did not work 100%, the user manual was not color printed and the order number was missing on the shipping mark.

5.0 Conclusions:

China is a manufacturing powerhouse with well established industries, competencies, state-of-the art technologies and good people.

The problem is that rapid growth had led to constant changes

  • Factories move suddenly to a new location, either driven by the need for extra space, cost or other;

  • The workforce is generally not stable – skilled workers often do not return to an employer after the Chinese New Year national holidays; product & process knowledge is diluted or disappears within the span of 1-2 months!

Furthermore the mindset of owners of small to medium sized companies is frequently “narrow”, penny wise & pound foolish. For example, it is cheaper to use newspaper to wrap precision machined AL parts and throw them in a shabby carton box for transfer to an external anodizing plant, than using solid trays/bins, bubble wrap, dividers etc. to avoid transportation damage!

As it is impossible for foreign companies to monitor supplier operations in China it is advisable to use inspection service providers in order to check materials, products, functions according to a strict inspection protocol with clear “pass/fail criteria”.

We have established our own QC function within Vela Eurasia to minimize the risk of quality defects or sub-standard products being shipped to customers. Every shipment gets inspected, be it a metal part, an electronic assembly or a high-performance injection molding tool. Our customers understand the value, so much so that they have asked us to carry out inspections for products that they source directly from China. The important differentiators are sound process knowledge, deep understanding of products and an eye for details. Our customers are served by experts who have not just done a single inspection but dozens spanning over several years

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This month we address “Sourcing”, including B to B sourcing platforms and methods to buy products in China. What works, what are the pitfalls and why it is good to have a competent sourcing partner in China. Light summer reading for you to reflect whilst you soak up the sun.

Happy reading - Roland Schmid

1.0 Introduction:

For many years we have seen purchasing people/buyers from all corners of the world visiting trade fairs in China, in particular Hong Kong (Electronics, Lighting, Hardware), Guangzhou (Canton Fair) and Shanghai (Chinaplas, China Die-casting, Automotive Mfg & Technology, International Hardware, …). Fairs are a convenient means for buyers to link with manufacturers and resellers, see products and gauge competence. Strategic purchasing staff from different international manufacturers also visited Asia with focus on component sourcing, notably metal parts, enclosures, printed circuit boards, connectors, …. , just to name a few.

Then came the sourcing platforms

  • Alibaba

  • Made-in-China

  • GobalSources

  • Haizol

  • Etc.

Interestingly, GlobalSources not only organized trade fairs but capitalized on the exhibitor profiles and visitors (potential customers) to setup an internet trading platform!

Let us assess a few sourcing models.

2.0 B to B Trading Platforms:

Purchasing via B to B trading websites has its advantages & disadvantages


  • Secure way for customers to get products as payment is administered by the trading platform;

  • Purchasing of standard products is relatively low risk

  • The buyer does not have to travel, visit different companies, face communication and cultural barriers, etc.

  • The trading platforms work with so called “qualified/star-rated” suppliers


  • Companies offering products are generally not high end – they produce mass-market commodities

  • Interest is on high volumes

  • Customization is difficult (single/standard product focus)

  • Companies are small, provincial with basic equipment, manufacturing & business skills (many cannot do export business in USD)

Customers who want to buy products from Asia/China often prefer to have direct contact with manufacturers to negotiate prices, discuss non-standard products/own designs etc.; the following example shows where the traps are.

One of our customers found a supplier for a “give-away/promotional gift” (a Stress Ball) using Alibaba.

What happened?

· The samples provided were ok (acceptable) – company logo printing and position were approved

· Our customer wanted us to check the order lot of 5k stress balls and handle payments to ensure that payments were in line with local standards and only made after product quality checked by our QC

· Mass produced stress balls did not reflect anything like the sample and the quality/workmanship was poor (e.g. logo was move to another position!)

· The defect rate was > 30%

· The supplier wanted to force our customer to pay double the price if he expected a better mass produced stress ball …

Fortunately we could stop the shipment and prevent payment of the balance of the order – however the manufacturing deposit was lost!


· Refrain from buying customized products via sources advertised on internet platforms

· Only buy advertised/standard products via B to B sourcing platforms as payments are only released if the goods are ok

· If a supplier consistently delivers poor product he will be struck of the B to B trading platform

3.0 Sourcing Agents

The limitations of B to B sourcing platforms gave room for sourcing companies in Asia.

To plug the holes of e-commerce and provide specific industry/sourcing expertise covering different commodities and customer needs, for instance stationary products, giftware, packaging products etc., there is a good selection of credible sourcing companies in the market.

The business model/way of operation may vary – typical scope of work is outlined below.

3.1 Strategic Sourcing/Consulting

· Identification of potential suppliers & filtering

· Linking customers with suppliers

· Help with benchmarking, negotiations, supplier assessments, etc.

· Carry out special assignments to qualify suppliers and products (see below)

· Help with logistics & shipment coordination

This model is fee based – customers purchase products directly from the manufacturers.

Example: Crystal Manufacturer Assessment/Factory Audit

We were asked to audit 3 factories in Thailand and China; this specific commodity required technical understanding of key process steps and impact on part performance/quality – the relevant manufacturing processes that we focused on are:

  • blank cleaning,

  • blank plating (electrode attachment)

  • etching (tuning)

  • annealing/curing (stress relief and aging)

3.2 Sourcing Agent

  • The sourcing agent handles all aspects of projects from RFQs to product delivery

  • Contractual relationship is between the purchaser and the sourcing agent

  • The sourcing agent provides a one-stop service, including arrangement of inspections, transportation, supplier payments, etc.

The challenges are in the segment “technical sourcing”. Here, many traditional sourcing companies come unstuck. The reasons are:

  • The technical understanding & knowledge for specific commodities/manufacturing domains is weak;

  • Staff are mostly buyers/purchasing people with little or no engineering knowledge


  • Most companies want their sourcing agent to take full responsibility for the management of all steps involved in a project, from RFQ to delivery

  • In some cases, using a strategic sourcing agent to link you directly with the manufacturers may be advantageous, in particular at the EMS/standard component level

4.0 Technical Sourcing – Different Way of Thinking

Advancements in materials, processes, manufacturing, etc., challenging times in logistics, issues with raw material costs and availability, energy prices etc. require a change in the traditional buyer – supplier relationships.

In technical sourcing, comprehensive in-house capabilities and knowledge matter,

such as:

  • Product design

  • Industrialisation

  • Commodity Expertise (eg injection molding tool design, manufacturing and testing)

  • Commercial skills

  • Problem solving and resolution capability

  • Project and cost management

  • Quality Control

  • Logistics (Import & Export rules, Tariffs, Transportation, Packaging, Preparation of Export Documents, Packaging, etc.)

  • Industry connections, supplier knowledge, effective project management, ability to travel and visit suppliers, reliable & trustworthy people are vital. This is particularly important if your source from Asia/China.

The complex nature of technical sourcing requires PARTNERSHIPS at different levels of management between the sourcing company and the customers.

Once you work with the right partner, it gives you a significant competitive advantage – the right technical sourcing relationships can be instrumental for the long-term growth and profitability of your business.

Furthermore you can capitalize on the extra brainpower, use an extended talent pool, boost capacity and maintain a foothold in a fast growing market.

Here is a case that demonstrates the value – PCB quality resolution

A German customer engages us as an advisor, technical expert, investigator etc. in case of quality, delivery, commercial or communication problems

I was asked to visit a factory selected by the customer producing PCBs to carry out a manufacturing process audit and to resolve the problem of a track plating issue

The findings were quite staggering:

  • The PCB supplier turned out to be an agent without an own production facility

  • The manufacturing plant shown to me was good and the agent had a good relationship

  • When I asked for process experts and QC personnel to join me to discuss the specific problems experienced by our customer the “sand-bagging” started Lunch time! Staff currently in other meetings/not available...

  • I was constantly shielded from talking to any person in the factory – then the penny dropped; for cost reasons (to maximize profit) the agent used another PCB manufacturer (lower grade) to produce the sub-standard quality product for our customer but showed me the premium facility of another manufacturing company…

  • The case was ultimately resolved (plating issue fixed!)


  • If you visit/audit Chinese manufacturers, always have a Chinese person with you who acts as a translator, understands what is being spoken, acts as another pair of eyes

  • Validate a company’s credentials – take pictures of the company license plate, certificates, etc. and match them with information/data given to you

  • Work with an experienced & trustworthy partner in China/Asia who knows the game; this saves a lot of headaches, endless arguments, time …

5.0 Conclusions:

Developing and maintaining a strong technical sourcing base with a knowledgeable and trustworthy partner in China is a strategic decision and must be endorsed by business owners and top management.

It means working together, sharing information, setting targets, investing to achieve high quality results.

In many cases, we have gone the extra mile for our customers because they understand that we are not a quotation house but a business partner that can solve difficult manufacturing, time to market and supply chain problems.

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