Chapter 16 – Inspecting the Manufacturing Areas

You got your first impressions of the factory upon arrival and learned more at the first meeting. Next, your job will be to look at the different production and storage areas in detail to find out if the factory complies with your company’s quality expectations.

In the previous chapter, I referred to the ISO Quality Management System, which the factory will claim to comply with. It is however best if you take a tour of the different factory areas and verify whether the factory is indeed practicing an effective Quality Management System.

Quality Control for Incoming Material and Components

Let’s start where materials first enter the factory. This provides a clear indication if the factory takes quality control seriously.

A busy factory will receive materials on a daily basis. These include raw materials, components, packing materials, and anything else needed from different vendors to support production. Ordering the materials took place week’s ago and normally coincides with when the factory receives the L/C for a particular purchase order.

The most important quality control starts with either a random or a piece-by-piece inspection conducted by a specially trained QC staff.

Your task is to check whether the factory has established a systematic and effective incoming material/components quality control system. Ask your factory representative to take you to the incoming area to observe the Q.C. staff conducting the incoming inspection.

A piece-by-piece (100%) inspection should be performed on critical components. An example is a thermostat that will installed into a portable space heater. It is a critical component that will either leave the heater useless if it fails or in a worst case scenario could start a fire. This type of component is not suitable for a random inspection of only a few parts.

The factory will of course tell you that they only buy from trusted vendors with a long established business relationship. It is their opinion that a piece by piece inspection is not necessary. Do not buy into this rational.

To understand what can happen, be sure to read about the failed example.

A Failed Example

A large German customer ordered more than 100K electrical fan space heaters. The specifications called for a special feature to be included. It was a “Frost Guard” function. The Frost Guard function allows the space heater to be placed in an unheated room where the temperature cannot drop below a certain level. The purpose is to protect growing plants from freezing.

If the temperature reaches the critical level the Frost Guard thermostat is suppose to switch the space heater on. This occurs at temperatures much lower than typical space heaters operate. All of the information was included in the P/O.

Our manufacturer did not have a climate chamber in their factory to simulate the low temperature to assure the thermostats from their vendors complied with our customer’s request. They trusted their thermostat vendor and delivered the goods on time for our shipment.

The inspection company that we employed to inspect this large order was not able to check this function either, so the goods were shipped to our customer without being fully inspected.

Back in Germany, our customer did have a climate chamber in their lab. During their incoming inspection more than 30% of the Frost Guard thermostats did not function at all.

The customer was running a promotion that became threatened when the thermostats failed. There was no time to ship more than 100K space heaters back to the factory for rework. The factory’s only choice was to send technicians to Germany to perform the rework. The customer’s promotion was saved but at a much higher cost than if those thermostats had gone through a piece-by-piece inspection at the factory.

Keep this example handy when the factory tells you that a piece-by-piece incoming inspection is not necessary. After all of that, the factory decided investing in a climate chamber was a good idea.

Rejected Materials and Components

Here is another way to check up on the factory’s incoming QC process. If the factory assures you they have an incoming materials/components QC process in place, ask to be taken to where the rejected materials/components are kept before being returned to the vendor.

If they try to tell you that they do not have any rejected materials or components, you can be sure that either the QC staff is either not being thorough enough or they are lying and they don’t have an incoming QC process. It is impossible that they have not discovered any rejected materials or components over an extended period. Normally, every shipment will have at least a few rejects.

By the way, ISO 9001 requires that rejected materials be segregated from approved production materials. They should be under lock and key to prevent them from entering the production stream.

If the factory is producing electrical products for EC countries that require ROHS compliance, these components must be also stored separately and the storage area must be marked with ROHS in order to avoid becoming mixed with non ROHS compliant components.

Visiting the QC Department and Testing Equipment

Now let’s go to another section of the factory that is important for maintaining a high quality level during production. 

Do not ever skip a visit to this department in order to save time. The QC department is management’s method for constantly monitoring the production quality of the factory. Here, you really want to find out if you are in good hands or not.

Larger factories have their own QC lab, which may even be certified by an internationally recognized certification organization. This enables them to perform their own tests without using any outside laboratories.

The average factory has a separate room with testing equipment and of one or more engineers to running it. When you enter this room, take note of how well they have organized themselves. You may find anything. It could be a complete mess or a well laid out testing room.

If the factory is producing more sophisticated products, they must have an adequate number of testing instruments. These should be in good working condition and must be calibrated on regular basis.

The room should be tidy and well organized. If tests are being conducted, you should find the test samples properly labeled and data sheets for the results nearby.

If the room has not been dusted for months and is cluttered with old test samples, you should assume that the factory does not take their QC duties very serious.

Why Does the Factory Need a QC Department?

It’s all about money. Every time goods have to be reworked or remade it costs the factory a substantial amount of money. Only constant monitoring of internal quality standards assures the factory that a major rework or remake will be avoided.

It is also necessary for obtaining ISO 9000 certification.

Separate QC Rooms for the Customers’ Inspectors

It is common for customers to send their own inspectors or hire an outside inspection company to perform at least a random final inspection before the goods ship. The factory is expected to provide a separate QC rooms for these inspectors.

It must be separate from the production area and must have all the equipment for the inspectors to perform their work properly. If the factory has a lot of orders in work at the same time it is very likely that you will meet several teams of inspectors in these QC rooms when you visit.

This is one time it might not be appropriate to take photos. The factory has an obligation to protect their customers’ confidentiality. Sometimes the inspectors may be inspecting OEM products where the design belongs to the customer and cannot be disclosed to third parties.

If the factory does not have a separate QC rooms for customer inspectors, you have to refrain from working with them because they certainly do not meet the minimum requirements for quality control.

Visiting the Factory’s Mold Shop

Are you aware that the plastics industry just turned 100 years old, thanks to the ingenuity of Belgian chemist Leo Henrik Baekeland? He invented the moldable, phenolic resin Bakelite in 1907, thereby ushering in the Age of Plastics and forever transforming how we all live.

Larger factories usually have their own mold shops where following different types of molds are made:

  • Die casting molds
  • Forging molds
  • Injection plastic molds
  • Stamping molds
  • FRP (Fiberglass Reinforced Plastic) molds

Mold making quality is not all about hardware and software. The most important area of the mold shop is the workbench area.

Molds will be designed and built by true craftsmen using CAD/CAM software, and CNC (Computer Numeric Control) and EDM (Electrical Discharge Machines) equipment. Good communication between mold makers at the bench and designer/programmers in the tool shop is important.

You should inquire whether the mold maker’s design work is in-house or farmed out because mold designs performed on the outside can lead to inconsistent quality, depending on whom the job is given to.

Nowadays, you will find more EDMs (Electrical Discharge Machines) in modern mold shops. They are more precise and create less process waste.

Typical mold classes available:

  • Class 101 molds – Built for extremely high production rates, and made with only the highest quality materials. Guaranteed for 500,000-1,000,000 cycles
  • Class 102 molds – Built for medium to high production rates. Good for abrasive materials such as glass or mineral filled polymers. Guaranteed for 200,000-500,000 cycles
  • Class 103 molds – This is a popular mold build for low to medium production, and has the best price range. Guaranteed for 100,000-300,000 cycles
  • Class 104 molds – This is a low production rate mold, and is used for a short product life with non-abrasive materials. Guaranteed for 5,000-10,000 cycles

Typically P20 or H13 hardened tool steel is used for the construction of the molds.

I assume that you are not an engineer and therefore maybe not very familiar with mold design and construction. It should be adequate for you to see if the factory has a mold shop at all and learn a little something about the technical equipment they are using. Since product quality depends heavily on the precision of the mold, you should be very concerned if the mold shop is using old and outdated equipment.

When the factory shows you a new product design and tells you the lead time for mold finishing, there might be a few surprises before production actually begins. Sometimes there can be a 1 -2 month difference between the mold’s estimated lead time and the actual finish date.

The delay could be caused by long hours of hand polishing instead of using a machine tool that cuts a better surface finish. You do need to consider the mold shop’s performance when selecting a new factory. A 1 – 2 month delay in the mold shop will also mean a long delay before your order is shipped.

Example of a Two Plate Injection Mold

The Old “the mold got broke in production” Story

Sometimes factories will offer an excuse for production delays by saying “their mold was damaged during production”.  I have heard this so many times that if that was true there should not be an undamaged mold left in China. It is mostly an excuse to cover up other shortcomings because you cannot check it out.

However, if you appoint a consultant like our company:

We can immediately verify for you if the factory’s information was correct or get to the bottom of the issue so that the problem gets corrected.

I don’t want to say that all factories are notorious liars but molds usually wear out gradually and don’t break easily. Therefore, the factory could have taken action well in advance instead of waiting until the inevitable happened.

If the factory does not have a second mold and the only mold was truly broken during the production run for one of your customers, you may be in real trouble because a new mold cannot built in less than 2-3 months time.

Sometimes Molds do develop defects. For a better understanding, I have included the following chart that summarizes the most common defects.

Molding DefectsAlternative nameDescriptionsCauses
BlisterBlisteringRaised or layered zone on surface of the partTool or material is too hot, often caused by a lack of cooling around the tool or a faulty heater
Burn MarksAir Burn/ Gas BurnBlack or brown burnt areas on the part located at furthest points from gateTool lacks venting, injection speed is too high
Color Streaks Localized change of colorMaster batch isn’t mixing properly, or the material has run out and it’s starting to come through as natural only
Delamination Thin mica like layers formed in part wallContamination of the material e.g. PP mixed with ABS, very dangerous if the part is being used for a safety critical application as the material has very little strength when delaminated as the materials cannot bond
FlashBurrsExcess material in thin layer exceeding normal part geometryTool damage, too much injection speed/material injected, clamping force too low
Embedded contaminatesEmbedded ParticulatesForeign particle (burnt material or other) embedded in the partParticles on the tool surface, contaminated material or foreign debris in the barrel, or too much shear heat burning the material prior to injection
Flow marks Directionally “off tone” wavy lines or patternsInjection speeds too slow (the plastic has cooled down too much during injection, injection speeds must be set as fast as you can get away with at all times)
Jetting Deformed part by turbulent flow of materialPoor tool design, gate position or runner. Injection speed set too high.
Polymer degradation polymer breakdown from hydrolysis, oxidation etcExcess water in the granules, excessive temperatures in barrel
Silver streaks Circular pattern around gate caused by hot gasMoisture in the material, usually when hygroscopic resins are dried improperly
Sink Marks Localized depression (In thicker zones)Holding time/pressure too low, cooling time too low, with sprueless hot runners this can also be caused by the gate temperature being set too high
Short shotNon-Fill / Short moldPartial partLack of material, injection speed or pressure too low
Splay MarksSplash mark / Silver StreaksCircular pattern around gate caused by hot gasCaused by the material (plastic) being damped prior to injection
StringinessStringingString like remain from previous shot transfer in new shotNozzle temperature too high. Gate hasn’t frozen off
Voids Empty space within part (Air pocket)Lack of holding pressure (holding pressure is used to pack out the part during the holding time). Also mold may be out of registration (when the two halves don’t center properly and part walls are not the same thickness).
Weld lineKnit Line / Meld LineDiscolored line where two flow fronts meetMold/material temperatures set too low (the material is cold when they meet, so they don’t bond)
WarpingTwistingDistorted partCooling is too short, material is too hot, lack of cooling around the tool, incorrect water temperatures (the parts bow inwards towards the cool side of the tool)

As you can see, it often depends on the skills of the experts performing the injection molding whether a defect occurs.

Here is a link to a very informative YouTube film covering mold making and plastic injection molding from a factory visitor’s point of view. The film is without a narrative but the content speaks for itself.

Here is another YouTube film with the title “Chill Mold Start To End”

It is more professional and shows many of the mold making details.

Now let us move on to another factory area.

Metal Punching Area

This area (usually a very noisy one) is home to Metal Punching, Shearing, Bending, and Forming Machines.

Similar to the mold shop, not every factory will have or need this equipment.

If they have it, it helps them control another part of their cost equation.

Examples of Factory Metal Presses

If a factory is using as 20 or more of these machines, you can imagine that their volume must be quite high, otherwise they would not have invested the money.

All these machines, including the Electrical Discharge Machines (EDM) mentioned earlier, are extremely expensive.

In this area, you may see borders marked on the floor. They are there for safety reasons. When visiting this area you should always keep a safe distance from any running machines. If the factory does not use border markings, it is a clear indication that they are not completely following ISO 9000 requirements.

In general, you should see these border markings all over the factory floor. They can mark off a dangerous area or indicate the path for transportation equipment along with having several other useful applications.

This area is noisy and there is not a lot to see. We will move along to the next area.

The Injection Molding Department

After you have seen the mold shop and learned how molds for the injection machines are made, you can now see them in operation.

Injection machines are also very expensive and some of them are as big as a large truck if very large plastic parts need to be injected.

Example of a Plastic Injection Molding Machine

So What is Injection Molding?

It is a manufacturing process for making parts from both thermoplastic and thermosetting plastic materials. Molten plastic is injected at high pressure into a mold, which is the inverse of the product’s shape.

The most commonly used thermoplastic materials are:

  • Polystyrene (low cost, lacking the strength and longevity of other materials)
  • ABS or acrylonitrile butadiene styrene (a ter-polymer or mixture of compounds used for everything from Lego parts to electronic housings)
  • Polyamide (chemically resistant, heat resistant, tough and flexible – used for combs)
  • Polypropylene (tough and flexible – used for containers)
  • Polyethylene
  • Polyvinyl chloride or PVC (more common in extrusions used for pipes, window frames, or as the insulation on wiring where it is rendered flexible by the inclusion of a high proportion of plasticizer).

Why You Cannot Get Your Sample in a Specific Color

The plastic injection machines are very expensive and at the heart of production. At some companies, these machines run 24 hours a day injecting parts with a single color. When you request samples in a different color, they have to stop the injection process, clean the mold of plastic remnants from the previous run, and then inject a few samples in the color you requested.

Of course, this is not feasible. You have wait until the color you requested is used in another production run.

How Injection Molding Works

After the molten plastic material has been injected it needs a predefined period of time to harden before the A and B parts of the molds separate and release or eject the ready plastic part(s). One mold can inject several plastic parts at one time if it was designed for it.

The ejected plastic parts have to be separated from the frame which is composed of the sprue (main channel from the reservoir of molten resin) and runners, which are perpendicular to the direction of draw, and are used to convey molten resin to the gate(s), or point(s) of injection.

The sprue and the runner system can be cut or twisted off and recycled, sometimes being granulated next to the mold machine. You can see this clearly in the first YouTube film that I provided the link to.

Workers use a sharp knife to remove sharp edges from the plastic parts. Since this job depends on the people skill, you will sometimes find uneven cut marks on the surface of the plastic object.

It is important that you understand the factory’s injection molding capacity. Often the injection capacity defines the factorys total capacity.

Assuming the injection capacity is 2,000 pieces per hour and the injection machine is running 24 hours a day, you would guess that the daily capacity is approximately 48,000 pieces. However, that is not quite accurate. After deducting time for maintenance and mold changes you end up with a lower figure.

If the factory has only one mold for your product, the maximum rate it can be injected becomes the maximum rate your product can be produced at. We already discussed that the molten plastic material has to cool down before it can be ejected. There is little room for variation in this process or the quality of the final plastic product will deteriorate. These are the factors that defining the production rate.

That concludes our visit to the Injection Molding Department. Next up is the paint department.

Spray Painting Department

The surfaces of some of the injected plastic parts may need to be further processed by spray painting them. This can be anything from sophisticated automatic spray painting tunnels to spray painting by hand using simple spray guns.

Example of Water Wash Spray Booths

Examples of Coating and Spray Booths

The following methods are commonly used in Chinese factories:

Spray Booths

Spray booths and coating booths are enclosures to contain spray-coating processes such as painting, powder coating, thermal spraying, and other finish coating methods.

Spray painting equipment atomize paints or liquid materials in order to apply coatings to discrete products or components.

Spray guns and applicators are used with both air and airless processes. Air spray guns atomize paint with compressed air. Forcing the paint particles into a high velocity air stream atomizes the particles into tiny droplets.

The shape and paint density of the resulting droplet cloud can be controlled by air pressure, paint viscosity, and gun tip geometry. Air assisted spray guns alter the paint pattern, but do not atomize the paint.

Airless paint spraying uses high fluid pressure to atomize paint by forcing it through a small orifice. Because less air is used, airless paint spraying poses fewer dry spray and paint bounce-back problems than air-assisted spraying.

Spray painting must be done in a spray booth that can control the emissions of particles and solvents.

Spray booths are usually classified by their types of construction and exhaust filtering systems.

Baffles placed in the ducts will remove some over-spray but require regular cleaning. Baffles are acceptable only for small paint rates or if the paint is applied electro statically. If the spray booth is used more or less continuously, the extracted air should be passed through an efficient filter or water scrubber to remove the bulk of the excess paint particles.

If spray painting is done only a few times each week, an air extraction system is adequate to dilute the solvent fumes.

To my knowledge it is however very unlikely, that Chinese factories will use their spray booths only a few times each week. You can expect they are used every day.

Another option is to install an activated carbon absorber in the exhaust duct. These cartridges will absorb solvents until they are “full” and then must be desorbed by steam or heat. The solvent can be collected and recycled and the cartridge used again.

If a wet scrubber is used to remove paint particles and solvent vapor, the spray nozzles should be checked regularly and the water maintained at the correct level at all times.

If a process requires large quantities of paint to be sprayed, as is mostly the case in Chinese factories, a spray booth incorporating an efficient wet collection device will be needed. An efficient wet collector incorporates a spray chamber containing enough spray nozzles and with enough water circulation to remove excessive paint particles. (Please refer to the above drawings and pictures).

An alternative to the spray chamber is the “No-Pump” Collection Device, in which water flow is controlled by air movement. To obtain maximum filtration efficiency with this type of collector, it is important to maintain the correct water level recommended by the manufacturer. An automatic water level control device must be fitted to all spray booths of the “No-Pump” type.

A water curtain is useful only to maintain booth cleanliness; it is not acceptable as a collection device. The efficiency of any spray booth is related to its cleanliness.

Another method for spray painting is Powder Coating which is used to spray resin powder onto the surface of a pre-heated component, where the powder fuses and cures producing a protective coating.

Powder coating equipment includes electrostatic coating equipment and fluidized bed systems. Electrostatic coating charges paint droplets or coating powder particles and then sprays them toward a part with an opposite and attractive electric charge.

Since the charged powders in the spray stream are attracted toward the part, the electrostatic process help minimize over-spray and waste.

Health Risks and Effects of Paint Overspray

You may find during you factory visits that some workers in the spray booths are not wearing a protective mask at all.

This alone will cause very serious health risks for them because when inhaling paint components and spray drift, humans can develop respiratory irritation and metabolic toxicity, particularly from paints incorporating isocyanates.

Solvents such as toluene and xylene are considered to be air toxic, and could cause health problems in humans.

If you don’t want to work with companies using child labor or forced labor, you really should not want to work with factories that do not care about their workers health.

Please consider that you will spend only a few minutes in this environment during your factory visit but the workers spend their whole day spray painting and cannot simply walk away.

Now that you have seen most or all of the fabrication areas, let’s move on to the assembly lines.

Production and Assembly Lines

This part of the factory tour is preferred by most visitors. There is so much to see including the lot of beautiful girls from all the different provinces of China. They are much more attractive than a metal punching machine.

1. Assembly Line (Pre-Assembly)

2. QC Inspector Testing Finished Parts

3. QC Inspector Online Testing

4. QC Inspector Online Testing

5. Injected Plastic Parts Wrapped for Protection

6. Injected Plastic Wrapped for Protection

7. Plastic Part Sorting

8. PCB with IC Components

9. Special Storage Boxes

10. Bar Code Scanner

11. Production Output Chart

12. Power Supply

Explanations to the Photos

In photos 1 through 4, you can see that the workers are wearing working coats in different colors which are provided by the factory. This is mostly standard in all Chinese factories.

The different colors distinguish between different jobs the factory workers have. Blue coats indicate workers assigned to the conveyor belt while the pink coats are for QC inspectors checking the work on the conveyor belt.

The red color coats are for QC inspectors checking finished products. Their job is most important because they actually control the overall product quality. Final inspection is only assigned to experienced workers. These people are very important to the factory because they cannot easily be replaced.

You will also find some workers are wearing white cotton gloves. This should be a requirement in a well managed factory for workers who frequently touch the surface of products that are sensitive or easily damaged.

In photos 5 and 6, you see that the injected plastic parts are packed in separate PVC bags. Keep in mind that as your parts progress through the factory, they need sufficient protection until they are assembled on the conveyor belt.

Sometimes, this good practice is ignored by factories to save cost (extra packing costs time and money!). The result is scratches on the parts that later need an extra polishing job or cannot be buffed out at all.

In photo 7, you can see that the worker has placed some extra cloth between the conveyor belt and the plastic parts. This is another way to protect sensitive plastic part surfaces or spray painted surfaces. It does not cost anything but a little time and makes a big difference maintaining the quality of the parts.

Photo 8, shows a PCB (Printed Circuit Board) with one main IC of a MP3 player. If you order a high performance Toshiba IC because your engineers recommended it, you really want to make sure that the factory is not substituting a compatible Samsung IC which may be much cheaper.

The factories are always searching for ways to reduce their costs and replacing more expensive components or parts with cheaper ones is an easy to do this.

If you did not specify a requirement, it is appropriate for the factory to use the cheaper component, but if you order a specific component, they must comply. Asking for a pre-assembly photo provides you with good evidence of the factory’s compliance with your specification.

Photo 9, shows some blue storage containers containing assembled products. Again, all products need to be protected with PVC bubble bags to avoid any damage, even when inside a protective container.

MP3 players are somewhat high tech products but factories producing cheap plastic household products may not invest the money for proper protection.

Whatever your product is, the factory must provide some type of interim protection until the goods are packed into their sales packaging. Of course it is best when the products can be immediately packed as they complete final assembly but that is not always possible.

Photo 10 shows a bar code scanner in operation. Readable bar codes are essential to almost all retail organizations today. If a retailer’s cash register bar code scanner cannot read the code correctly, the product will not be recognized or it might register as a different product, which will cause havoc with the retailer’s ordering system.

Typically, inspection companies provide a bar code scanner to their inspectors but factories should also have the equipment. Something else you want to check on during your visit.

Photo 11, shows something which you can find in all factories but may not have paid much attention to. It is a production progress chart displaying either the production progress per production line or of complete projects. The chart in the photo is from the very beginning of production and for us it was important to see the total daily output the factory was capable of. We learned that the assigned production lines for our order were insufficient and requested the factory add one or two more production lines. MP3 players are time critical and usually shipped by air. There was no time margin for a late shipment because everything had been planned for the customer’s Christmas sales.

Photo 12, shows a stabilized power supply for testing the MP3 players. It is important that you check if the factory has modern testing equipment and the specific equipment needed to inspect your goods.

The required equipment is determined by your specific  products but I am sure that the Chinese factory that used lead tainted paint on the ToysR’ Us products did not have the right equipment to test either supplied parts or paint coming from a supplier. It makes a good example of why you want to make sure your factory is equipped with all devices needed for through and proper testing.

Closing Thoughts About the Production Areas

Check if production is arranged in a logical order. Common sense applies here but factories do not always follow common sense. Incoming material should be at one end of the factory, next should be the part fabrication areas, followed by the paint area. Coming out of the paint area should be either a temporary storage area or the assembly areas. A warehouse area should be at the end of the assembly areas or in an adjacent building .

If the daily injection capacity is much lower than the assembly capacity of the factory, the factory needs to begin this process early to build up a supply before beginning assembly. If this does not happen, other fabricated parts will need to be stored until the injection molding is complete. This causes another set of problems like storing parts in the production areas where they interfere with production and the parts are at risk to be damaged. Or in an even worse case, they will be stored outside in the weather that I warned about back at the front gate.

Workers are not typically allowed to talk to each other when working at the conveyor belt. If they are talking or arguing with each other and nobody intervenes, it is another sign of poor management.

Insist on seeing where finished products are stored. You wan to be sure they are stored properly. The finished and completely packed products should be either stored in one of the factory’s finished goods warehouses or if it is a small quantity order, kept in a separate storage area in the production building.

You may come across ongoing production of goods for other companies, even your competitors. It is a good idea to take notes and photos because this information can be important for your sales managers back home.

While examining the goods of other companies, you might uncover that the factory has lied to you about having exclusive distribution rights to the product in your sales region.

The factory representative should try to show you everything you request. However, they cannot bring production to a halt just to show a small detail to you. You will need to be reasonable with your requests.

Ending this chapter on a positive note, your factory visit could reveal that your products are coming off the same assembly line as some world famous brands. In that case, you have probably found a dependable Chinese factory.

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