Quality Control Process for China 12

[breezy83]

Hello,

I've been having a product manufactured in China for about 1 year, and currently we have a 3rd party do an Final Random Inspection on ~7.5% of the 1st completed container of the build. So far the quality has been good and we haven't had any major issues, but this process doesn't allow us much course correction in the case that we do find issues. To alleviate this concern, I'm considering switching to an inspection after X% of the build is complete. I'd really appreciate any feedback for the following questions I have:
- Is there a recommended percentage or product quantity to use here? Our current inspections have been for ~150 units, so I was thinking of doing the same here (first ~150 units made).
- Should we also do an inspection at the end of the build (100% complete)?
- After a certain period of time where the quality bar has been met, would it be acceptable to reduce the frequency of inspection (e.g. not every build), as long as no design/assembly changes have been made?
- Are there any other standard quality checks we should be performing for products that are in the mass production stage?

 

[Prometheus21]

1. "- Is there a recommended percentage or product quantity to use here? Our current inspections have been for ~150 units, so I was thinking of doing the same here (first ~150 units made)" - Not knowing what the product(s) are and how many we are talking about my general answer will be no. There is no recommended percentage or product quantity as this is completely dependent on customer specs, your specs, manufacturing methods, requirements in general, industrial standards for your sector that may apply +++. There is no general rule here that applies everywhere.

2. "Should we also do an inspection at the end of the build (100% complete)?" - ...Yes. Most customers prefer to have a complete product at their hands. Would be a darn shame if that wasn't the case. I have never seen (and hopefully never will) a completely assembled product in my company that has NOT been inpected (and tested) after completion; then again it depends on your industry; customer requirements and local regulations if those apply.

3. "- After a certain period of time where the quality bar has been met, would it be acceptable to reduce the frequency of inspection (e.g. not every build), as long as no design/assembly changes have been made?" - No. Never. An inspection is not just to ensure that the product is built correctly, but to detect possible anomalies that might occur, sometimes by pure chance; e.g. broken machining tools during machining, bad batch of O-rings in the assembly due to sunlight exposure during said assembly, faulty machining equipments, faulty and out of spec parts in general. Maybe the assembly technician is sick and a new person was in charge in that time period and he has no idea what he is doing. You get the gist; the possible deviations and anomalies are countless, and Murphy's Law reigns supreme.

Or as in my personal slightly more morbid experience; the supplier of the base components changed the composition of a certain brass alloy to cut cost without informing us, leading to an explosion due to thin-walled rupture during leakage testing, therefore leading to a massive lawsuit. Long story short we have a new supplier and extremely rigid inspection requirements.

4"- Are there any other standard quality checks we should be performing for products that are in the mass production stage?"

Again...how big is a house? Without knowing the specifics this is impossible to answer properly.

As a general layout?
Is the function of the part/product maintained? (Should be if the product is manufactured according to the drawing(s) - one would hope at least...
Maybe pressure testing if that applies. Maybe alloy composition check. General material properties check of the rods being used during machining. Ultrasonic inspection certificate of said rods? Certificate of the stress relieving process?
Cleanliness inspection if that applies...
And so many...many more. All of the above are standard - depending of course on the specific industry you are in.

 

[Jboggs]

Consistent quality from China? Good luck.

Of course, if you wanted to, you could go through the whole ISO certification process. Again, good luck getting a Chinese company to comply with any standards.

 

[Prometheus21]

Good point. Not to mention the traceability requirements described in ISO would require consistent quality checks across the board anyway.

 

[ctopher]

My experience visiting a mfg plant in China, their inspection process is if it's not right, rework/rebuild it.

Chris, CSWP
SolidWorks
ctophers home

 

[Jboggs]

"it's not right, rework/rebuild it"
No such thing as rejection. Its an unknown concept.

Or as a friend of mine used to say: "If it fits in the box, ship it."

 

[GregLocock]

We used a 32mm stabiliser bar out of China. We wanted one 31mm stabiliser bar. Our proto supplier quoted months as getting the barstock would be tricky (more likely, in retrospect, they didn't want the hassle).

Our Chinese supplier said no problem and supplied one in a week. It's amazing what two guys with an angle grinder can do.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[EdStainless]

We sat down with old MIL AQL tables and began building risk assessments.
We did this for each component/feature of the sub-assembly coming from any outside source.
The only difference with overseas suppliers was that we had less opportunity to personally check on them.
For any new supplier we did the oversight for the first few shipments.
In our system this was considered a procurement expense and not QA.
We would relax our inspection intervals over time, but the vendor didn't know it.
Their inspection rules didn't change.

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P.E. Metallurgy, consulting work welcomed

 

[Nescius]

Depending on the nature of your specific product, my experience may or may not be applicable to your situation.

As Prometheus21 essentially says above, there is no prescribed formula to ensure good parts.

At best, even in US production of tightly regulated products, a mathematically airtight scheme of monitoring will only approximately describe the actual product variation. Weird stuff happens. Mostly though, it's "human" stuff happening.

Lots of "human" stuff happens in Chinese production and, again, depending on your specific product, statistical monitoring may not work at all. So, you might choose to check "enough" product and forego looking for deeper meaning in the numbers. The cost of checking more and the risk of not checking enough are the poisons you must choose from.

I know this advice isn't a revelation. My earned experience is that there might not be any revelation to be had. It's great that you're proactively thinking about it, and you know your situation and risks better than most. You're already on the right path.

Use your best judgement on the "when" and "how much" to check questions. Be guarded against bad faith actions, including changing designs or materials, and even bribery of your 3rd party monitor.

 

[pierreick]

Hi,
First thing to do is to inspect the facility prior to sign a contract. This will tell you a lot about their quality/inspection system in place.
You cannot relax the inspection, hire or pay the service of a QA inspector.
In China you have good companies with good practices in place, pay attention to the standards (GB vs others)
Good luck
Pierre

 

[pierreick]

Hi,
Be aware, in Asia you have different qualities, one for domestic market and one for export market.
To be taken into consideration.
Pierre

 

[EdStainless]

I should mention that in China we visited 11 different companies to find two that we were willing to work with.

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P.E. Metallurgy, consulting work welcomed

 

[Tmoose]

Hi Mr Stainless,

Was there a consistent "reason" the 9 were un-willing?
No experience with Your referenced standards?
Some requirement of yours too tight?
Some material or process they had not worked with before ?

 

[geesaman.d]

My experience is with dealing with QC problems, not so much building QC plans. Someone reading this may interpret me as griping or trash talking a whole nation but please, I do believe each of these experiences is a risk that can be mitigated and I'm offering them for that consideration.

But here are some experiences I've had working in those quantities:
- A vendor who built/quoted a complete assembly quickly flipped it into a product they sold within China. Lesson learned: Never give a vendor more proprietary data than a couple of component drawings and handle all assembly in our facilities.
- A vendor who built/quoted a complete assembly began substituting little components - like 1/4" NPT grease relief fittings. They became home-made assemblies with machine screws as the poppet. I have many other stories from when we bought subassemblies - suffice it to say we simply don't do overseas subassemblies anymore unless the vendor really is reputable.
- Bearings were very cheap, very poor quality. Even bearings with the same brand markings from previous POs have no meaning because they don't enforce against knockoffs so even Chinese brands are being knocked off.
- Subsuppliers and batches vary widely from one purchase to another. On one bad PO, we had cast iron housings that fractured when we tried to disassemble them. They tested around 11ksi when they needed to be 30ksi.
- Inspection reports deliberately falsified. Their CMM reports would show a hole at .0013, .0023 off nominal location but their true position value would be .0006 (drawing limit was .001, and the calculated true position is .0053 for my example numbers)
- Quoted cost and lead time is always a SWAG. After the first PO is accepted and they get paid, they will work to reduce cost on subsequent POs to make up for inaccurate cost estimates rather than adjust their cost to meet your technical requirements.
- As you're probably aware, the Chinese government is their friend, not yours. So anything that needs to be a certain way, needs to be witnessed or verified by your people.
- Root cause analysis and resolution is mostly not practiced. If you reject the parts they'll have you scrap it due to high transportation costs and of course then the next order is no more likely to meet the specs since they never figured out why the previous lot failed. While this costs them money, this can cost you a lot more.
- Beware of fallacious thoughts like "well it all comes from China anyway - might as well not overpay". Yes, it's true that many of the world-leading items are produced strictly in China. But never forget that any product can be 'made' on the spectrum between top quality and junk and China makes the entire range.

Working in 100-200 lots is a bit tricky. I suggest keeping everything in separate components and if you can't afford to reject an entire lot upon its arrival, have someone witness inspect in-country. Explore 3rd party inspection and testing companies there that will work directly with you and verify that their data is correct and accurate. It's big enough that companies will compete for the work but not enough to change they way they do business.

My company started out whole hog having an importer bring in subassemblies of our product. The initial quality was acceptable and the price was good. But then both sides got greedy and we ended up paying even less for true junk. Our rework costs were quite high - for a few years we had to tear down every subassembly and rebuild it, replacing some components. Nowadays we purchase loose components from overseas and inspect them rigorously. When things get screwed up our lead times suffer somewhat but the issue is limited.

There are definite cost savings to be enjoyed. But not all components will measure up to savings when it's all said and done. Most MBAs are foolish enough to assume their inspection plans for parts made by reputable vendors in-country are adequate for vendors coming from China or other best-cost-countries. You will/should ramp up inspection and give back some of those 'savings' to ensure you're actually getting usable product.

 

[EdStainless]

TMoose, In most cases it was related to the disconnects in their system.
In many cases the planning, manufacturing, QA, and labs are all run as separate operations and have very little contact with each other.
This is not good.
Finding out about the status of an order is nearly impossible.
As is getting preliminary inspection or test data before shipment.
A lot like going to a medical specialist.
They don't care about your overall health, just that you don't die from the part that they are looking at.
And we saw the same issues in some other countries.

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P.E. Metallurgy, consulting work welcomed

 

[kokerkov]

There is something called AQL. If you are a QC staff, you should be familiar with this.

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I am Chinese from a Chinese factory. I am sharing my experiences dealing with our peers.

We need to purchase some die springs for our client, because we dont produce such thing and this client wants us to buy for them. I am the one who is reaching out to these die spring manufacturers. I finally found one good supplier that their products don't have problems yet before having two failed factories.

1st factory: they use Silicon-Carbon steel(65Mn, you probably dont hear them) to make die springs. Wrong Material. I dont even know why they can exist because die springs are made by Cr-Si alloy or Cr-Va alloys by default, so i didn't ask them in the first place.
2nd factory: they use Cr-Si alloy. Things went well first, then one model have greater forces than tolerances. And then, they confess that they use the JIS B(Japanese standard) wire to make these springs while I was ordering ISO 10243 die springs. They said they can refund me, they wont remake because they dont want to buy wires to make ISO springs.(wires have rectangular cross-section, so need to be customized)

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Yes, we have many companies that are shitty. It takes you time and effort to find good partners. EVEN for us.

 

[Sparweb]

Back in school, I had a course in statistical process control. I was too young to care most of the time, but there was one lesson that made me pay attention. I've tried to reproduce the point in the sketch below.

In words, there are manufacturers that will use a process to make a part that has poor controls. The results are too variable for the customer's spec, but they make up for the process by inspecting most of the parts and selecting out the bad ones. If you receive enough of these parts to measure them statistically, their measurements form a strange distribution, that you might mistake for a Weibull or Rayleigh distribution.

The course instructor then told a story about a manufacturer that subcontracted parts and did this measurement on the lots they received. When they realized that it wasn't a Weibull distribution but actually a Normal distribution with the bottom cut off by selective scrapping of the rejects, they canceled the contract. It was expected that once they turned their backs, the subcontractor would relax the inspections and out-of-spec parts would get through.

That teacher telling that story was the moment when I finally got the point of these process controls.

 

[geesaman.d]

The course instructor then told a story about a manufacturer that subcontracted parts and did this measurement on the lots they received. When they realized that it wasn't a Weibull distribution but actually a Normal distribution with the bottom cut off by selective scrapping of the rejects, they canceled the contract. It was expected that once they turned their backs, the subcontractor would relax the inspections and out-of-spec parts would get through.

This type of thing is a challenge in all low-cost countries but I it's most acute in mainland China.

This can quickly sound racist but I'm a firm believer that this is tied to the intensely competitive, unregulated environment that the Chinese government maintains. And that seems to center around always siding with the Chinese side of any transaction, which encourages downgrading quality as much as possible on exported products.

A good friend of mine with a career in nuclear engineering told me a story today about when he worked for a major auto/truck/tractor component supplier who opened a factory in China. They were only able to produce good parts when the company had six engineers present at the factory on the floor at all times. (two per shift, three shifts per day). If there weren't enough of 'their' people on the floor the factory staff would immediately revert to the incorrect processes and materials and put out bad product. I suspect those guys would have loved the luxury of using non-Weibull distributions to spot problems. For processes where inspection will not reveal all flaws, it takes boots on the ground.

The same company had not had such QC challenges when their Chinese factory made parts for the Chinese market. Taiwan has been much, much better to work with.

 

[mfgenggear]

What happens if China attacks Taiwan.
Good luck

 

[geesaman.d]

What happens if China attacks Taiwan.

Those suppliers will change. Likely not for the better, from our point of view. Investing in Taiwan now is highly risky, which has probably softened their economic power and makes them more susceptible to military attack.