Welcome


Welcome to my blog for all things related to business quality (processes, systems and ways of working), products and product quality, manufacturing and operations management.

This blog is a mixture of real-world experience, ideas, comments and observations that I hope you'll find interesting.

Pages

July 2009
M T W T F S S
« Jun   Aug »
 12345
6789101112
13141516171819
20212223242526
2728293031  

My top ten fixes for ‘the loose screw problem’

My favourite interview question for manufacturing and design engineers goes like this: “If your customer complains there are loose screws rattling round in the bottom of the equipment you have just delivered, what are you going to do to make sure it doesn’t happen again?”

After they have answered, I say “suppose you do all those things but he phones up again the next month and says there are more loose pieces inside the latest units”.

Then they give more ideas and I ask the same question over and over again until their ideas dry up.

It gives you an insight into the experience and creativity of the interviewees and it’s a genuine scenario – it has happened to me and I have learnt how difficult it can be to keep large, complex equipment clear of all unwanted parts and debris.

Now, be honest, you probably think this a trivial and easily remedied problem. Think again! Your organisation may not have suffered from it but for many companies it causes real difficulties and is indicative of underlying quality shortcomings.

So if it happens to you, what can you do about it? Here are my top ten solutions:

Clean out the unit then shake it
It sounds obvious but there should be a process of thoroughly cleaning out and inspecting the unit before its enclosure is finally sealed. You won’t see everything, so use a formalised, specified process of shaking the unit or rolling it several times through all axes of rotation (use a jig if it’s heavy) and listening for any noises that indicate loose parts – then inspect again.

Do bump and vibration testing
Your equipment may start off being clean but screws, nuts, etc, may work loose on its way to the customer; are you sure this can’t happen? Take the unit to your local environmental test house and get them to test it under severe transit conditions and see if anything works loose and needs redesigning.

Torque the fixings
Too many manufacturers rely on their operators’ un-calibrated wrists to judge how tight a screw should be. Don’t. Work out the torque settings for all screws and use calibrated torque drivers; then, if they come loose, you have an objective measure that you can adjust.

Use thread-lock and/or locking mechanisms
Thread-locking compound (Loctite), Nylock nuts and locking washers can reduce an obvious source of problems. Make sure that your screws are long enough – Nylocks or Loctite won’t help if you only have one thread engaged! And if you are supposed to be using Loctite, or Nylocks, or locking washers, make sure that all your staff really are using them all of the time.

Design out the problem
Avoid the problem – use different types of fixing such as clips that are moulded or pressed into the casework, then there’s nothing to come loose. If you do use threaded fixings, consider using captive washers as separate washers often get dropped and roll out of sight.

Make sure that debris can’t get in
There is no point in keeping the unit debris-free if bits can simply enter through holes or ventilation grilles, so make sure the design prevents this.

Count them all out and count them all back
If you use a Kanban system, or give free access to fixings, there is nothing to prevent the operators using more fixings than they should and losing some. So kit up the exact number of screws, nuts, washers, etc, and put them in a separate bag per unit, then if the operator doesn’t have sufficient it warns you that some may be lost inside the unit and you can investigate.

Cleanliness is next to Godliness, especially from above
Without doubt, the cleaner the area the less chance there is of getting debris in the equipment; look at a satellite assembly clean-room or the McLaren F1 assembly area – immaculate. I once saw a classic case of loose parts inside bought-in subassemblies that was only resolved when we saw that the subcontractor’s plastic fixings bins were on a shelf above the assembly area. Operators reached up to take fixings out of the bins, and occasionally some would stick to their hands or their magnetic tools and fall unseen into the equipment. The problem went away when the shelf was removed.

Use traceability
Sometimes the problem is related to one faulty tool or workstation or person. If you use traceability in your materials and processes it makes it easier to find out exactly where the problems originated and take corrective action.

Train the workforce
If your people don’t know about the problem, and don’t know what they have to do to prevent it, then it will happen again. So tell them about it and train them in preventive techniques; they will be key assets in preventing recurrence.

The solution to a persistent loose screw problem is not to pick and choose from these solutions, it is to implement all of them.

But now I’ve given the game away so I’m going to have to think up another ‘impossible’ interview question!

By the way, if you have any other ideas about how to fix the problem I’d love to add them to the list – do get in touch.

Share

5 comments to My top ten fixes for ‘the loose screw problem’

  • Emily

    Thanks for yr sharing. That is good and useful.To be point, good design and error-proof tooling are always working well on trouble shooting:)

  • Tom G

    Thanks Emily!

  • vivian xie

    dear tom, we have a product and would like to have you or your company review it in china, will you think its possiable to quote us?

  • Tom G

    Hi Vivian, thanks for making contact, I am always happy to discuss providing services, I will email you directly.

    Best regards

    Tom

  • NYJITH

    IN STAMPING TOOLS STRIPPER BOLTS ARE GETTING LOOSENED,SO CAN YOU SUGGEST ME HOW TO AVOID THIS PROBLEMS..BECAUSE ITS MAKES DIFFICULT TO RUN LONG PRODUCTION

Leave a Reply

 

 

 

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>