Featured this issue:

Bolt Factor in Assembly
Poke Yoke – The be-all-end-all of the manufacturing world
Ask the Expert – Steps to Zero Defects

Bolt Factor in Assembly

There are a number of assembly tools available in today’s market. Years ago the only power tool available was an impact wrench – which assembled even critical applications such as automotive seat belt assemblies and lawn mower blades. If you talked with the operator on the floor you couldn’t break the impact out of their hands and replace it with something else. These same operators, if left on the same job became very skilled at stopping the impact accurately before bolts were broken or stretched.

The bolts used on these assemblies are big, to say the least, and heavy. Big and heavy does not lead to lower fuel consumption and other “ECO” words now heard everywhere. Since the bolts were big so too was the torque range of the tools used. If you are using a tool in assembly that has +/- 40% accuracy like an impact, your bolts better be big to accommodate this variance.

How to Reduce Costs

Even pulse tools, which have slowly replaced the impact bone-rattler described above to greatly enhance ergonomics, still only offers +/- 30% accuracy. Stall tools come in next at +/-25%, shut off, gear driven tools follow at +/-10-15% and then battery (not the home depot tools) and DC electric tools are most accurate at +/- 3%-5%.

If you use more accurate methods of fastening your products together smaller fasteners can be used to assemble them without any sacrifice in strength and clamp force between your two mating surfaces. Consider the overall cost of your fasteners when choosing tools along with assembly constraints and ECO concerns. More precise tooling may lead to lower product costs and lower warranty claims. A good deal anyway you look at it.

Contact one of our sales associates for help with your process!

Check back next month when we talk about screw feeders and screw presenters.

POKE-YOKE the be all and end all of the manufacturing world

You have a manufacturing problem – you have to poke-yoke it right? RIGHT??

Well – maybe not. Poke yoke is a excellent method to control your process but if your process is bad – i.e. bad parts, poor materials etc., this poke yoke process will only serve to provide red lights and buzzers all day long- no production – no process improvement,  just an indications that’s there something wrong with the process- so what gives? You poke yoke the process – isn’t that it? Is that where it stops?

We tend to forget that POKE is designed to work with 85% existing part acceptance. The last 15% is what we simply forget or miss because we are human. Thinking about the big game, your girlfriend, whatever. The point is YOUR PROCESS; the parts you provide to manufacture must all be within specification. Poke yoke does not correct for poor parts – it only will tell you have a lot of them. Even if you decide to use DC electric transducerized tools with all the bell and whistles- it will not compensate for your poor parts. You can, however, use the tools mentioned to identify a problem which will now become very expensive. It is certainly a good choice to poke yoke, but there has to be a dedication by the company to resolve the issues completely otherwise we find these poke yoke are just disabled shortly after installation due to the “red light” and the loss of production.

The moral of the story is: fix your part problems and then POKE yoke- otherwise you better be on call 24/7.

Once you fix the process there is an array of POKE YOKE products available- if we are just talking about assembly- just about any air tool can be poke-yoked, or error proofed.

DC tools have a couple of options: fully transducerized and current or algorithm tools. And for lower production the use of click wrenches with electronic signals can also be implemented to control a good process.

Make a good process outstanding with POKE YOKE – don’t make a poor process a bigger headache.

Contact our knowledgeable sales department for a comprehensive choice.

Ask the Expert – Steps to Zero Defects

Step one in error proofing begins with the tool shutting off at the required torque, or “torque OK”. Typically, the end user decides critical versus non-critical fastening and will choose the appropriate tool based on the safety level for each fastener.

Step two, bolt counting, when “torque OK” is not enough. The operator now has a method to certify that the fasteners are correctly installed. For example, in a complicated assembly where an operator must hit ten fasteners, a visual signal is given after the assembly process is complete. This is basic counting.

Step three of error proofing can be achieved through angle and/or time monitoring – The later being not as effective dependant upon the joint. Torque is based on friction generated – a shut off signal only says a friction level has been reached and a typical (air/battery) tool will not tell you if you have achieved both torque and angle (is the fastener seated?) – it will shut off at “torque OK”. This does not detect if the fastener cross-threads. Additionally, it does not detect if there are a missing washers, lock rings or gaskets. Angle or time monitoring allows you to detect all of these items within their respective limitations. Adding angle/time constraints to your torque strategy will determine that your part is assembled to the required torque and in a seated position. Line control is typically a standard option with these types of technologies.

Step four is collecting data. Typically, a transducerized tool is used to determine the exact date, time and serial number of the part being assembled. DC controlled transducerized nutrunners are capable of storing joint information and time of assembly, creating a log of historical data for reference at any time. This can be a crucial time saver in the event of a recall. Transducerized tools also have the benefit of line control, which allows you to physically stop the line if any of the above methods are missed. Don’t forget that non-transducerized tools i.e. current or algorithmic tools do not have a traceable transducer on board therefore do not provide traceable torques! You get what you pay for watch out for sales people “grazing” over the real capabilities.

The Production Link

Bosch Rexroth tools are guaranteed to be calibration and maintenance free for 1 000 000 cycles. There is nothing on the planet like them. There are never regrets when you invest in quality.