This section explores the balance between worker responsibility for assembly and tool/system responsibility for assembly.
1. A worker with a set of wrenches and sockets.
The worker has complete control over the assembly process including throughput and quality. Being totally employee dependent may not be as risky when you have a well established, experienced workforce. But what about new hires or seasonal workers? Can you control throughput and quality with a less experienced workforce?
2. A worker with a set of torque wrenches. The worker is responsible for choosing units of measure, torque values and ensuring that proper technique is used to maximize accuracy and quality. Post assembly inspection is still critical in evaluating and maintaining required quality levels because there is no documentation that the work was done properly.
3. A worker with a preset wrench. With the preset torque wrench the worker no longer has the responsibility to select units of measure and torque values. There is no documentation that the work has been done properly. Add a switch to the torque wrench and it can be tethered to a Programmable Logic Controller (PLC) providing notification to the production system and the worker with simple OK/NOK feedback.
4. A worker with radio equipped wireless tools. In the most basic application, paired with a simple process monitor a radio equipped click wrench can provide OK/NOK feedback on
each fastening. On the high end of the scale a process controller can organize up to 16 tools, 100 parameters, 100 jobs, and provide the worker with a predefined assembly sequence. Responsibility for the assembly sequence is shifted to the controller and associated tools.
These systems have built in error proofing processes to ensure quality and limit variables or work arounds.
The sophisticated process controllers have the ability to change parameters quickly, convey results in "real time" or results can be stored and downloaded later. Throughput increases and the digital data documentation gives management excellent insight into as much detail as they want while still providing a broad based view of the operation.
5. A worker or a robot with a DC Nut runner. The speed, power, control, and accuracy you get from adding DC tools come with an appropriate price. If you have the volume and the budget these solutions can provide real ROI for your assembly. There may be a trade-off. In this case the trade off may be the ability to access all of fasteners and gain the control that you have with the DC tool. Wireless hand torque tools and process controllers may still play an important part of the equation if you want supervisory control and data acquisition.
6. Total Robotic Assembly. The ultimate assembly solution comes at a premium price. You gain ultimate control and in exchange give up the flexibility. Ask the robot to step outside the tasks for which it was designed and your investment of resources can be stretched to the limits.
Scenarios #1 and #6 are the extremes in the error proofing spectrum. While a nut runner is highly effective the typically cannot reach all fasteners. What do you do then? And, When you tighten those fasteners how do you get the performance data and documentation integrated into the MES? That is where Scenario #4 really adds value to the equation.
By looking at which scenario best represents your current situation you can explore other options to increase throughput, cut rework, and gather required data.
Error Proofing From A Different Angle: Definition of error proofing and some observations by W. Edwards Deming.
Finding The Balance: In error proofing "one size fits no one." To find what fits in your organization, start with the fundamental question of "How much responsibility for error proofing should be given to the tool and how much should be operator responsibility?" This section provides more on this concept.
Six Error Proofing Scenarios: Error proofing solutions all have trade offs. You can have control or you can have flexibility. Rarely do you get both. This page looks at error proofing extremes as well as the middle ground.
How Much Are You Investing In Errors? If your current error proofing system or approach still leaves you with errors you are investing in errors, not error proofing. Error proofing is about quality and it is also very much about dollars and common sense. This pages digs into that.
Understanding The Common Centerline: Not having a common centerline is one invisible place where your error proofing approach can introduce errors instead of eliminating them. If you want to know how to calculate a common centerline and why it is important this page is for you.
There is more about error proofing in our tool pages. If you need more, your Sturtevant Richmont Sales Professional is a great resource to help. here.
To read more about error proofing, explore these pages:
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