Conduit Cooler Project

PROFESSIONALLY BASED PROJECT - STAENG / HELLERMANNTYTON (COMPLETE)

PERMISSION TO SHARE PROJECT REQUESTED AND GRANTED BY COMPANY

Whilst working for ISO9001 compliant, specialist wiring harness manufacturer STAENG as a wiring harness technician, I was temporarily tasked with assisting an operative with completing a large volume of work that was placed on order by one of our clients. After spending a few days familiarising myself with production process, I identified a number of key areas in the process that could be improved upon. The existing manufacturing process had remained unchanged for a substantial amount of time and I endeavoured to initiate a project which would improve this process. The project was spearheaded and proposed by me and worked on in the spare time I had available around doing my full time duties as cable harness technician, as process development was not directly part of my role within the company. It was brought to life by working closely with the engineering team working out of the HellermannTyton Plymouth branch as they had access to CAD software, initial designs were manually drafted and then developed into a design that could be manufactured.

The existing process:

To begin with two Steinel heat guns were equipped with narrow nozzles, one heat gun was set at its minimum temperature and it was used as cooling device, the other heat gun was set to a relatively high temperature of 150 degrees. A box of plastic convoluted conduit stock was placed on the workbench as well as a bag of adhesive lined heat shrink boots, the length of the conduit and format of the boots could be varied depending on what variant of conduit assembly was being produced.

A piece of plastic conduit stock was removed from the box and a adhesive lined boot slid over one end of the conduit, this was then shank down with the heat gun that was set to the hotter temperature, when the boot had been fully shrunk down, a quality inspection was done and the conduit assembly was placed on top of the nozzle of the heat gun set to its minimum temperature to cool down the adhesive lined boot and set the glue.

After a period of around a minute and a half the assembly was removed, given a final inspection and then placed into a box, which would be shipped when the total quantity of conduit assemblies needed had been made.

The following observations were made upon full understanding and observation of the existing production process:

The process was very noisy, having two heat guns running constantly.
The working environment for the operative was very hot, despite one heat gun set to a lower temperature, it still contributed to adding heat to the immediate workspace.
This process resulted in a high turnover of equipment, with both heat guns running constantly, accelerated wear of the heat guns was generated and therefore a shorter service life. Steinel heat guns are top of the range, professional equipment and retailed from upwards of £115, this high turnover added excessive expenditure to the business.
As the temperature of the cooling heat gun was above ambient, an excessive cooling time was observed before the adhesive had set and the assembly could be packed, resulting in adding unnecessary production time to the process.

The following objectives were set for this project:

Design a dedicated piece of machinery that would replace the 'cooling' heat gun.
Ensure that the flow rate of the machine met or exceeded the air flow rate of a Steinel heat gun (17.6 CFM).
Modify the existing manufacturing process to incorporate the new machinery.
Eliminate the excessive turnover of equipment by using the dedicated cooling device in the production process instead of a heat gun for cooling purposes.
Improve working conditions for the operative by replacing 'cooling' heat gun with dedicated machinery that would circulate ambient air.
Improve working conditions for the operative by replacing 'cooling' heat gun with dedicated machinery that would utilise a low noise fan to circulate air.
Speed up overall production time by cooling conduit assemblies more quickly and multiple assemblies simultaneously.

Proposed design for cooling device:

The dedicated unit was designed to be a tabletop device that could run off standard mains power, an off the shelf metal enclosure would be used to eliminate the need to manufacture a bespoke enclosure, reducing production costs. an axial ventilation fan would be used to draw ambient air from the underside of the base of the unit and push air through a set of 9 tubes mounted on the top of the device, the fan that was selected was from Farnell and was part number 1908969, this fan produced a maximum flow rate of 175.8 CFM The tubes would be made to a diameter that resulted in a tighter fit compared to the fit between the plastic conduit and original heat gun nozzle, this was to ensure that minimal airflow was lost out the gap between the tube and plastic conduit. Variation in the internal diameter of the plastic conduit was closely observed however, to reduce the risk of a conduit with a smaller internal diameter not fitting over the tube.

The tubes were to be comprised of a standard grade of steel to reduce material costs and have a small radius on the outer tip, to aid in slipping the conduit assembly over the tube for cooling. A total of 9 cooling nozzles would be installed on the unit, to enable 9 conduit assemblies to be cooled at the same time, with the potential to speed up production time substantially as well as quality, as the adhesive could be set more quickly reducing the risk of it running and causing drips.

Proposed new production process:

The new process would be relatively similar to the original method, so minimal training would be required for the operative in regards to use of the new equipment. The variation in the new process came when a conduit assembly needed to be cooled, it would be placed on one of the 9 cooling nozzles of the device, the next assembly would be placed on another and the process would continue until all 9 nozzles were occupied. When this occured, the assembly that had been placed on the cooling device first was removed and packed and replaced by an assembly that had just completed the heating and shrink down process. This 'hottest on, coolest off' approach ensured that the conduit assemblies that were removed for packing were as cool and set as they possibly could be.

Implementation of the new machinery and improved production process:

The new device was given a green light for manufacture and it was made to all relevant standards and put to work, all of the original objectives were met, along with a happier operative who had a more comfortable environment to work in. The elimination of the original two heat gun method enabled the company to not only reduce costs by not having to replace worn out equipment, but also provide a much better environmental position, with a reduced amount of electrical waste output which would have to be disposed of accordingly. Overall the project was a success with substantial gains evident, the device has been in use within the company for the last 4 years and is still going strong.

Finished conduit cooling device put into production:

Conclusion of project

Some future work could involve automating the whole process by designing machinery that could both provide heat, cool and pack the conduit assemblies with the only human intervention being loading conduit tubing and adhesive lined heat shrink boots.