Automating Engine Assembly Stations Yields a 170% ROI

Patti Engineering recently automated several manual assembly stations for a major automotive manufacturer, completing the projects with no disruption to ongoing production. Each project’s payback period is under five months and the first-year return on investment (ROI) is over 170 percent.

By Patti Engineering Senior Controls Engineer Dan Ragozzino

Overview

Patti Engineering has recently completed several projects converting manual engine assembly stations into automated stations for a major automotive manufacturer. Each automated solution used the manufacturer’s existing Siemens controls systems to minimize costs and took approximately five weeks from kickoff to commissioning. The projects achieved a first-year return on investment (ROI) of over 170 percent.

Manual Engine Assembly Station Description

The facility had several similar manual assembly stations targeted by the manufacturer for automation. Each station had a similar design and layout, with an engine arriving on a pallet. Due to lose tolerances, the station’s original design relied on an operator to manually finesse the incoming engine into alignment with an array of nut runners. The operator would then simultaneously push two buttons, activating and extending a nut runner array. These would torque down various bolts within the engine assembly and then retract to their original position.

Designing the Automation of the Station

Due to its repetitive nature and minimal operator input requirements, the station could be readily automated by Patti Engineering. To do so, the automated solution needed to address the primary functions completed by the operator:

• Positioning the incoming engine in alignment with the nut runner array
• Activating the nut runner sequence

Additionally, appropriate safety equipment was needed to effectively safeguard the area.

Trusted Advisory Leads to Design Optimization and Flexibility

Because of Patti Engineering’s longstanding relationship with this manufacturer, the engineering team was already familiar with the customer’s internal standards for station automation. These standards required higher-end controls hardware and a full code rewrite, both of which would have significantly increased the project’s cost without improving safety or functionality. Instead of doing so, Patti Engineering collaborated with the manufacturer’s corporate engineering team for approval to ease these internal standards. As a result, the automated stations were designed to use the existing Siemens 1516Pro F-2PN PLCs. The code was updated rather than fully rewritten to automate the station’s operation and incorporate the new safety monitoring equipment.

Designing the Safety System to Protect the Station

Depending on each station’s safety needs, Patti Engineering implemented either light curtains or area scanners. Safety input cards were added to the station’s existing PLC rack to integrate these devices.

Updating the Controls

Each station’s automation required two primary changes to the controls:

• Automated activation of nut runner sequence: The code was updated to replace the operator’s manual button push input with an automated signal.
• Safety equipment: The controls code was updated to incorporate the new safety equipment, either light curtains or area scanners as appropriate for the particular station. An isolated E-stop event was implemented to protect the area such that when the safety equipment is tripped, control power is cut, freezing the station without tripping the rest of the line upstream or downstream. The isolated E-stop also allows for a quick reset.

Stabilizing and Positioning the Pallet

To address the issue of positioning the engine in consistent alignment with the nut runner array, Patti Engineering partnered with Taurus Tool and Engineering. They designed a custom locking device that engages with each pallet from the underside via existing holes. Their pneumatics-based device stabilizes the pallet into a repeatable position and raises the engine in alignment with the array of nut runners. Once the bolts are torqued down, the device lowers the pallet.

As an additional benefit, the custom locking device can be used to meet similar positioning requirements at other stations throughout the facility.

Flexible Installation and Collaboration

As requested by the manufacturer, Patti Engineering worked with the client’s internal trade teams to complete the mechanical and electrical installations. The work was primarily done without impacting production, with each station taking approximately seven days to complete.

The customer’s strict internal hardware standards required certain specialized components with lead times of up to 14 weeks, a substantially longer timeframe than the five-week lead time for Taurus Tools’ custom locking device. To prevent project delays, Patti Engineering collaborated with the customer to address this problem. The decision was made for Patti Engineering to borrow cables and safety devices from the customer’s on‑site inventory, later replacing them when their own orders arrived.

Profitability: Return on Investment and Payback Period

Each automation project has been highly profitable for the manufacturer. The

following estimated first-year metrics illustrate the financial impact for each station:

• Project Cost: $100,000–$120,000 per station (average: $110,000)
• Annual Savings: $300,000 per station
• Net Return: $190,000 per station (annual savings minus average cost)

Return on Investment (ROI)

ROI = Net Return Project Cost × 100 = $190,000 $110,000 × 100 ≈ 172%

Payback Period

Payback Period = Project Cost Annual Savings = $110,000 $300,000 ≈ 4.5 months

Summary

• Each project pays for itself in under five months.
• Each project achieves an estimated 172 percent ROI in the first year.

As outlined above, Patti Engineering’s automated solution for the nut runner array stations was straightforward to implement and highly cost-effective. By stabilizing the engine into a repeatable position with a custom mechanical locking device, the nut runner array could be autonomously activated to torque down the target bolts. Given these results, the manufacturer is now evaluating additional stations that can benefit from similar automated solutions.