Tradition in the air5 December 1999
Scott Miller looks at lifting trends in the US car industry
Henry Ford is famously quoted as saying that buyers of his cars could have any colour they wanted, as long as it was black. Thankfully, when it comes to material handling, US-based American and Japanese auto makers enjoy a wider selection of models, and colours, for their overhead lifting requirements.
In the US horseless carriage industry, low-tonnage pneumatic and electric-powered hoists support a wide variety of tasks in an automotive plant’s main and ancillary assembly lines including engine installation, engine-to-transmission mating, and axle and frame assembly. While weight requirements, lift distances and processes vary, automotive hoist duty tends to share many similarities. And where differences do exist, they appear to do so for cultural and historical, not technical or process-related, reasons.
The majority of automotive hoists fall into the one ton and under category because most sub-assemblies and components weigh less than 2,200lb (1t). In both US and Japanese factories, lifting speeds usually range from 16 to 32ft per minute (fpm) (4.9 to 9.8m/min) and traversing speeds from 80 to 120fpm (24.4 to 36.6m/min). Electric hoists are usually powered by 208V, 240V and 460V, three-phase alternating current sources. Pneumatic hoists are generally furnished with 90 pounds per square inch (6 ibar) of low-humidity, filtered and lubricated compressed air.
Both Japanese and US industries are biased towards air-powered hoists in their main assembly lines because of tradition. This particularly applies in the US, partly because the ‘Big Three’ (Ford, GM and Daimler-Chrysler) tend to embrace the “that’s the way we’ve always done it” manufacturing mantra. However, the bias is well founded: historically, air hoists were more advantageous than their motorised counterparts because they didn’t have heat restrictions that often placed limitations on their electric counterparts.
On the secondary manufacturing lines, like those that feed engines to the main line, there are more electric hoists than air hoists in Japanese plants and fewer in US sites. Japanese ancillary product lines often have endless loop monorail systems, which are better suited for electrification than festooned air lines.
Both Japanese and US manufacturers are taking advantage of the benefits of automated crane operation, which include increased productivity, reduced product damage, enhanced quality control, smoother flow of work-in-progress, and lower labour costs. The Japanese preference for automated crane processes stems from a long history of labour shortages in Japan. Also, when the Japanese build new plants in the US the facilities engineers employ what they learn in Japan – that is, processes that rely more on material handling equipment to reduce labour costs.
Conversely, American car makers have historically leant towards manually operated processes because of an abundance of labour. This bias has permeated the domestic car manufacturing culture since its inception, and still holds today, especially in the US’s more mature plants. The Japanese car industry is younger and, in some cases, less influenced by convention.
Some new US and transplant plants rely less on “traditional” bridge cranes because alternative overhead lifting methods like enclosed track and workstation cranes are used instead. Both of these systems require hoists, whether with air or electric power. Regardless, the electric and air-operated hoist still plays an essential role in both countries’ manufacturing processes, and there are advantages and disadvantages to both.
Trends in automotive hoists
A number of distribution and technology trends in the automotive industry are influencing and re-defining this market. The role of the distributor in the marketplace is changing. Hoist distributors are more sophisticated and more knowledgeable than ever before, placing them on a firmer footing to help end users make more informed choices.
Distributors are recommending and ordering more electric hoists than before, for two main reasons: distributors have a better grasp of advances in electric hoist technology; and they are more “application-savvy.” There is a growing trend towards specialisation and process-specific application engineering at the distributor level. Compared to 10 years ago distributors are more sensitive to their customers’ needs and they understand their customers’ processes better. The larger distributors are growing, but not specialising, which creates a vacuum for the smaller distributors to market specialised services, especially at the process or application level.
Electric hoist technology has advanced greatly in the past two decades in response to a growing need for more portable, ergonomically correct, multi-speed lift equipment. Advances in multi-speed motor control technology, heat-resistant motor materials, and more user-friendly and functional motor controls have greatly improved the operation and duty-cycle of electric-powered hoists.
For example, to limit costly downtime due to equipment failures, some hoist vendors, like Harrington, have introduced hour meters that provide a log of hoist usage over time. The hour meter provides a real time digital read-out of motor starts and cumulative motor run time. With this data operators can schedule preventive maintenance items such as oil changes, inspections, etc. on an as needed basis. Also, the meter allows plant personnel to plan contactor and motor replacement during slack production periods, rather than respond to equipment failures on a ‘fire-fighting’ basis when the line is in production.