Automotive Industry

All parts of new cars, right up to the entire car itself, are made in factories which use millwrights to a greater or lesser degree.  Assembly lines, conveyors, and automated machines and robots all require our skills to install, properly set up, maintain, and troubleshoot and repair.  For this month's feature industry I will focus on just one aspect of the automotive industry:  the manufacturers of the seats.  Everyone knows that you won't enjoy your new car if you don't find the seat comfortable, so seat manufacturing is both familiar and important to anyone who drives or rides in a car.  Therefore, this type of auto manufacturer's supplier will serve as a good example of the industries supplying the auto makers.

Most seat factories use a system of belt-type conveyors to move their products along the assembly lines.  Basically, a belt conveyor consists of a set of pulleys moved by a drive motor.  

The Head Pulley is the largest pulley, used to reduce flexing of the belt.

The Snub Pulley increases the arc of contact on the pulley it is used with.

The Bend Pulley changes direction of travel of the belt (in this case, from horizontal to vertical).

The Take-up Pulley tensions the belt, usually by use of gravity (counterweights); although occasionally the take up is done with manual adjustments.

The Tail Pulley turns the belt from the return side to the loaded side.

Quiz Question:

Here is a diagram of the head pulley on a belt converyor system, seen from above.  

The top diagram shows a belt tracking correctly on the center of the conveyor.  

The next diagram shows the belt misaligned, and running to one side of the conveyor.

This month's quiz question is:

What can be done to get the belt in the lower picture to track correctly?

The seats are often made in separate factories from the auto manufacturer and shipped to them ready for installation. Basically, seats are produced from the simple elements of a frame, foam, and fabric, with the appropriate hardware system to allow the auto maker to install the seats in their various products.  The elements are put together by the people on the lines who insert, bolt, staple, and otherwise fasten the parts into a complete seat.  The seats must be consistently uniform to allow their use in the assembly lines at entirely different locations from that where they are made, and so always pass through an inspection before being shipped.  In some cases, even the shipping itself involves conveyors:  specialized transport trailers also contain conveyors which, powered from the loading area, run the skids of finished seats into the truck in just the right way to be unloaded quickly and correctly when they arrive at the auto maker's receiving area conveyors.  

Here are some links to let you learn more about automobile seats:

Lear Corporation has an interesting article on how they are using recycled bottles to produce one of their products: http://www.lear.com/g/g4.htm

Take a plant tour at General Seating:  http://www.gseating.com/plant.html

Here's a story about how Delphi Auto researches their next seat design:  http://www.delphiauto.com/index.cfm?location=1111

And if you're in the market to replace your auto seats, here's a source for competition aftermarket seats (they also have some pretty useful links themselves):  Corbeau USA http://www.corbeau.com

CCU Auto Trim's site explains how they do consumer seat repair and upholstery:  http://www.ccuautotrim.com.au/html/workshop.html

Check out the magazine for the latest trends in the aftermarket upholstery industry:  Auto Trim & Restyling News http://www.atrn.com

Conveyors can track incorrectly for several reasons.

One of the most common explanations is shown in the diagram:  the shaft of a pulley, (or the idlers), may not be square with the conveyor. This must be corrected by realigning the shaft. In the example, this would be done by repositioning the bearings:  bearing 1 would be moved to the left, and bearing 2 would be moved to the right, until proper tracking was achieved.  If this pulley happens to be the driven one, you would also have to check the drive belt or chain after this adjustment.  After adjustment, test runs will show if the belt is tracking properly.

Other reasons that a belt may be travelling off center for all or part of its travel may include:

• There may be material build-up on one of the pulleys--in that case, maybe the conditions that the conveyor is operating in can be cleaned up with better housekeeping, and a "scraper" or cleaning device can be installed across the belt just ahead of the pulley in question.  
• The load may be landing on the belt in such a way as to deflect the belt's position--in this case attention must be focused on improving the load zone.
• It may only be running off in one section of the belt--this would point to damage to the belt in this area.  Moisture could be causing belt shrinkage on the damaged side.  If this is the case, the belt section which is damaged may be cut out and a new section spliced in.
• The belt may be spliced improperly, and you need to re-splice ensuring that the join is square.
• The belt might be bowed from incorrect storage or handling.  If a new belt does not straighten out when broken in, it will need to be replaced.
• Although this is unlikely in a light manufacturing system such as a seat factory, other belt systems may include "self-aligning" and/or "troughing" idlers which, if not doing their job, can affect tracking.  This may be because of failure or because of incorrect adjustment.  If they have seized due to lack of lubrication, obviously they must be replaced and maintenance must be kept up on them.  If they are set improperly, the idler frames can often be moved.  To affect belt tracking, they may need to be moved so that the high side of the trough is towards the direction of belt travel; or you may shim the high side.  Also, if the belt is just not troughing enough, you may need to slow down the conveyor to allow a heavier load to build up; or change the belt for a lighter, more troughable belt.

Check the archive to see past months' feature industry and quiz:

• cement plants archive1.html  
• pasta factories archive2.html

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