IDENTIFICATION & MARKING

Systems Mark Engine Blocks,
 Give Bores A Passing Grade

A US automotive manufacturer needed to imprint manufacturing codes, including cylinder bore grades, on the front of its engine blocks. Bore grades also needed to be marked on the top of the blocks for pistons, so that they could be easily matched to cylinders for optimum fit and engine efficiency.

This production line uses highly automated machining centers, with rough castings entering on a conveyor where they are machined, measured, bored, milled, and drilled. When the blocks exit the computerized machining center they are nearly finished. To mark each block at this stage, a Telesis PINSTAMPr TMM5100 is mounted inside the machining center. The marking system receives data directly from the machining line and imprints it on the front face of the engine block.

The bore grade designations identify the actual cylinder diameter variance from the nominal on each of the six cylinders of the 2.5L and 3.0L engine blocks. The numerals 1, 2, and 3 denote: (1) a cylinder that is smaller than the nominal diameter by 0.020" or less; (2) a cylinder that is equal to the nominal diameter; and (3) a cylinder that is larger than the nominal diameter by 0.020" or less. In addition to the permanent marking on the front of the engine blocks, the automaker had been using an ink jet marker to imprint the bore grades on the top of the blocks. However, these marks were often illegible by the time the blocks reached the assembly area.

When another marking station was needed, the automaker again chose Telesis' TMM5100. For this application, a custom six-pin cartridge was designed to mark the six characters of the bore grades in a column rather than a single line. This would make it easier for the assembly workers to read the characters when matching the pistons to the cylinders. The cartridge has six pins in a split configuration. Three pins mark the bore grades for the three cylinders on the left. A space separates these marks from the right side cylinder bore grades, which are marked by the second set of three pins. A carat at the top of each set indicates left or right cylinder bore grades.

The marking system was designed to use the data from the existing marking system computer. A custom support structure was built to mount the marking system to the conveyor, positioning it to mark the top surface of the engine blocks several stations downstream from the first marking station.. This "inchworm" type conveyor moves the engine blocks up and down, as well as forward. The marking head has to retract from the marking position between print cycles to avoid collision. A pneumatic slide mechanism moves the marking head back about 11" to ensure clear passage for the engine blocks.

The automaker wanted to use the same electronic console and computer for both marking systems. To accomplish this, custom software was written to enable two active marking patterns. A queue stores the bore grade data for access by the second marker. The sequence of marking operations is:

• The first marking system imprints the appropriate codes on the front face of the engine block
• The bore grade data is placed in a queue for later retrieval by the second marking system
• The engine block exits the machining center for additional manufacturing steps
• The engine block enters the second marking station where a PLC (programmable logic controller) activates the slide mechanism
• When the marking head is extended, the PLC signals the second marking system to imprint the set of bore grades from the queue
• The second marking system signals the PLC when finished, and the marking head is retracted to the idle position.

The flexibility designed into the Telesis system enables the manufacturer to place the marker wherever it is needed on the assembly line without software modifications. Since the bore grades are stored in the queue until retrieved by the system, it does not matter where in the manufacturing process the second marking system is located.

The total time required to mark the bore grades on the top of an engine block is about three seconds: one second to extend the marking head, one second to mark the bore grades, and one second to retract the marking head to the idle position. The eight characters (two carats and six bore grades) are " high in a 5 ' 7 matrix font. Two TMC100 controllers, one for each marking system, and a single computer share a wall-mounted NEMA-rated enclosure.