Promess marries riveting and electronics

The closed-loop Interwest system monitors and controls the entire riveting operation. Click to enlarge

Alone, riveting usually is not considered as an alternative in applications where high-precision functional results are required. But, Promess Inc. has found, when combined with a modern multi-axis position-sensing press and a sophisticated monitoring and control system, it can deliver significant cost savings that cannot be matched by some other systems.

Such a marriage has taken place at Interwest Automation, which makes latches (and other seat components) for cars, trucks, buses, and off-highway equipment. Latches are a difficult application, Promess says, because they require strength and durability combined with a narrow range of actuation effort on the part of the user: apply too much peen, and the latch is difficult to operate; apply too little, and the assembly is not reliable.

The Interwest Solution uses a Promess electromechanical assembly press (EMAP) system to drive an orbital riveting head mounted on the ram of an otherwise conventional riveting press. The EMAP has integrated sensors and provides closed-loop feedback for accurate control of the riveting operation. By connecting the EMAP to a Promess electromechanical assembly controller (EMAC), a completely closed-loop system is created to monitor and control the entire operation. The EMAC provides both the control capability and the real-time process-monitoring intelligence required to make the application work.

The "real key," according to Promess, is Signature Analysis, a technology in which the characteristics of a known good operation are captured and used as a benchmark for subsequent production operations. By setting upper and lower tolerances for this "signature," production of good assemblies is ensured without the need for subsequent inspection.

The EMAP delivers real-time torque and position information to the EMAC, which continuously compares that information to the profile of the nominal operation. Any deviation beyond programmable limits will flag the assembly as a potential problem and alert the system operator. In essence, the process "clones" a good operation by ensuring that all subsequent operations exhibit a similar torque/distance "signature" curve.

This Promess electromechanical press is set up for the Interwest seat-riveting operation.

Signature Analysis not only detects bad assemblies, it frequently pinpoints the cause of a deviation. The exact shape of the signature provides important information about the individual parts being assembled, which can be used as a control input to other processes. For example, rivets that are too hard or soft or too short or long will produce a distinct change in the signature, as will out-of-tolerance details such as hole diameters.

Interwest's system is a three-axis orbital riveting station designed to handle a range of rivet sizes in multiple locations on multiple assemblies. The fully programmable system can handle rivets of different lengths and diameters anywhere within its working envelope. Each of the rivets on the assembly are analyzed and compared to a nominal torque/distance signature for that specific rivet.

In this application, the Promess EMAC controls both the electromechanical press with the orbital riveting operation and the X/Y motion of the pallet while performing the signature analysis, giving the user a common interface for all motion programming. The system can be reconfigured for a variety of parts by changing the pallets that carry the work-holding fixtures and reprogramming the control.

- Patrick Ponticel

TAOS sensor digitizes light

The TSL2550 from TAOS is said to be the first ambient light sensor that converts light intensity to a digital output capable for display and IP uses.

The first sensor that converts ambient light intensity to a digital signal capable of direct SMBus interface has been developed by Texas Advanced Optoelectronic Solutions, Inc. (TAOS). The TSL2550 helps reduce overall system power by measuring available light to control display-screen backlighting in GPS-based navigation systems as well as overall instrument-panel lighting. Display screen backlighting, which can account for 30-40% of total platform power, now can be adjusted automatically with the new single-chip light sensor.

The TSL2550 uses an all-silicon technique that combines two photodetectors to measure light brightness as perceived by the human eye. One photodetector is sensitive to both visible and infrared light, while the other is sensitive only to infrared light. The outputs of both are converted to a digital format and stored in separate registers accessed through the SMBus. The combined information compensates for the effect of the infrared component of ambient light, thereby approximating the response of the human eye, and is used to calculate light intensity in units of lux. The technique eliminates the need for a costly photopic filter. The ratio of infrared to visible light can be used to determine the type of ambient light source (i.e., incandescent, fluorescent, sunlight), thereby allowing more intelligent control of display contrast and/or color.

The TSL2550 uses an analog-to-digital converter that can measure light over a 12-bit dynamic range. Its integrating-conversion technique virtually eliminates the effect of flicker from ac-powered lamps, thereby increasing the stability of the measurement.

- Kevin Jost

Technifor marking unit

The CN312Cm marking unit from Technifor uses Data Matrix technology and a camera mechanism to verify the correct markings and thus ensure part traceability.

The CN312Cm is a compact marking unit with a 50 x 40 mm (2 x 1.6 in) marking window from Technifor, Inc. The unit was designed to provide improved depth consistency without part distortion while meeting IAQG (International Aerospace Quality Group) marking criteria on metal and plastic parts in various shapes and surface conditions, according to the company. The CN312Cm uses 2-D Data Matrix symbology in conjunction with an innovative 100% mark-verification system from Technifor that uses a camera mechanism to physically "see" that each part receives the intended mark for thorough traceability. Data Matrix technology, developed originally by RSVI (Robotic Vision Systems Inc.) and NASA, is in the public domain.

The electromagnetically powered CN312Cm has a low operating noise and the ability to be integrated into automatic or semi-automatic assembly lines, test stations, and other industrial applications. The unit is also available column-mounted for stand-alone requirements. User-friendly integrated software that eliminates the need for an external PC or PLC to program the unit allows calculation of variable data that includes date codes, shift codes, serial numbers, and a full range of management of text style including choice of fonts, logos, compression, spacing, and automatic centering. The unit also provides linear, angular, radial, inclined, inverted, and mirror marking. Character marks range from 0.5 to 45 mm (0.2 to 1.8 in) in height in steps of 0.1 mm (0.004 in).

- Jean L. Broge