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Assembly in Action: Robotic Laser Cuts and Pierces Frame Rails

Northern Tube (Pinconning, MI) was early to recognize the advantages of CNC bending and robotic laser cutting over traditional drill and pierce equipment in hydroform applications. The company is a Tier Two supplier of tubular products for light-, medium- and heavy-duty trucks. Searching for a way to increase quality and productivity, the company recently replaced its original robotic laser cell system with two new cells featuring Fanuc (Rochester Hills, MI) robots mated with Trumpf Laser Technology Center (Plymouth, MI) lasers.

The system consists of two identical cells. Each feature two laser-cutting robots and a Ferris wheel type part indexing device. The system also incorporates two material handling robots, incoming conveyor, flush booth, operator console and main power panel. A key improvement is its ability to verify the presence of the holes cut during the process vs. the old post-process probe method. A beam switching capability allows the supplier to fix any problem during the cutting process, providing high uptime.

The laser portion of each cell comprises two HL 1003 D 1-kilowatt Nd:YAG lasers. The HL 1003 D laser has a beam quality of 12 mm-mrad, which is optimal for cutting. The focal diameter and position of the beam remain constant, even when the laser power is changed. This allows consistent processing results.

Minimizing the time the laser cavity is opened, so that contaminants have little access to reflective surfaces, is key to successful operation of lasers in a harsh plant environment. The model HL 1003 D has a modular design that protects the internal laser cavity. Each laser cavity has its own power supply that is a slide-in module for easy service and maintenance.

Flash lamps are in the lid of the laser resonator. When the top is opened, placing a cloth over the chamber to shield the mirrors protects the laser cavity. The HL 1003 D resonator is very reliable, operating with no water leaks, pumping chamber faults, rod failures or fiber faults.

The lasers deliver fiberoptic beams through Z-axis cutting nozzles that use noncontact height sensing. Two six-axis M161 robots manipulate the nozzles of each system. Each robot moves to a specific point where the laser beam is activated to produce the specified hole in the part.

A dual trunnion Ferris wheel part indexer that transfers the parts in and out of the laser enclosure holds the frame rails. Both trunnions can manipulate the rail during processing to allow ideal positioning to the robots.

Frame rails are delivered to the robotic cells by two-tiered rail conveyors, which deliver both right and left rails. A material handling robot then transfers the rails to the Ferris wheel indexer and the flush booth. A second material handling robot takes the rails and stacks them in a pallet.

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Each frame weighs about 40.5 kilograms and is made from 4-millimeter-thick cold rolled steel. The lasers' cutting speed is 3 meters per minute with hole-to-hole repeatability of ±0.3 millimeter. The holes vary in size from 6 to 72 millimeters and come in a variety of shapes. The two robots in each system cut 60 holes and trim the rails to length, processing a left and right pair in 5 minutes.

An added value of the system is the availability of remote diagnostics. If the system experiences trouble, the operator can dial an online troubleshooting service. Up to 600 system parameters can be monitored and accessed at any time. Connecting with a modem permits remote transmission of all operating and control data, allowing help to analyze and quickly provide fault correction.

For more information on the robotic laser systems, call Fanuc at 800-477-6268, visit www.fanucrobotics.com or Reply 3.

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