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The Challenge:
To develop an online inspection system for 5000 tonnes SPS press and integrate it with existing system. The SPS press is used to punch holes into metallic sheets of 8-12 meter long with 400 mm width. These sheets are later Bent, processed to form chassis of Light Motor Vehicles (LMV) and Heavy Motor vehicles (HMV) manufactured by Ashok Leyland.
As the cycle time of SPS press was 20 sec/sheet with line rate of 4m/sec, the challenge was in capturing the entire image, and counting number of punches on line and intimating to the user actual number of punches in the sheet.
The Solution:
The automated inspection system for SPS 5000 tons press uses National Instruments PCI- 1428, PCI- 6518 and Atmel line scan camera. The software was developed using NI Lab VIEW 8.0 and NI Vision 8.0.
The SPS 5000 tons press is an automated system that picks individual sheets and punches holes as per the configuration selected by the user. Once the sheets come out of the system the sheets are stacked. The inspecting system is positioned to monitor the sheets that are coming out of the punching machine. This is the only press contributing to the entire production of LMV’s and HMV’s manufactured by customer.
The inspection system acquires images from punched sheets coming from the output conveyor moving at 4 m/sec. The desired accuracy of 0.5mm on a 12 m long sheet is not feasible using ‘Area scan’ camera, hence we used ‘2k Line scan’ camera with maximum scan rate of 28k lines/Sec. Also we used High frequency fluorescent light source which operates at 40 kHz so that we can capture the image of the object moving at high speed. The Off delay timer is used to avoid Triggering delay between Proximity sensor and Camera.
The Chassis are the main structure in assemble line on to which various components will be mounted and assembled in a stage by stage manner at the end of the assembly line a full fledged vehicle is assembled. If the absence of punch is not determined at the initial stage of the assembly line, then a significant amount of time, material, labor is wasted contributing to production loss. Hence it is of prime importance to detect any absence of punch during punching stage it self before the sheet goes to the assembly line. In the absence of hole the signal is sent to PLC of the SPS which will stop punching machine. This contributes to save time and reduce re work/wastage of material and increase the production rate significantly.
Application:
The inspection system requires the length of the sheet and number of holes as inputs before starting the counting process. The user selects configuration according to the sheets being monitored.
The camera starts the acquisition based on the proximity/limit sensor the image acquisition. After the length of the sheet is scanned the system analyzes the image captured and counts the number of holes present on the chassis. If the holes counted are matching with the configuration selected a digital signal high indicting that the sheet is ok will be provided. If the above condition is not met then a low signal is generated. The result along with the configuration details are maintained in database for report generation.
The schematic setup shown above in figure 1.0 indicates the existing machine setup.
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