Injection moulding processes for plastic components can benefit from 100% quality control using thermal imaging inspection.
Precision sensor manufacturer Micro-Epsilon has developed an inline thermal imaging system for the early detection of defects and quality fluctuations in injection moulded parts. The system is particularly well suited to large, complex, multi-layered or transparent moulded parts and can be easily retrofitted to existing injection moulding machines. Materials include all plastics, polymers, elastomers, rubber and even glass.
With modern injection moulding machines, the injection-moulded component is removed by a robot or other handling system and transferred to a conveyor system or transport container. Automatic removal, particularly of high value, high specification moulded parts, involves making a ‘good/bad’ quality decision on the part, in order to avoid further problems downstream.
By looking at the temperature of the parts as they leave the injection mould, the moldCONTROL infrared thermal imaging system from Micro-Epsilon is able to detect any defective areas of the component or fluctuations in temperature that may indicate a quality issue. Weaknesses or thinning in a part can also be identified, which can be used to modify the mould tool design to improve the process.
In order to evaluate moulded parts, the handling system or robot presents the newly injected part to the moldCONTROL thermal imaging camera (from one or more sides) while an infrared image is taken. This recorded image is synchronised with the handling system such that the image(s) are taken automatically after the corresponding measuring position has been reached.
100% quality control of parts
moldCONTROL inspects the complete part according to predefined parameters. 360-degree inspection is possible, with up to six views of a moulded component. The integral evaluation software compares the infrared images associated with the component (actual) to stored references (target). Based on the identified temperature differences (references to current component) a good/bad decision is made. This decision is reported back to the handling system, which sorts or removes any defective parts.
Chris Jones, Managing Director at Micro-Epsilon UK comments: “Up to now, injection moulding companies have relied on vision cameras or other shape detection systems to inspect the geometrical shape of moulded parts, but these are relatively expensive compared to moldCONTROL and do not tell you anything about the quality of the mould – only if the geometry is correct.”
“However, with moldCONTROL, the thermal imager measures the temperature distribution of the moulded part immediately after it is injection moulded. From this, the user can see whether that part is the correct geometry and thickness. moldCONTROL records the defects, providing the operator with a photo image of the defect and a thermal map. Due to the high resolution and temperature accuracy of the thermal imager, combined with the bespoke evaluation software, moldCONTROL is a unique inline inspection system for quality, production, automation and process control environments, particularly where continuous improvements are critical to the injection moulding process,” adds Jones.
“If you are moulding transparent parts, vision cameras can find inspection of these parts very difficult. When measuring the temperature distribution, as MoldCONTROL does, transparent parts are no problem whatsoever. Optimised production processes require an effective quality control system. Defects in injection moulded parts that are recognised late can result in high failure costs, reduced productivity and wastage. MoldCONTROL is a high precision inline inspection system that provides 100 per cent quality control of every moulded part produced,” explains Jones.
moldCONTROL is able to detect a number of different defects, including incomplete injected components; temperature deviations in extruded parts; temperature fluctuations in the mould tool; temperature deviations of individual cooling circuits; low or fluctuating pressures (via the de-moulding/removal temperature); and is able to detect missing pieces inside a moulded 2-component part by analysing the temperature profile.
The evaluation software supplied with moldCONTROL operates independently of the injection moulding machine. A trigger is set up to inform the thermal imager when to take a snapshot profile of the moulded part. Using the software provided, operators can configure and adapt moldCONTROL to suit new moulded parts with little training required. It’s a fully automated 100% inspection system that can be installed and commissioned with support from Micro-Epsilon engineers.
Today, many injection-moulded parts have complex shapes and multi-part moulds. Traditional vision cameras struggle to inspect moulded parts like these, particularly if they are multi-layered or if a potential colour contrast issue arises with, for example, dark grey and black coloured parts. Similarly, transparent or translucent moulded parts are equally difficult to inspect using traditional vision cameras, as they do not have the required resolution that moldCONTROL has.
The moldCONTROL system includes a compact, high speed thermal imaging camera, a miniature industrial PC, a 10m USB cable, an I/O unit for process integration and unique evaulation software. A range of IR cameras are available from Micro-Epsilon to suit the size of the moulded part. The complete system is delivered from Micro-Epsilon.