Rapid tooling: investigation of soft-tooled micro-injection moulding process characteristics using in-line measurements and surface metrology

Abstract

Purpose The purpose of this study is to demonstrate and characterise a soft-tooled micro-injection moulding process through in-line measurements and surface metrology using a data-intensive approach. Design/methodology/approach A soft tool for a demonstrator product that mimics the main features of miniature components in medical devices and microsystem components has been designed and fabricated using material jetting technique. The soft tool was then integrated into a mould assembly on the micro-injection moulding machine, and mouldings were made. Sensor and data acquisition devices including thermal imaging and injection pressure sensing have been set up to collect data for each of the prototypes. Off-line dimensional characterisation of the parts and the soft tool have also been carried out to quantify the prototype quality and dimensional changes on the soft tool after the manufacturing cycles. Findings The data collection and analysis methods presented here enable the evaluation of the quality of the moulded parts in real-time from in-line measurements. Importantly, it is demonstrated that soft-tool surface temperature difference values can be used as reliable indicators for moulding quality. Reduction in the total volume of the soft-tool moulding cavity was detected and quantified up to 100 cycles. Data collected from in-line monitoring was also used for filling assessment of the soft-tool moulding cavity, providing about 90% accuracy in filling prediction with relatively modest sensors and monitoring technologies. Originality/value This work presents a data-intensive approach for the characterisation of soft-tooled micro-injection moulding processes for the first time. The overall results of this study show that the product-focussed data-rich approach presented here proved to be an essential and useful way of exploiting additive manufacturing technologies for soft-tooled rapid prototyping and new product introduction.

Investigating demoulding characteristics of material jetted rapid mould inserts for micro­injection moulding using in­line monitoring and surface metrology

“…The significant increases in Ed. for FA experiments compared to SA also signify that cooling in between cycle times is crucial, which will keep the soft mould inserts below their glass transition and minimise mould and, hence, part deformation (Gülçür et al, 2023a). is due to the activation of uncured bonds on the mould surfaces, which reacts with the injected polymer at 190°C, leading to occasional deviations, particularly with matte inserts, due to the imperfections and surface irregularities and variations in P c .…”

“…Advances in additive manufacturing (AM) enable the prototyping of product or mould designs with significant design flexibility and abundant material selection with ever-improving properties (Kokare et al, 2023). This resulted in an increasing interest in AM tooling, or "rapid tooling", made from polymers that can be an alternative to accelerate product and process development for hot embossing, injection moulding and forming processes (Gülçür et al, 2023a;Gohn et al, 2022;Kuo et al, 2021;Kuo and Li, 2017). AM challenges conventional machining processes in delivering mould or cavity features in terms of cost and speed by using its additive nature (Kuo et al, 2022).…”

Rapid Tooling for Microinjection Moulding of Proof-of-Concept Microfluidic Device: Resin Insert Capability and Preliminary Validation

“…The combination of the material and manufacturing technologies to produce an insert, as a tool for a mould, can affect the efficiency, life cycle capabilities, and required lead times for tooling production [29]. In recent years, soft tooling has emerged as novel approach, alongside hard tooling, for the rapid fabrication of mould inserts, despite having limited cycle capacity [30]. Although metallic inserts such as stainless steel, nickel, and bulk metallic glass are preferred for moulding devices with micro-structures and precise surface features like LOC [31], these materials do not allow rapid tooling for µIM, a crucial factor for the effective prototyping and scaling of products.…”