Moulding Tools Research Articles

Thermally sprayed sensor coatings for spatially resolved temperature detection

In injection moulding, knowledge about the cavity surface temperature and its distribution is vital for process understanding and part optimization. The measurement of cavity surface temperatures in moulding processes is often infeasible due to the harsh process environments and the limited amount of space. Therefore, a multi-layer coating system was developed for future measurement of the temperature of the injection moulding tool surfaces. A temperature-sensitive semiconducting TiOx/Cr2O3 coating is applied between two Al2O3 isolation coatings and electrically contacted with NiCr conductor paths outside the isolation coatings. The current study focuses on a proof of concept by correlating the coating’s electrical resistances with occurring temperatures using the modified Arrhenius equation. Furthermore, the reproducibility of measurements is investigated in the temperature range of T = 80–320 °C, which corresponds to the conditions during injection moulding processes. Conducting paths and measurements spots in the multi-layer coating system are designed precisely by ultrashort pulsed laser ablation. Parameters are developed for each individual layer of the coating system without negatively affecting underlying layers. Investigations are conducted focusing on minimal measurement area size resulting in geometries less than A = 1 mm2.

Evaluating the machining parameters for milling P20 HH mould steel using a specific end mill

P20 HH Steel is commonly used for plastic injection mould cavities and tooling. The machining parameters should be decided in such a way that the Material Removal Rate (MRR) is high without compromising on the surface finish. This paper considers the data provided by the steel supplier and end mill manufacturer to arrive the required machining parameters; spindle speed, feed and depth of cut for a computer controlled Vertical Machining Centre (VMC). Taguchi L9 array and Response Surface Methodology (RSM) techniques are used and the output analyzed in MINITAB 17 software.

Stereolithography (SLA) utilised to print injection mould tooling in order to evaluate thermal and mechanical properties of commercial polypropylene

Injection moulding is a widely-used industrial-scale manufacturing method for plastic parts high volumes due to its high-scale economy and manufacture ease for several resins. Moulds are expensive and are only economical for large production batches. Additive manufacturing offers the ability to produce complex designs without moulds; but it isn’t economical and is only suitable for small parts numbers. We describe a hybrid IM/AM process, which utilises AM to produce moulds for IM, employing polymer-based systems for their short processing times, high resolution and ease of finishing. Due to the printed moulds insulating nature, it’s necessary to conduct trials to assess the moulded parts’ properties. Polypropylene (PP), a semi-crystalline polymer often used in IM, was selected for trial. We aimed to evaluate the thermal and mechanical properties of the moulded parts emphasising the PP crystalline structure. The resins used for printing moulds were photocurable polymers, while tooling-grade steel was utilised as industry standard control. Results indicate the insulating nature of the AM inserts affected the moulded parts’ crystallinity, but these parts had similar mechanical properties to parts moulded using a regular steel tool, indicating this system may be used for short and pilot runs in applications where these properties are critical.

Optimising open and closed cooling time for hybrid injection moulding of polypropylene with polyamide inserts from multi jet fusion

ABSTRACT To reduce the lead time and costs for developing short run production injection moulding tools the potential of additive manufactured mould inserts is investigated. These hybrid moulds are compared to conventional steel-based moulds, considering mechanical and thermal differences. For part production and insert material, respectively polypropylene and polyamide12 manufactured by Multi Jet Fusion (MJF) are chosen. Moldex3D simulation results show that lower clamping forces and injection pressures are sufficient upon using MJF inserts due to a 20 times lower thermal diffusivity compared to conventional steel, resulting in thinner skin layers and increased solidification times. Practical injection moulding parameters have been optimized by reducing the cooling time with 75 seconds (60%) using forced convectional cooling at 15 °C. Core and cavity inserts show a deviating cooling behaviour linked to the higher amount of insert material and presence of steel. The wear of the mould inserts is minor after producing 360 parts. .

Numerical Analysis and Fabrication of Battery Holder for Two Wheelers

The high-performance plastics usage is increasing in the automobile field because of its advantages over other metals and alloys. Corrosion resistance, light weight, low cost, flexibility in design are the major advantages of plastics above the conventional metallic materials. In this paper a metal version component converted into plastic version in order to increase efficiency, reduce the overall cost of a two-wheeler and to improve the production rate of component. Different types of material such as PP + 15% TALC, PP + 30% GF, PP + 30% TALC, Nylon 6 + 15% GF, Nylon 66 UF, Nylon 6 UF, Nylon 66 + 30% GF, ASA LI941 and ASA LI913 tested for 10,000km road test, vibration test and fitment test. An injection moulding used to produce the component and ‘Mouldx3D’ software was used for mould flow analysis and other simulation. The different parts of injection moulding tool made up of C45, P20 and D2 materials. Among different materials, ASA LI913 was selected since it has better weather resistance than others and the impact strength matched to metal version component. Finally, it was found that the cost of the component made of Plastic considerably less than same component made of metal.

Analysis of an as-built metal additively manufactured tool cavity insert performance and advantages for plastic injection moulding

Abstract Metal additive manufacturing (MAM) of mould components is associated with cost-intensive post-process finishing operations, which are currently one of the main drawbacks preventing wider industrial adoption of MAM. This work analyses the current possibilities and limitations of MAM for plastic injection moulding tool applications, demonstrating the opportunity to limit post-processes to heat treatment and the machining of the MAM insert outer geometry, which was only intended to ensure the assembly of the insert in the injection moulding frame. The results focused on evaluating the as-built insert cavity geometrical characteristics and the dimensional replication performance of the injection moulding process. The as-built cavity surface texture was comparable to a surface roughness that would be alternatively manufactured by electrical discharge machining (EDM). The cavity texture and features was replicated to the plastic injection moulded samples with an average replication fidelity higher than 95 %, enabling the direct production of inserts with integrated enhanced surface properties and aesthetics. Additional geometrical characteristics, such as global cavity dimensions, corner radii, and the staircase effect of selected features, typical of MAM products, were examined to gather further knowledge of the MAM process resolution and the corresponding replication capabilities of the IM process. Additional considerations with regards to the insert mechanical loading conditions and its durability in terms of the expected fatigue lifetime were addressed, verifying the usability of the MAM insert for production batches of at least 2⋅106 injection moulding cycles. Finally, the improvements in terms of lead-time reduction and production costs associated with MAM compared with conventional tooling technologies were evaluated and discussed, confirming the potential of the presented process chain of MAM for injection moulding tools production.

25 Years Ago November 1995

Mould tool making meltdown; CD-ROM machine tool spec database; ABB’s two decades in robots; DSG’s manual/CNC combo; deburring specialist’s success; aqueous degreasing; cam technology come-back; Renishaw founder’s award

Acceleration of crystallisation rate in injection moulded PLLA by stereocomplex formation

An experimental study has been performed to examine the crystallisation rate of poly(L)lactic acid (PLLA) blended with poly(D) lactic acid (PDLA) in order to reduce injection moulding cycle time. Optically pure PLLA was melt blended with up to 15wt% of its enantiomer PDLA in a twin screw extruder. Flow properties, melt strength and thermal properties of the blends were assessed. PLLA/PDLA blends were then injection moulded and allowed to crystallise using two different methods, either non-isothermally in a high temperature injection mould tool or isothermally by annealing moulded samples in a hot oven after conventional injection moulding. Mechanical and thermomechanical properties of the moulded samples were investigated and optical measurement of crystal formation using polarised light microscopy was performed at conditions representative of both crystallisation methods. Addition of PDLA was found to accelerate crystallisation rate by up to 80% and the resulting morphology demonstrated increased heat resistance, melt strength and stiffness, with a corresponding reduction in strain at break.

Metamodelling of the Correlations of Preform and Part Performance for Preform Optimisation in Sheet Moulding Compound Processing

In the design of parts consisting of long-fibre-reinforced Sheet Moulding Compounds (SMC), the potential for the optimisation of processing parameters and geometrical design is limited due to the high number of interdependent variables. One of the influences on fibre orientations and therefore mechanical part performance is the initial filling state of the compression moulding tool, which is defined by the geometry and positioning of the SMC preform. In the past, response surface methodology and linear regression analysis were successfully used for a simulation-based optimisation of rectangular preform size and position in regard to a part performance parameter. However, the computational demand of these increase exponentially with an increase in the number of design variables, such as in the case of more complex preform geometries. In this paper, these restrictions are addressed with a novel approach for metamodelling the correlation of preform and the resulting mechanical part performance. The approach is applied to predicting the maximum absolute deflection of a plate geometry under bending load. For metamodelling, multiple neural networks (NN) are trained on a dataset obtained by process and structural simulation. Based on the discretisation of the plate geometry used in these simulation procedures, the binary initial filling states (completely filled/empty) of each element are used as inputs of the NNs. Outputs of the NNs are combined by ensemble modelling to form the metamodel. The metamodel allows an accurate prediction of maximum deflection; subsequent validation of the metamodel shows differences in predicted and simulated maximum deflection ranging from 0.26% to 2.67%. Subsequently, the metamodel is evaluated using a mutation algorithm for finding a preform that reduces the maximum deflection.

3D Printing Journey

Banbury-based Plastic Parts Direct is a company of 17 years standing, although its personnel boast some 35 years’ experience in the injection moulding business. Earlier this year, this small company announced it had entered the world of 3D-printed mould tools. Andrew Allcock called by, pre-pandemic, to learn more

Multilayer coatings based on the combination of perfluorinated organosilanes and nickel films for injection moulding tools

Different multilayer coatings consisting of NiO and Ni layers supporting a 1H,1H,2H,2H-perfluorooctyltriethoxysilane/1,8-bis(triethoxysilyl)octane (PFOS) layer have been studied as possible alternatives for typical injection moulding tools. The NiO layer has been obtained by thermal annealing of an electroless Ni layer, whereas the PFOS layer was deposited by dip-coating. The physical and chemical properties of the as-coated steel have been studied by FIB-SEM-EDX, AFM, contact angle, Raman spectroscopy, X-ray photoelectron spectroscopy and PM-IRRAS. Furthermore, cyclic voltammetry, linear-sweep voltammetry, EIS and Mott-Schottky analyses were performed to determine the electrochemical properties of the coatings. Thermally grown NiO leads to a nanoporous surface layer with n-semiconducting properties, whereas the addition of the PFOS induced a decrease in the roughness of the studied samples. The corrosion resistance of the thermally grown NiO is strongly improved in comparison to the non-oxidised Ni-coating. Contact angles showed an effective reduction in surface energy on adsorbed PFOS-film. Injection-moulding tests using polyamide (PA6) and polyamide with 30% glass fibre content (PA6-GF30) were performed on a tool coated with PFOS/Ni to assess the anti-adhesive properties of this coating. After 150 cycles, the PFOS/Ni coating displayed remarkable stability, improved wear resistance and anti-adhesion properties to the studied polymers compared with the uncoated and TiN-coated tool.

Experimental Characterization of Dimensional and Surface Alternation of Straight and Angular Cutting on Self-lubricating Composite: A Wire EDM Approach

Demands on better control over the kerf dimension deviation, surface roughness, and corner accuracy are now on the increase for the two-piece aluminum metal composite mold tools. In this investigation, straight and triangular profile cuts attempted with wire electrical discharge machining (WEDM) on the aluminum 6061 self-lubricating composite-reinforced boron carbide (5–15 vol%) and hexagonal boron nitride particles (10 vol% hBN) fabricated using a stir casting method. Rational video measurement showed an increase in B4C particles reduces kerf width dimension deviation only at TON, TOFF and gap voltage (V) parameters. Optical microscope measurement showed an increase in the corner area inaccuracy increases with both low and high pulse-on duration conditions caused by insufficient material removal and a high order of erosion, respectively. There was a large reduction in corner area inaccuracy with increasing wire feed rate. Surface characteristics were examined using a scanning electron microscope (SEM) and XRD to enable observation of the structural damages and recast layers. Composite with 5% boron carbide showed a re-deposition layer over the machined surface, whereas 15% boron carbide composite went through uneven erosion causing the formation of craters and pits on the cutting surface resulting in higher surface roughness.

Direct Polymer Additive Tooling - Economic Analysis of Additive Manufacturing Technologies for Fabrication of Polymer Tools for Injection Molding

This research project aims to analyze the economic feasibility of Additive Manufacturing (AM) as supportive technology in Injection Molding (IM) tool manufacturing by estimating the potential cost-savings and lead-time reduction. Cost and lead-time considerations during small part quantity production are analyzed by developing an extended estimation model for the integration of AM in tool production. Based on six different real reference parts, the developed model shows the projected savings and the current limitations of AM applications in tool production due to material constraints. Furthermore, this extended model offers a holistic view on part cost and lead-time information, by considering tooling as well as production phases in IM and integrating tool life as a key variable. Hence, this research project closes a literature gap and facilitates the integration of AM into the IM process chain.

Chitosan Modified Bio-Fibre Based Board as Antimicrobial and Anti-Crack Board

Bio-based products represent a key component of global bio-economic growth. In the process of forming a bamboo fibre-based bio board in this study begins with the preparation of bamboo fibres to make it compatible as a filling material in polyester polymers. The mixing of bamboo fibre is done by considering the composition of the fibre material with the polymer used, namely polyester at a ratio of 90%:10%, 80%:20% and 70%:30% of the total weight of the mixture. This mixture is added with a natural substance that has been investigated to have resistance to microbial contamination (anti-microbial), chitosan at a ratio of 1%, 3% and 5% by weight of the total mixture of all components. Bio board printing is carried out using a hot press (moulding) tool. The functionality of bio-based and conventional natural fibre-based materials was investigated for a series of bio boards. The tests include tensile, antimicrobial activity and morphological testing using Scanning Electron Microscopy (SEM). The overall test results put bio board with a ratio of 70%:30% with the addition of chitosan as much as 5% wt as the best sample with a tensile strength value of 147 Mpa, the flexural value of 0.09 kN. The sample shows a good interface appearance of the bond that occurs between the polymer and the filler under the electron microscope.

Ceramic Coatings via MOCVD in Injection Molding Tools to Influence Thermal and Demolding Properties

AbstractTool surfaces can be protected against corrosion and wear by thin film coatings. In addition to the protective properties, ceramic materials with low thermal conductivity, such as yttrium-stabilized zirconium oxide, can thermally insulate tool surfaces. In an injection molding process, the thermal insulation enables a more precise partial tempering and can thus be used to reduce surface defects on the plastic parts produced. Furthermore, the coating can have a positive effect on the demolding of the plastic parts. The coatings are applied in a hot wall reactor by metal organic chemical vapor deposition (MOCVD). This enables a homogeneous application of zirconium oxide based thin films on steel tools with complex 3D surfaces. The performance of the coatings was evaluated in various injection molding tests and assessed by the quality of the manufactured parts.

Mold cooling in thermoplastics injection molding: Effectiveness and energy efficiency

Energy use by thermoplastics injection molding machines is estimated to result in global CO2 emissions in the order of 80 million metric tons annually. Shortening the molding cycle time is a key factor in improving energy efficiency and since cooling occupies a major part of the cycle, effective design and operation of cooling systems is essential. While guidelines exist, there is a lack of quantitative generic information to complement these. To provide this, a parametric study of mold tool cooling is carried out using numerical simulations, examining coolant channel layout, coolant flowrate and temperature, and tooling thermal properties. Briefly, some findings for representative cases include:Within recommended guidelines for coolant channel layout (channel diameter, pitch and distance from the cavity) cooling time for the worst case was found to be 70% longer than for the best.Reduction of coolant temperature by 5 °C (35 °C to 30 °C) allows reduction of coolant flowrate by a factor of more than two while keeping the cooling time unchanged.Use of an aluminum tooling alloy reduces cooling time, as compared with tool steel, by about 30% (15 s–10 s in an example) across a range of coolant flowrates and temperatures.If the maximum plastic temperature variation on ejection is to be no more than 5 °C, coolant channel pitch should be less that 50 mm when the channels are 10 mm from the cavity, and 80 mm when at 20 mm.A coolant heat transfer coefficient of 5,000 W/m2K is recommended. This corresponds to a Reynolds number of 10,000 in a coolant channel of 10 mm diameter.The effectiveness of higher heat transfer coefficients is limited by the thermal resistance of the tool and rapidly increasing pumping costs.Cooling times can be collapsed onto a single line when plotted against an overall thermal resistance that takes into account the coolant channel layout, tooling thermal conductivity, and coolant heat transfer coefficient.A widely promoted formula for cooling time is found to be inadequate and an improved formula incorporating this overall thermal resistance provides better estimates.The need for careful balancing of opposing effects to optimize energy use in cooling is emphasized. The present results will assist with this in the early-stage design, with the aim of shortening cycle time to better amortize base loads. Furthermore, insights gained will be valuable in providing better estimates of cooling time for predictions of productivity, energy use and environmental impacts.

Selective laser hardening of injection mould components on multi-axis machining centers

This research describes the selective laser hardening of components used in the injection moulding industry. The use of fiber-reinforced plastics is accompanied by increased wear in injection moulding tooling compared to conventional plastics. Selective hardening of locations in contact with these plastics prolongs the lifetime of these components. This paper focuses on selective laser hardening of two mould materials, stavax ESR and Sverker 21. Experiments are performed on a laser setup integrated into a multi-axis machining platform, allowing fabrication and hardening within one single clamping. Initial laser hardening tests were performed on ground samples consisting of the component base material. Microhardness measurements showed a maximum achieved hardness of 614HV for Stavax ESR and of 810HV for Sverker 21 after laser hardening. Following initial experiments, three injection moulding components, shredder blades, injection nozzles, and textured moulds are laser hardened.

Design and Fabrication of Cost Effective Mould Tool

As one third of the plastics are injection moulded, the detailed study of design and fabrication of cost effective mould becomes inevitable. This work focuses on the elaborate procedure for designing and fabricating a mould tool. Optimal setting up of injection molding process variables plays a very important role in controlling the quality of the injection molded product. We designed and produced cable clamp for various purposes. What makes this product unique from others is that low cost and high productivity. Solid edge Software is used for designing and analysis. Material used for this production is polypropylene. The production rate will be high with low cost.

Tool Life Performance of Injection Mould Tooling Fabricated by Selective Laser Melting for High-Volume Production.

Rapid Tooling processes are developing and proving to be a reliable method to compete with subtractive techniques for tool making. This paper investigates large volume production of components produced from Selective Laser Melting (SLM) fabricated injection moulding tool inserts. To date, other researchers have focused primarily on investigating the use of additive manufacturing technology for injection moulding for low-volume component production rather than high volume production. In this study, SLM technology has been used to fabricate four Stainless Steel 316L tool inserts of a similar geometry for an after-market automotive spare part. The SLM tool inserts have been evaluated to analyse the maximum number of successful injections and quality of performance. Microstructure inspection and chemical composition analysis have been investigated. Performance tests were conducted for the four tool inserts before and after injection moulding in the context of hardness testing and dimensional accuracy. For the first reported time, 150,000 injected products were successfully produced from the four SLM tool inserts. Tool inserts performance was monitored under actual operating conditions considering high-level demands. In the scope of this research, SLM proved to be a dependable manufacturing technique for most part geometries and an effective alternative to subtractive manufacturing for high-volume injection moulding tools for the aftermarket automotive sector.

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