Red Arch Manufacturing Ltd has recently received requests from several OEM automotive customers to produce high quality heat shields with reduced investment costs. The RA Advanced team has taken on this project and developed a creative solution which minimizes tooling and production costs.
The driving factor for this work is to drastically reduce tooling costs for our customers and to provide flexibility and adaptability to the heat shield manufacturing process. Current processes often use expensive press tools machined from solid steel. Red Arch believes that this is excessive and unnecessary for pressing thin aluminium heat shield materials, and through a broad programme of research has identified a new, cost-effective method to deliver high-quality pressed heat shields without high cost.
Our process starts by 3D printing two casting moulds for two-part press tools using conventional, readily available materials (PLA or PVA). This allows us to rapidly (typically less than 48 hours printing time) incorporate custom details into the heatshield design at a fraction of the cost of machining traditional metal press tools.
Our in-house Raise3D Pro2 3D printer has a build volume large enough to accommodate casting moulds with dimensions of 300(L) x 300(W) x 250(D) mm. Where larger heat shields are required, we can produce a modular casting mould which assembles to produce a much larger press tool.
As part of the development process, we have produced an example casting mould with approximate dimensions of 250 mm x 300 mm, printed in PLA. The material cost of the combined sacrificial casting mould is less than £100.
Figure 1 – A 3D model of the Red Arch casting mould (left) and the final 3D printed PLA casting mould (right) for casting the positive press tool.
Having produced the casting moulds, Red Arch identified toughened polyurethane resin as an ideal press tool material, with excellent mechanical properties (less brittle and more resilient than many plastics, e.g. PVC), being machinable and allowing for fine surface detail reproduction. At a material cost of less than £15/kg, press tools are produced quickly and cheaply to any design.
Each half of the tool was cast and, with a cure time of only a few hours, the 3D printed casting moulds quickly removed to reveal a tough, detailed press tool. Guide rods were added to ensure evenly applied vertical compression and process repeatability.
Figure 2 – Side-by-side view of the two halves of the Red Arch press tool, cast from toughened polyurethane (top) and the assembled press tool with guide rods (bottom)
With a rapid prototype tool produced in a matter of days, Red Arch completed initial pressing trials at our Innovation Centre, making use of a laboratory scale 20 T hydraulic press. A flat, pre-cut blank of 0.5mm embossed aluminium heat shield material was placed between the press tool halves. The pressing force was increased in 1 T increments from 1 T to 10 T.
Figure 3 – The Red Arch two-part polyurethane press tool with 0.5mm aluminium blank, before pressing, at the RA Innovation Centre.
Figure 4 – Progression of heat shield forming detail at pressing forces of 1 to 9 tonnes. Fine detail emerges in the pressing at 4 – 5 tonnes.
Repeating these tests illustrates that the polyurethane press tool is sufficiently robust to form 0.5mm aluminium into finely detailed shapes at forces as low as 5 T, with the press tool able to tolerate at least 10 T.
Figure 5 – Heat shield pressed using with 10 T, using RA polyurethane tooling.
Through a series of tests we have identified that by reducing the amount of brim material, which is pressed flat or folded, surface details are clearly visible with reduced pressing force, as the reduced folded brim provides significantly lower resistance to forming.
This case study has shown Red Arch’s ability to rapidly prototype and cast a tough polyurethane press tool capable of producing detailed heat shield pressings for automotive applications, with as little force as 4 to 5 T.
Red Arch has initiated the process of sourcing a larger-scale, 54 T press with 4 independently operated platens, each with a bed area of 775mm x 1550mm, giving a total pressing area of 3100mm x1550mm and a maximum opening height of 765 mm, providing capacity to produce heat shields with up to 380 mm draw depth. The platens can also be locked together in combination to press large area heat shields occupying the total 3100mm x 1550 mm bed area.
Our plan to maximize the benefits of such a press include dedicated process stages for each of the 4 platens:
- Cutting blanks from aluminium sheet
- Pressing with polyurethane press tool
- Trimming excess material from edges
- Folding sharp edges where required
We envisage that the complete heat shield production process can be competed at a single workstation by a single operator, reducing overall cost and improving efficiency, without sacrificing product quality and dimensional accuracy. The new heatshield production cell will be commissioned and ready for first production parts in early 2020.