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Manufacturing and optimization of a PEEK scroll by fusible core injection moulding

Final Report Summary - THERMOPLASTIC SCROLL (Manufacturing and optimization of a PEEK scroll by fusible core injection moulding)

Executive Summary:
The objective for this program is to design, build and test a scroll in thermoplastic, without jeopardizing the functionality of the scroll, in thermoplastic material in order to reduce the component weight by 50%, reduce manufacturing cost by 30% and reduce lead time by 50%. The second objective is design a scroll such that it can function in a harsh environment with high ambient temperatures and a high mechanical fatigue environment.

The objectives for this program are met. Egmond Plastic has manufactured several inlet scrolls for this program which are approx. 50% lighter compared to the existing scroll for considerable lower cost and lead time using the fusible core technology despite the various challenges.

The challenges in this program were severe and included the following:
- The fusible core technology has never been used with the type of thermoplastic specified in the program.
- The fusible core technology has never been used for such a large component such as an inlet scroll for a single aisle aircraft
- In the air management system for an aircraft, no components have been made from Peek thermoplastic material using the fusible core technology

The program has shown and demonstrated the following:
- The program has demonstrated that the use of this material (Peek with 40% reinforced carbon fibres) can be successfully applied for an inlet scroll.
- The program has demonstrated that the fusible core technology can be applied successfully with large a component such as an inlet scroll.
- This is the first time that the fusible core technology in combination with Peek thermoplastic has successfully been applied for an inlet scroll of the air management system for a typical single aisle aircraft.
- The program has validated that the fusible core technology has a high degree of reproducibility. Several inlet scrolls in various production batches have been produced.
- The program has achieved readiness level 5.
- The fusible core technology has demonstrated that a high degree of integration can be used. In other words, an assembly of multi components can be produced as one component, reducing the number of possible failures.

The change from aluminium towards Peek thermoplastic material will result in some major savings during the lifetime of an aircraft. It is expected that the jet fuel saving for an average single aisle aircraft will exceed the €35.000,00 over the life time. It is expected that other parts can be replaced with thermoplastic material to further reduce the weight of the air management system of an aircraft and reduce the CO2 emission of an aircraft.

Project Context and Objectives:
The goal of this project is to design and produce an inlet scroll from thermoplastic using a fusible core technology with injection moulding. A typical inlets scroll for a mid size, single aisle, aircraft have been used as a basis for this project and the design has been modified in order to reduce the weight by 50%.
The scope of work has been focused around the selection of an inlet scroll and to review the possibilities to produce this inlet scroll using fusible core technology in combination with injection moulding. The partners in the program proposed to use an existing inlet scroll from a typical midsize and single aisle aircraft as a starting point. The design has been modified considerably to maximize the benefits of using the fusible core technology. This technology allows us the integrate a two piece part into a single piece resulting in a 50% weight reduction compared to a aluminium version.
Extensive work has been carried out by the partners to modify the model such that it meets the mechanical requirements of this application. In addition the new design has been reviewed against the requirements of the fusible core technology. Where required, the model has been modified for moulding purposes.
In the meantime a provisional mould design has been made in order to minimize the risk and to assist the design engineers with advise on the manufacturability of the inlet scroll.
The project faced a considerable delay due to the fact that WP3 required much more time than anticipated. A revised plan was presented to the stake holders with a proposal to maintain the end date of the program.
The project met the expected outcome. An Peek inlet scroll, made through the fusible core technology, was presented at the end of the program.

Project Results:

This project consisted of several challenges which stretched the boundaries of injection moulding: Each of them are described below:
- Identify the correct material for the fusible core. As described in section two, Bismut material is the common material to be used for the fusible core. However, the typical applications in which bismut was used were for low or mediun temperature materials. This mass temperature of these materials varies between the 200 degr. C and 300 degr. C. The inlet scroll specifications specifies the use of Peek 90HFM40 material. This material has a mass temperature for injection moulding around the 380 degr. C up to 420 degr. C. The risk is that the fusible core melt during injection process, resulting in various foreign material in the thermoplastic inlet scroll. After further investigation, the decision was made to use a Bismut alloy which has a different melting point, allowing to withstand the injection pressure of the machine, cope with the mass temperature of the Peek 90HFM40 and at the same time provides easy removal after moulding without damaging the inlet scroll.

- Heat management of the mould is key essential for the success of the moulding process. To extend the life of the fusible core (or in other words, to extend the time that the core starts melting) the mould should have provision to deal with various temperatures. Basically the mould can be divided into two sections:

o The hot section in which the temperature is in the range of 160 to 200 degr. C. This temperature is required to get the correct flow of Peek material. This data is provided by the supplier of Peek material. Heating is done by means of oil heaters
o The cold section of the mould. This section is required to cool the fusible core during injection moulding to extend the life time of the fusible core. Cooling is done by means of water coolers

- The injection pressure of 120 MPa was a considerable challenge in the program. The injection pressure, required to get a 100% filled product, created a tremendous pressure on top of the fusible core such that the fusible core started to bend. It was essential to improve the flow path such that the pressure build up on both sides was identical to minimize the pressure differential between the upper side and lower side. Extra flow paths were created to achieve this result.

- No other injection molding company have been able to mould a thermoplastic product using a fusible core in combination with Peek material with 40% reinforced carbons. This project is the first demonstration of the use of Peek 90HFM40 with a fusible core. The program has demonstrated that the unique features of Peek 90HFM40 can be used with a fusible core.

- The complexity of the thermoplastic inlet scroll not only required the unique use of a fusible core but also required several unique features on the outer side of the inlet scroll. Several undercut issues have been solved by using separate insert blocks in the mould which have been manually removed after moulding. By using these features, the required changes in the design of the inlet scroll were minimal. The benefit is that a one to one bench marking can be achieved with the current aluminum design.

- Another challenge was that all the stainless steel inserts required overmoulding. In other words, the inserts were inserted in the mould before the actually moulding process started.

- The removal of the fusible core as a post moulding activity was a substantial challenge and risk. As mentioned earlier, a certain temperature was required to melt the fusible core. However, although the melting point of Peek is around the 320 degr. C.,the bismut melting temperature is beyond the glass temperature of Peek. As a result, the Peek material is considerable weaker and the dimensional stability is less. When the melting process takes too long time, this can result in an inlet scroll not meeting the dimensional properties anymore. The fusible core can be removed by means of an oil bath. It is therefore required, that the temperature control of the oil bath is under control and the time set to melt the core is fixed. After several attempts, the correct settings were found. We have seen two inlet scrolls out of specification due to the fact that the duration of melting process was too long in time.

- To meet the tight tolerances on the drawing. Several tolerances were so tight that this tolerances can only be met by a post moulding, machining operation. The inlet scrolls were machined to meet the drawing. Due to the high content of carbon fibers, the wear on standard tooling were considerable. Investigation has found out that special coated tooling is too be used for machining the inlet scroll. For as far as spindle speed and spindle feed, normal settings (as it is stainless steel) can be used.

- The size of the inlet scroll was another major challenge. Due to the size of the inlet scroll, a 800 Ton injection moulding machine was required, able to heat up the Peek material towards 425 degr. C.


This program has demonstrated that it is possible to injection mould a inlet scroll for a single aisle aircraft with Peek carbon reinforced fibers using a fusible core. 10 demonstrators have been sent to the topic manager for testing purposes.
This program demonstrated also that fusible core technology allows for further integration. A two part product has been successfully transferred into a one piece product.
In terms of of benefits, thefollowing major benefits can be listed:

- Less CO2 emision due to reduced fuel consumption:
By moving away from aluminium towards Peek material a 48,4% weight savings is to be expected. Based on a typical single aisle aircraft with approx. 150 seats (such as a Airbus 320 or Boeing 737), the following saving is to be expected of a flight from London to Dublin (1,2hr).

The savings per kg. 0,67kg for a 1,2 hr. flight. The total fuel saving per 1,34kg based on two inlet scrolls per airplane. That is 174 gram CO2.per flight.

- Improved unit price:
It is expected that the cost for Peek based inlet scroll is as follows:
- The expected recurring price is approx. 30% less compared to the aluminium version. The savings will be even higher when we take into consideration that the assembly work is reduced.
- The breakeven point for the non-recurring cost, including the manufacturing of the tooling, is to be expected at 250 units. This will mean that the return on investment is within half a year.

- Based on product readiness levels, this program has reached a readiness level of 5. Egmond Plastic has demonstrated that the fusible core technology can be used to produce an inlet scroll. We also optimized the moulding process and post moulding activities. However, further process optimization as well as tooling optimization is required for readiness level 6.


The following recommendations are to be made:
- The heat management in the mould has to be improved. Especially in the area of the outlet duct, the slides require a further improvement in the heating circuit. The current heating circuit is not sufficient. As a result a higher injection pressure was required in order to get the outlet duct completely filled. The improvement will result in a lower injection pressure thus lowering the pressure on the fusible core.
- The fusible core consists of various sharp corners. This will lead to a reduced life time of the core during moulding. Due to the flow, the sharp corners can easily melt. Fillits are required to be added for future scrolls. Fillets will reduce the amount of possible wear of the core during injection moulding.

- The mould is a demonstration mould only, produced to produce a handfull demonstrators (E.g. the slides are operated by hand only). For serial production, heat management of the mould should be further optimized as well as hydraulically operated slides.
- Add flow paths on the outside of the scroll. This will result in a lower pressure on top of the fusble core and reduced the risk of a collapsible core.
- Review the need to use Peek 90HFM40. Although the mechanical properties of this material is outstanding, less expensive Peek materials are available (such as Peek 150CA30) which might meet the engineering specification.

Potential Impact:
This program has resulted in a game changer for the air management system on boards of single aisle aeroplanes. The program has demonstrated that considerable weight and cost savings can be achieved when the inlet scroll of the air management system is made through injection moulding with the fusible core technology. The results of this project will result in less CO2 emission. The program also demonstrated that the readiness level is high. 10 demonstrators have been produced and apart from some fine tuning, this program has shown that the fusible core technology has matured to a stage that is consistent scroll can be produced that can be used for future new programs as well as a retrofit package for existing programs.

The program has also provided Liebherr to opportunity to enhance their air management system and, in particular, the inlet scroll design of their air management system. Under their supervision and engineering efforts, the next generation of inlet scrolls have been developed and tested. The program has reached a readiness level such that based on the results of this program, an enhanced version of the inlet scroll can be developed for the current programs as well as new programs.

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