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NICE Rapid Hearing Aid Case Study

Job Description:                                                                                                                                     Body-Worn Hearing Aid Components

Project: ALD_SLIDE_CLIP_REV_54+ ALD_TOP_REV_58                                                                             Process: CNC Machining, EDM, Polishing and Plastic Injection Moulding

Processes: Plastic Injection Molding                                                                                                      Materials: Tooling – NAK-80

Tooling Material: NAK80 polishing steel                                                                                               Plastic Injection – ABS 757

Injection Material: ABS plastic                                                                                                               Lead Time: 16 days

Surface Finish: SPI-A3 external, SPI-B1 internal                                                                                Quantity: 5000 units/year

Cavity: Family mould 2+2

Tooling Lead Time: 16 days 

Tooling Lifetime: 50,000 shots  


About The Product

These parts are an enclosure for an all-digital, multi-channel, WDRC hearing aid.Fireproofing is necessary 

and, as requested by the customer, the Top is glued onto the circuit board with E6000. The Slide Clip 

slides between the Top and the circuit board.  


About The Customer

Pixation Corporation (http://www.pixation.com), specialises in developing hearing aids, hearing aid fitting 

systems and speech processing, with the primary objective to help individuals with severe/profound 

hearing loss.Pixation would like to improve their design of the outer covering of the Pixation BWHATM

During the R&D phase, they needed a partner company who could provide technical suggestions on 

building, reduction of lead time, production quality and loose MOQ. NICE Rapid was chosen after an 

extensive selection process. mould


Production - Preparing The Mould 

Customer Requirements: Two parts, with different shapes and sizes, but made from the same material, in 

the same quantity.

NICE Rapid Suggestions: A double four-cavity mould was the optimum layout in order to save cost and time.

As the surface finish of the parts was SPI-A3, NAK80 polishing steel was suggested as the tool material.



Preparing The DFM

As the basis of the surface finish and tooling lift time was provided by the customer, we gave specialised suggestions on the tool manufacturing and injection moulding process. (Please see general information below).



For more information, we prepared a DFM document that showed the surface finish, gate location, parting line, ejector and draft angle locations. We exchanged our ideas with the customer in relation to the DFM and, once approval was sought, we proceeded to build the tool. 


          


                            Above data is the least draft angle of Universal materials in VDI





Electrical Discharge Machining

A conductive electrode from copper was machined in the precise size and shape that we wanted to reproduce in the mould. EDM cut the metal with an  electrical charge, which was achieved very quickly and with high fidelity. In this process, the electrode itself was eventually consumed, which was considered an acceptable sacrifice. Finally, we made 20 electrodes to form the two cavities.




Polishing

After machining, in order to get the A3 surface finish (SPI #A-3), the cavity was carefully polished by grade #15 diamond buff. (RA 2-3 micro-inches). 


Fitting The Mould
After confirming that each tooling component (cavity, core, slide, angular lift and ejector), was smooth and had good mobility during the moulding process, (when opening or closing the mould), we moved the tool to the moulding workshop.

Material identification
A materials datasheet and COA certification, provided by our material supplier, ensured that the materials met the customer’s requirements. 


                                 


Plastic Injection Moulding

During the moulding process, the following work was undertaken:

Step 1: Injection parameters are set in accordance to the materials datasheet. This ensures that the injected parts are applied to the correct function and usage requirement.

Step 2: A lower injection pressure was used to test whether the feeding rate on each cavity was balanced or not. We found that the feeding rate on the Slide Clip was lower than the Top. In order to solve this problem, the gate size of the Slider Clip was enlarged accordingly. 

Step 3: After adjusting the injection parameters, a cosmetically pleasing part was produced. When the inspected dimensions were acceptable, we also confirmed a stable part weight from several shots. Finally, the moulding process for the parts began and the injection parameters were recorded on the Mould Testing Report.


                                                                                         

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