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
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.
