Drive Visor & Endcap
Project: Plastic Parts “Drive Visor & Adapter”
Processes: Mold Manufacturing & Plastic Injection Molding
Materials: Aluminium 7075 (Mold); PA66 – 15%Glass Fiber (Part)
Lead Time: 12 days
Quantity: 1500 -2500 Units
We wanted to deliver the parts to the guys of Caravan Company* very quickly without compromising quality. The challenge for this project however was the wall thickness of 0.5mm on the round shaped part. We opted for hand-loaded inserts that we add and remove manually from the mold during injection molding. It was a wise choice as the parts came out of the machine perfectly. It was a pure pleasure realizing this project and I thank Caravan Company for this opportunity.
Design and Project Specs:
Caravan Company* builds some of the finest comfort and convenience products in the United States for the RV industry. Their previous supplier of visor products had stopped their support, so the guys from Caravan – David (engineer), Don (purchasing) and Lisa (project management) – started looking for alternatives in Asia. Star offered parts of equal quality but a lower price, and most importantly Star was able to deliver fast. The mold was finished and a test run completed in just twelve days. Caravan was therefore able to continue supplying their customers with no interruption of deliveries.
*names are changed
How the Part / Individual Components Are Made:
We needed to make two parts of different shapes, but we wanted to make them in a single mold to save time and money. One of the designs called for a long, thin tube with a wall thickness of only .5mm, which was challenging.
Step 1: Verify Mold Material
We chose to use aluminum 7075 for the plastic injection mold tooling, which is relatively easy to machine. Incoming material was verified with an optical emission spectrometer (OES), which uses an x-ray to identify the exact constituency of the metal. Once confirmed, cavities were cut out of the mold using electrical discharge machining (EDM).
Step 2: Electrical Discharge Machining and Polishing
EDM requires the use of a sacrificial electrode which is in the shape of the desired feature or part topography. As the electrode discharges its electrical capacity, minute amounts of material are eroded from the mold surface. In all, ten electrodes were required to form the two cavities.
The surface of the cavity was still rough and required careful hand polishing to achieve the texture of the finished part, which is transferred from the mold to the piece during injection.
Step 3: Machining of Hand-Loaded Inserts
Hand loaded inserts were chosen instead of automated sliders, since making the later would require more time and expense. In this case, since the build quantity was only 2000 pieces, hand loaded inserts were more economical although they took more time and effort per molded piece. The inserts were made with CNC machining.
Step 4: Plastic Injection Molding
The finished mold cavities were installed in a master mold base and then placed into the machine. The thermoforming plastic chosen was PA66 +15% GF (glass fiber). The advantage of PA66 is that it can withstand temperatures above 200°C. Test parts were fully inspected and sent to the customer for approval before completing the production run.
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