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Manufacturing Parameters
Manufacturing Parameters
Spikes
Spikes
10/22
Successful: generally good, spikes fully made.
Defects: bit of flash, ejector pin marks.
11/21
Production Run
Injection molded 71 copper spikes on the new machine. We had to tune the parameters since we were using a different machine; this also got rid of flash from the trial run.
Base
Base
10/29
Injection mold attempt with base mold #1
- Two halves did not align - coordinate system issue?
- Need to re-make molds
11/5
Fit nicely inside, but not a press fit.
Injection mold attempt with base mold #2
- Re-made mold to align halves
- Tried fitting with spikes
- Base too small for press fit
- Need to increase base mold diameter to get interference
11/14
Injection mold attempt with base mold #3
- Successful press fit!
- Small amount of interference, stays inside once pressed in
12/3
Base production run!
We had a small amount of dishing in the middle due to uneven cooling, so we increased packing pressure and shot size to solve the problem.
Belly
Belly
11/12
Our first try was not great. We first had flash, then decreased our shot size and got short shot.
We learned our lesson though.
Belly
Successful injection molding. The legs and nose don't fit all the way through the holes, meaning we will need to modify our design for the belly. We plan to increase the hole size so the parts fit through.
12/3
We re-did our belly mold and changed the geometry of the holes so that the legs could easily be placed in the correct orientation during assembly.
Nose
Nose
11/5
Successful: parting line is minimally visible, overall good parameters
Defects: ejector pins a bit raised
Injection molding issues:
- Nose got stuck in wrong side of mold sometimes. To solve this, we sprayed with mold release, increased the cooling time, tapped the sprue with extra threads, and added a piece of paper under the molds to ensure proper alignment.
11/26
Production Run
- Successful once we got the noses to stop sticking inside the mold using the methods listed above.
Legs
Legs
Week of 10/29
- Injection molded legs! Success!
Progression of parameter adjustments shown in picture. The best one is on the left. We used the smallest shot size and highest clamping force, but there is still a little bit of flash.
11/27
Production Run
We used our new mold to improve the leg fit with the belly. These legs are approximately the same size as the previous legs but have a triangle shape at their base. To avoid sticking in the mold, we used mold release and increased the cooling time to 20 seconds.
When tuning our parameters, we noticed the ejector pins sometimes went through the part if the cooling time was too low and if we didn't use mold release. As a result, we decided to use mold release every 3-5 runs and increased the cooling time.
Stand
Stand
11/12
Thermoformed base successfully. The foot holes don't line up perfectly with our yo-yo legs, so we will need to re-make this part. We also plan to print a grass pattern on the part. Part doesn't always eject properly, perhaps due to machine not being warmed up enough.
11/22
To make the stand more interesting and similar to grass, we added texture to our die using grains of rice. Then we thermoformed a new stand for our hedgehog.
Once the parameters were tuned, we printed grass on the plastic sheets.
11/26
Production run.
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