Corner radius

When considering product appearance and strength, ensuring the resin within the mold flows as smoothly as possible is imperative.
This means avoiding any sudden changes in wall thickness and designing corners with maximum radius to avoid.

If the inner radius is missing or small, the stress due to the load will be concentrated and the strength will be in a severe condition. The graph shows the relationship between the size of R and the stress concentration factor (degree of stress concentration) with respect to the plate thickness T in the case of cantilever bending.

As shown the stress concentration factor decreases with increasing R, as does the negative impact on strength. However, when R surpasses 75% of the wall thickness (R/T: 0.75), the stress concentration coefficient doesn’t significantly alter, negating the necessity to unduly increase R. Conversely, when R is below 25% of the wall thickness (R/T: 0.25), the stress concentration factor notably escalates, concentrating stress at the corners, which could precipitate whitening or destruction.

[Reference] Troubleshooting : Molded product cracks