Plastic latche for tool chest(box)

Hello guys

I am designing palstic tool chest(box). Most of job regarding the design is already done, however I am still confused about right variant of plastic latch I should pick up.

There are two size variants of box: 20 and 22 inches big. Biggest is up to 25 kg.

I chose 4 types of latches I am interested in(visible on the picture.

What pros and cons they have and what should I consider before selecting the final variant?

The one piece designs, blue and yellow, are made for close tolerances and little or no squeezing tension. The two part latches have more closing tension any will tolerate more mismatch for a process such as blow molding.

yes, that is right

the parts are going to be injected, however the tolerances could be an issue here.

That is why I am keen to pick up tension latch design. Has anyone oy you ever calculate it or design tension latch?

Do you have an engineer you are working with, either in house or at the factory level?

My old boss would have told me to just model up the latch with different tolerances. 3D print them and go with the one that felt best.

I think - finally - I will end with prototypes, and tune the the solution.

I have next question regarding the walls draft or taper of plastic chets

Most of them are drafted with min 2 deg. I made my first design also with drafts included.

However, I like the way DeWalt made it box system, and it looks like there are no drat, or at least it is less than 0.5 deg.

How did they achieved this? Is there any other reason to make drafts apart of molding requirements?

Intuitively the upper box rim will be stiffer and hold its shape better with an increased “draft” angle. Vertical walls and the top edge is going to flex inward in plastic molding.

Good place to start.

We would build the mold starting with the thinnest likely plastic cantilever and then cut away metal (add plastic) until we got to the desired target.