Moldy Panels

[Blakbird]

DISCLAIMER: This post is only for those who are nerdy enough to care about irrelevant details that have nothing whatever to do with the goodness (or lack thereof) of a set or part.

Some of you may remember my recent review of the 8264 Hauler. In that review, I was looking at the new solid panels and made the following observation:

If you look closely, you can see that the beams embedded in the side of the panels are slightly narrower than a standard beam. An inserted pin sticks all the way through. I'm not entirely sure why they did this.

Since I am unwilling to let anything go unexplained, I have been racking my brain on this one and I believe I have come up with the answer. On a normal Technic liftarm, beam, or brick, the holes have a slight countersink. This allows the interlocking flange on the end of the mating pin to snap open into place and remain firmly attached. The countersink prevents the pin flange from protruding beyond the face of the part. In the case of this panel, the entire surface is moved back instead of using individual countersinks. Why? I believe that the reason is so that the parts can be removed from the molds. A normal beam can have the die on either side parted to release the part. In this case, since these features face inward, there would be no way to release the mold from the part if the faces were not planar (unless you had an expensive collapsible mold).

There you go, mystery solved. You may now go back to your lives without this question continually nagging at your brain.

[Front]

DISCLAIMER: This post is only for those who are nerdy enough to care about irrelevant details that have nothing whatever to do with the goodness (or lack thereof) of a set or part.

Some of you may remember my recent review of the 8264 Hauler. In that review, I was looking at the new solid panels and made the following observation:

Since I am unwilling to let anything go unexplained, I have been racking my brain on this one and I believe I have come up with the answer. On a normal Technic liftarm, beam, or brick, the holes have a slight countersink. This allows the interlocking flange on the end of the mating pin to snap open into place and remain firmly attached. The countersink prevents the pin flange from protruding beyond the face of the part. In the case of this panel, the entire surface is moved back instead of using individual countersinks. Why? I believe that the reason is so that the parts can be removed from the molds. A normal beam can have the die on either side parted to release the part. In this case, since these features face inward, there would be no way to release the mold from the part if the faces were not planar (unless you had an expensive collapsible mold).

There you go, mystery solved. You may now go back to your lives without this question continually nagging at your brain.

You are quite right. It would be nearly impossible to produce the counterbore diameter on the backside of the beam (the one furthest away in your picture), without some very complex mould.

Can you see the two depressions on the beam left and right ? These are inlet points, telling that the fixed mould part is underneath the element as shown in this picture. The moving mould part, including the inlet points) is then making the top part of the element. With holes in four direction, you could predict that the mould additionally need four sliders to mould this element.

Edited April 8, 2009 by Front

[CP5670]

I like to know these kinds of obscure facts about Lego too.

This would also explain why the holes on pieces like this have incomplete lips from the inside.

[Blakbird]

I like to know these kinds of obscure facts about Lego too.

This would also explain why the holes on pieces like this have incomplete lips from the inside.

Good point. You can see that the mold obviously is removed from the bottom. I suspect there are quite a few of the more complex parts which have certain features defined by the mold parting plane. Probably Bionicle parts in particular.

The stereolithography process can make any geometry imaginable, even with inaccessible internal voids. There are some fascinating developments in this area including being able to use metals such as titanium 6Al-4V. If it could used for ABS, there would be a huge wealth of opportunities. Not very scalable for large production though.

You said you liked obscure.....

[Front]

Good point. You can see that the mold obviously is removed from the bottom. I suspect there are quite a few of the more complex parts which have certain features defined by the mold parting plane. Probably Bionicle parts in particular.

I have done the 3D-modelling of many of the more complex Bionicle elements in the last couple of years, based on designers sketches or in most cases "simple" 3D models. The first thing to draw is often the parting planes, between ejector side, inlet side and in some cases the sliders too. That way the design of the element inherits what is possible to do regarding the mould. This mean that there has to be found a compromise that satisfies the designer as well as the tooling department.

First of the mould need to be made as simple as possible, especially with Bionicle elements which have a shorter life span, compared to more standard elements. Bricks that probably are to be produced for the next 10+ years, allow for a heavier investment in the tools. At the same time a 2x4 brick or similar need to look like other bricks, so all the compromises tend to favour the final look of the element, in some cases increasing the complexity of the mould.

Here are a couple of the elements I've "technically designed":

Vamprah mask

Krika mask

A look up close on these masks with a magnifying glass, will reveal that these two elements are made without sliders, that is, only with two mould parts. Simple moulds compared to the Technic element shown in original post, but complex geometry and parting planes.

Edited April 8, 2009 by Front