Strange markings on almost every piece?

[ChrisXY]

Hi,

bought a bulk and those cylinder pieces are all marked almost on the exact spots on every piece. Can someone guess or explain? I dont think it´s a mold injection point? So what happened here? The marking also appears occasionally on other pieces.

[Murdoch17]

Mold marks. Typical of a great many parts, and they are 100% unavoidable. It's part of the process of making the parts.

[ChrisXY]

39 minutes ago, Murdoch17 said:

Mold marks. Typical of a great many parts, and they are 100% unavoidable. It's part of the process of making the parts.

Oh wow, so they are really mold marks? They look quite deep also. Like someone pinched them with a sharp knife. I also thought they moved the molding marks to a different point for "newer" parts (reddish brown).

I almost wanted to throw those pieces away and order new ones :D

[Mylenium]

1 hour ago, ChrisXY said:

I also thought they moved the molding marks to a different point for "newer" parts (reddish brown).

They do, but molds cost money. Not the millions LEGO always claim to keep alive the myth why their stuff is so expensive, but still... The rest is complicated. Different factories have different generations of injection molding machines, many molds exist multiple times to even produce sufficient numbers of pieces and they may have minor differences, block sizes of individual molds can differ, differently sized elements require different placement inside the mold as well as cooling and pre-heating, the thickness of the metal to accommodate the pressure has to be considered, elements need to break off easily for quick and efficient mass production and so on. It's not a simple matter of placing your sprue attachment points on the underside and hope for the best. They already do it where possible like in some plates and tiles, but this simply isn't possible with every element and even when it is, they need to do it methodically to not make things worse. And it's not that this is a LEGO-only issue. All brick toy manufacturers struggle with this and finding the best placement of these injection marks has become an art form in itself.

Mylenium

[JopieK]

38 minutes ago, Mylenium said:

They do, but molds cost money. Not the millions LEGO always claim to keep alive the myth why their stuff is so expensive, but still... The rest is complicated. Different factories have different generations of injection molding machines, many molds exist multiple times to even produce sufficient numbers of pieces and they may have minor differences, block sizes of individual molds can differ, differently sized elements require different placement inside the mold as well as cooling and pre-heating, the thickness of the metal to accommodate the pressure has to be considered, elements need to break off easily for quick and efficient mass production and so on. It's not a simple matter of placing your sprue attachment points on the underside and hope for the best. They already do it where possible like in some plates and tiles, but this simply isn't possible with every element and even when it is, they need to do it methodically to not make things worse. And it's not that this is a LEGO-only issue. All brick toy manufacturers struggle with this and finding the best placement of these injection marks has become an art form in itself.

Mylenium

A mold can easily be 100.000 euro b.t.w. and they do wear, so also need maintenance. LEGO also tries to maximize precision. But apart from that you are right.

Those marks @ChrisXY are the connections (called gates) where the molten plastic is was injected into the part cavities of the mold. For most parts they are somewhat hidden, mold designers try to place them at covert locations but that is not always feasibly and actually virtually every molded part has them (not only LEGO).

See: 
https://prototool.com/sprue-in-injection-molding/
https://www.dakumar.com/knowledge/The-Ultimate-Guide-to-Sprues.html

[Stereo]

I checked a recent set (creator expert Vespa) with the 1x1 round bricks and it still has the visible mold marks on the sides.  A lot of the time they put them on studs now but that part hasn't got one.

[Mylenium]

13 hours ago, JopieK said:

A mold can easily be 100.000 euro b.t.w. and they do wear, so also need maintenance.

No argument on that, but at the same time it's not every mold that costs this much and that is basically is where LEGO is being very liberal with the truth, to put it mildly. If it really was as complicated as they claim, molds would be unaffordable and that's simply not the case. Every little piece of plastic you can buy out there basically disproves it, including LEGO themselves churning out tons of new molds every year.

13 hours ago, JopieK said:

LEGO also tries to maximize precision.

They all do. It's not that even some cheap plastic bowls you can buy at the dollar store would per se have less precision than a LEGO brick. You know, last I looked at the calendar it was 2025 and CNC milling, galvanic erosion and computer-based construction as well as 3D-prototyping have been around for a while. Long before even committing to drill into that steel block everyone has run simulations and checked every detail. Likewise, tempering/ hardening molds can be done with unprecedented precision these days by controlling temperatures to fractions of degrees or using methods like local induction heating. Point in case: This isn't rocket science and the technical means are available to everyone these days. LEGO only still sells it as if it was still done like back then in the 1980s to keep up the myth.

Mylenium