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

[MAB]

Remember also tolerances can be different for different parts. Lego needs very high precision moulds where the connection point is a single stud and it is a building part, as it needs to be high clutch enough to grip but not too tight that it doesn't come off. Whereas for a part with many connections, a slightly lower clutch is acceptable and probably preferable. And a minifigure accessory can typically have quite poor precision (relatively) since the parts are not used for butting up against others so it doesn't matter so much if the mould is worn. The CMF Princess had a lot of complaints as her headgear was poorly made, and kept falling off. Presumably there they went just a little too big on the antistud in the headgear.

[Mylenium]

1 hour ago, MAB said:

Remember also tolerances can be different for different parts.

Just to be clear about terminology: It's not really "tolerance" when it's built into the element. That is more "play/ backlash" or whatever you want to call it in a given context. You are right that it is different for different elements and different materials, but again, this isn't rocket science on any level and is a contingency you can plan for. Moldex or whatever is the current favored flow simulation tool/ module in your CAD will tell you in detail how those pieces shrink/ expand/ warp and what you need to do to optimize your new mold. And let's be realistic here - nobody intentionally produces "bad" molds and many plastic products have as high precision requirements as LEGO bricks. Just think of medical equipment or bottle caps that need to be tight. I can also attest that many industrial machine components fall into that category like parts in pneumatic vents or electronics. Keep in mind that those have to meet ISO/ DIN standards and other such stuff. Again, not meaning to upset anyone, but I think LEGO are just making a lot of noise about something that is simply an industrial standard process because it benefits their marketing.

Mylenium

[MAB]

11 minutes ago, Mylenium said:

Just to be clear about terminology: It's not really "tolerance" when it's built into the element. That is more "play/ backlash" or whatever you want to call it in a given context. You are right that it is different for different elements and different materials, but again, this isn't rocket science on any level and is a contingency you can plan for. Moldex or whatever is the current favored flow simulation tool/ module in your CAD will tell you in detail how those pieces shrink/ expand/ warp and what you need to do to optimize your new mold. And let's be realistic here - nobody intentionally produces "bad" molds and many plastic products have as high precision requirements as LEGO bricks. Just think of medical equipment or bottle caps that need to be tight. I can also attest that many industrial machine components fall into that category like parts in pneumatic vents or electronics. Keep in mind that those have to meet ISO/ DIN standards and other such stuff. Again, not meaning to upset anyone, but I think LEGO are just making a lot of noise about something that is simply an industrial standard process because it benefits their marketing.

Mylenium

It is a little more than that in that the mould can wear out more and still be usable or even not be manufactured to such high precision in the first place. Quite a few CMF parts, especially early ones, had little bits of flashing or bad sprue marks on. And also, as they are not building bricks going next to each other, I doubt the moulds for some of those parts, especially ones where it is a hand held object and has only a bar as a connection point (like a shield), cost anywhere near what the ones requiring higher precision do.

[Lyichir]

Yeah, these are molding marks. Often on parts with solid studs like basic bricks and plates they appear on one of the studs (so very easily hidden), but they tend to be especially common on the sides of parts without studs or with only hollow studs. Once you've learned where on a part they tend to be, you can often try to hide them by facing them toward where other parts cover them—but try not to get too obsessive over it, because there's only so much you can do.

Lego also sometimes revises molds to try to make these marks less obtrusive. Currently I've noticed a change like this taking place with 1x1 tiles, with some parts featuring the molding mark on the side but other parts using a newer mold that hides it in the center of the underside. These sorts of running changes don't happen all at once, so I've noticed that some colors have already changed over while others (which are probably working from inventory produced earlier or at a different facility) have yet to make the change.

[Mylenium]

49 minutes ago, MAB said:

And also, as they are not building bricks going next to each other, I doubt the moulds for some of those parts, especially ones where it is a hand held object and has only a bar as a connection point (like a shield), cost anywhere near what the ones requiring higher precision do.

As they say on the London Subway "Mind the gap!". Even a sword or club needs to have the right tightness to fit into those tiny minifigure hands. You need to get that part right. That said, I don't think this is even an issue. I really just get worked up over people thinking that this is some sort of witchcraft and LEGO in their endless generosity and greatness are the only ones who have figured it out...

Mylenium

[MAB]

35 minutes ago, Mylenium said:

As they say on the London Subway "Mind the gap!". Even a sword or club needs to have the right tightness to fit into those tiny minifigure hands. You need to get that part right. That said, I don't think this is even an issue. I really just get worked up over people thinking that this is some sort of witchcraft and LEGO in their endless generosity and greatness are the only ones who have figured it out...

Mylenium

Hands act a bit like a spring grip in this case so being slightly out doesn't really matter. If you wrap some tape around a handle or paint it,  it still works fine. And the rest of the object doesn't matter either. Whereas bricks need to be correct all over.

[Mylenium]

9 minutes ago, MAB said:

Hands act a bit like a spring grip in this case so being slightly out doesn't really matter. If you wrap some tape around a handle or paint it,  it still works fine. And the rest of the object doesn't matter either. Whereas bricks need to be correct all over.

Well, aren't you defeating your own argument? Of course it matters. As a standardized system those hands are designed around a certain measurement as well. That they are springy and tolerate more deformation is more or less just coincidental. I'm pretty sure that in the long run any such hand that has been holding a bar doused in paint or wrapped with thick tape would show signs of its mistreatment. Not meaning to be all academic, but we're fast approaching that "legal technique" thing here. And at the cost of repeating myself until someone throws up: From a technical POV there isn't much of a difference between a brick or a bar beyond the "play" and tolerances that have been built in. Why would you even make such a distinction? Just because you potentially could get away with it doesn't make it a good decision. It would just be sloppy.

Mylenium