When does LEGO use hollow studs vs solid studs, and why?

Comments

• 560Heliport Member Posts: 3,910

  August 2018

  I think most of the time, it's because "solid" studs are hollow on the inside, i.e. from the bottom. the hollow studs are pieces where they can't easily be made hollow on the inside- for instance, due to the horizontal holes on Technic beams- so they make them hollow on the outside/top side to save plastic.

  

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• omnium Member Posts: 831

  August 2018

  I have no idea. But one thing I notice with the hub that has a mixture of stud types: the "System" sections have solid studs, and the "Techinic" sections have hollow studs. Which reflects how System and Technic bricks are made.
  

  

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• Mr_Hobbles Member Posts: 321

  August 2018

  Those reasons seem reasonable! Though it begs the question, why does the stud need to be hollow at all? Clutch power reasons? Cutting down on plastic usage...?

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• Oldfan Member Posts: 706

  August 2018

  Some of this depends on the molded part: when injection molding, if at all possible you want to keep the thickness of all the different features of the part ("wall thickness") consistent everywhere on the part.  If one feature (e.g. the side of the brick) is 5mm thick and another feature (e.g. the stud) is 10mm thick, it can be difficult to fill the molding cavity and cool the plastic evenly during molding and you might end up with warping, "sinks" (depressions in the plastic surface), and other physical irregularities.  I've noticed that some solid-stud parts actually are hollow on the underside to try and achieve this.

  Another good reason for hollow studs is the ability to insert the end of a bar into the stud to achieve a certain look during a build...

  

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• 560Heliport Member Posts: 3,910

  August 2018

  I like your "easier to mold" better than my "uses less plastic" idea! I'm looking at the LEGO I have here at work (#30525 The Guardians' Ship and #75165 Imperial Trooper Battle Pack) and it seems all studs are hollow on either the "top" or "bottom". I'm sure there's some exceptions, but it seems pretty consistent.

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• omnium Member Posts: 831

  August 2018 edited August 2018

  SNOT bricks have hollow studs on the sides...

  
  

  So perhaps the hollow is to do with what is behind/underneath the stud? i.e., if it's a hollow thing, like a plate or brick, it have a covered over stud. And If it's a solid thing, like the back of a SNOT bracket or a Technic brick with axle holes, it's hollow.

  
  

  That doesn't explain jumper plates, mind you.
  

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• Baby_Yoda Member Posts: 1,295

  August 2018

  ^ Because the stud on a jumper plate is situated over the tube on the bottom of the part, whereas on a regular plate there's nothing underneath it so there's room to make it hollow from the bottom.

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• Aleydita Member Posts: 952

  August 2018

  The 'easier to mould' reason is the explanation I was given years ago - almost all studs are hollow, either below (preferable) or on top if that's not possible.

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• Lyichir Member Posts: 1,018

  August 2018

  One factor I've seen mentioned is that when designing parts is that solid studs are often considered preferable for them (especially compared to completely open studs like those on 1x1 round bricks), because even though they offer less connectivity they display the logo more prominently.
  
  Of course, that's just one consideration—many other factors are applied in that decision-making process as well, like a part's similarities or differences with existing part families.
  

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• Recce Member Posts: 923

  August 2018

  Is it possible TLG limited the hollow stud parts due to other brick companies already patented the designs? 
  
  I would think that having all bricks with hollow studs gave much more flexibility than solid ones.
  
  Also, as mentioned above branding could be another major factor in favouring the solid studs with the Lego word prominently exposed in each and every stud. 

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• Astrobricks Member Posts: 5,481

  August 2018

  Aleydita said:

  The 'easier to mould' reason is the explanation I was given years ago - almost all studs are hollow, either below (preferable) or on top if that's not possible.

  I’m pretty sure this is the main reason. Not only do you need to be able to get plastic into all areas of the mold evenly, you also need to be able to open it cleanly afterward.

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• CCC Member Posts: 20,526

  August 2018

  The open studs are for attracting and containing the maximum amount of dust and dirt possible to annoy AFOLs.

  
  

  

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• Pitfall69 Member Posts: 11,454

  August 2018

  Baby_Yoda said:

  ^ Because the stud on a jumper plate is situated over the tube on the bottom of the part, whereas on a regular plate there's nothing underneath it so there's room to make it hollow from the bottom.

  Aren't the new jumper plates hollow? There isn't a tube underneath.

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• Baby_Yoda Member Posts: 1,295

  August 2018

  ^...Consistency?

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• Fodder Member Posts: 356

  August 2018

  Don’t jumper plates have slightly lower clutch?

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