Please note; Due to its very nature, this post is very subjective and is not intended to be a definitive list of categories. It is merely an attempt to offer one perspective of what has been suggested, and to ask "How should we move forward?"

Sometimes it is a bit hard to see the wood for the trees...

Following on from tjb1's meta post, Post Closing Issues, it seems like we should widen the scope and be less strict about what is, and what is not, on-topic. What do people think? What additions, if any, should be made? Are there things that definitely should be on the list, that aren't currently?

So, with respect to our On-topic page, which needs updating, in order to get an idea of what people have been asking ("why has my question been closed?"/"why is X not allowed"), I've gone through the Meta questions and come up with a list of questions that mentioned the words "ask" and "topic". I then pulled out the questions relating to specifically what types of questions can/can't be asked.

A number of them seem to be able to be labeled as duplicates (inasmuch as they asked more or less the same thing), and so I have attempted to group them according to their suggestion request. The full list is at the bottom of this post.

Even though I went through both lists twice - also, I didn't read every question and answer listed below fully - there may be some suggestions that I have missed. Please feel free to either suggest a change, or edit this post directly and add any that have gone astray (in that respect, maybe this question should be a wiki?).

Whilst we maybe don't want to change the aim of the site too much (as doing so may put off some regular users), maybe the scope needs to broaden slightly, as to have a wider appeal and be more inclusive.

BTW, a useful post to read is What should our documentation contain?

Any thoughts, questions, additional suggestions that have not already been posted, agreements, or disagreements?


The list below was integrated into the on-topics page, on the 8th June 2019. See On-topic has been updated - finally! for further discussion.

TL;DR - Suggested topics

In the list below,

  • Italics are used for notes
  • Strikethrough is used for definitive no-go topics

Whilst there may be some overlap, duplication and/or mis-categorisation, the list of suggested on-topics seems to be, essentially:

  • Recommendations (Hardware and Software)
    • Note: Usually banned from SE - with the exception of Hardware Recommendations
    • General Shopping - opinion based
    • First printer - opinion based, see "Best first printer" wiki/blog/closed-question
    • Best printer
      • Overall - opinion based
      • For specific task - opinion based but allowable, although speed as a task is in a very grey area... this question Fastest FDM printer? was closed for being opinion-based
    • Best software
      • Overall - opinion based
      • For a specific task - opinion based but allowable
  • Software issues
    • Firmware
    • Tools
    • Coding/Compiling firmware (see Misc - Coding)
    • 3D modelling (same as CAD?)
  • Websites (could come under Software and/or Tools)
    • Recommended sites
      • for knowledge
      • for models
      • for online tools
    • Issues with web based tools
  • CAD
    • Needs to show relevancy to 3D printing! (See Meta questions)
    • Overlap with SE.Blender?
  • Printer DIY
    • Repair and maintenance (both commercial and DIY repair of both commercial and DIY printers)
    • Construction
    • Mechatronics
  • Components (could come under Printer DIY)
    • Thermistors is a good example, see note 1 below
    • Help and Recommendations
  • Electronics
    • Printer related electronics
    • Common electronic gotchas
  • Print Services
  • Scanning
  • Bio-printing
  • 3D Models
    • Feasibility
    • Availability
  • Sharing recommended settings
  • Legal issues
    • Copyright (i.e. Lego)
    • Guns/Weapons
    • Insurance (i.e. fire damage)
  • Manufacturers
    • Best manufacturer - opinion based
  • Materials
    • Filament
    • ABS
    • PLA
    • PETG
    • etc.
  • Makerspaces
  • Medical
    • Materials for medical use
    • Medical quality printing
    • Medical applications for 3D printed objects
  • Health
    • Closely related, and may overlap with safety
  • Safety
    • Fumes
    • Print material suitability for foodstuffs
  • Non-3D Printing related
  • Misc
    • Not strictly 3D related, see Non-3D Printing related above
    • Anything 3D related
    • Other
      • FFF (Fused Filament Fabrication)
      • FDM (Fused Deposition Modeling)
      • SLA (Stereo Lithography)
      • DLP (Digital Light Processing)
      • SLS (Selective Laser Sintering)
      • DLMS (Direct Laser Metal Smelting)


Admittedly, there will be overlap with some other SE sites and whilst we need to avoid the too-broad-black-hole, we should also welcome all things that are 3D Printer related, so as to keep all relevant knowledge in a central location.

1 WRT Components, and taking the thermistors meta question as an example, my first thought is that questions like this should remain, as they are pertinent to 3D Printing, otherwise we could theoretically end up compartmentalising printers and migrating off a lot of stuff to SE. Electronics, SE.Engineering, SE.Hardware Recommendations, etc.

2 The same applies to the Misc/Anything 3D related, in particular the Connecting 3D parts question. Yes, as some of the comments state, you could remove the 3D printer part and then it is basically an engineering question. However, when taken as a whole, this question is pertinent to 3D printing of large models, in parts.

3 Also under Misc/Anything 3D related, Coding Ultimaker Cura is a SO type question, but it is also 3D printer specific

Additional suggestions in the future

Instead of posting a new question, it might be a good idea to post an additional answer, containing the suggestion, to this question - in order to keep everything grouped together. This will save on the pain of having to go through all of the Meta questions as I have just done.

However, that might mean that the suggestion request would not have such prominence that it would do if the suggestion was posted independently as its own question... So (at the risk of duplication), if a new question/suggestion is posted, then it could be a good idea to also copy that new post and add it as an answer below.

Meta Suggestions

These are the meta questions that I used to create the categories above:

ask - 89 questions in total

General scope questions



Software Suggestion




Printer not working:

Discovering 3D Printing

  • null

Print services

Model Feasibility

Model Availability


Bio Printing

on-topic - 56 questions in total

Sharing Settings through out the community

Printer construction - DIY

Legal issues






Actual questions (not meta)

Closed - 73 questions in total






  • $\begingroup$ Well given how we botched that last users hot question. Not only did we lose a traffic magnet, they clearly think we "banned their question." IDK the question didn't seem that off topic if we cut out their poorly chosen expression that it was opinion based. It wouldn't have different that much from the questions I post calibration guides to. $\endgroup$ – StarWind0 Mod Jul 10 '18 at 18:40
  • $\begingroup$ @StarWind0 and anybody else - That "project for a child question" would come under a topic of Model recommendation (for a specific purpose), which currently isn't on the list, even under 3D Models... so should it be? We only have availability and Feasibility. $\endgroup$ – Greenonline Mod Jul 11 '18 at 15:24
  • 1
    $\begingroup$ What about asking questions on 3D Printer manufacturers? IMHO that could be on-topic. $\endgroup$ – 0scar Mod Feb 6 '19 at 7:20
  • $\begingroup$ @0scar - Ok, I'll add that, just before "Materials". Any particular sub points? Feel free to edit and add them yourself, cheers. $\endgroup$ – Greenonline Mod Feb 6 '19 at 16:08
  • 1
    $\begingroup$ New CNC-type question, 3dprinting.stackexchange.com/q/10610/4922 $\endgroup$ – Davo Jul 16 '19 at 12:58

A couple of points:

Asking for a machine to solve a specific problem, or software which can do something 'specific' is not really a shopping question, so long as the question is asked in the right way. We do need to avoid subjective questions, but sometimes this can be the result of a misunderstanding (i.e. find me a non-CN supplier of this budget Chinese printer {which also seems to be a decent product}).

Topics which bridge into something like Electronics can be useful because the field is very large, and EE.SE makes an assumption of near degree level expertise. Useful answers here could be more 'off the shelf' routes to achieving what could potentially be fairly 'textbook' to someone with the right background.

Same with making trivial changes to firmware, using a complex software tool for a trivial task, etc. If the task is common, relevant and bounded then a 'hand-holding' answer here will be much more valuable/findable than pushing questioners to a more specific site. Once people move from trivial use of these tools they may well end up needing to self-educate before they reach a point that EE.SE, or SO will accept their questions.

We're at a difficult point between a mass market consumer product, and emerging tech. The IoT site has similar challenges.

  • $\begingroup$ WRT 1st point, ok cool thx. I have that covered with "For specific task - opinion based but allowable?". I just need to remove the question mark(s). 2nd point, yep totally. If it relevant to printing then it should stay. Would you agree that the same applies to compiling code and printing related IDE help too (which may in the past have been shunted to SO)? $\endgroup$ – Greenonline Mod Jul 11 '18 at 14:42
  • 1
    $\begingroup$ I was tempted to be more restrictive with compile/ide, but again we're potentially dealing with people who need hand-holding for common tasks... $\endgroup$ – Sean Houlihane Jul 11 '18 at 14:48
  • $\begingroup$ Yeah exactly, and they are more likely to get a 3D printing oriented response than they would on SO $\endgroup$ – Greenonline Mod Jul 11 '18 at 14:58
  • $\begingroup$ I've added Electronics explicitly to the list (I'd forgotten that, or assumed it was in components or DIY), also added Medical and Health and Safety $\endgroup$ – Greenonline Mod Jul 11 '18 at 15:01

I pondered this question a while ago and tried to come up with a coherent and minimalistic strategy. This would be my suggestion, as to what is on-topic or off-topic:

Suggestion for topic policy

So, basically, on-topic would follow the formula:

(formingMethod == additive OR substractive) AND (instrument == machine)

Off-topic would have the formula:

(formingMethod == transformative) OR (scale == mass) OR (instrument == human)

This is just my suggestion and I invite everyone to put forward their argument, if they think, that a better strategy or community can be created, if the boundaries are to be moved or the criteria re-defined.

Vacuum forming on an individual/batch scale, for example, would be a topic, that is close to the other "green fields". If we want vacuum forming to be on-topic, we would have to give up the "transformative" criteria. I'm sure, there are other points like this.

I also assume, such a strategy would have to be adapted in the future, when these methods have either matured, have been adopted by the masses, or other methods have been discovered.

  • $\begingroup$ CNC and Laser Cutter are currently not considered on-topic in most circumstances. The ones where it is on-topic deal with dual-purpose or converting. It is pretty much "additive Manufacturing". $\endgroup$ – Trish Feb 4 '19 at 17:02
  • $\begingroup$ Only just seen this... I like the matrix very much, nice presentation, better than my unwieldy list. I'll need a day to two to digest this and I'll come back with some comment. $\endgroup$ – Greenonline Mod Feb 6 '19 at 16:11
  • $\begingroup$ What about 3D printer options for welding, EDM, injection molding, or vacuum forming? I ask because we have all of these in prototype phase where I work. $\endgroup$ – Davo Mar 5 '19 at 14:57
  • $\begingroup$ Welding can be considered IMHO as "additive", friction welding is more "transformative" $\endgroup$ – 0scar Mod Sep 5 '19 at 12:37

I propose that we add Direct Ink Writing (DIW) and Melt Electro-Writing (MEW) to the list of on-topic subjects at https://3dprinting.stackexchange.com/help/on-topic

Direct Ink Writing:

Direct-Ink-Writing (DIW) is an extrusion-based additive manufacturing method heavily utilized in meso- and micro-scales. In DIW, the liquid-phase “ink” is dispensed out of small nozzles under controlled flow rates and deposited along digitally defined paths to fabricate 3D structures layer-by-layer.

Melt Electro-Writing

MEW utilizes an electric field uniquely coupled with AM technology for the controlled deposition of a molten polymer jet, which rapidly solidifies into a fiber. These submicron fibers can be consistently laid on top of each other, resulting in the ability to direct-write complex and multi-scaled architectures and structures, and overcoming the resolution challenge that a majority of other additive manufacturing technologies encounter.

My request to have these additive manufacturing techniques added to the list of on-topic subjects is driven by the facts that:

  1. These are valid Additive Manufacturing processes; and

  2. The company for which I work, Hyrel 3D, has customers (mostly at universities) using these processes.

  • $\begingroup$ Only just seen this. OK, I guess it could/should be added... if people agree with the proposal..? Personally I have no idea what they are. Are they additive printing? The name suggests that they are just writing (similar to engraving). Do you want to add them because they are similar to CNC? Maybe I'm being dumb, but maybe you could expand upon your proposal and say what they are and why you want them added(?) $\endgroup$ – Greenonline Mod May 15 at 17:41
  • 1
    $\begingroup$ @Greenonline Proposal added to, thanks. $\endgroup$ – Davo May 17 at 11:53

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