How to Design Objects for 3D Printing

by Jason King on October 12, 2015

RC Truggy Tyre DesignWhen you take delivery of your first 3D printer you’ll probably spend lots of time downloading cool stuff from sites like Thingiverse, so you can add them to your ever increasing queue of objects to 3D print.

We’ve all done it and in the early days of owning your first 3D printer there’s nothing wrong with downloading and printing everything you can.

This initial excitement will eventually wear off though, which isn’t a bad thing as it was costing you a fortune in plastic and you probably found yourself downloading far more than you could actually print.

Although you may have already dabbled in designing your own objects to make, it’s at this point that your mind really turns to designing more and more cool stuff yourself. You may even want to upload some your own designs to sites like Thingiverse, for others to download and print.

After all, maybe it’s time to give something back to these sites which we all raided so vigorously when we were downloading and printing anything and everything.

Designing your own 3D printable objects is great fun, it’s a way of giving something back to the 3D printing community and it’s a natural step in our journey into the world of 3D printing.

However, you cannot just design anything and expect your printer to churn it out without any problems. Unfortunately it’s not always as simple as that. There are a number of things you need to take into consideration first.

As your designs become more complex, useful and popular will need to consider more and more potential issues. Otherwise your designs might be unprintable, cost a fortune to make, or much worse, they could land you in some trouble.

As you read on, don’t be put off by all these considerations as for your early designs you won’t need to worry too much about most of them. In fact I’ll detail them in the natural order I’d expect you to want to know about them.

The fact that your early designs print at all might be your first and possibly only consideration. This is because if your designs don’t even print you won’t need to worry about much else. So, with that in mind let’s start with printability…

Object Printability

As the word itself implies printability is the ability of your design to actually 3D print and transform into the tangible object your design represents.

One of the benefits of 3D printing is that it allows you to create complex objects which cannot be created using traditional manufacturing methods.

However, that doesn’t mean you can 3D print absolutely anything without considering the type of printer and its suitability to a particular design.

Prevent Warping

Most home 3D printers are FFF printers, which print objects layer by layer on a build plate. When each layer of your chosen thermoplastic is as applied it will cool and an unfortunate property of most plastic is that it shrinks when it cools.

I’ve written before about how to help your first later cling to the build plate to prevent warping (Blue Tape, Hairspray, Rafts) but here we’re talking purely about design.

Skull Rafts SupportsAlthough it’s good to include a perfectly flat side in your design which will fit nicely on your flat build plate, it’s important that this side isn’t too large else the effects of shrinkage will be in increased and so will the chances of warping.

Also, think of the pattern (tool path) in which the plastic is applied, straight lines back and forth will create shrinkage in one direction, increasing your chances of warping, so large flat areas with straight sides (squares) will be very prone to warping.

For the side of your design which you intend to be on the build plate ensure it’s not too large and has random curvy sides where possible. At least try to avoid large areas with straight sides.

Don’t use a very small side as your base (on the build plate) either, or your design will be liable to topple over during printing. You could use a raft (removable flat base) if you really need to but you’ll need to remove this after printing and it’ll leave the bottom side of your object looking a little rough.

Thinking about a reasonable sized, non straight edged (if possible) flat base in your design is an important consideration when designing a printable object for an FFF printer.

Avoid Supports

The idea of 3D printing and building up an object layer by layer is great and in most cases it works fine. The exception in the case where our design includes overhangs, as you’ll be asking you 3D printer to print parts of your design in midair.

FFF printers have issued printing layers of plastic onto fresh air so in these areas you’ll need supports. Explaining this is much easier by example so I created this YouTube video to help explain when and where supports are usually required. If you’re short of time, skip ahead to 2:15 and watch it try to print the cross bar on the “T”:

Although supports are useful as you’ll see from watching my Makerbot fail to print the 3D letter “T”, you’ll need to remove them after your printing is complete. This can be tricky, time consuming, wastes plastic and can make your 3D print quite rough where the supports have been removed.

So, if possible avoid the need for supports in your design by considering the YHT principles described in the video above.

Orientation

The orientation of your object when printing is important for a number of reasons, related to what we’ve discussed already. Simply by spinning your design around and changing which way up it will be 3D printed, you can often prevent warping and eliminate the need for supports and rafts too!

If you’re printing a large object then you may need to change the orientation so it fits the build area if your printer. Printing something which is 7 inches tall in a build area which has a height of 6 inches won’t work, but if the build area has a width of 8 inches then a simple 90 degree spin of your design could be your solution.

One last consideration is strength. Your object will be strongest across the layer lines and weakest along them (a bit like wood grain). So if for example you designed a coat hook which would be attached to a wall/door at this angle: / it might be best to lay it flat when printing: _ rather than upright: | as it will be strongest this way.

Just remember that you don’t have to 3D print an object the same way up you will design or use it, if it makes more sense to change its orientation. Orientation is as much a design issue as it is a 3D printing issue.

Thickness, Gaps and Details

As the title suggests, this is a mixed bag of considerations but it’s all about small dimensions and the impact they can have on 3D printing your design. Any 3D printer has a limited resolution and cannot perform miracles beyond its limits.

For example, you might design an object which you intend to be hollow, maybe so you can put something in it, to make it lighter or to Reduce 3D Printing Costs. If so you need to ensure your wall thickness is enough so it’s possible to print in the first place as well as to ensure the final object is strong enough and fit for purpose.

Small gaps in a part or between separate parts need to be big enough so that the parts either side if the gap don’t fuse together. Also, the resolution of the printer probably means it cannot physically handle tiny gaps.

Shapeways RingFine details like long thin parts or small gaps again could mean that your design cannot be 3D printed without fusing or breaking.

When designing fine detail just consider the resolution of the printer, the strength of the material and the strength of your design itself.

Some good examples of these limits can be found in Shapeways 3D Printing Criteria. These are specifically for strong and flexible plastic, but they have slightly different rules for different materials. Even though Shapeways use high end, high resolution 3D printers they have some strict limits regarding what they can and cannot print.

Product Safety

When someone starts to talk about safety, many people just switch off and think it’s boring and not going to be applicable to them. However, with 3D printing safety really an issue with almost anything you design and make.

Let me use the example of a simple drinking mug. I’ll briefly describe just some of the issues with designing and 3D printing such an object and although there are some obvious issues with this I think you’ll be surprised at the rest.

Let’s start with the obvious one. Whether you chose to use ABS, PLA or any other plastic that FFF printers use, it will melt at well below the temperature of a hot drink like tea or coffee. I use warm water at about 65 degrees in order to intentionally bend PLA plastic objects I’ve made.

Any warmer than this and PLA will have a consistency much like chewing gum. Try finding that out the hard way when you fill your newly designed and 3D printed mug with coffee for the first time. Even objects designed for the inside of cars will melt on a hot day, so designing any item that might be used above ambient temperature could be a bad idea.

Another issue with our mug is that although PLA plastic is less toxic than ABS, being organic rather than petroleum based, it still isn’t usually FDA approved for food and drink use. I’m no lawyer but this might make it illegal to sell such items if the material isn’t FDA approved.

There are FDA approved materials you can use in your 3D printer like ColorFabbs Copolyester XT, however due to the nature of FFF printing, your mug probably won’t be water resistant either due to the tiny microscopic holes between the layers of plastic.

These same holes are a great home for bacteria and no matter how much you try to clean your new mug you’ll struggle to get rid of this bacteria as it’s able to hide inside the plastic itself. Remember you cannot use hot water to clean it either as the mug might just turn to mush.

So there’s a few good reasons why you shouldn’t design such an item, it would melt during use, might be illegal to sell, would be riddled with bacteria, not even be water resistant and could be toxic itself too.

Another aspect of safety that is important but not fitting to the mug example is the issue of small parts being a choking hazard, for children in particular. If you’re designing small items that children might use you might want to rethink this too.

A little while ago I wrote about the Dangers Involved in 3D Printing so you might want to have a read of this at some point. None of this is intended to scare you, it’s just that we need a basic awareness of these potential problems. For our mug example the hot liquid issue was probably obvious to you but I bet the FDA approval and bacteria issues weren’t so obvious?

Production Costs

Production costs in 3D printing are basically down to material use, material wasted, time and economy of scale.

Remember that with 3D printing there is generally no economy of scale, so if it costs you $5 to make one item, it’ll cost you $5,000 make a thousand. Some 3D printing companies offer bulk discounts but many explicitly state they can’t, due to this lack of economy of scale.

This in itself means that you should use 3D printing for custom, one off items (like my logo below) or low volumes but if you want to produce hundreds or thousands of the same item, 3D printing is great for Prototyping but you’ll be better off using other manufacturing methods for final production.

3DPrintHQ Logo OpenSCADThis affects what you design if you intend to use 3D printing to make your design. Design something which can easily be customised, or something to make in low volumes, or maybe a prototype for a high volume object.

Don’t design something like a clothes peg, which you’ll need to make lots of to be of any real use, unless it’s just a prototype for a high volume injection molding project.

Material usage is a consideration too for your designs. If you can make the object smaller and make it hollow or at least use minimal infill (5% to 10%) you can save a lot of money on material usage. The degree to which you can do this depends on the required strength of the item the intricacy of the design.

A ball for example would be easy to make hollow or with minimal infill, saving a fortune on material costs. Something intricate like a tree or mesh structure wouldn’t benefit much from being hollow, so consider all this in your designs.

Going back a little to when we mentioned supports and rafts earlier, these are all removed after 3D printing and then thrown away, unless you have a Filabot Recycler or something similar. If you can design without the need for supports and rafts your design can be made with zero material wastage and sometimes with significantly less cost too.

Finally there’s the time consideration. The resolution (layer height), print speed, infill and those supports and rafts all affect the print time. FFF 3D printing is quite slow by its very nature so any time savings usually end up being money savings too.

Cost is always important when designing your objects to 3D print, but I hope these pointers have given you some things to consider and to make you a more cost effective designer.

Intellectual Property

The Increasing Growth in 3D Printing and scanning is going to cause a real headache (but lots of profit) for intellectual property lawyers. It’s so easy nowadays to scan a patented, copyrighted object including trademarks and then to distribute the design for anyone in the world to download and 3D print it.

I dread to think what court cases will result from this in the next few years. It’s also something we as designers need to be very careful of. Does your design infringe any existing trademarks, copyrights or patents?

It can sometimes be tricky to be sure it doesn’t but we should do everything we can to ensure that we don’t upset any big companies who might be ready to take us to court. Scanning any existing object, whether we redesign it afterwards or not could land us in trouble if we distribute the design or 3D printed tangible version afterwards.

Like everything else I’ve covered in this blog post, intellectual property is just something else to consider and not something we should be scared of, as long as we have took reasonable precautions to avoid infringements.

Parametric Designs

The most amazing design concept I’ve discovered recently is parametric designs, so I want to give it a quick mention here. These are designs which will change themselves depending on some numeric values.

RC Truggy TyreWhat this means is that if you want to design something that can easily be modified to fit different requirements then this is how you’d do it.

A good example is the Parametric OpenRC Truggy Tyre I designed and uploaded to Thingiverse. By changing a few numbers in the code it’ll automatically re-render a new design so I can easily change all of the following in seconds:

  • Wheel diameter
  • Wheel width
  • Tyre aspect ratio
  • Number of spikes per row
  • Number of rows of spikes
  • Spike base width, point width and depth
  • The list goes on…

To achieve this I use an open source design package called OpenSCAD which is free to download and use. You can download the source code for my tyre from Thingiverse too and try it in OpenSCAD. I made the designs source code available to everyone for free so anyone could customise it for their own requirements and regenerate it for 3D printing.

OpenSCAD is a programming based precision design package, so it’s tricky to design organic looking objects (you may need something like Blender for that), but I love using it and it’s worth taking a little time to download and learn. Designing has never been so much fun since I discovered it.

Outsourcing

Finally, I’m going to suggest something which eliminates a lot of the above design considerations completely! Many of them are related to FFF printers which are by far the most common type of 3D printer for home use.

However, something I recently started doing is designing and prototyping using my own Makerbot FFF printer, then outsourcing the 3D printing of the final product to a company which uses different 3D printing technologies.

Outsourcing can immediately eliminate the worry of warping, supports, rafts and orientation as well as many of the safety issues, as they can make your stuff in a wide range of materials, including steel. That’s quite an achievement.

Some 3D printing service companies like Shapeways even offer 3D printing in porcelain so you can design and make that mug after all with none of the safety worries we mentioned for it earlier, just promise me you won’t ask them to make it in plastic 🙂

To me this is a game changer and I’ve been using other companies to make solid bronze, solid silver and even Rose Gold Plated Jewellery. In fact the last article I wrote was specifically about How to Start 3D Printing for $10 and with no equipment, so you might want to read that too before you go.

If you’re interested in learning more about 3D printing at home then download my FREE Beginners Guide to 3D Printing at Home eBook today. Also, please feel free to Like, Share and Comment on this blog post.

Thanks for reading and happy designing.

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