We used to have “Design for Manufacturing” (DFM) but now as the early majority is starting to catch wind of 3D printing technologies and their amazing potential, a new acronym–Design for Print–will gain traction. There are now many articles that state the advantages of 3D printing but in short they are: extreme customization, the ability to fabricate the most complicated of structures with ease, quick lead times, low cost and highly efficient part production. All great motivations, but now that you’re convinced, you have to know how to print in 3D.
UPDATE: it turns out DFP is already used for the old 2D printing industry. Thus I’ll have to modify my acronym: DFP3? DFP3D? DF3DP? What do you guys like? Vote here!
While there are not many limitations for 3D printing in the sense that the world is your oyster, but there are a few design aspects you should consider (if this is the first you´re reading about 3D printing, consider reviewing some of the articles posted below):
- Material Selection – while there are up to 90 or so materials can be successfully printed (see Shapeways.comfor some great options), you are fairly limited in what materials you can print from. In my limited experience, ABS plastic is often used. It´s highly dependent on the machines being used and the functional requirements of your part. Again, you likely wouldn´t want to print a new axle for your car with a 3D printer. Not only would it be expensive, but you´d be heavily limited on materials strong enough to handle all the horsepower coming from your transmission…even if it was a Ford Festiva.
- Physical Size – while there are now 3D printers that can print on the micron scale (the diameter of a strand of hair is about 100 microns) to the meter-scale (for example, Enrico Dini is trying to print entire houses). But if you´re not Jay Leno–who was a very early adopter of 3D printing–you might want to stick to parts that could fit into a shoebox. As you get larger, you reach the limits and precision of the mid-level 3D printers (I´m referring to ones like MakerBot Industries up to Dimension Printers). Not only will large parts likely require a lot of “support material” that will need to be placed in a diluted acid bath for considerable amounts of time to dissolve, but the part itself will take a long time to print (I´ve seen one customer turn down our offer because it would take about 55 hours to print…not including etch time for the support material).
- Part orientation– since the majority of these parts are printed by digitally slicing them into many “layers” and then printing layer by layer in the vertical (or Z, zeta, zed etc. I will call this the print axis) direction and thus are structurally weaker in this direction. This is because as opposed in the x and y directions, the material is typically continuous (whether it´s sintered or extruded), and therefore it is stronger. Thus if you have a hole that you´d like to insert a rod into and then lock down, it would be better (if your design permits) to put the circular axis parallel with the z direction, thereby aligning the hoop stress with the continuous material plane. (we need a good analogy here–can anyone help?). Additionally, if your part would have branched out features in one direction or another (technically, that might be described as structures that extend in the x-y plane at a z height greater than zero)–thereby requiring a support material to be built up to support that structure–you´d likely want to consider re-orienting your part such that there are few overhanging pieces, or such that they’re closer to the print axis. This may be a non issue with some 3D printing styles (such as stereolithography), but even beginners will see the limits in strength, perpendicular to the print axis. The figure here to the right (as borrowed from www.imastresd.com) shows the orientation of the part. The grey base part is a structural support which supports the desired part during fabrication).
- The 3D STL file – while programs like SolidWorks and other 3D CAD programs offer STL as a standard file type (save as…*.STL), there are some options you should know about. Namely the “precision” and the “degree” options for these types of files. Three D printers are simply interpolating datapoints from a digital file that has volumes and other shapes embedded. And the computer / 3D CAD programs form these shapes as the sum of many uniquely shaped tetrahedrons. The size of these tetrahedrons define the accuracy of the curves in your design. For example, if you were to print a sphere in 3D, this sphere would be created by summing any number of tetrahedrons. You could imagine that if you only had a few tetrahedrons, your sphere would look like the Walt Disney World epicenter dome (i.e. not smooth). However if you had infintesimally small tetrahedrons, then those surfaces would smooth out and appear like a more continuous curve. This comes at a cost for file size, but more importantly, not all 3D printers are created equally and some have may not have these precision capabilities. Currently (as of April 2012), a recommended precision limit set to 0.01mm and a degree value of 5 are a good mix of small file size and smooth surface output. There´s a nice webinar (Objet Inc: Tips and Tricks for 3D Printing with SolidWorks) put on by the team at CADD Edge (a distributor of 3D CAD software) which explains some Solidworks tips and tricks on 3D printing.
- Fluidic access to “support material” in acid bath – If you can’t avoid having an excess of structural support material, then another design concern you may have is how to fully remove support material from your part. That is, if you’re using a 3D printer like the Dimension Elite, that has dual head which not only extrudes ABS plastic but also a structural support material that provides a foundation for new parts with overhanging sides and which need support during 3D print construction. However, if you have enclosed holes or other features which will not permit fluid flow over and on top of the structural material, you’ll lose a bunch of time with parts in the cleaning bath as the material will not have the agitation and access needed to remove away the support material. Just think to yourself, “if I were support material, where would I hide? I’d hide in a dark hole where only one side of me was exposed.” Then, ask yourself, “how could we get that material out of that hole?” and hopefully your design offers you flexibility to add a access port or complete exposure. Not the end of the world, this support material but it’s annoying enough to take note of how to minimize its presense or rid yourself of it quickly.
- 3D Printing Services – again, not all printing services are equal. Some have better technology, some have better prices, others have faster lead times, etc. Some host a wide arrange of parts ready to print and others allow you to modify the 3D models of other people. For whatever you need is, in my experience and personal opinion, the most important factor for 3D printing is lead time. For me, I’m constantly optimizing designs and I care less about the exterior surface finish and more about the functionality of the part. Thus I want the part in my hand now or ASAP so I can make my next design move. Therefore, I´d find a local 3D printing service and use them exclusively. OR…if your awesome like me, you might simply decide to invest in your OWN 3D printer and really get involved. I recently purchased the MakerBot Industries Replicator, dual extrusion head, 3D printer. It’s still “in production” and I’m waiting patiently or more accurate, impatiently for it to arrive. I already have a queue of parts to print and until then I’m using one of my two favorite local suppliers (to Madrid, Spain) 3D printing services: www.imastresd.com and www.stereoprint.com. Here’s a promotional video we made quickly for www.imastresd.com to illustrate their process:
So what are you waiting for? Now you have all the info you need to start playing in the 3D Printing sandbox. But wait, “I don’t have CAD models…I don’t know what to print” you might exclaim.
Not to fear, like I mentioned, places like www.thingiverse.com, www.3Dcontentcentral.com and other sites already have parts for you to download and print. There are 9-year olds (like Schuyler here) already 3D printing and starting mobile phone apps so you have no excuse. Confront your fears, put down the remote and start printing in 3D!
Interesting 3D Printing Articles:
Other 3D printing services and related websites (stolen from our Hands-on Rapid Innovation course website):
- www.mfg.com – upload your mechanical drawings and get quotes from all over the world
- www.protomold.com – upload a 3D CAD file and get a detailed quote on fabricating a mold and the parts you’d like to manufacture
- www.firstcut.com – get parts that you upload as 3D CAD models, machined and on your doorstep in less than 48 hours.
- www.objet.com – multimaterial 3D printers
- www.dimensionprinting.com – provider of high precision, higher cost 3D printers.
- www.makerbot.com – low cost 3D printer provider. Chris just bought one…the ReplicatorG. He’s never been this excited in his life.
- www.shapeways.com – “Passionate about creating”
- www.123Dapp.com – free software for 3D modeling from AutoCAD
- www.ponoko.com – very cool site that allows you to form development teams, hardware, software, electronics, etc.Excited to see where this one goes
- www.imaterialize.com – somewhat pricey but they have next day service, instant-quote and are local to Europe.
- www.sculpteo.com – again, another 3D model upload and printing service. These guys however also have an iPhone app which allows you to do some cool customization on common every day objects.
- www.kraftwurx.com – same 3D printing style service however their website was very glitchy and I´d be nervous to order from them today (April 2012) The need some website clean up first.
- www.protomold.co.uk – upload a 3D CAD file and get a detailed quote on fabricating a mold and the parts you’d like to manufacture
- www.firstcut.eu – get parts that you upload as 3D CAD models, machined and on your doorstep in less than 48 hours.
- www.imastresd.com – get prototypes printed right here in Madrid, Spain.
- www.materialize.com – like FirstCut. They also offer digital quotes.
- www.quierofabricar.com – rapid prototyping from Barcelona, Spain
- www.stereoprint.com – Madrid based 3D printing laboratory