3D Printing Terminology
Infill: The internal support structure used inside solid parts to save on material usage and print time.
Parts can be plenty strong even at only 20% infill!
Wall Thickness: The number of solid perimeters used to construct the outer shell of prints before printing the infill.
This typically has more impact on final part strength than infill percentage does.
Layer Height: 3D printing builds parts one layer a time. We can define how thick those layers are to achieve desired structural or aesthetic properties. Larger layers means faster prints at lower fidelity, smaller layers means longer print time but higher fidelity. Layer heights can range from .08mm to .6mm thick (dependent on nozzle diameter), a height of 0.2mm is considered the average.
Nozzle Diameter: FDM 3D printing uses metal nozzles that are heated and then have plastic forced through them to deposit material. We have a range of nozzle diameters that, similar to layer height, allow us to trade speed of printing, for print quality and vice versa.
A larger nozzle has the added benefit of generally leading to stronger prints.
Average nozzle diameter is 0.4mm but can range from .1mm to 1.2mm.
Print Orientation: One of the side-effects of the layer-by-layer printing process is that the orientation you print your model in actually matters quite a lot. Your part will be weakest along those layer lines. Parts will most often fail by shearing off between two layers. As such, the part will be oriented for printing in the most advantageous direction relative to where the loads are on your part.
Overhangs: Because parts are printed from the bottom up, each subsequent layer ideally needs to have some form of support directly below it. In overhangs, portions of the part will reach out into thin air without being fully supported. These will typically not print well, when the overhang is greater than 60°. This will impact the part both aesthetically and structurally.
Bridges/Bridging: Similar to overhangs, bridges are when the printer needs to create an unsupported line between 2 or more points. Think the letter "H", when trying to print the middle bar in "H", there will be noting to support the line in the middle and the plastic will begin to droop.
With adequate cooling, most printers are able to handle bridges. Our machines are capable of bridging a span of over 200 mm, though note that this will cause print quality to suffer.
Support Material: In both overhangs and bridges, most printers can compensate with adequate cooling, however there are some cases where this would either compromise the aesthetics/strength of the part, or are simply too extreme for the machine to handle on its own. In this cases, support material is used. Support material is a sacrificial print the software will generate to support these tricky areas. Support material is then easily broken off of the final part after printing.
Slicing: The process of taking a 3D model and preparing it for 3D printing. The part is brought into a software that will allow us to slice the virtual part into layers and define all of our print settings like layer height, infill, wall thickness, and over 200 additional settings.
Slicer: Slicers are the software used to perform slicing, the act of cutting a model into layers to prepare it for printing. There are around a dozen different slicers currently in use, though we almost exclusively use Cura to do our slicing.
3D Printing FAQ
Are 3D printed parts strong?
3D printed parts can be made to be quite strong if they're designed and printed correctly. Thicker walls, higher infill percentages, proper applications of engineering principals like the use of stress relievers (fillets and chamfers), material selection, and proper orientation of the printed part relative to the loads it will experience all have significant impact on the final strength of the part.
How long does 3D printing take?
Unfortunately, times for prints vary wildly depending on the size and complexity of the part, as well as the desired print settings like those discussed above. Smaller prints could take an hour, whereas large ones have taken over 3 days to complete.
NOTE: Slicers will provide estimates for print time. For a variety of reasons, these estimates are always lower than actual print times, varying by anywhere from 5% to 50% depending on a variety of factors.
How much do prints cost?
Cost will also vary greatly depending on the complexity, size, quantity, quality, and material choice of each order. Certain materials can cost 10X more than others, and as mentioned previously, some parts can take 10x longer to print. The amount of post-processing required for prints will also drastically alter the cost of parts. Machine time is relatively low-cost, but man hours are where the real cost comes in. The easier the piece is to prepare, slice, and finish once off the machine, the cheaper it will be.
It is typically more economical to order basic prints and do the final finishing (sanding, painting, addition of misc. components) yourself.
We are more than happy to advise on proper finishing techniques.
We can print in a number of different materials. Below is a list of the most common materials we utilize so you can choose what's best for your project. While we list the most common materials, there is a wide array of materials available but that are not listed here, so please feel free to ask if you are uncertain what material is right for you.
PLA is an excellent go-to for most 3D printing projects. PLA is a corn-based thermoplastic that is easy to print with, and is strong enough for some light duty applications. One major weakness is temperature resistance, softening at only 60°C (140°F), leading to deformation if left in a hot car for example.
Trickier to print with than PLA, ABS machines much more nicely than PLA. Recommended for parts that will require sanding, drilling, or other machining done to the finished part. Has superior temperature resistance to PLA, softening at 100°C (221°F).
Similar temperature resistance (Softens at 88°C [190°F])and mechanical properties to ABS, but with the ease of printing of PLA. This is a great choice for mechanical components that will see some use and abuse.
A flexible, rubber-like material available in a range of hardness. We typically use 95A shore hardness, equivalent to about the rubber used in shopping cart wheels. When printed thin, it performs excellently as a living hinge or joint. While easy to print with, it will require slower speeds and longer print times.
Mostly ideal for aesthetic pieces like props, this is PLA that has been impregnated with actual wood. This lends to an authentic look and feel that can be sanded and stained just like real wood.
There are a number of composite materials similar to wood-fill that utilize higher-end materials such as carbon fiber or even various metals (copper, iron, bronze, etc). These materials are very expensive and tricky to print with, but yield both aesthetically appealing prints and ones that are functionally stronger than other materials in some cases.
Tolerances and Fit
What kind of tolerances can I expect?
As with any machining process, there are a number of factors that contribute to the tolerances you can hold. Print settings such as print speed, layer height, and nozzle diameter will all influence part tolerances.
Our prints typically hold 3-5 thou (0.076 - 0.127 mm) tolerances in X and Y and 1-3 thou (0.0254 - 0.076mm) in Z *.
Setting proper clearance for printed parts can be difficult. As mentioned above, a number of settings can drastically alter surface finish and final dimensions. The table below should provide a baseline for dimensioning your parts. If fitment is critical, we recommend modeling mating surfaces oversized (pins) / undersized (holes) and machining them into tolerance. This typically requires some light sanding/filing or reaming to be accomplished. We do provide these post-processing services however we will charge for the additional man-hours required.
Printed part to printed part
Example: Simply by printing at a higher speed, the square shaft went from "Free Running" to a "Tight Fit" in a 0.520 in hole.
Printed part to machined parts
*This is best case scenario for print tolerances.