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3D Printing at the Milwaukee Makerspace

So you want to learn about 3D printing? We have quite a few printers at MMS in many stages of repair. A list of many of them can be found on the Equipment page. There are usually a few that are able to print attractive plastic objects at any given moment.

Process Overview

3D printers use G-code, a sort of standardized language for CNC machines of all sorts. You start with a CAD design, export a mesh (aka an STL file), and run it through a program called a slicer. The slicer needs to know about the design, the printer, and the material you're going to use in order to do its job. The slicer cuts the mesh into thin slices called layers, figures out how to coordinate all the moving parts of the printer to produce the object you desire, and stores the printer instructions in a gcode file. Getting the best results from a 3D printer depends on knowing about the process in general, the specific printer you're going to use, and how to apply different slicer options to the design you're going to print. Expect to have some failures along the way- it takes some experience to get good at it, but you'll figure it all out with a little practice, and there are experts at the Makerspace who can help you.

Before Training

Before you are trained on a printer, you should learn a little about 3D printers, a little about materials, a little about CAD, and a little about creating sliced models.

A Little about 3D Printers

There are many different kinds of 3D printers. MMS primarily uses two types of additive manufacturing: filament-based printers using FDM (Fused Deposition Modeling) or FFF (Fused Filament Fabrication) technology, and resin printers using MSLA (Masked Stereolithography) technology.

Both types of technology have quirks that make them nothing like traditional 2D printers where you can simply press “print” and expect a finished product in seconds with little to no complication. Objects can take several hours or even days to print depending on their size and complexity. Settings in your slicer, the model you are printing, the material used, and your preparation can make the difference between success and failure. While 3D printing has gotten substantially more accessible in the past few years you will still need to experiment and troubleshoot to achieve the best results.


FDM/FFF printers operate like hot glue guns that apply a thin layer of melted plastic on top of the print bed and previously deposited layers. The melted plastic is quickly cooled by a fan to solidify in place. This is by far the most accessible and common method of 3D printing on the market today. It is great for rapid prototyping and larger decorative items and is very versatile because of the variety of possible materials that can be used. This technology is also relatively easy to scale into larger format machines allowing for large build volumes. Due to the nature of melted plastic, this method suffers when encountering steep overhangs so support material is often required to achieve optimal results of complex geometries. This technology also struggles with very fine details and produces noticeable layer lines in completed parts.


MSLA printers use a photopolymer resin which cures with exposure to UV light. A high-power UV LED shines through an LCD screen which masks off the light to only cure very precise parts of the liquid resin. The very fine control of light allows for incredible detail comparable to injection-molded plastic parts. This technology is very difficult to scale up in size which limits the build volume far more than on FDM printers. Additionally, while the cured resin is completely safe to handle, the liquid resin is very toxic and can be quite damaging to the environment so care is required both during and after printing to limit exposure to uncured resin.

A Little about Materials


All of the MMS FDM/FFF printers use spools of 1.75mm diameter plastic. One spool can print hundreds of small parts. There are several material options available.

Name Ease of Printing Notes
PLA Very Easy Most popular, strong but brittle, low heat tolerance
PET/PETG Easy Not as strong as PLA but slightly flexible, better impact resistance and heat tolerance
ABS/ASA Difficult Good impact resistance, very high heat tolerance, noticeable odor when printing, enclosure recommended while printing
Nylon Very Difficult Very tough and strong, very high heat tolerance, absorbs water from the air very quickly, must be printed directly from dry box, enclosure recommended
PVA Easy Water soluble, good for temporary support material on multi-material printers
TPU Difficult Flexible/rubbery, very tough, must be printed slowly

Most filaments absorb water from the air. Water in filament can cause it to become brittle and also causes steam bubbles to from at the end of the nozzle during printing. The best way to keep filament dry is to store it in an air-tight box with Calcium Chloride (DampRid) from the dollar store. Replace it every few months or when it becomes a solid mass.


MSLA printers can use a variety of different photopolymer resins that cure under 405nm UV light. Bottles are most commonly sold in 500g and 1000g capacities which is enough for dozens of large or hundreds of small models. It is important to note that uncured resin is toxic and extremely hazardous to the environment. Different brands of resin will have slightly different qualities so it is incredibly important that they provide an MSDS (Material Safety Data Sheet) for your review before handling. If the manufacturer does not provide an MSDS for the resin you are considering using, do not purchase it!

Common risks of uncured photopolymer resins include:

  • Toxicity if ingested (I shouldn't have to say this but don't drink the resin)
  • Eye and skin irritation (Wear gloves and wash off any uncured resin immediately with soap and water, wear safety glasses)
  • Respiratory irritation from vapors (Wear a mask or respirator depending on your personal sensitivity)
  • Immune system sensitization (Prolonged and repeated contact with uncured resin can cause you to develop a severe allergic reaction)
  • Environmentally hazardous, especially to marine life (Do not pour uncured resin down the drain or outside. Do not throw uncured resin in the garbage)

In addition to the hazards of uncured resin, all objects will require post-processing in 97-99% isopropyl alcohol which produces its own vapors and is highly flammable. While these hazards may seem scary, resin printing can be both safe and fun with the proper PPE and a healthy level of respect for the chemicals involved. If you spill uncured resin on a surface use a strong source of UV light to cure it before disposing of it. Anything contaminated with uncured resin is considered hazardous waste and must be disposed of properly if it cannot be cured.

A Little about CAD

CAD stands for Computer Aided Design. It's a way to tell a computer about a 3D object so you can display and manipulate it in 3D. It is highly recommended that you learn how to use CAD to get the most out of 3D printing but you do not need to know how to use CAD to use a 3D printer.

There are many different CAD packages available. Video tutorials are a great way to see how they are used. Some CAD packages are easier to use than others. You'll see a lot of on-line posts about SketchUp being one of the easy ones to learn. While it is true that it's easy, for a bunch of technical reasons, SketchUp isn't good for designing parts for 3D printing. If you want easy, try DesignSpark Mechanical. OTOH, if you really want to dive in and learn a fully-featured professional package -there are well-paid jobs for people who can use professional CAD- plan on devoting 200-500 hours to become proficient at creating models.

Name Cost Docs Notes
Fusion 360 Free for Makers (for now) Web Help See web site for details
Tinkercad Free Web Help See web site for details
FreeCAD Free, Open Source Web Help Great for Linux users
OnShape Sorta-Free, Closed Source Web Help Professional, Cloud-based, any OS
DesignSpark Mechanical Free, Closed Source Web Help Limited capabilities, but easy to learn - Windows Only
Blender Free, Open Source Web Help Steep learning curve, mostly used for CG art
RhinoCAD About $1000 Web Help Free Trial
OpenSCAD Free, Open Source Web Help More like programming than most CAD
SketchUp Make Free-ish Web Help Less than optimal for 3D printing - best avoided

For those who are CAD-adverse, you can download pre-made models from web sites like and Be forewarned that some of the models at those sites are unprintable on FFF printers like those at the Makerspace. When a model is printable, its author usually posts a photo of the printed object. If you don't see a photo, it may require adjustments to make the object printable. Unprintable models can often serve as inspiration for you to design a better, printable version of the object. Ultimaker has a nice list of model sources here

Once you have a model, you need to create a mesh file (usually either an STL file or an AMF file). Shapeways has a good list of options for creating them if you are having trouble: If someone else created your mesh file and it's broken, you can use tools like MeshLab to repair them.

A Little about Slicing

Slicing software cuts your 3D object into layers that can be stacked to create your object. They can convert solid areas into 3D grids and create extra material to support upper layers with nothing underneath them (like an outstretched arm in a model.) The Slicer outputs a file unique to the 3D printer that you will use. It controls the 3D printer's movement and the speed that it squirts out plastic. Tuning a slicer for a specific printer can take many hours and failed prints. The printers at MMS have pre-made configuration files for Slic3r that work well for most models. Many printers use the G-Code language. You can use a tool like to visualize the g-code that a Slicer creates. Here is a reference for writing/debugging G-Code.

Here are a few Slicer packages:

Name Cost Docs Notes
Slic3r Free, Open Source Web Help Widely used, most configuration options for power users
PrusaSlicer Free, Open Source Documentation Based off Slicer, highly configurable and very well tuned. A favorite at MMS
Cura Free, Open Source Web Help Great for Ultimaker printers, more versatile but lower print quality than PrusaSlicer
KiSSlicer Free, Closed Forum Haven't tried it
Simplify3D About $150 Web Help Haven't tried it
ChituBox Free/Premium license, closed Web Help Required slicer for Chitu ecosystem resin printers

Ready for Training

Before you are trained, you should be at least vaguely familiar with creating a 3D model, turning the model into a mesh, and slicing the mesh. Like all of the plug-in tools at MMS, you have to be trained on each model of 3D printer you would like to use. Training usually takes about an hour per printer and is preferably done in small groups. You will learn some of the quirks of the specific printer and get to know the guidelines for using that printer. To get trained, post to the Members Only Mailing List and offer a few dates and times that are convenient for you in the next week or two. Don't expect to be trained in less than a few days or to meet your deadline. All the trainers are volunteers and they have no obligation to train anyone. They train because they love to teach curious people new things. Tell them about a project you have in mind. Encourage others to be trained with you to minimize the number of training sessions required for each printer. Show up to Tuesday meetings and hang out in the 3D printer lab to learn from other members.

After Training

Review your notes of the training and try a print on your own. If you aren't familiar with something or forgot how to do something, find someone to ask. Many members have used the printers or know someone who knows. If you can't find someone within arms reach, post to the mailing list. Experiment with different temperatures, materials, shapes, etc. Most importantly, have fun, learn, and share your findings with others.

3D Printers at the Makerspace

spacedocumentation/3d_printing.txt · Last modified: 2022/12/18 23:17 by wildapricot-klein_john