Desktop 3D printer

3D printers produce plastic parts under computer control. The process of 3D printing is especially useful for the smaller insect-class bots, where weight is a severe limitation to design. However, even Heavyweight-class builders use 3D printing to make composite reinforced components, custom compartment insulators, and wire guides. Keeping electrical parts and cables away from metal plates and sharp edges reduces the risk of damage and short circuits.

3D Printing is widely used in one specialized division of combat robotics, the Plastic Ants class, where the chassis and weapons (if any) must be made of plastic in order to qualify.

If you don't own a 3D printer, you may be able to get help from your local library or makerspace, or from your fellow bot-builders. Some people will want to design their own bots, which requires knowledge of 3D modeling using a computer or app for the purpose. Others will choose to download a premade design (see below). Once you've got a bot design working to your satisfaction, you can print a supply of replacement plastic parts, which can be used for repairs after your bot becomes damaged.

Selecting a Printer

Selecting a printer for 3D printing a combat robot can be a big decision, and here are some factors to think about when purchasing your printer.

Budget

Desktop and office 3D Printers can range from as low as $150 to over $10,000 depending on their hardware, capabilities, build volume, and other factors. Here's a quick overview of what's available:

Budget-friendly/hobbyist 3D printers: Range from $150 - $750, normally limited in materials and build volume. These include machines like the Creality Ender 3 series, and will normally have a maximum nozzle temperature of 245-250° Celsius. These machines are meant for printing PLA, PETG, and ABS, but with varying degrees of modification can print more advanced materials like Nylon and TPU.
Advanced materials printers: Range from $750 - $3,000, and are capable of printing materials like PLA, ABS, PETG, TPU, Nylon, Nylon Composites, and Polycarbonate blends with minimal or no aftermarket modifications. These will have a maximum nozzle temperature around 295-300° Celsius.
Engineering grade printers: Range from $3,000 - $10,000+, with few materials outside of their capabilities. These printers are often able to print not only advanced materials but also multiple materials using multiple extruders or multiple tool heads, allowing for even greater complexity. Dual extrusion can allow for a multi-color part (Black PLA/White PLA), multi-material finished product (PLA/PETG), or soluble support material like PVA/BCOH.

Printable Filaments and Materials

The materials that a FDM (Fused Deposition Modeling[1]) 3D printer can extrude must melt at a given temperature, maintain a consistent flow of material through the nozzle, and solidify in a consistent fashion. These materials include thermoplastics, waxes, and even chocolate! With specialized printers it is possible to use such materials as ceramics, glass, and concrete.

Most 3D prints in combat robotics will be made from rolls of plastics and plastic composites on an FDM printer. "Resin" printers are becoming more common in larger sizes at budget-friendly prices, and more options for resins are available to purchase on a regular basis.

The list of common 3D printable plastics below proceeds roughly from weakest to strongest.

PLA

PLA is inexpensive, but brittle.[2] It is the most common 3D printing filament. It rarely warps in use and is great for tiny parts.[3] It's a great starter material, and recommended for printing prototype parts. Many builders prefer other plastics, especially for their active weapons or armor. Pure PLA is made from cornstarch[4] and gives off a corn syrup odor which reminds some people of waffles.

PLA+

Various manufacturers offer "PLA+" and/or "Tough PLA," which are modified PLA filaments that are meant to be less brittle. With an acrylic additive, for instance, it may show much better impact resistance.[5] Inland and eSun claim their PLA+ products are 10x stronger than regular PLA.

PETG

PETG (a copolyester) is more heat resistant, more flexible, and less brittle than PLA.[6] It is well suited for 3D printing mechanical parts. Since it is more likely to flex under impact its resilience may be useful to the bot builder, but it is 2-3% heavier than PLA. Observe manufacturer's recommendations when printing, as it tends to stick very strongly to smooth print beds. You'll notice a fairly mild hot-plastic odor when printing.

ABS

ABS is a strong and reasonably impact-resistant material at a moderate price, but warps easily and smells worse while printing. Its low density makes it one of the lightest of all printable plastics (PLA is about 20% heavier for the exact same print). You'll probably need to print it in an enclosure for best results; this keeps its temperature even during printing, so that it only shrinks after printing instead of curling or warping during printing. Many hobbyists ventilate the enclosure to the outdoors with fan(s) due to the odor.

Nylon

Nylon is tough and flexible. Regular nylon is hygroscopic and must be kept in dry storage, or it will absorb moisture from the air and become spoiled after a few weeks. Consider buying a hybrid nylon material that doesn't require as much attention to storage.

PC

Polycarbonate is super strong - your robot arena walls are probably made from it! Many printers can't print it, though, because it must be heated to an extreme temperature (about 275°C/525°F).

CF Materials

Carbon-fiber reinforced materials are extremely tough, and ideal for combat robotics. These are usually polycarbonate or nylon with chopped fibers embedded inside. You should strongly consider using these when plastic parts are needed for beetleweight designs.[7] This material requires a hardened printing nozzle, as the carbon-fiber strands or particles are highly abrasive.

Tips and Best Practices

Nearly all 3D printers can handle PLA and PLA+. Most other materials require printing onto a heated surface (the "print bed"). Check the specifications and instructions of your printer to find out what materials it can handle.
A basic limitation of 3D printed parts is that they can crack or break apart along layer lines, since they are made from layers of plastic. Generally, the tougher the plastic the more likely the layers will also hold together.
Pay attention to the orientation of parts on the print bed - consider orienting parts so that the direction that needs to be the strongest lies horizontal during printing.
You can make adjustments each time you print. Thicker walls (shells) and a higher percentage of infill add density and strength to your bot, but also increase weight. Remember to re-weigh your bot after changes have been made.

Robots you can Print

You can download and print robot designs from sites like Thingiverse and Prusaprinters. Just 3D print the robot body and other provided parts, then assemble them with the working parts of the robot. Some have helpful instructions and buying suggestions for finishing the working parts; however, some have little or no guidance, and you will need some experience to try them.

Below are links to over 80 bot designs that have been shared by the robot building community. Limited consideration has been given to whether each of these is buildable, or will meet the stated weight class.

150g Combat Robots

150g bots are in the US Fairyweight weight class (Antweight in the UK, EU, and Australia).

1 ~ A

B ~ E

F ~ J

K ~ S

T ~ Z

All other weight classes
Bot	Class	Type	Provided by	ID #
4WD Wedge	1lb	Wedge	TeamLiftoff	4723564
(Unnamed)	1lb	Vertical spinner	kkbittle	2036647
3DAD	1lb	Horizontal spinner	drcameron	3908901
Backlash	1lb	Horizontal spinner	clingmanr	3146568
Blockhead remix	1lb	Paddle spinner	shultiskevin	3111090
Blue Screen of Death	1lb	Horizontal spinner	chrismik	4075681
CheeseWej	1lb	Plastic ant Wedge	Teamd20	4885071
Doom Stone V1	1lb	Plastic Ant Vertical spinner	kmcelroy	3297944
Eureka	1lb	Plastic ant Wedge	Teamd20	4800332
Flapjack	1lb	Drum spinner	shultiskevin	3160354
Future Killer	1lb	Vertical drum	altapowderdog	3793747
Half-SMEEEEEEEEEEEE	1lb	Long split wedge	TheN00b	4675230
LifeSteal	1lb	Plastic Ant Horizontal spinner	Posey	4910548
Mega Looon V1	1lb	Vertical spinner	thesaxmachine
MI	1lb	Full-body spinner	RattlerRobotics	2828234
Mr. Roomba	1lb	Plastic Ant Ring spinner	Kylellrc	3170974
Mr. Twister	1lb	Plastic Ant option Vertical Spinner	AdamDC	1401358
Plastique	1lb	Shell spinner	AdamDC	2813722
Simple	1lb	Wedge demobot	mightygrom	3962507
Tiger Shark V5	1lb	Horizontal spinner	thesaxmachine	3819420
Tiger Shark V6	1lb	Horizontal spinner	thesaxmachine
WejFu	1lb	Plastic Ant Wedge	Teamd20	4843171
Mega Don G V2	3lb	Plow	thesaxmachine
Munchkin	3lb	Drum spinner	Creative_Instigation	3731962
Rapid Unscheduled Disassembly Mk6	3lb	Undercutter spinner	TeamMagicalLipoFire	3179067
Vector	3lb	Horizontal spinner	Endbots	3917039
Vertex	3lb	Vertical spinner	Proxy303	4741317
Vertigo	3lb	Vertical spinner	Insertbattlebotsjokehere	4241833
Deadlift	1.5kg	Lifter	Noursicus	4232399
Plastic Donk	1.5kg	Wedge	Noursicus	4230265
Razor	1.5kg	Horizontal saw	AlexKorvin	5022333
Wall Chaser	1.5kg	Vertical saw	AlexKorvin	4967207
Mars Attacks (itself)	unknown	Shell spinner	shultiskevin	3160993
Combat Robot 2.0	unknown	Drum spinner	altapowderdog	1688510

3D Printing

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