3d printing

This year I’m lucky enough to have access to a 3D printer.  These things are amazing.  It is incredible to be able to design something in CAD and then have it in your hand the next day.

Our process has been design the whole robot in a web-based CAD package (like Fusion 360).  As an aside: OMG – web based CAD!  I can’t believe it exists and is free!  Hat tip to Tom Oinn (@approxeng) for introducing me to the idea of it.

CAD allows you to see how the whole thing is going to fit together before you’ve spent a single penny on anything ‘real’.  Once you’re happy with the design, you can download an STL file (the 3D model of the part) and load it into your slicer software.  The slicer’s job is to turn the 3D model of the part into a list of movements of the print head (aka g-code).  It is here that you decide what the infill of the part will be and if you need any support material, etc, etc.

You then send the g-code file to the printer – in our case by copying it onto an SD card, though I’ve recently set up Octoprint on a spare Pi, which gives me a web server to control the printer (i.e. upload g-code files, start prints, etc) and a webcam so I can watch it work while I’m at work.  Prints take HOURS.  Our V2 chassis took 12 hours to print – which is why being able to monitor prints from work is awesome.

Nothing beats being able to discuss and modify the design of a robot part at lunchtime with your team-mates, then kick off a print and be able to bring in the finished part the next morning to hand over and have them try it out on the robot that evening.

3D printer prices have dropped massively recently – my machine is a slightly more expensive one (a genuine Prusa i3 Mk2S kit for those who care) but clones of this machine can be bought for £100 now!  Note that the cheaper kits often take more time to get “dialled in” than the more expesive kits – you need to decide if you are time-poor or cash-poor…

As for running costs, printer filament (usually PLA) costs about 25GBP per kilogram reel.  My slicer (slic3r) tells me how much filament will be used to print a part, and our biggest part (the chassis) used about 7GBP worth of filament.  I think we’ll end up using most of a reel for Tigerbot and 25GBP is cheap compared with all the electronic parts, and is MUCH cheaper than if you buy ready made parts (wheels, etc).  Speciality filaments like the rubbery TPU can be more expensive (we’re using TPU for the tyres).

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