Printing TARS, Part 1: Chassis and Hull

Now the printing gets real. The chassis and hull are the largest parts of TARS, the body everything else bolts onto, and they are long, multi-hour jobs. This lesson is less about which button to press, the TARS-AI guide tells you exactly which files to print and in what order, and more about the maker skills that no parts list can give you: running a long print job without disaster, and recognizing what has gone wrong when a print fails.

The print-farm mindset

A quick keychain print is one thing; a robot body is another. A single TARS part can print for many hours, and you will run a whole sequence of them over the month. That changes how you work. You are no longer standing over the machine, you are running a small production line: you plan which large parts print overnight, you keep enough filament stocked so you never run dry mid-job, and you check in on prints periodically rather than watching every layer. The one moment you do not skip is the start of each job. Watching the first minutes of a print, long enough to see the first layer lay down flat and stick, is the single highest-value habit in 3D printing, because a failure caught in the first two minutes costs you two minutes, while the same failure discovered at hour five costs you the whole job and a spool of plastic.

Warping: the enemy of big flat parts

Large, flat parts like a chassis are the most prone to warping, where the corners curl up off the bed as the plastic cools and contracts. If you see a corner of a big part lifting partway through a print, that is warping, and the part will come out distorted or the lifted corner will eventually catch the nozzle and wreck the job. Warping is an adhesion-and-temperature problem: it is fixed by a clean, level bed, the correct first-layer and bed temperatures, and keeping cold drafts off the printer so the part cools evenly rather than shrinking faster at the edges. Everything comes back to that first layer sticking firmly across its entire footprint; if it does, warping rarely happens, and if it does not, warping is almost guaranteed.

Stringing and layer shifts

Two other failures show up more on big prints, and telling them apart tells you what to do. Stringing is thin wisps of plastic strung between separate areas of a print, left behind when the nozzle oozes a little as it travels across a gap. It usually means the temperature is slightly too high or the retraction setting needs a nudge, and it is mostly cosmetic, you can often just pick or brush the strings off. A layer shift is far more serious: at some layer the entire print suddenly jumps sideways and everything above is offset, leaving a permanent step. That is a mechanical problem, the print head hit something, a belt is loose, or it moved too fast, and no amount of cleanup fixes it; you check the mechanics and restart. Learning to glance at a failed print and say "that is stringing, keep going" versus "that is a layer shift, stop and check the belts" is exactly the kind of diagnostic instinct this month builds.

As each big part finishes, actually inspect it: clean layers, no stringing on surfaces that matter, no layer shift, and correct dimensions where it has to mate with another part. A little patience here, and a willingness to reprint a part that came out warped rather than trying to assemble a bad one, pays off enormously when you reach assembly and everything simply fits.