3D printing the Sawppy rover

It’s been a few weeks since the last post, but here’s why – I’ve been busy printing:

What you see above is the result of almost 144 hours of print time and 792 metres of plastic (or the best part of 3 reels).

Firstly, whilst the original Sawppy was designed and iterated using PLA plastic, the final rover was done in more durable PETG. I have opted to use PLA myself though, for a couple of reasons.

  1. Cost: I can get PLA for about 2/3 the price of PETG
  2. I have not yet printed with PETG. I’m comfortable I can get good results with PLA, so thought for the first version this would work best for me.
  3. My rover will not be subjected to the same heat that the original one would have been in California, so might just last a little longer.

Once this rover is built, I’ll get myself some PETG and learn how to use it. Then when this rover’s parts start degrading, I’ll replace them as needed with the more durable PETG.

Learning points

I chose to print as per Roger’s suggested settings. 0.3 mm layer height, with 3 perimeters and 4 top and bottom layers with 30% triangular infill.

This is the first time I’ve tried running with 0.3 mm infill. To my eyes, I can’t even tell the difference between the 0.2 mm I have previously used and 0.3 mm, but it prints in two thirds of the time. I might just use this layer height more often in the future!

Secondly, I had been playing with a magnetic flexible build plate to make it easier to remove prints, but due to the size of some of these prints, I was getting quite a bit of warping, which was lifting the build plate itself! I have never had this issue with PLA before, only ABS.

So just before printing the wheels, I went back to the tried and tested combination of painters tape on top of a glass bed and this pretty much fixed it from there. I’d say that flexible plates are now pretty much out of favour and I’ll be sticking to glass for the time being.

Ok, on to some of the specifics. I won’t cover every item that was printed, that is all referred to in the excellent set of instructions provided here.

Wheels

It’s when you print the wheels that you begin to get a feel for the size of this thing. Just one wheel practically fills my build plate. At 8 hours 40 mins and 39.6m of filament, these wheels are the single largest prints I have ever done. I mean, just look at this.

Out of interest, as far I could work out, Roger used the wheel design from the upcoming Mars 2020 rover. Incidentally, those treads there are called grousers, so there’s a new word I learnt…

…and here’s the first wheel in my hand for a better sense of scale. I would not have had the confidence of printing these overnight if they weren’t a material I had worked with before.

Satisfyingly large, yet still only about 113g in weight! Those spokes only take up the first couple of centimetres, as the motor housing will sit inside the wheel.

Differential brace

I knew this part would be problematic, as Roger’s printer had a 200 x 200 mm print bed whilst my old Wanhao Duplicator 4x only has a 220 x 140 mm area. This meant I would never be able to print this brace in one go, so had a find a fix for that.

The fix for me came from the Puzzlecutlib in OpenSCAD. This allowed me very quickly to chop the brace in half, whilst giving me the ability to snap the two parts together easily.

These two items above easily fit onto my build plate. Here’s a closeup view.

With a slight tap of a hammer and a bit of superglue for luck, I’ve got my required part, which feels almost as solid as a single item would be.

The rest of the items pretty much printed as I’d expected, it just took a long time with only a few hours print time available every evening.

Next up, I’ll talk about the non 3D printing finishing that needed to be done to the prints.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s