The Grand Printx

The files for this model are available here.

Last week, I discussed how we can use the extruder head to our advantage during co-processing. In this post, I’ll be going a little bit more in depth into that idea. You may have noticed that in last week’s post I had three co-processing steps: placing the spring into the print, cocking the hinge back, and latching on the trigger mechanism. This week, I will reduce that from three steps down to one step, and get the part not just off of the build plate, but out of the printer, using one of the simplest machines: the wheel!

The cross section of the wheels and axle on a 3D printed toy car, designed to be printed in one part.
The cross section of the wheels and axle on a 3D printed toy car, designed to be printed in one part.

Regarding the overall design, I haven’t really changed that much, I’ve just eliminated some of the more complicated parts to the system, including the spring and the hook. The only thing the printer head touched in last week’s post was the latch piece, so let’s just focus on that. As you may recall, the printer head hit the latch piece, triggering the spring, allowing the part to grab onto the rails of the printer, and as the printer head moved, the part was pulled off the plate and left hanging. Here’s the GIF again to jog your memory:

My print removing itself from the build plate.
The print removing itself from the build plate.

Instead of having the part do the grabbing so that it can pull itself off the build plate, let’s just have the extruder head do more of the work for us.

The printed part getting pushed off the build plate
The printed part getting pushed off the build plate

As you can see from the GIF, this part is a lot less complex and gets us similar results. The only thing that is happening here is that the extruder head is pushing the car off of the build plate. There are no non-printed parts in this product; everything is printed! So how did I employ co-processing?

The finished product, off the build plate.
The finished product, off the build plate.

The rear wing of the car was connected to the car body via a hinge, which I describe how to make here. The wing was printed in a horizontal orientation, and after the body of the car finished I rotated it into its upright orientation. Similar to the case of the printer climber, the part is now taller than the extruder head height. So once the extruder head finishes the buffer piece, it draws a horizontal, floating line as dictated by my CAD file.

An image of the CAD of the racecar part, with the buffer piece in the back and the hovering line to push the car forward.
An image of the CAD of the racecar part, with the buffer piece in the back and the hovering line to push the car forward.

The extruder head thus pushes up against the rear of the car, driving it forward and off the build plate. So I have now reduced the number of co-processing steps needed to get a part off the build plate from three to one. The trick is to design the part so that it can be easily removed from the build plate. This means very minimal surface area contacting the build plate during the print, which will make leveling the build plate pretty tricky. BUT BE CAREFUL: if the part is stuck too well to the build plate, you run the risk of messing up your extruder head. While you are rotating the rear wing up, you may want to loosen the adhesion a bit by wiggling the car around. Once you get it right, the part pops off the build plate.

The extruder head pressing up against the rear wing of the car, about to push it off the build plate.
The extruder head pressing up against the rear wing of the car, about to push it off the build plate.

But that’s not all. The extruder head isn’t the only thing that moves forward, in fact, the entire guide-rail system moves forward. Which means that we don’t just have to print one car, we can have a race to see who gets off the build plate first!

Two printed racecars about to be pushed by the printer head.
Two printed racecars about to be pushed by the printer head.

By doing co-processing to get parts off of the build plate, we are shifting the focus from the end product of the print job toward what we can create during the print. In this example, I’ve shifted the emphasis from the end product of the toy car and toward its “race” off the build plate. We can use such techniques to bring even more stories into our print jobs.

Thanks for reading! Please watch below for more details and videos of the print.

Alex Crease

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