Ventilator Challenge – Part 2

Some more thoughts on the before-mentioned Ventilator Challenge:

As mentioned in the first part, I am not a medical professional, and everything I say here is my shot-from-the-hip opinion and should not be taken as fact or good practice.

The specifications of the Codelife Ventilator Challenge are a bit thin. There is a longer, well done specification for an emergency-type ventilator from the UK government.

If we look at the history of ventilators, most of them seem to have volumetric pumps as pressure sources, often a kind of bellows that moves with the same frequency as the lungs of the patient. Accordingly, there are some designs of emergency ventilator concepts (example) that use bag valve masks and add a motor-driven mechanism to push on the bag – and therefore air in the patient’s lungs.

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3D-Printing, at last

Since my first contact with 3D printing, about a decade ago, I have had some prototypes printed, but never got into operating a printer myself. That has changed.
About a year ago, I bought a Creality Ender 3, a ridiculously popular and very affordable FDM-Printer. I am still amazed at how much high-tech you can get for the price of a good pair of shoes.

That being said, getting the Ender 3 to work properly was quite a hustle in my case. At this price point, not much is spent on quality control. Creality is said to have good customer service, but I decided to take the hard way and spend some evenings debugging and learning:

Warped Bed

The building platform arrived deformed, which appears to happen often. The platform needs to be perfectly planar, so the first layer of plastic can be evenly squeezed onto it by the nozzle. I found that taking apart the platform assembly and carefully bending (hand and knee) the Aluminium sheet can get you within about 0.05 mm, from initially ca. 1.5 mm “concavity”.

Nozzle Temperature

This one seems to be less common, or is at least not mentioned in the plethora of YouTube videos about the Ender 3. The temperature sensor of my model is round about 20 K too low, so my prints would not stick to the bed when I used the recommended settings for the material used. Also, the layer adhesion was extremely bad. Fortunately, I have a small USB thermal camera (that cost more than the printer, by the way), so I found the issue filming the hot-end and adjusted the temperature setting in the slicer accordingly.

Contorted X-Axis Profile

Granted, this one was my fault. I carried the printer without taking off or securing the spool, which fell on one edge of the bed. Enough to twist the 20 by 20 mm Aluminium profile forming the X-axis. The effect of this is a literal brain twister because the bed seems to be perfectly level during manual bed levelling, but prints fail miserably. With a lot of measuring, I managed to twist the profile about half a degree back in the other direction.

With this, and a lot of other, less essential modifications, I think my Ender 3 is a fantastic machine for its price, but definitely nothing for someone who is not interested in the process, but in results out of the box.