![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/IMG_1259_Edited-768x1024.jpg\")
<\/figure><\/div>![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/IMG_1260-768x1024.jpg\")
<\/figure><\/div>The easiest approach would have been 3D printing these, because the hood is under positive pressure any leakage should be pushed outwards. There are a few issues though:<\/p>
- The only printers we have available are FDM, meaning we’re printing them standing on end so the layers are aligned with the tension load of the hose\/hood, the potential failure mode is a shear across the layer which would be catastrophic<\/li>
- FDM printers have high porosity, much larger than the particulate we’re trying to block. Although when the hood is powered it’s under pressure, there may be exposure to a hazardous environment when the blower is off (power runs out, it’s been removed for storage\/etc), meaning we could be absorbing particulate then blowing it into the user’s helmet when it’s powered on again<\/li>
- 3D printing at accelerated speeds yielded about an adapter every hour and a half, we needed to make at least 32 of them and possibly more with a goal of a few day turnaround. Although we have a large farm, this is still a lot of print time and post-print cleanup<\/li>
- 3D printing leaves a lot of sharp\/hard edges from stringing and layer to layer bonding. We don’t want to have our adapter damage\/abrade the hood or we’re causing more harm than good<\/li>
- We love 3D printing, but it’s sometimes not an appropriate application beyond prototyping. . .<\/li><\/ul>
The first step was trying to ascertain the scope of the challenge – quantity, turnaround, cost, etc. In this case the desired cost was zero, quantity high enough to merit some optimization, and the turnaround fast. We tried to hunt down a model and once we figured out the model of the hose (3M Adflo) it was quick to find this adapter on Thingiverse<\/a>. The hospital didn’t have a working caliper but via some pictures with a reference ruler in frame we were able to confirm the dimensions were in the ballpark:<\/p>
![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/WeChat-Image_20200411192811-768x1024.jpg\")
<\/figure><\/li>![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/WeChat-Image_20200411192848-1024x768.jpg\")
<\/figure><\/li>![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/WeChat-Image_20200411192858-1024x768.jpg\")
<\/figure><\/li>![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/WeChat-Image_20200411192909-768x1024.jpg\")
<\/figure><\/li><\/ul><\/figure>The next step was brainstorming available materials. The OD and ID matched up reasonably well with 1-1\/4″ schedule 80 pipe, but on a weekend it wasn’t feasible to pick up thick wall plumbing pipe as all the true plumbing supply stores were closed. We stumbled around for a bit until we realized that a 1″ schedule 40 pipe ID was still great, but if we glued a coupler onto the outside it’d get us up to the OD ring size we needed to get the hose coupler to lock. <\/p>
![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/IMG_20200412_144455-768x1024.jpg\")
<\/figure><\/div>A run to the hardware store yielded plenty of fittings:<\/p>
![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/IMG_20200414_114957-1024x768.jpg\")
<\/figure><\/div>We weren’t sure how to couple to the hood, we thought a slip ring to a taper lock would work well and wouldn’t require tools or any other supplies so we printed a sample:<\/p>
![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/WeChat-Image_20200412131947-768x1024.jpg\")
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<\/figure><\/li><\/ul><\/figure>![\"\"](\"https:\/\/www.sector67.org\/blog\/wp-content\/uploads\/2020\/04\/IMG_20200414_093719-768x1024.jpg\")
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