Shop-Vac Tool Adapters for 2½" Hose

Other adapters in this series:

• Shop-Vac 1¼" Locking End to Non-Locking End

These adapters are designed to go on a Shop-Vac brand wand/nozzle and allow the use of tools of other diameters. The fitment needs to be precise. Even a 0.1 mm difference is noticeable, and 0.2 mm is the difference between a good fit and an uncomfortably tight or loose fit.

I found that whether I printed from PLA, PETG, or ABS, the adapter's cones shrank. ABS shrank more, of course, but to my surprise, even PLA and PETG did not stay true to size. What's worse, the shrinkage was uneven, it depended on the wall thickness and the cone diameter.

This is a nightmare scenario. Add various filaments and printers to this mix, and you get an unpredictable final size in a situation where even a little change matters.

Normally, you can make a part larger or smaller in the slicer by using scaling, or make it thinner or fatter by using Horizontal Size Compensation, a.k.a. XY Size Compensation.  But such an approach may not work with these adapters: you may be in a situation where the wand end needs one size compensation, while the tool end needs another.

First, print the adapter, making sure not to overheat it (do not select higher temperatures than needed). Use the fan. PLA does best with 100% fan; PETG can tolerate ~25%; ABS can tolerate ~10%.

Does it fit well? If so, we are done. If not, you can follow the CAD link and use configurations to adjust the diameters slightly. You do not need to know the CAD to do that, you only need to pick the values from the already-defined configurations.

Here is how it works. Follow the link to Onshape at the end of this page. All the adapters on this page are reducing adapters, since the tool diameter is less than the wand diameter. Click the “Reducing Adapters” tab at the bottom. Now look at the top left of the screen, where it says “Configurations”. These are lists and checkboxes that modify the part. If the “Features” panel partly blocks them, position the mouse on top of the “Features” panel until the mouse pointer changes to the “slide” icon and drag the “Features” panel down a bit. This way you will be able to see all pre-defined configurations possible for this part. In particular, you should be able to see the following configurations:

• Adapter - pick the one that you want, for example 2½" to 1¼"

• Adjust Wand End - larger numbers make the Wand End fit looser

• Adjust Tool End - larger numbers make the Tool End fit tighter

• Labels - check the box if you want the labels

For the models I have uploaded here, 

• Adapter=2½" to 1¼", 2½" to 1½", or 2½" to 1⅞"

• Adjust Wand End=0.0 mm

• Adjust Tool End=0.0 mm

• Labels=yes

This does not imply that the models I have uploaded are true to size. This merely means that the PLA shrinkage that I have experienced is already built into the model's dimensions. PETG shrinkage should be similar. However, if your material or printer behaves differently than mine, these adapters will not fit well, and you will need to go to Onshape and choose non-zero values for "Adjust Wand End" and “Adjust Tool End”. Negative numbers will shrink the diameters, positive numbers will enlarge them. For the ABS, expect to adjust +0.2 mm for the wand diameters, 0.0 mm for the tool diameters.

To export the model from Onshape, first set all configurations as you want them. Then, right-click the "Reducing Adapters” tab and select “Export…”. Choose “Format: STL”,  “STL Format: Binary”, “Units: Millimeter”, “Resolution: Fine”.

It may take a few tries to get these to fit just right.

Printing Considerations

Perimeters

With a 0.4 mm nozzle, I suggest setting the perimeter count to four (this way you are asking for four inner and four outer perimeters, eight in total). Although the adapter's wall thickness varies between 2.2 mm and 2.8 mm and is less than eight perimeters of 0.4 mm each, setting the perimeter count to four does not hurt and in Simplify 3D v.4.x it made the difference between having an unfilled gap between the outer and inner shells and having it filled. No matter how you do it, once the adapter is sliced, run the print simulation to make sure that the gap between the outer and inner shells is filled, otherwise you will end up with a weak adapter that makes crackling sounds when squeezed.

The Seam

When an object is printed on an FDM printer, there will be a seam at the start of a layer. Objects with sharp corners may be able to hide the seam at the corners, but a cone-shaped vacuum adapter cannot do that. The preferred option is to put the seam at the back of the adapter (opposite to the labels). Another option is to make the seam random, so each layer starts at some random point. This will disperse the seam, but will likely cause little blobs all over the surface. By playing with the retraction length, you may be able to minimize these blobs, but if not, you may find that one straight seam looks better than a hundred little zits.

Layer Lines

Layer lines affect these adapters in two ways. One is the diminished lateral strength. To compensate, these adapters have thicker walls than their injection molded counterparts. Second is the negative effect on the friction fit. As long as these adapters are attached to injection molded or metal tools and wands, this is not a big deal. Also, you can vary the friction by printing these adapters from different plastics. However, if two 3D-printed adapters are attached to each other using friction fit, layer lines will act as miniature locks. Smoothing 3D printing surfaces is a separate subject, I will briefly mention the possibilities:

• ABS prints, sanded and smoothed with acetone vapors

• Polymaker PolySmooth PLA, sanded and smoothed with alcohol vapors

• Any plastic that can be sanded and painted with sanding primer

If you plan to sand these adapters, you will likely need to adjust the diameters to account for it.

CAD Link:

https://cad.onshape.com/documents/c96d293d33ba346439b55efa/w/6a299c1617cd377fc4040d9c/e/ef5ee08dd41ff113bd42a18b

Honorable Mention

I happened to see this video in 2018, just after I bought my Shop-Vac. Evan and Katelyn do not mention fitment problems that will likely bedevil these adapters: if you order the prints online, especially without testing them first, they may not fit well. But I am thankful, and this was the starting point of my 3D modeling.