Engineering with SOLIDWORKS and 3D Printing = A Restroom Rescue!

by Lauren McGarry

Last Time on Workplace Restroom Rescue

As a new GoEngineer Applications Engineer I was encouraged to give 3D printing a try. When I learned that the stall door in the women’s restroom didn’t close properly, I knew I had my first project. I used a combination of SOLIDWORKS and the uPrint SE Plus printer in GoEngineer’s San Diego office to easily design and execute a solution. With the stall door properly closing, a new piece of restroom hardware in need of 3D printed rescue stepped into the spotlight.

“Are you going to fix the toilet paper dispenser soon?” my coworker asked. Time for another Workplace Restroom Rescue!

Engineering a Solution with SOLIDWORKS

The cause of the problem was obvious when I compared a functional model to our toilet paper dispenser. 

Our dispenser is missing several components, most importantly for this project, the left and right roll-holding arms. Detail of functional dispenser (left) and nonfunctioning dispenser (right)

What’s the plan?

The simple solution, I thought, was to attach new holders, approximately the same size and shape as hubs in the middle, to the walls of the dispenser. Before heading to SOLIDWORKS, I took some quick measurements of the dispenser and of the toilet paper roll. Because both sides of the dispenser needed new paper-holding arms, I created two different designs. One was meant to match in height, width, and shape the hub in the center.

For the other, I made changes to improve the arm’s gripping power on coreless toilet paper rolls.  These are ones that that are held in place by being pinched between the arm and the central hub. The second design is conical, instead of domed, and a little taller in order to better pierce into the divot in the center of the toilet paper rolls.

Both include broad, flat bases made with simple boss extrudes for easier application of double-sided tape. I considered shelling the parts to save material but printing “sparse” used less material than shelled versions of the parts. Though the cone model was printed sparse low density and the dome model was printed sparse high density, they took about the same amount of time to print. With FDM 3D printing the number of layers has a much greater impact on print time than interior fill structure.

It’s time for 3D Printing!

Fans of the Workplace Restroom Rescue series will remember that for the stall door bracket we used a uPrint SE Plus 3D printer, a fused deposition modeling printer. This time we printed both designs on two different machines: the Fortus 250mc, an FDM machine, and the Objet 500 Connex3, a PolyJet printer. The models, saved as .stl files, were processed in Insight for the Fortus. Objet Studio was used for the Object 500. Insight offers more control over toolpaths than CatalystEX, which we used to process our .stl files when working with the uPrint SE Plus.

PolyJet parts, while visually impressive, can be brittle. To offset this we printed the parts in Digital ABS, the strongest PolyJet material.

Polyjet vs FDM

Usually PolyJet is a faster printing method than FDM. In this case, the Fortus 250mc finished in about half the time—45 minutes compared with the Objet 500 Connex3’s 1 hour and 20 minutes. If we were printing more pieces or switching between support material and base material more than once, the Object would have had an advantage. For this project, the pieces were oriented so there was support material only on the bottom of the pieces. The FDM pieces were also printed with a sparse interior fill structure, for which PolyJet printing does not have an option. 

Eager to compare the two shapes, I snapped off the support material, cut some squares of double-sided tape, and headed to the restroom.

I found I had misunderstood the process of reloading toilet paper, so I had a little trouble with the tamper proofing. Luckily, it was no match for the potent one-two punch of Google and office supplies.

The shorter, domed hub worked better. With the conical one attached to the wall, it was difficult to slide the metal exterior back into place over the rolls of toilet paper. It kept poking into the rolls and getting caught between the layers. So, when the PolyJet parts finished printing, I replaced the conical FDM part with the round PolyJet part.

The support material on the Digital ABS part was soft, rubbery, and water soluble and had to be washed off. The stickiness of the “glossy” finish on the part made it more difficult to attach the double-sided tape.

Overall, FDM made more sense for this application. I didn’t need PolyJet’s precision or smooth finish and the material in which we printed the FDM part, ABSplus thermoplastic, worked better with the double-sided tape. As an unusual bonus, the FDM parts also printed faster in this case. 

Workplace Rescue Complete

Even with the domed hubs, closing the dispenser over new bathroom tissue rolls is not the easiest task because of where and how the new arms are attached. Though working now, this solution merits some revision. Not every idea works perfectly on the first go and 3D printing is a good tool for prototyping and testing functioning models to improve a design. Especially with parts of this size, it is quick and relatively cheap to print, test, redesign, and reprint multiple iterations.

That said, toilet paper will not be falling on the bathroom floor anymore, and that counts as a success.

 

 

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