Expanded Zipit Bottom Case: my first 3D printing adventure

3D printers have been around for quite a while now. When I first read about them I had a million ideas for things I could make. Unfortunately the introductory cost and learning curve were too much to bear. My 3D buzz wore off and the world continued on perfecting the new technology. It’s 2016 now and after seeing this article on Hackaday about a low cost, decent quality beginner 3D printer, I decided it’s about time I do something with 3D printing. That brings us to the Zipit. The original batteries for it are not available and finding a suitable replacement is not easy either. Let’s make a replacement bottom case for the Zipit with more room for a bigger battery.

My 3D modeling skills are non-existent and I didn’t want to spend days learning how to use some advanced CAD program. This led me to Autodesk’s Tinkercad. It’s pretty basic but has a good library of shapes and a simple UI which I got accustomed to very quickly. The program is browser based and you have to create an account to get access. Fortunately, they do allow exporting so you can download your 3D model at anytime. Calipers in hand, I got started with a basic bottom shell replacement for the Zipit.

I started with a box that matched the outside dimensions of the bottom case with a 20mm height then cutout an area for the empty inside. Next, I added three posts for the screws. These posts have a large square base that switch to a cylinder at the top (near the board) which provides beefier support for the bottom and prevent the posts from touching any components at the top. Cutouts were added for the MiniSD card, volume buttons, headphone jack, dock port, and DC jack. A recess was created around the edge where the top and bottom cases meet. I also added some support posts for the volume buttons, DC Jack and an extra support in the front right corner near the card slot. The final step was to curve the front edge and add the curved cutout where the notification LED’s are.

I still don’t have a 3D printer yet so I needed to find someone to print it. The exported case design was uploaded to 3D hubs and ordered from the 3d-printing-chicago hub. I chose to print in Colorfabb XT Grey filament at a layerheight of 200 on a Craftbot 3D Printer. Ten days later the print arrived at my door. It would have arrived sooner if the postal service had not sent my package all over creation. A quick test fit of the case showed a few problems but overall, it was pretty close.

The screw posts were about 1mm to tall and were trimmed off with a Dremel cut-off wheel. The original Zipit screws were not long enough to go through the posts I made so I replaced them with 3 longer ones from my parts bin. I forgot to add the edge recess to the front curves and forgot the cutouts for the plastic clips that hold the top case to the bottom. A razor blade fixed these easily. The DC Jack placement was incorrect by almost 4mm and had to drill a new hole for it. The headphone jack and dock cutouts are a bit wide but work fine.

Until I find the largest replacement battery that will fit the allotted 69L x 60W x 12H battery area, I made a parallel 3 cell pack from Zipit batteries. Charging it takes considerably longer. Possible battery candidates:

I have modified the original design to (hopefully) remedy the issues noted above. I haven’t decided yet if I will get another printed since the first works well after modifications. Perhaps I can use this as an excuse to get a 3D printer. Here are links to the design files if anyone wants to get their own printed or modify the design to suit their own needs.

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