I've been looking at picking up a automotive voltage gauge for my car as I recently had a battery go dead on me. I could not find one on http://www.thingiverse.com/ so I decided to make one up myself in Sketchup.

Step 1: Materials Required

Tools Required

1. 3d Printer
2. Paint Brushes
3. Sand paper / Files
4. Sketch Up
5. PC

Materials Required

1. Spool of ABS (correct size your printer)
2. Primer
3. Paint (color of your choice)
4. Electrical tape
5. Volt meter (Link)

Step 2: Sketch Up

Just as a head up, I know NOTHING about 3d modeling. I just started messing around with Sketch up and my 3d printer.
I got my dimensions from Autometer. You will also require a Sketch up STL plugin.

1. Open Sketch up and start a new Sketch.
2. Select and Delete the person
3. Switch to top down view
4. Zoom in to your preference. (mouse wheel)
5. Start your first Circle. Sketch up shows you the radius. (Which is half the diameter) (57.2 mm diameter)
6. Use the push pull tool to pull the bottom face down 2mm to 4mm down.
6. Start your second circle, this is part of the inner tube. (52.3 mm diameter)
7. Do a third circle about 1mm to 1.5mm smaller then the second circle. (51mm diameter) If its any thinner it will be too weak and break easily.
8. Now use the push/pull tool and pull up the small circle 30mm
9. After this you are on your own. The next steps will depend on what type of Volt meter you have purchased.
10. Export to STL.

Here is a link to my finished STL and Sketch up files on Thingiverse

Step 3: Load STL File Into Cura and Print.

As most people with 3d printers know, each 3d printer has its own tweeked settings. I have my settings in Cura and I pre-pair the print (my default settings are saved) and then load the gcode file into Printer interface. Use your own settings pre-pair and print!

Step 4: Assembly and Installation.

You'll need to file / sand down any rough parts of the print. Test fit your voltage meter. Glue the holding plate to the back of the gauge unit. Make sure you let the holding plate and holding bracket cool before you peel them off of the print bed or they will warp. I painted the face of my unit, used some acrylic primer and acrylic metallic grey. My voltmeter was a 4 wire setup, but the one I linked is a two wire. Red is positive and should go to a ignition positive wire. Black is ground, and needs to go to ground wire or exposed metal part of the body.