Rain Gauge (using advanced techniques and PVB)

Update History:

11th April 2021:

• Added links to my other related designs at the end of the description

24th March 2021:

• Added a photo of IPA smoothing using a brush

23rd March 2021:

• Provided the 3MF files for download. Now can directly start from my print settings.
• Added information about my new experience with PVB that has been dryed for about 4 weeks
• Added more information to the intro

Introduction

I wanted to print a beautiful rain gauge as a present for my wife. So this is the design I came up with. One main design goal was to be able to both measure very small quantities of water, as well as larger amounts, in case of prolonged heavy rain. So the measuring cup has a unique, conic shape. Also I was very keen on trying transparent material, so I really had a lot of fun with this project and extended my knowledge and experience with 3D printing quite a lot.

This design is not for the faint of heart, since it makes use of some advanced techniques, such as:

• Spiral vase mode
• Multi color printing by swapping filaments between certain layers
• Bridging (for the numer/raindrop infills)
• PVB printing with IPA smoothing
• Using over-extrusion to print a stronger cup using a standard 0.4mm nozzle

But don't worry: The heavy lifting has already been done. Just follow the step-by-step instructions below. All you have to do is get the required materials, download the 3MF files, hit the slice button and print away.

Also, if you are like me - always looking for some challenges and new experiences with 3D printing - then give this design a try and dive deeper into the 3D-printing sea.

Parts required

This photo shows all the parts required to assemble the rain gauge:

In addition to the printed parts (see details below) you will need some screws:

• 4pcs 2.2mm x 4.5mm flathead screws for connecting the “number scale” and “decoration scale” by using the “top scale connector”
• 4pcs M3 x 4mm flathead screws (ISO7380) for mounting the “number scale” and “decoration scale” to the “bottom ring”
• 2pcs M4 x 10mm flathead screws (ISO7380) for mounting the “bottom connector” to the “bottom ring”
• 6pcs 2.2mm x 16mm flathead screws for connecting the main assembly to the “top ring lower” and “top ring upper”
• A 12mm rod (e.g. aluminum tube) to mount the rain gauge to your garden

Since you most likely want to use the rain gauge outdoors, the screws must be made from V2A or other suited material.

Printing

Most of the parts are printed in PETG, using the colors

• clear/natural (transparent)
• black
• blue translucent
• yellow

I recommend printing the cup using PVB natural. My first print of the cup was also from PETG, so if you do not want to go fancy, just stick with PETG.

I have printed all parts on the textured PEI powder-coated spring steel sheet (I really love this sheet and only use the smooth sheet for TPU and PC printing).

Good news: The parts have been designed with 3D printing in mind, so you will not need any supports at all.

Printing the cup

The cup is printed using the spiral vase mode in PrusaSlicer. I did add a 10mm brim to make sure the rather tall print with the rather small base will not detach itself from the print plate. However the material (both PETG and PVB) did stick so well, that it probably was not really needed:

The cup can be printed in clear PETG. This is what my first cup was made of. But a few months ago Prusa announced their new Prusament PVB natural. So I bought a spool and reprinted this part using this brand new and fascinating material. After printing I have used IPA for smoothing the part. By applying IPA inside and outside with a brush multiple times (with longer pauses to let it dry) the part becomes transparent - almost like glass:

Don't forget to let the part dry for another week or even longer, to get rid of the residual IPA in the material.

The result is astonishing. Look at the comparison to the PETG print:

For printing PVB in spiral vase mode I also did try Prusa's new 0.8mm nozzle, printing in 0.3mm layer height . By performing some more tests, I found out that you can achieve almost the same result (I did not notice any visual differences after smoothing) by printing with a standard 0.4mm Nozzle in 0.2mm layer height, simply by using an extrusion multiplier of 1.3. This technique surely is also interesting for many other prints in spiral vase mode.

There is one special feature with IPA-smoothed PVB you should be aware of: I noticed that even when drying the cup for one or two weeks, the PVB material still becomes milky white when in contact to rain water for some hours. This effect seems to be reversible - at least my cup became clear some hours after removing the water. In fact this effect might be useful when using the material for this rain gauge: You can clearly see (pun intended) what part of the water has been in the cup for a longer time. So you can easily read how much water has been added by today's rain:

I am right now experimenting with a second cup that has been left to dry for multiple weeks. I am keen to see if the effect of becoming white has been eliminated.

Update: I now have tried the second cup, that has been drying for about 4 weeks or so before touching any water. Now the cup seems to stay perfectly clear and not become white from water any more. So I recommend letting the IPA-treated PVB dry for about a month.

Printing the other parts

Printing the other parts is almost straightforward. The main thing you have to care for is the color changes for the scales:

For the two different type of scales (decorative and number) you have to print 2 parts each in 0.15mm layer height. Please inspect the bridging direction after slicing: I recommend using a 45° orientation for bridging the rain drop and number fillings. You also have to swap filament to change the colors at certain layer heights:

• For the “number scale”:
  • start with black
  • switch to yellow at 0.8mm
  • switch back to black at 1.4mm
• For the "decorative scale":
  • start with black
  • switch to yellow at  0.8mm
  • switch to blue at 1.4mm
  • switch back to black at 2.6mm

Another part where you might want to use color swapping is the "top scale connector". Print in 0.15mm layer height:

• start with black PETG
• switch to clear PETG at 3.2mm

Recommended print layer heights and colors for all the other parts:

• "bottom connector": Blue translucent PETG in 0.25mm
• “bottom ring”: Clear PETG in 0.15mm
• “top ring lower": Clear PETG in 0.15mm
• “top ring upper”: Blue translucent PETG in 0.3mm

The STL files already are in the recommended print orientation, so you will not have to change orientation of the parts for printing.

Assembly

When all the parts are printed successfully and you have managed to find or order all the screws required, the assembly is very easy if performed in the correct order.

Step 1 is to connect the decorative and the normal scale at the top. You will need 2 screws 2.2mm x 4.5mm for each pair of scales:

Step 2: Now it is time to connect the bottom ends of the scales to the “bottom ring”. You will need 2 screws M3 x 4mm for each side:

Micro-step 3: Now the scale assembly is finished:

Step 4: At the bottom now attach the “bottom connector” which connects the gauge to a 12mm rod. Use 2 M4 x 10mm screws:

Micro-step 5: So here we are with only a few steps left:

Step 6: Next take the 6 2.2mm x 16mm screws and screw them from below the “top scale connector” through the “top ring lower”:

Step 7: Now comes the most rewarding step: Slide the cup into the scale assembly. It should fit nicely:

Step 8: Finally use the already attached screws from step 6 to attach the “top ring upper”:

Finisher step 9: Congratulations - you are done:

Now find a nice place in your garden and mount tuck gauge onto a 12mm rod - I prefer using an aluminum tube.

Design and Source Code

I have used OpenSCAD to create this design:

The source code is provided, so if you want to adjust this design to your needs, just go ahead an do so.

Happy printing!

If you like this design, then please leave a like and also post a photo in the comments. Also check out my other designs. The rain gauge fits really well with the following designs:

Colorful Wind Wheel:

Modular Plant Tagging System: