Rebuilding the Focusing Mechanisms of Old Microscopes Using 3D Printing

My first semi-professional microscope was a brand commercialized by an Italian company in the 70-80ties (the one with a black frame in the cover picture). It was a wonderful birthday present from my dear parents, who opened the doors to the fascinating microscopic world. That was the most advanced tool I disposed of for my biology exploration, and I enjoyed using them every time. However, disappointment comes after a few years when the fine focus screw stops working for the breaking of the internal mechanism caused by the poor quality of the material and design. It was disappointing but not a big problem for my early studies. After many years, the revolution of personal manufacturing using additive 3D printing finally allowed me to fix my old microscope and others I have collected in time.

In this instructable, I will share the files I have used to reconstruct the focus mechanism in two broken microscopes. I hope they can cheer up another nostalgic microscope enthusiast having a similar problem.

• An old broken microscope!
• OpenScad software.
• A 3D printer slicer. I have used the great Prusa Slicer but Unimaker Cura works great as well.
• A 3D printer. I have used a Creality Ender 5 PRO.

The attached file contains two modules:

• FineFocusSlider(). Model on the left side of the figure.
• CoarseFocusingSupport(). Model on the right side of the figure.

The first one was used to generate the fine focus slider of one microscope, while the other is the casing model for the coarse focusing rack and pinion mechanism. Both contain comments describing the different parts that they generate.

I have used a Wanhao i3 plus and a Creality Ender 5 3D printer to print the STL files generated by the OpenScad script. I have used layers of 0.2 mm and 80-100% infill.

The microscopes that I have repaired are probably Japanese manufactured but and were commercialized by am italian retailer with the brand name PAIM, and the second from Germany with Rewe. If you are familiar with OpenScad programming, it should be challenging to adapt to minor variations in microscope sizes or constructions design.

I will show the results of my reparations in the following steps.

The fine focus mechanism in bot the microscope consists of a slider attached to a coarse mechanism case that can slide into the guide in the main body arm of the microscope. A conic wedge attached to the fine focus screw is located at the bottom of the guide. There is a small steel sphere on the top of the conical wedge. The conical wedge moves horizontally when the fine screw is rotated, pushing up or down the sphere. The sphere is in contact with a block-shaped groove to accommodate the sphere and protrudes from the fine focusing slider. Another rectangular block on the top of the first one is used to support a spring that pushes down the slider to assure a stable contact of the sphere with the wedge.

In my first microscope, the metallic alloy used to make the slider cracked and broken first the bottom block and the lower part of the slider (visible on the left side of the Figure). Unfortunately, I am not good at metalworking, and I am not sure what material has been used for these parts, so I decided to try using plastic and a 3D printer to create a model of the broken part.

The model was strong enough to allow the microscope to work again. I am unsure how long this reparation would last if the microscope is often used. The part can be reprinted or even used to cast a metalling replacement.

Happy of this results, I tried to fix in the same way another microscopy having a different problem.

In a second Japanese microscope, bought from eBay in Germany and branded Rewe (probably resold in the homonym chain of German supermarkets), the metallic block containing the guide for the rank and pinion coarse focusing mechanism cracked and broken is shown on the left side of the first picture. I tried to repair it by gluing the two parts, but I thought it could be much more fun and a better fix to create a 3D model. And again, it was a success as shown in the second Figure. Well, at the least, for putting the microscope back into one piece, as shown in the third figure. I was even happier to notice that it holds together, but it also works! 

Note from the Figures that the fine focusing slider for this microscope differs from the first. I think it is a better design as it does not use instead of casted blocks to old the sphere and the spring, screwed support. 

I hope this project can help a nostalgic amateur microscopist repair his/her old microscope forgotten in a loft and bring back memories of past adventures in the worlds hidden in drops of pond water.