monkeys at the zoo

Design and fabrication of polarizing filter holder Olympus 7-14mm lens

When working as a photographer, there is sometimes the need to reduce the glare on certain indoor surfaces of homes such as glossy wooden floors and tiles as it detracts from the image. The task at hand was to design and fabricate a filter holder to hold at 100*100*2mm Haida circular polarizing filter.

The first step was to design the filter holder in a parametric solid modelling program to get an idea of fit and form. The idea was to have the part machined in 30mm thick XPS foam board. An alternative was also getting the part 3D printed in PETG on the QIDI X-Plus.

Step 1 > design in CAD

image 1: The initial design. If fabricated like this, the holder will partially obstruct the view though the lens wide open at 7mm.
Image 2: The end design with cut down on each of the four corners.
Image 3: cross section of the filter holder.
Image 4: The profiles (yellow lines in image 2) saved out as a .dwg file ready to be imported into the CAM software.
Image 5: to create this part on the QIDI X-plus would take almost 6 hrs. Too much for this impatient monkey.
Image 5: One way to reduce the time is to decrease the infill but decided to CNC instead of 3D print.

Software used to create the tool paths Vectric Cut2D.

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Step 2 > Creating tool paths

Image 1: the tool path to create the outside of the filter holder. Note it travels clock-wise and on the outside of the profile.
Image 2: Approximately 10 passes needed to cut down 30mm .
Image 3: the tool path that will be used to create the section where the lens will sit. Note it is on the inside of the corresponding profile
Image 4: How the foam will look after the outer tool path and the inner tool paths have be done.
Image 5: The tool paths to generate the four pockets.
Image 6: What the part will look like after the 4 pockets have been completed.
Image 7: The final part with a 100*100*2mm section for the filter to sit.

The CNC used was a desktop Genmitsu ProverXl 4030. Being a novice in CNC, I was happy to work with foam as its a very forgiving material and creates very little noise when machining,

Have a heavy duty vacuum cleaner as lots of foam dust. The total machining time was just over 30 minutes, but this did not include the time taken to cut the initial foam stock, mounting the foam to the spoil board, remove and subsequent cleaning of the foam particles with a vacuum cleaner.

Use Candle to operate the Genmitsu, make zero position

Step 3 > Machining with CNC

Image 1: The XPS foam has been fixed to the coreflute spoil board with painters tape and super glue.
Image 2: Always wear ear and eye protection and make sure no loose clothing.
Image 3. The outline of the filter being machined. Note the CNC is working in a clockwise direction.
Image 4: The outline is finished and the CNC is working on the part where the lens will fit.
Image 5: Machining the pockets so the filter holder does not obstruct the field of view when the lense is wide open at 7mm.
Image 6. Machining the third pocket
Image 7. machining the section where the 100*100*2mm filter will sit
Image 7. The surface finish.

The initial test of the filter holder had it sitting on the Olympus 7-14mm lens sitting firmly without moving. With the unpainted blue foam version, there were reflection off the filter visible in photographs so a decision was made to paint it black. To keep the design simple, the filter was held in place with two rubber bands. Not a good long term solution.

Mote to follow.

Step 4 > Testing the part

image 1: The final piece after machining as a small amount of sanding.
Image 2: Blue reflections on the periphery of the photograph
Image 3: The filter ready to be mounted.
Image 4: The filter holder in the process of being painted with matte black paint.
Image 5: The filter holder in place.
Image 6: The filter mounted on the filter holder. The fit is not perfect due to the paint.
Image 6: The back of the filter holder with obvious lack of quality control from the paining department visible.

Without the polarizing filter and with the polarizing filter with the Olympus 7-14 wide open at 7mm. Notice the reduction of glare off the tiles.

Without and with polarizing filter at 14mm.

Part B is to replace the rubber bands & use a 3D printer part to attach the filter to the machined foam part.