This parametric lens cap design is partly based on a number of old caps of mine and adapted for 3D printing in a combination of a hard front face and a grippy TPU ring, printed as one.
More than a year ago I designed very similar caps for various odd lenses, using TinkerCad. The results worked well, but the design was time-consuming to modify and the overall model quality wasn't so good.
Wanting to make a few more lately, I have ported the design to OpenSCAD and have made significant improvements. It is straightforward to customise and offers extensive additional control of the profile. A text label of one or two lines can also be added.
Script dimensions are in millimetres.
Possible Future Improvements
- An alternative script with the ability to scale up certain parameters automatically, based on rimDiameter, to simplify the generation of caps with features optimised for their general size.
- Option to add .svg file for embossed face graphics.
Main Parameters
- rimDiameter: Internal diameter of the gripping area. Measure the front of the lens barrel with vernier calipers for this. To adjust for a tighter fit, try reducing by 0.1mm - 0.2mm.
- rimHeight: Measure and determine how deep the grip rim should be. Higher values give more grip depth and holding power. It needs to be not so much so that the cap fit is too tight and also that it can fit all the way on without hitting the focus ring (at infinity focus) or some other feature on the barrel.
Additional Parameters
- faceHeight: Thickness of the cap face (part printed in a stiff material.) It helps to increase this for large diameter lens caps.
- edgeGrip: Extension of the face edges for finger grip, assists removal of cap.
- edgeChamfer: Amount of chamfer on face edges.
- rimThick1: Thickness of grip rim at base (front-facing.) A good value is around 2 * rimThick2 for strength. Too low a value can affect the durability of this important area.
- rimThick2: Thickness of grip rim at top (rear-facing.) Lower values may have affect on initial push-on force and/or fit strength.
- rimStepW: Inward extension to grip rim to improve mechanical strength of dissimilar polymer bond and cushion front edge of lens barrel.
- rimStepH: Height of rim step (Normal is 0.4 - for two 0.2mm print layers.)
- detail: Number of faces formed around model. Higher number = smoother finish and higher contact area with lens barrel.
Text
- text1: Fill quotes “” for a single label.
- text2: Optional second line. When filled, text1 is shifted upwards.
- text1Size / text2Size: Height of font.
- text1Font / text2Font: Fill “” quotes. Looks in system-installed fonts. The “:style=” is optional, but must be used if applying a style.
- textEmboss: 0.4mm embossing into face as default.
- textLineSpacing: The gap between two lines.
- textVAdjust: To tweak the position of the whole text up or down.
A couple of my examples pictured include an embossed logo. To include text and graphics, either text line can be filled, then adjusted up or down. Then add a separate .stl or .svg as a negative volume on the cap in your slicer.
The "Fira Sans Condensed" font family used in the script can be found at https://fonts.google.com/specimen/Fira+Sans+Condensed
Material Options
There are a lot of variables and possibilities!
Material combinations I've tested and know bond with TPU:
- PLA
- PETG (Clear, uncoloured PETG can be used to make a white-balance cap.)
- ABS
- ASA
Only going off exactly what I have tested, though. Your results may vary.
The TPU I used is Amazon Basics Black TPU, which is Shore 95A. A lower hardness could have an affect on the fit, but I have not tested others.
TPE filaments do not like bonding with other plastics in my experience, but I'd like to be proven wrong. PP + TPE may work. Possibly PA+TPE?
Single-material options:
- TPU: Works well, but the face will flex a little and may touch the lens glass if pushed in. Fine for small caps.
- TPE: Results similar to TPU, but the matt finish is maybe slightly grippier.
- PLA: Trial-and-error. Can work, but very stiff and the fit may be wrong if not absolutely accurate.
- PETG: A little more flex than PLA, so may have a slightly more forgiving fit.
- ABS/ASA: Not tested yet. Probably similar results to PLA.
- Other: Try something and let me know!
Printing
The script is written for 0.2mm layers and a 0.4mm nozzle in mind - probably not a big deal if using a different setup, but it will help to check the parameters vs. slicer settings so that it looks right.
100% infill is recommended for strength.
For dual material, slice for printing the cap face (up to "faceHeight") with a rigid filament, then set a change to TPU for the grip ring. This will require setting mid-print gcode changes to limit the TPU printing speed, and possibly also to temperature and cooling (refer to the included .3mf examples.)
Go with at least the manufacturer's recommended melt temperature for TPU, possibly a little higher if this helps with bonding to a higher melting face material.
For single material, use whatever settings work for you.
Geoff
