Spectacle Design | Dimensions of Spectacle Frames | Devon 3D CAD

Dimensions of Spectacle Frame by Neil Taylor at Devon 3D CAD
Dimensions of Spectacle Frame by Neil Taylor at Devon 3D CAD
Dimensions of Spectacles Frame

Look carefully at your spectacles and you will see, on the inside face of one of the sides, a set of numbers; such as 47-18-140. These numbers show you the fundamental dimensions of spectacle frames.

47 is the width in millimeters of the width of each lens. The width of the lens is usually measured at its widest position horizontally.

18 is the width of the bridge. The width of the bridge is the dimension of the closest points between the two lenses. I initially thought that this would be a dimension the dispensing optician could actually measure on the frame and on the customer’s face. But no. Perhaps this is too difficult to achieve. This is a pity because I am beginning to find out that this is important for finding a frame that fits properly. The width between the nose pads is crucial in getting a fit that allows the spectacles to give you the best vision.

140 is the length of the sides. Not shown here.

Range of sizes.

All major suppliers of spectacles have a range of sizes in stock for most styles of frames. But the dimensions are only an approximate guide to how well each frame will fit. It is still the skill of the optician to find the best fit in a style that complements the customer’s face. The designer must still stick to the conventions of dimensioning so that the optician is confident in selecting the best options.




NHS Innovation helped by Health Innovation Support and Devon 3D CAD

I have recently begun working with Alan McLeod, at Health Innovation Support, whose aim is to help innovators within the NHS to develop their ideas. There are some outstanding individuals working within the NHS and I hope to play some part in realising the potential of their innovations.

Medical Product Design. Here are a few reasons why I love this type of design:

  • Designing medical products is a worthwhile activity. I can’t get too excited when asked to design an add-on gizmo for the latest iphone. With good medical products you are potentially making a real difference to people’s lives, or even keeping them alive.
  • Most Medical Product Design involves some degree of advanced technology or ways of combining technologies to make a new product.
  • Because Devon 3D CAD is a small business, I get to work with small innovative companies. Focus on the outcome without layers of management or design by committee. This gets the brain working and collaboration with people eager to make a difference is the driving force.

Health Innovation Support has a long history of guiding innovative ideas along the Development Pathway to success as Medical Products. I hope to add my skill and experience to this important venture of NHS Innovation.

Click Health Innovation Support for more information.

Click Devon 3D CAD for more information.

Sheet Metal Design

Sheet metal design is one of the basic skills of a mechanical design engineer. I am a big fan of SolidWorks 3D CAD solid modelling software; it has a great suite of design tools specially for sheet metal design.  Here is a quick look at converting a solid part into a sheet metal part. This is not a masterclass in design, just a small, simple example of how good SolidWorks is at handling all the tricky bits of bends and folds.

For more sheet metal design go to the website of Devon 3D CAD.

Converting a solid part to a sheet metal part.

It is sometimes very convenient to start with a solid part, specially when you have already worked out the shape beforehand. Here is the finished part to get an idea of where we are heading.

Steel Cover DemoThe part is similar to a box with two flanges.











I started by modelling the basic shape as a solid. I always try to use geometry in design when I know that the part is symmertical, here about the Right Plane. The sketch is extruded a certain distance either side of the midplane.

Steel Cover Demo - Base part Sketch steel cover demo solid base by Neil Taylor at Devon 3D CAD

Next I shelled the part using the wall thickness I had chosen for the sheet metal.

steel rear cover demo solid base shell

Using the ‘Convert to sheet metal’ tool I choose one face to be static and choose the edges that will have to folded to form a sheet metal part. The software tool makes a break between the faces and allows you have a lot of control over how the folded faces meet at the intersections.

steel rear cover demo corner detail





You can see I have used an overlap feature where two faces intersect. The small gap between edges allow the part to be laser cut from the flat pattern.








Next I add a flange on one edge.

steel rear cover demo add flange









Then I mirror that flange about the top plane.

steel rear cover demo - mirror flange









Then I add mounting holes by extrude cutting 2 holes in each flange.

steel rear cover demo - add mounting holes









The ventilation holes are made by cutting one hole then propagating it using linear patterns.

steel rear cover demo - add vent hole









The first linear pattern makes one row of holes.

steel rear cover demo - add linear pattern









And the full number of holes is completed by patterning the row up and down the face.

steel rear cover demo - add second pattern









Finally a cable entry hole is added on the bottom face.

steel rear cover demo - add cable entry hole









And this is how the part is laser cut using the flat pattern from the 3D data.

steel rear cover demo - flat pattern