JBR MILLING GUIDELINES FOR OPTICAL MIRRORS AND LENSES

1、 Introduction:

This specification should be applied for the machining of all punches which are destined to inject parts with an exclusive optical function such as : 

punches for lighting mirrors with following surfaces : Parabolas, SC1, SC1+, SC2, SC3, SC3X, elliptic…etc , and also for the punches to inject plastic lenses.

2、Recommendations concerning “Machining Techniques and Strategies”

High speed milling (>15000 revolutions/minute) is recommended for the machining of the punches for optical parts, this in respect to the usual curves and in function of the machining times generated by the complexity of the optical .

For the final milling the CAM program CATIA V5 , which gives the best results in respect to the surface finishing and in respect to the surface shape, is highly recommended. During the final milling the diameter of the tool and the step will be calculated in function of

the topology of the applied surface. In any case the step should not generate a ridge between to steps, which overruns 0,005 mm perpendicular to the surface shape.

3、 Requirements concerning machining and tool cutting path:

• In a vertical direction, for a punch with a complex optical surface placed in the same position as on the vehicular.
• In the direction of the ridges of the surface, if they exists or following the is parameters (u , v) of the surface.
• The cutting tool must be disengaged all the way around the contour which limits the optical surface. This  has to be previewed in the conception of the part. If this is not the case, the toolmaker should inform this anomaly immediately to the Valdo project group.
• All milling stops and all machine slow downs must happen outside of the optical surface. All machine stop on the surface is forbidden because this is generating dazzles on the final part.

4、 In the case of plastic lenses:

•  The punches and cavities for plastic lenses should follow the same rules as the punches for the reflectors for machining and polishing such as :
• Final milling with small cutting tools and in the direction of the eventual ridges this to obtain a minimum of polishing.
• No machine stop on the surface / Machining from top to bottom and from bottom to top without machine stops and with the necessary cutting tool disengagements.

5/Control for optical punches:

All mechanical l part with an optical function must have a 3D surface control and will be followed by a quality sanction following operating instructions in the blue text here under

The basic requirement is:

The standard deviation for the global optical surface should not exceed +/-0.005mm.

The local maximum allowed deviation should not exceed +/-0.02 mm

These figures could eventually be modified in function of the requirements resulting from the optical study (e.g. the punches for elliptic modules could generate specific restraints inducing a more restricted tolerance gap). The final interpretation is the responsibility of the Valero optical Laboratory. 

After measuring of the surface of the punch the unit of points are to be repositioned by “PROSE” or equivalent. Display of the results is done by “is deviations”, or by “local cuts” as shown in the example here under.