Small diameter aspheres are often significantly more difficult to manufacture than their optical performance alone would suggest.

In many projects, manufacturability issues are only discovered late during supplier discussions or fabrication quoting. By that point, redesigns, delays and unexpected cost increases are common.

One reason is that not every fabrication technology is suitable for every asphere geometry.

The applicability of computer controlled polishing (CCP) methods strongly depends on parameters such as:

clear aperture
smallest local radius of curvature
material
required tolerances
surface roughness

For small aspheres in particular, the number of applicable fabrication methods can become very limited.

Why fabrication feasibility becomes critical

In optical development, designers often optimize for optical performance first.

However, two lenses with similar optical performance can behave very differently from a manufacturing perspective.

Some geometries can only be fabricated using highly specialized processes. Others may not be manufacturable at all using standard fabrication approaches.

This becomes especially relevant for:

small diameter aspheres
high accuracy optics
steep local curvatures
tight roughness requirements

Without detailed fabrication knowledge, these limitations are difficult to predict during the design phase.

Examples of how PanDao evaluates manufacturability and fabrication cost can be found in the optical manufacturing use cases.

The “Pea Puffer” polishing approach

One example is the so-called “pea puffer” polishing approach, presented at EOSAM 2024.

The idea is relatively simple:

Instead of fabricating the final small asphere diameter directly, the asphere is temporarily enlarged to enable additional CCP polishing methods.

After polishing, the optic is center-ground back to the required diameter.

Illustration of the pea puffer polishing approach for small aspheres.

The diagram shows an aspherical lens temporarily enlarged beyond its final clear aperture diameter. The larger “pea puffer” diameter enables additional CCP polishing methods to be applied. After polishing, the outer regions are removed by centering or grinding to obtain the final asphere diameter.

This approach increases the number of applicable fabrication methods and can significantly reduce manufacturing cost and risk.

Example: manufacturable vs non-manufacturable

The following example from the EOSAM paper demonstrates the impact clearly.

Comparison table showing the impact of the pea puffer polishing approach on two small aspheres (Gudr1 and Gudr2).

For Gudr1 made of N-SF6, fabrication is not possible when pea puffer polishing is disabled. When enabled, the lens becomes manufacturable using CNC sub-aperture grinding and CCP bonnet polishing at a fabrication cost of €18 per lens.

For Gudr2 made of K-VC78, fabrication without pea puffer uses precision glass molding at €182 per lens. With pea puffer polishing enabled, the fabrication chain switches to CNC sub-aperture grinding and CCP bonnet polishing, reducing the cost to €19 per lens.

For one asphere design (“Gudr1”):

without pea puffer polishing → the lens could not be fabricated
with pea puffer polishing → fabrication became possible at approximately €18 per lens

Another example (“Gudr2”) showed an even larger cost difference:

precision glass molding chain → €182 per lens
pea puffer fabrication chain → €19 per lens

These examples illustrate how strongly fabrication feasibility and cost depend on the selected manufacturing approach.

How PanDao evaluates fabrication feasibility

PanDao digitally models optical fabrication chains and evaluates whether a lens geometry is compatible with specific fabrication technologies.

The software analyzes:

manufacturability
fabrication risk
required technologies
cost implications
alternative fabrication chains

This allows engineers and decision-makers to identify manufacturing limitations early — before production or supplier discussions begin.

Instead of relying solely on fabrication experience or iterative quoting, manufacturability can be evaluated directly from the optical design data.

Conclusion

Manufacturing feasibility is often underestimated during optical design.

Especially for small aspheres, fabrication constraints can strongly influence achievable cost, risk and supplier options.

Approaches such as pea puffer polishing demonstrate that alternative fabrication strategies can sometimes enable optics that would otherwise be difficult or impossible to manufacture efficiently.

By evaluating fabrication feasibility early, costly redesign iterations and supplier surprises can be avoided.

Want to evaluate manufacturability for your own optical systems?

Try the PanDao demo environment and explore how fabrication chains, risk and manufacturing cost change depending on lens geometry and production requirements.

Run your first analysis!