Are You Finished with Finish Blockers?

By Christie Walker
When you’re a reporter, people have a tendency to talk to you. So when the topic of finish blockers was on the editorial calendar, I decided to talk to people to get their thoughts on this segment of the lens processing business. By talking with some people, I heard that the finish blocking area was a problem area with the most breakage and requiring the most skilled labor. If there is a problem here, you’ve just ruined/wasted all the time and effort and material used to bring the lens to this point.

Basically there are two options when it comes to finish blocking, manual and automated, with a third option—a single lens block carrier—looming on the horizon. Here’s what I was told:


The traditional method of applying a finish block involves a lensometer and a highly skilled technician. The lens is aligned manually and the block is applied. This is very primitive but still the most effective method.


A verification device is used but it is not, according to some, as accurate as the lensometer and a GOOD technician. Automation eliminates the need for the “highly” skilled technician who can be replaced by “any” employee.

Next Generation:

A new system about to be released will employ a single lens block carrier that moves the lens from surfacing through coating, eliminating the finish block all together. This will “revolutionize” the industry.

But if you really want to know how finish blocking is actually performing in an optical laboratory, you need to go to the trenches, get a little polish on your sleeve and ask a lab guy or gal. Here’s what your peers have to say on the subject.

Ted Mabry

Vice President Production, Interstate Optical

Mansfield, Ohio

I don’t believe conventional finish blocking is the best or most accurate because it still involves human judgment. Finish blocking for us has gone from a labor intensive high-breakage area to a low-breakage simplified area first through the use of CAD blockers, then the Weco Verifier took care of all single vision orders and then the A&R RobControl took care of inspecting and blocking almost all the rest. In the future, I can see further enhancements to a machine such as the RobControl seems likely. I don’t think finish blocking is worst area in the lab but what is will depend on which day you ask me, I believe the most labor intensive/breakage producing area is finish assembly while the most erratic would be hard coating.

John Greco

Operations Manager, Superior Optical

Ocean Springs Miss.

I’ve been in this business for around 38 years and have seen it all. I can remember “hand chucking” lenses for edging in the late 60’s for the old Shuron edgers. There was no block. It was all hand/eye coordination and like you stated above, it takes a person with attention to detail and precision to do this.

Then in the 70’s we used alloy blocks with the old Coburn system. That was another tedious method that used a lens pre-coat that was less than adequate.

Then along came leap pads and metal blocks changing to leap pads and plastic blocks. For these methods the optical tech had to look through and block on cross hairs like a gun site to avoid parallax. This took an experienced person.

I’ve installed the other devices such as automation robotics that inspects and blocks the lens for edging. The Weco Verifier that does the same. There are several out there that use automation. The problem I see is that labs can’t find the “old timers” or people with experience to do it the old way but let me say this…if the automated machine gets out of calibration, look out. Everything is wrong! My point…it still takes someone with that unique skill and keen sight to look at a lens on the block to see if it’s blocked correctly, even when done on an automated machine.

Is the finish blocking the worst area of the lab? I think not. Let’s talk about the nightmare that is “super hydrophobic” AR coated lenses. Now there’s a beast we all face. Key word here is “slippage” in the edger after finish blocking. I could write you a book on this one.

Corrine Hood

President, Katz and Klein

Sacramento, Calif.

I feel that conventional finish blocking is still the best/most accurate way to go since the verification devices still don’t do everything and are not always accurate. We agree with what you have been told above—everything is important but layout and blocking is crucial. We’d like to see a stay-on-the-same-block system for surfacing that went through finishing as well. We’d also like to see better frame tracers and LMS systems that will handle more tracing points. We don’t think finish blocking is the worst step in the lab. We believe the hand work for special frames and wraps is the hardest thing even with the sophisticated edgers today.

Dale Parmentari

Vice President, Balester Optical

Wilkes-Barre, Pennsylvania

As far as finish blocking is concerned, we use the Satisloh SL60 finish blocker. We have four and these serve as a blocker and an additional inspection station checking for power, axis, prism. The machine will not allow the lens to be blocked if the items measured are not correct. The SL60s take a little more time. However, you are inspecting as well as blocking. With these machines you do not need the level of skilled help needed with a traditional lensometer; however, you still need a traditional lensometer for single vision polarized and a few other products that cannot be read by the semi-automated blockers.

We feel the addition of this technology has reduced spoilage at finish blocking and the added inspection station has improved our overall accuracy and first time success helping overall turnaround time.

From our perspective at Balester, the finish blocking step, although critical, isn’t the worst spot in the lab. The worst spot in the lab is frame dimensions and the collection of this data from the ECP. Many of these jobs would be classified as “frame-to-come.” This is where the most lens breakage results in my opinion. We are at over 50 percent uncut. Often the information from the ECP or the pre-collected tracing point data files is inaccurate. For this reason, we grind the lens to uncut form and wait until we receive the frame to trace it and update the dimensions, if needed, to save the lens. Many of our frame-to-come jobs need to be recalculated.

John Barry

Operations Manager, Soderberg Ophthalmic Services, Inc.

Saint Paul, Minn.

In my opinion, without question, conventional blocking is still the best/most accurate with the human interface providing the best consistent results. The information you’ve been given is not out of line, but it just doesn’t address the advancements made to reduce errors and simplify this stage of production. Now this step is not as demanding as it once was in terms of the skill level of the operator. An ideal platform would be one that was consistent with Red Light/Green Light or Pass/Fail accuracy and that would not be subject to frequent calibration and LMS troubleshooting.

The finish blocking step is not the “worst thing” in the optical lab and has not been for some time. Due to advancements over time, this step has been greatly simplified. In my estimation Public Enemy Number One is scratches.

Bob Lommerse

General Manager, Toledo Optical Lab, Inc.

Toledo Ohio

Whether you are doing it the “old fashioned” way, or utilizing newer automated or semi-automated technology, nothing is perfect. Each has its own pros and cons. Human error, even from a highly-skilled individual, is always possible. To a degree, the newer technology removes some of that possibility. You could argue that to evaluate today’s highly advanced lenses and materials with a manual lensometer that was designed to read relatively simple glass lenses doesn’t make sense. In spite of this, in the right hands, this instrument continues to have value in today’s laboratory. There is something to be said for analyzing a lens by being able to examine and focus the target by actually seeing it with your eye. Our feeling is that automated technology has the ability to “look around these things and pass the lens as OK. The presence of a wave can be missed. Also, some lenses with very low or high power can be misread. Some automated devices have difficulty with polarized lenses as well as lenses with prescribed prism.

Having said that, in the hands of a trained individual, an automated analyzer/ blocker can be a valuable tool. They can become proficient fairly quickly and produce a good volume of accurate work. We utilize two Dimetrix machines we’ve had over five years with fairly consistent results. As with all machines they are as good as the information they receive as well as operator calibration and maintenance to insure accuracy.

As far as the next generation of finish blocking is concerned, we would like to see continued improvement in accuracy in reading or mapping the lens as well as blocking. As with any piece of equipment, we’d appreciate an increase in speed of operation to help with the volume of work that could go through that device. In regard to the single block carrier that allows the lens to move through the surface as well as finishing, that technology is intriguing. We believe it will be some time before most labs have the resources to invest that much money in a system like that.


Labtalk June 2020