Prism on blocker and generator

Prism can be included on lenses in the surface blocking and/or generating phase. In the case of digital designs, prism can also be included in the backside design - see section Prism on Digital Designs for information on this.

When considering a non-digital design, some amount of prism might be required for a job. Some (or all) of the prism might be sent to the surface blocker, and some (or all, or a remainder) of prism might be sent to the generator. In the case of alloy blocking, the preference might be to send the first X amount of prism (in either prism diopters or angular degrees) to the blocker, and any remainder to the generator. With ART blocking, the preference might be to “reserve” Y amount of prism for the generator, and block the remainder (if any).

Block first, remainder to generator

To set the preference to block as much prism as possible and send the remainder to the generator, set up the blocker interface with the maximum amount of prism that the blocker is able to block. With many blockers, the maximum varies depending on the base curve of the blank used, so it is best to be conservative in the max value. For example, to set the maximum value as 4.50 angular degrees of prism, the device interface screens would include the following settings:

Open

The “Device max prism” field shows the maximum prism to be sent to the device (4.5 in this case), and the option to send this as angular degrees is set on the Other tab. Thus up to 4.50 angular degrees of prism will be sent to this surface blocker for a job.

On the generator device, the maximum amount of prism will similarly be set:

Open

When manufacturing a job with more prism than can be blocked, the prism will be split between the two devices. You can view how much prism was actually blocked by looking at the “View device info” on an order after it has been blocked:

In the case of a job requiring a total of 6.00 prism:
Blocker - 4.50 prism
Generator - 1.50 prism

Generate prism first, block remainder (up to maximum)

When using ART blocking (or in some other instances where generating the first X prism is preferred), we need to indicate in the blocker interface that some amount of prism should be set aside (or reserved) for the generator first.

On the blocker tab in this case (we will assume all devices again have the option “Send prism as angular degrees (PIND=0)” set:

The “Reserve prism to generator” setting with take the first 2.00 angular degrees of prism and NOT send it to the blocker, but instead “reserve” it for the generator. If more than 2.00 prism is required on the job, the amount above 2.00, up to a maximum of 4.50, would be sent to the ART blocker. Note that if more than 6.50 angular degrees was required, this job cannot be manufactured on the equipment with the settings as they are.

In the case of a job requiring a total of 6.00 prism:
Blocker - 4.00 prism
Generator - 2.00 prism