Direct-to-Glass UV Printing: Designing a Primer and Adhesion Trial
Zero failures in 30 independent adhesion trials still allow a one-sided 95% upper failure-rate bound of about 9.5%.
This application example uses public references and explicitly stated planning inputs. Figures derived from assumptions are estimates for evaluation, not measured customer results.
Production question
What can zero observed adhesion failures actually establish in a first-article trial?
Worked calculation
For 30 independent trials of one fixed print recipe with zero failures, the exact one-sided 95% upper failure-rate bound solves (1 − p)^30 = 0.05, giving about 9.5%. At 60 independent trials with zero failures, the bound is about 4.9%.
How to validate it on the shop floor
Run separate primer and unprimed trials on the intended glass, ink and preparation process. Predefine the adhesion method and conditioning time. Sample across panels and batches, since neighboring marks on one panel may be correlated.
What to do with the result
Separate the trial by substrate batch and print recipe, and decide the pass criterion before looking at any results. If the acceptance goal is a failure-rate bound below 5% with zero failures at one-sided 95% confidence, at least 59 independent trials are needed under the binomial model. Record whether failures occur at the glass interface, between ink layers or under the test itself, as those outcomes lead to different corrective steps.
Practical follow-up
Does zero failures across 30 coupons establish outdoor durability? A binomial bound applies only to the tested conditions and sampling design. Service exposure requires its own qualification.