Printing Distortions Research Articles

Battery screen print defect detection based on stationary velocity fields neural network matching and optical flow rectification.

In this study, an automatic defect detection method is proposed for screen printing in battery manufacturing. It is based on stationary velocity field (SVF) neural network template matching and the Lucas-Kanade (L-K) optical flow algorithm. The new method can recognize and classify different defects, such as lacking, skew, and blur, under the condition of irregular shape distortion. Three critical processing stages are performed during detection: (1) Image preprocessing was performed to acquire the printed region of interest and then image blocking was carried out for template creation. (2) The SVF network for image registration was constructed and the corresponding dataset was built based on oriented fast and rotated brief feature matching. (3) Irregular print distortion was rectified and defects were extracted using L-K optical flow and image subtraction. Software and hardware systems have been developed to support this method in industrial applications. To improve environment adaptation, we proposed a dynamic template updating mechanism to optimize the detection template. From the experiments, it can be concluded that the method has desirable performance in terms of accuracy (97%), time efficiency (485ms), and resolution (0.039mm). The proposed method possesses the advantages of image registration, defect extraction, and industrial efficiency compared to conventional methods. Although they suffer from irregular print distortions in batteries, the proposed method still ensures a higher detection accuracy.

Problems of determination of MultiJet 3D printing distortions using a 3D scanner

Purpose: Analysis and the review of 3D scanning methods, methods of combining 3D scans and tables available on the market (rotary, tilt and turn) as non-destructive testing systems of polymer materials. As the problem of deformation testing of elements produced by 3D printing is relatively novel, so far a small number of publications on this subject have been observed in terms of current solutions in the area of methodology and devices. Design/methodology/approach: 3D print samples have been prepared using MultiJet Printing (MJP), also called PolyJet Printing. The first sample was left in a UV oven and the second one in a dark cabinet, without access to sunlight (standard conditions 23/50 as described in ISO 554:1976). Non-contact structured blue light 3D metrology grade scanner was used to capture the entire part geometry for inspection. A comparison of subsequent scans after postcuring with reference scans after printing can indicate dimensional changes. The resulting scans are detailed enough to monitor shape and size changes over time. Findings: Universal 3D printing model beneficial in distortion analysis has been proposed. The method of evaluating 3D print distortions was verified using a metrology class 3D scanner. The results of this study show that deformations are declining through time to near the same values, the only difference is the rate of change of dimensions. Practical implications: Due to popularity and lower cost of polymer 3D printing, in comparison to metal 3D printing, an initial attempt to analyse the distortion of the locally melted substrate was done using MultiJet 3D printing with photopolymer material. The universal 3D print test part was proposed for verification of 3D printing deformations. Finally, the framework for the determination of 3D printing distortions is presented, taking into account the influence of UV postcuring. Originality/value: Analysis of a method to measure 3D printing distortions using a metrology grade 3D scanner is presented in the paper. Recently, this matter is becoming more and more important because many prototypes are increasingly produced by 3D printing and 3D printing distortions may cause many difficulties during the manufacturing and assembly process.

Ink-Particle Simulation for Continuous Inkjet Type Printer

Industrial continuous inkjet printers are typically used for printing directly onto various types of products such as cans, bottles, and food packaging in production lines. To enable their application to higher speed production lines, their print quality needs to be improved. This means that ink-particle simulation technology is needed to clarify the factors that affect print quality. Print distortion is caused by certain droplet shapes in inkjet breakup and aerodynamic and electric interference among the ink particles flying from the nozzle to the print target. A simulation technique has been developed that enables the breakup into droplets and the trajectories of the ink particles flying from the nozzle to the print target to be calculated with initial data obtained by breakup simulation. Printing of a line of seven dots was simulated well with this simulation code without initial particle input data. Also print distortion was prevented by inserting dummy particles between charged ones in the simulation.

Levels of Visual Stress in Proficient Readers: Effects of Spectral Filtering of Fluorescent Lighting on Reading Discomfort.

Visual stress (VS) affects reading in 5-12% of the general population and 31-36% of children with reading disorders. Symptoms include print distortions and visual discomfort when reading, and are exacerbated by fluorescent lighting. Prior research has indicated that VS can also affect proficient readers. We therefore examined levels of visual discomfort in a group of expert readers (n = 24) under both standard and spectrally-filtered fluorescent lighting. Participants rated their awareness of six symptoms of VS under each lighting condition. Under the standard condition, 4(16.7%) of the group recorded moderate to high levels of VS. Differences in symptom levels and reading speed between conditions were analysed using the Wilcoxon Signed Rank Test. Under the filter condition, the group reported less discomfort regarding all six symptoms of VS surveyed. The differences were significant with respect to three of the symptoms (p = .029 - p < .001), with a medium effect size in all of them (r = .31 - r = .46) and total score (p = .007; r = .39). Variations in reading proficiency included significantly fewer self-corrections (p = .019) and total errors (p = .004). Here we present evidence that VS-type symptoms of reading discomfort are not confined to populations with reading difficulties and may also occur in proficient readers, and that simple adaptations to fluorescent lighting may alleviate such symptoms.

Development of Ink-Particle Flight Simulation for Continuous Inkjet Printers

A method of simulating ink-particle flight for industrial, continuous inkjet printers (CIJPs) was developed to clarify the factors that influence print distortion. Print distortion is produced by aerodynamic and electric interference between the ink-particles flying from the nozzle onto the print target. The necessary functions to do this, such as the calculation of electrostatic force in the electric field between the electrodes, Coulomb's force from other charged ink-particles, and the drag force in the inkjet stream for many flying ink-particles were added to a Lagrangian method in the software to analyze the fluid dynamics that was used in the simulations. The trajectories of the ink particles flying from the nozzle onto the print target and the air flow caused by them were simultaneously calculated in the simulations. The results from simulations for the velocities and trajectories of the flying ink particles were compared with the experimental ones obtained with a high-speed camera. These simulation results were in good agreement with the experimental ones, and the developed simulation helps to clarify the factors that influence print distortion and to create algorithms that decrease it.

Ink-particle Flight Simulation for Continuous Inkjet Type Printer

Industrial continuous inkjet printers typically are used for printing directly on various types of products such as cans, bottles, and food packaging in production lines. Their application to 3D printing (additive manufacturing) also has recently become a promising area of research. To enable their application to higher speed production lines, their print quality needs to be improved. This means that ink-particle flight simulation technology is needed to clarify the factors that affect print quality. Print distortion results from aerodynamic and electric interference among the inkparticles during their flight from the nozzle onto the print target. A simulation technique has been developed that enables the trajectories of the ink particles and the airflow around them to be calculated simultaneously. The functions needed to accomplish this, such as calculation of the electrostatic force, the Coulomb force, and the aerodynamic drag force for many flying ink particles were added to a Lagrangian method used for fluid dynamic analysis. The simulated velocities and positions of the flying ink particles agreed well with the experimental ones and helped clarify the factors affecting print quality. Simulated printing of multiple-dot lines revealed that the lines on the print target were distorted. This was because the trajectories of the charged particles in the lines were distorted by electric and aerodynamic interference during flight. Simulation showed that the appropriate insertion of dummy particles reduces the print distortion in computers.

IMAGE ANALYSIS AND FUZZY INTEGRATION APPLIED TO PRINT QUALITY ASSESSMENT

ABSTRACT We present an image analysis and fuzzy integration based option for the assessment of print quality in rotogravure printing. Values of several print distortion attributes are evaluated employing image analysis procedures and then are aggregated into an overall print quality measure using fuzzy integration. The experimental investigations performed have shown that the print quality evaluations provided by the measure correlate well with the print quality rankings obtained from the expert. The developed tools are successfully used in printing shops for routine print quality control.

A controlled field study of the use of coloured overlays on reading achievement

This study investigated the effects of using Irlen coloured overlays on reading rate, accuracy, fluency and comprehension under regular class conditions, with class teachers instigating the study and conducting the assessment. All subjects in grade 3 at Whitney and McKinley Elementary schools were screened for symptoms of Irlen syndrome, with 31 subjects identified at Whitney and 40 subjects identified at McKinley. The effects on reading achievement were investigated under conditions of immediate use and delayed use, with one group (Whitney) provided optimum coloured overlays for 3 months and the other group (McKinley) delayed treatment for 3 months. The effects were then assessed for a further three months with both groups. After three months of use of overlays, the Whitney group demonstrated a significant improvement in reading achievement with mean gains in grade equivalence scores of between 1 year 2 months and 1 year 7 months. However, between the three to six month period of use, the gains for the Whitney group reached a plateau, with no significant improvement in reading achievement. The McKinley group had negligible gains in reading achievement during the first 3 months without the use of overlays, but significant gains during the 3 month to 6 month phase with the use of overlays, which ranged from 1 year 8 months to 2 years 8 months. It was suggested that the reported reduction in print and background distortions may improve accuracy of word recognition and allow attention to be directed more to the meaning of what is being read than to word recognition thus enhancing reading comprehension. The plateau effect identified for the Whitney group between 3 and 6 months could be related to the fact that after 3 months of overlay use, many students had reached grade level in reading achievement.

Irlen lenses & adults a small scale study of reading speed, accuracy, comprehension & self‐image

This study investigated the effects of using Irlen coloured filters on reading speed, accuracy, comprehension and self‐image over 6 months of use. Three study groups were used (immediate lens use, delayed lens use and control), involving 33 subjects ranging in age from 18 years to 62 years. The experimental groups demonstrated significant improvements in reading accuracy and comprehension over the 6 months of the study, although there was a plateau effect for the second half of the 6 month study period. The experimental and control groups also improved significantly on scores of self‐esteem over the 6 months. It is suggested that the reported reduction in print and background distortions may allow attention to be directed to the processing of continuous text rather than to the identification of individual words, although improvement will be restricted if basic word attack skills ore not fully mastered.

Coloured Lenses and Reading: A Review of Research into Reading Achievement, Reading Strategies and Causal Mechanisms

The paper reviews investigations on the use of coloured filters in relation to possible causal mechanisms, effects on reading achievement and effects on eye movement. Studies of causes suggest a retinal - sensory after-imaging problem, possibly related to the magnocellular visual neurological pathway. Studies of reading achievement suggest this disability may be one causal factor in reading problems but improvement will be influenced by prior word attack skill and willingness to be involved in reading. Investigation of reading strategies suggest that the claimed reductions in print distortions could allow more reading fluency and enable attention to be directed to meaning rather than word identification, which in turn facilitates access to text context as a supplement to word recognition.

Coloured lenses and reading: A review of research into reading achievement, reading strategies and causal mechanisms

The paper reviews investigations on the use of coloured filters in relation to possible causal mechanisms, effects on reading achievement and effects on eye movement. Studies of causes suggest a retinal ‐ sensory after‐imaging problem, possibly related to the magnocellular visual neurological pathway. Studies of reading achievement suggest this disability may be one causal factor in reading problems but improvement will be influenced by prior word attack skill and willingness to be involved in reading. Investigation of reading strategies suggest that the claimed reductions in print distortions could allow more reading fluency and enable attention to be directed to meaning rather than word identification, which in turn facilitates access to text context as a supplement to word recognition.