10-27-2020, 11:56 AM
I followed your suggestion and ran a range of exposures: 20, 40,80, and 160 seconds. i measured at the corners and mid points of each rectangle element. The 160 second print did have a ridge along the midpoints of each side of the rectangle and from the ridge corners to perimeter corners. I've only attached a picture of the last one. The results in the chart for that group are measured close to the outer perimeter to avoid the ridge. The height of the ridge was about 0.25-0.30 mm more.
All of these films are very thin and cleaned on the FEP after draining. They were left on the film and then subjected to curing from both sides. The twenty second film was only post cured for 2 minutes which might not have been enough as it curled shortly after removing from the FEP. The others had 6 mins of curing on each side. They curled slightly but the 20 second one was curled bad enough that I really had to squeeze the caliper to flatten it and that might have induced some measurement error.
From the chart it really doesn't seem that front edge is being over exposed relative to the rear edge. The differences in the average thickness of the front measurements to the rear measurements is mostly less than 0.01 mm and half the exposure groups are smaller at the front edge. It's hard to conclude anything since this is a single trial set and differences are very small relative the measurement tools/ technique. I'd probably have to run at least 10 replications to analyze the data mathematically with a reasonable confidence interval. The average of all data within an exposure group for both 80 seconds and 160 seconds are the same: 0.3675 and standard deviations of 0.016 and 0.014 mm. Ignoring the ridge for 160 s, this means the data population look the same. Pulling believable data from the noise on this technique will not be easy.
Hopefully Elegoo will respond with some suggestions as I don't have any great ideas of what else to look at.
All of these films are very thin and cleaned on the FEP after draining. They were left on the film and then subjected to curing from both sides. The twenty second film was only post cured for 2 minutes which might not have been enough as it curled shortly after removing from the FEP. The others had 6 mins of curing on each side. They curled slightly but the 20 second one was curled bad enough that I really had to squeeze the caliper to flatten it and that might have induced some measurement error.
From the chart it really doesn't seem that front edge is being over exposed relative to the rear edge. The differences in the average thickness of the front measurements to the rear measurements is mostly less than 0.01 mm and half the exposure groups are smaller at the front edge. It's hard to conclude anything since this is a single trial set and differences are very small relative the measurement tools/ technique. I'd probably have to run at least 10 replications to analyze the data mathematically with a reasonable confidence interval. The average of all data within an exposure group for both 80 seconds and 160 seconds are the same: 0.3675 and standard deviations of 0.016 and 0.014 mm. Ignoring the ridge for 160 s, this means the data population look the same. Pulling believable data from the noise on this technique will not be easy.
Hopefully Elegoo will respond with some suggestions as I don't have any great ideas of what else to look at.