G&R Labs Creates UV Light Meter for Ember

Posted by Owen Smithyman on Sep 10, 2016 9:30:00 AM

gr-labs-model-222-radiometer-head-in-ember.jpgThe foundation of any stereolithography (SLA) 3D printer is its light source. Ember builds 3D models layer by layer by exposing light-sensitive resin to ultraviolet light from a DLP projector. Understanding how the projector’s light affects your prints and calibrating the projector to provide the proper light dosage are essential to mastering 3D printing with Ember or any DLP machine.

Ember uses a Wintech Pro 4500 DLP 405nm Projector. In our lab, we use radiometers (also called UV light meters) to check the near-ultraviolet light intensity of each printer and calibrate the projector accordingly. This is especially important when using a resin we haven’t tried before, but it’s also useful when switching resin trays or printing on trays with evidence of clouding in the PDMS window (which reduces the amount of light that’s transmitted onto the build area).

To optimize the process of calibrating our printers, we began working with G&R Labs – a light measurement and calibration company with extensive experience creating custom radiometers for 3D printers.

While a custom solution could be put together to measure the 405nm light used in Ember, G&R has developed an off-the-shelf radiometer that is optimized to work with Ember: Model 222.

Model 222 allows anyone to accurately calibrate their Ember and help ensure that the machine produces excellent prints.

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Model 222 measuring the intensity of an Ember, with a reading of 25.27 mw/cm2.

Using a radiometer is critical to arriving at usable settings for the resin you’re using. Some resins have very stringent dosage requirements in order to cure properly. Dosage is the total energy delivered to a layer of resin, which can be expressed as Dosage = Light Intensity * Time. If the dosage is too low, the resin won’t adhere to the build head properly and you’ll end up with under-cured resin fragments instead of a finished part. If the dosage is too high, the cured resin will stick to the PDMS window and cause the printer to jam. Using a radiometer to determine the exact light intensity emitted by the printer allows you to determine correct settings more easily, and also to ensure that correct settings will consistently produce good results.

With a custom head designed for Ember’s specs, Model 222 is able to measure both light intensity and dosage, making it a great tool for characterizing new resins and optimizing print settings to get extra use out of old trays. More importantly, its ability to measure dosage allows for the use of resins that have very tight dosage requirements -- some as little as +/-10%.

Radiometers are very sensitive scientific instruments, so make sure to handle your radiometer gently. G&R recommends calibrating it every year to ensure consistency.

Prior to the development of Model 222, we recommended the use of G&R Model 221 with a special 420nm head, and tuning the Ember projector to ~20 mw/cm2. Model 222 measures a different part of the UV spectrum, so it reads about 25% higher than Model 221 at the correct brightness. If you’re using Model 222, tune your Ember’s brightness to ~25 mw/cm2 (±2 mw/cm2).

Features of the G&R Labs Model 222:

  • Optimized 405nm probe fits under Ember build head
  • Measures both UV light intensity and dosage (total energy over time)
  • NIST Traceability: ±3.0%
  • Each range scale is linear to <1%

We’re thrilled that researchers, jewelers, dental manufacturers, and many others are making Ember the tool of choice in pushing the boundaries of their fields. If you have any questions about radiometers or Ember, please browse our support docs or send us a support request.

Topics: 3D Printer, DLP SLA, Pro Tips, resin trays