Calibration: Elephant Foot

Sometimes when printing without a raft, with the model directly on build plate, you may notice that the bottom layers are slightly larger than the rest - this is the famous elephant's foot.

While most of the time it is unnoticeable and unimportant, it can pose a large problem when printing objects for practical applications. It drastically decreases tolerances, making it much harder to fit pieces together. This defect often arises in larger prints and higher bottom exposure times.

There are various ways to counter this problem:

1. Design the model with a offset/chamfer on bottom layers (Hard - Unpratical)
2. Tune exposure times and use the less possible time you can go with (Medium - Will not fix the problem completly, risk of not stick to the build plate)
3. Offset bottom layers on slicer (Easy - pratical)
4. Use UVtools to erode or dim bottom layers (Easy - pratical)

So from the previous options we can conclude that the method 3. and 4. are the way to go, but there's still a problem, what is the right value to use? Well this is where UVtools and this guide come in action:

Preparation

1. First prepare a dummy file, sliced in your slice of preference with the right settings for your printer, this file will be overwritten and blanked with the new calibration test. You can also use a old file that you no longer need, or an actual file but when saving the file use the "Save as" option to keep your original file.
2. Open file in UVtools
3. Go to: Calibration - Elephant Foot
4. Tune values as required and apply
   • UVtools only generate the number of tests that can fit in build plate. If overflow, those models will be discarded and you need to print them in other round
5. Analyze the output, check if the tests are what you desire and save the file
6. Print the file, remove and clean the parts

Analyze the results

Due to the nature of the shape, there are 3 edges that won't be considered, they will always have the elephant foot effect and those can be used as reference without having the original part. To analyze the results you should always look at the affected edges which are color marked below:

Legend:

• n = Part number ordered
• UVtools EP = Elephant Foot test
• x um = layer height in microns
• s/s = Bottom exposure / Normal exposure seconds
• E: ni = Erode with n iterations
• W: n B: x = Dimming wall with n pixels at x brightness level

1. Order the parts from the Original to the more aggressive erode iteration and dim brightness (Use the number on top to keep same order)
2. Start sequential comparing the parts, bottom layers must flush and align with the remaining layers or at least very close to, look from both front and back sides:
   1. Find for the best teeth alignment (Right side)
   2. Look inside the hole and check if is all way up/down same diameter
   3. Look at arc below the hole, it must align
   4. Look at top left offset arc, it must align
   5. From a general view, select the parts that gives you the overall best aligment and visual, if you are between two parts where one have a minor elephant foot and other is a bit retracted, go for the retracted one or repeat the test with fine tuning wall dimming parameters, as erode don't allow middle values.
3. If none of the parts reach your requirements, repeat the calibration test adjusting the values, on small build plates you may need two prints, otherwise on larger plates, you can do a very wide test
4. When found the right values, keep the valid part(s) for reference, write down the printer and resin name.
5. For the remaining parts, don't throw them away, they are perfect keychains, offer to someone, they will have a original piece while having a bad time trying to decode the UVtools inbuilt message, is that maybe a locker combination? Who knows...
6. (Repeat the test when change any of: Printer, LED's, resin, exposure times)

Future slicing of files

Now that you have the values, what to do with them?

1. Turn off any elephant foot compensation that you slicer may have. (Otherwise tune there and discard the following steps)
2. If you goes with Erode:
   1. Go to: Tools - Morph
   2. Select bottom layers
   3. Select Erode
   4. Put the iteration number given from the calibration part (i)
   5. Save a profile with printer name, resin name for latter re-use and reference
   6. Hit apply - done
3. If you goes with Dimming:
   1. Go to: Tools - Pixel arithmetic
   2. Click "Elephant foot compensation" preset
   3. Put the wall thickness given from the calibration part (W)
   4. Put the brightness given from the calibration part (B)
   5. Save a profile with printer name, resin name for latter re-use and reference
   6. Hit apply - done

Erode or Dimming

Erode:

1. Model information is lost, n pixels will be eroded from boundary
2. Coarse tunning, can't support middle values, so you can never have a in middle result
3. Less steps, "easier"

Dimming:

1. Keep the model information
2. Better fine tunning, allowing to define a wall thickness and dim it to a brightness level
3. Requires a compatible anti-aliased file format and printer
4. More steps, "harder"

Given that i'll recommend Wall Dimming if your printer supports anti-aliased files, but pick whatever you fell best for you. If works for you, don't let others say otherwise.

Just for curiosity

• Elephants know every member of their herd and are able to recognize up to 30 companions by sight or smell.
• They can remember and distinguish particular cues that signal danger and can recall locations long after their last visit.
• An elephant’s memory is not limited to its herd, nor is it limited to its species. In one instance, two circus elephants that performed together rejoiced when crossing paths 23 years later. Elephants have also recognized humans that they once bonded with after decades apart.
• The elephant boasts the largest brain of any land mammal as well as an impressive encephalization quotient (the size of the animal’s brain relative to its body size). The elephant’s EQ is nearly as high as a chimpanzee’s.
• The elephant brain is remarkably similar to the human brain, with as many neurons and synapses, as well as a highly developed hippocampus and cerebral cortex.
• Elephants are one of the few non-human animals to suffer from post-traumatic stress disorder.
• The elephant’s large cerebral cortex allows them to be great problem solvers, which elephants display in many creative ways.
• Don’t try to outsmart an elephant! They have an understanding of basic arithmetic and can even keep track of relative quantities.
• Elephants communicate using everything from body signals to infrared rumbles that can be heard from kilometers away. Their understanding of syntax suggests that they have their own language and grammar.
• Elephants can recognize 12 distinct tones of music and recreate melodies.
• Elephants are the only non-human animals to mourn their dead, performing burial rituals and returning to visit graves.
• Elephants are one of the few species who can recognize themselves in the mirror.

Elephants are amazing and deserve everyone respect, help save them and preserve the species.