Single print to determine first layer height
I frequently have problems setting the first layer height. I'm always lower than this because i have a fear of poor bed adhesion, leading to elephant feet, leading to poor fit and function when I am printing mating parts. To overcome my poor subjective first layer height determination skills, I've created a model that takes advantage of printing known overhangs on the 2nd and above layers to compensate for the elephant foot. Using knowledge of the size of the overhangs and under which overhang the elephant foot disappears, we can easily (and much more objectively) measure how wide the elephant foot is. From this we can correlate that extra width to layer height using a simple cross sectional model of a single extrusion. I have then added graduations indicating the layer height.
In short...
1. print model (takes about 20-30 minutes)
2. find the part on the edge where the elephant foot disappears
3. read the graduations on the printed part
4. you know your first layer height, and can now adjust your printer accordingly!
Assumptions:
1. The model needs to be printed at 0.200 mm layer height on the first layer
2. The target extrusion width is 0.45 mm
3. The layer height is within .100 mm
If any assumption is not true, this specific model will not work. However, a new model can readily be made to account for any first layer height and target single layer extrusion. This technique is therefore agnostic of printer, but process parameter dependent. This wouldn't replace the built in first layer calibration, but rather it would be a second step after you complete the first layer calibration to get it close enough.
I've posted the model on thingiverse:
https://www.thingiverse.com/thing:3293142
I've also documented the the model, math, and part design in a power point that i'm not sure the best way to distribute (or if anyone would care to see it).
Re: Single print to determine first layer height
Thanks, I like this analytical approach!
I just printed it, "unfortunately" it seems that my layer hight is perfect, 😆
I have one suggestion though: (actually two)
Can you put the unit of measurent (mm) somewhere onto the plate? Just to avoid confusion with inch.
Also, I would find it more intuitive you would write "mm too high/low" onto the plate. Otherwise there could be the confusion of: "Is my layer too high by .05 mm or do I need to go .05 mm higer?" I had you read your description twice, just to make sure I don't mix it up.
Re: Single print to determine first layer height
Thank you for the feedback Spacemarine!
I've made another model stating explicitly the height is in mm and refers to the layer height being too low or high.
I also made another version that prints in only 5 minutes, as compared to 25 minutes of the original. It was slimmed down and all of the words are removed, but works just as well.
Both of the links can be found in the updated description section on thingiverse.
Re: Single print to determine first layer height
Thanks! I've downloaded and printed the file. Is there any reason, why the plate with the text doesn't touch the ground and floats in air?
Your thin strips are especially usefull if they are placed across the entire bed to check for xy-dependent first layer hight problems. Maybe one could come up with some sort of grid-like structure, that covers the entire bed to show the correct hight over the full area?
Re: Single print to determine first layer height
When I sliced the verbose version to check how long it would take, I didn't notice the floating you mentioned. In the CAD, the origin is inside the part, so I'm not really sure whats up with that.
As for the correct height over the entire area, I think this tool isn't quite what you would be looking for. In my mind there are two quantities: 1) first layer height and 2) bed levelness. I'm imaging this test print to inform the first layer height, and another test print that would just show if you have elephant feet depending upon where you are on the print bed.
If you 1) assumed your bed was level, 2) printed the first layer height in the middle of the print bed and set the height, and then 3) you could confirm if your assumption about the bed level was good by something like printing a 3x3 array of 10mm×10cm×1mm pieces. After they are printed you could then inspect each object for elephant feet. If some do and some don't then you know you don't have a level bed. If your bed isn't level, then changing the first layer height won't help, you would have to go find the piece of filament between the steel plate and the heating element or whatever.