Elephant's Foot Compensation

[JasonsBigBox]

I'm modelling a small but complex part that I need to be relatively accurate dimensionally and have a good surface finish.

To reduce the number of supports on visible faces, I can sit the model with a flat face directly on the bed. 

The face has a number of small holes in it but over exposing the first layers leads to the holes closing over when using the standard slicer settings 0.2mm.

I have modelled a test piece with different edge offsets to see if I can find the correct setting but am finding that the chamfers are overlapping and risk the part not attaching to the bed. 

The picture attached shows what I mean.

Has anyone already done this and can share settings?

I've had issues with the part not adhering to the bed so the initial exposure is up to 90s !!

(I'm using an Elegoo Mars Pro but I suspect the settings will be very similar)

Thanks for the help!

 

J

[cliffyk]

Are the holes "through holes" or "blind holes"? If blind holes they will need to be "vented" to prevent suction from pulling the model away from the build plate; things print upside down on our printers. Each "upside-down" blind hole, when coated with uncured resin, becomes a very powerful "suction cup" hanging on to the FEP for all it's worth.

If vent holes are not practical then tilt the model and use "supports" (actually hangers because of the upside down thing) so that the holes can drain between layers.

Here's a somewhat extreme example, it's a block for holding 4 mm hex bits, printed with the open end of the holes facing down (toward the FEP); note the vent matrix i created to prevent the aforementioned suction from tearing the base away from the platen--it was the only way I could get it to print without being pulled from the platen half-way through:

[JasonsBigBox]

Thanks, the holes on the actual part go through that section so suction is not an issue. The picture is of my test piece which I admit has not got vent holes.

The problem I have is that the first layers are sealing over the holes as the elephant's foot effect is too large. The smallest holes are 0.75mm but even with a 1mm chamfer, the hole is still closed over.

If I can get even a pinhole in the face, I can run a drill through to clean it up but I can't if it's solid as I can't be sure of its position.

Anybody got some settings they use?

PS: I'm using Prusa Slicer.


Thanks 

Jason