Purge block question  

Re: Purge block question

Good question. No clue.

It could be speed. The only value in dropping Z would be to not have to print the simple scaffolding on the layers that don't have an exchange. For me, that prints *very* quickly, zip around the edge and a few zig zags in the middle.

The other reason could be collisions. If you are at the same layer, you can do a simple 2d non-overlap to ensure it will work. If you drop the height of the purge block you need to start thinking about the geometry of the extruder to ensure you don't collide with the print while printing the purge block.

They may avoid that optimization because the current approach is likely just about as fast, doesn't consume much extra filament, and is simpler/safer.

Re: Purge block question

Seems like it could work like this:
1. Print the part as normal until a color change is needed.
2. Save z of the printed part's next layer.
3. Move to the purge block area's x/y.
4. Drop the z to the current height of the purge block.
5. Add a new layer to the purge block.
6. Raise the z to the printed parts saved z from step 2.
7. Move to the printed part's x/y and resume.

Might need to retract the filament a bit to prevent strings but it seems like this setup should work. I dont have my unit to test, but the current waste associated with the purge block seems insane.

Re: Purge block question

It is a great idea BUT here are the disadvantages that I can see:

1. If configured incorrectly it may crash on the model.
2. You will lose big amount of print volume to prevent crashing.

Re: Purge block question

Gotcha, that is definitely something I hadn't considered. I wonder if the ability could get added as an option to save plastic (assuming the model is small enough - mine usually are). I might try to add it myself once it gets here.

Re: Purge block question

It might not save that much filament. The purge block is full/solid layers whenever there is a layer with every filament change. However, layers with no filament change use very little filament on the purge block. Is that what you are trying to save? I'd say it's <10% of the weight of the purge block.

It would work. The slicer would simple need to be aware of the geometry of the extruder head just as it would be for sequential printing to ensure when it drops it doesn't collide.

Efficiency can be increased in three ways:
- print many objects. Purge block stays the same size
- Purge to an object. Pick something you don't need to be consistent color (haven't tried this yet)
- Purge to infill. Might only work with solid or dark colors so you can't see through. Or an extra perimeter.

Re: Purge block question

Adding extra perimeters to hide filament that is purged to infill will add time to your print and increase the plastic used in the print... which may negate some of the benefits of trying to reduce purge waste.

regards Joan