A musing- why you *shouldn't* print at an angle (Patreon)

PSA: I don't know where this idea of printing pistol frames at an angle espoused from, but here's an example of why you **SHOULDN'T**. (pic was from a tester that I asked permission to share on Twitter) 

This thread was previously published on Twitter, but I'm sharing it here to collect all medium format blog postings.

When you print at an angle, you are reducing the surface area that the walls and infill can bond to (generally speaking).  This can spell disaster for critical areas: pins, structural geometry, etc.

In the picture above, the separation happened right along the layer lines. This likely happened when the slide reciprocated back.

My hypothesis is that as the barrel engaged downward with the locking block (a clockwise force pivoting slightly forward of the block/barrel), the trigger pin (a principal component that interfaces with the frame) experiences a forward force towards the front of the gun.

This causes the pin to shear against the thinner wall and geometry, and because there was less surface area for the walls to bond against (in this case, above the trigger), the layers separated, and fracturing above and to the right of the trigger pin occurred.

While early on, there was debate and confusion about printing "magwell down" (right-side up) or "magwell up" (upside-down), this was left up to the developer to specify in the documentation. (I specified standing up in my docs for the DD43.1.)

Advantages of printing of right-side up include better defined geometry for internal parts. Beginner printers definitely should print right-side up, especially if they haven't dialed in their settings to omit imperfections like blobs, slight wobble, or stringing.  

However, right-side up printing means that the undersides of the exterior print would be unappealing to look at, namely due to overhang or supports. (That's just the nature of 3D printing!)

Printing upside-down leaves a little more to chance for a "pretty" exterior though. Upside-down leads to risks like your internal geometry potentially requiring post-processing in most cases. Optimized and well-tuned slicer settings can make printing upside down a non-issue.

In worse case scenarios though, printing upside down will lead to plenty of clean up, or introduce uncertain variations to necessary dimensions, which means your parts may not necessarily fit as designed. 

A conscientious developer would account for such tolerances in fitment, or explicitly specify an orientation to print.

Because someone will ask- NO, you should NOT print any frame on its side unless it's specified by the dev.  Example: If you print an AR-15 lower on the side, the walls around the pins can separate from the infill (again because the surface area is so thin). Another example: on thicker frames like pistols, you will have to spend time cleaning up the magwell and internal geometry after you remove supports.  Printing on the side is a terrible idea, and is almost never recommended.

tl;dr-  Read the instructions. Print right side up if you are new or as a baseline. Print upside down at your own risk with a tuned printer. Read the instructions. Don't print at an angle. Don't print on the side. Read the instructions. Ask for help if you are still confused.