These corner brackets were designed to interface with the Flashforge Inventor 3D printer and the glass plate upgrade from Flashforge USA. Supports glass dimension (L x W x H) 9 x 6 x 0.15 inches. Glass must be installed on top of the Flashforge build tape and aluminum build plate. You may require four washers to prevent the hex nuts from going through the gaps of the corner brackets.
The corner brackets are designed to be of sufficiently low profile to accommodate the build plate movements in proximity of the internal filament spools. The corner brackets can be fastened using the existing build plate hardware and are flush with the surface of the glass.
I would like to say that this project worked on the first attempt but it would be false. What started as a deliberate design attempt turned into a series of trial and error. It took me six versions to get it right.
In order for these brackets to work at bed temperatures up to 100 degrees Celsius, I recommend using Proto-Pasta Carbon Fiber HTPLA for printing these and then following directions from Proto-Pasta for annealing. I do not recommend the use of regular PLA or ABS for this project as they will become soft and rubbery during heated bed operation.
Each corner bracket file is labelled with a letter A, B, C, or D. Refer to the included photo to determine where each corner bracket goes.
To ensure compatibility with your system, here are the measured dimensions of the parts that the brackets interface to:
Original Aluminum + PCB + Tape Build Plate (L x W x H) 232 x 153 x 8.25mm
Glass Plate Upgrade (L x W x H) 229 x 152.45 x 3.8mm
I recommend tightening the nuts once the build plate is fully raised and pre-heated to 60-70 degrees Celsius.
Step 1: Measurements
I measured the dimensions of the original build plate, including the diameter and distances of the bottom screws from the edge of the build plate. I also measured the dimensions of the glass plate upgrade and the available screw threads length so that I could establish the maximum thickness of the bottom of the corner brackets. I intended to leave four screw threads sticking out after the nut. Unfortunately, that precisely what the screws had available in the first place. I decided on going with 1mm bottom thickness so that the brackets would have some reasonable strength and the trade off was that it only left two screw threads after the nut (or one if using a washer). I inputted the dimensions in a table in MS Excel and determined the exact dimensions required to hold the glass firmly in place.
Step 2: Initial Designs
I drew a basic 2D side profile of one corner bracket, extruded it to a reasonable thickness, and projected a canvass on the base to draw the screw hole. Having some knowledge of the printing characteristics of my 3D printer, I estimated the required tolerances and ensured that I oriented my model so that it could print with few supports. In my original version, I made the brackets 25 x 25mm and later realized that they were sticking out too much on the sides to accommodate the use of internal filament spools. I also made the mistake of making a screw hole instead of a slot, which was quite embarrassing when I could not get the screw through the hole. Once I got the two front corners to fit properly, I designed the back ones. All four corner brackets are different.
Step 3: Prototype Prints
I made six prototypes in order to get the right fit, which ended up completely different that my original calculations. The first trials were close but unsuccessful so I had to tweak the designed tolerances. This was partly due to the printer print characteristics (vertical edges not sufficiently flat) and possibly partly due to the presence of remnants from the supports used. I tried printing at different angles but my orignal angle looked the sharpest. By the fourth version, I thought that I was done. However, this is when I discovered that the brackets were catching on the internal spool holders and that the PLA that I was using was getting too soft at temperatures greater than 60 degrees Celsius.
Step 4: Final Print and Assembly
After making redesigning the brackets to be lower profile, I printed them using Proto-Pasta Carbon Fiber HTPLA with 100% infill and then cleaned up the part prior to annealing them in the oven (using a pyrex plate) at 200F for one hour. The end result was stunningly good.