Parametric Design of Plastic Y-Axis Backplate for 8", 10" or 12" i3v

[PyramidDave]

I have been looking at a way to replace this part for a while & having my clip brackets work so well with the LCD housing & Right side electronics cover, I realized this same idea might work for the Y-Axis Back Plate. I am ready to print my last test prints hopefully & thought I would see if anyone else has some suggestions for this design. I have been bouncing some ideas off of voodoo28 this week who has a 12" i3v. I have a 10" Prusa i3v, so that is the only one I can really test it on. I did get the key dimensions from Colin for the 8" version, so they should be correct. I already had the dimensions for the 10" & 12". I am test printing just the top & vertical profiles before printing the final part. The exploded view of this assembly should show how it will go together. I am not using nut traps, but clips on the sides with 3 holes for M3 bolts. There is 18mm of plastic to go thru, but might be able to countersink the bolts & nuts to use M3x16mm bolts on each side. The 2 peg holes on each side, I made an insert with a M3 hole in the center, so I can put a M3 bolt thru the center of 1 or both peg holes on each side. It seems like that should work. I am using M5 bolts for the middle clips, but may not be able to countersink those since there might not be enough clearance. I started to use M3 bolts there, but M5's for that structural support seem to be needed. I was also pondering some ideas for hole patterns to dissipate vibration & decided to try an f cut under each V-slot like are cut in Violins. I added a few more cuts for the 10" version, but have not added any others for the 8" or 12" before seeing how well these work.

One dimension Colin was not sure of on the 8" was the offset distance for the slots in the top of each side where the heat bed bolts clear. It seems to be the same for the 10" & 12". The dimensions I have for those slots are measuring from the center of V-Slot to the Left side of the slots, I have 36.2mm on the Left side & 24mm on the right.

I could print these 2 backplates in either of 2 orientations, either like they are or back face down. I am planning to print them back face down, since that seemed to work well for the Front Y-axis. I am using openscad for this design & DraftSight for the 2d geometry calculations. I also have an option for a L bracket under each V-slot. I was playing around with an offset angle bracket to use with 12" version that would connect to the side of the V-slot & angled towards the bottom middle. I included 3 screen shots that show the Assembly of parts, the Key dimensions and an earlier version that shows what that angle bracket looks like.

I am planning to print the final version of this in PETG with 50% 3d honeycomb infill.
Let me know if you have any suggestions.Y-AxisBackPlateParametric_10inch_Rev20.JPGY-AxisBackPlate_KeyDimenions.JPGY-AxisBackPlate_10inch_WithVSlotBrace.JPG

[PyramidDave]

I am pretty happy with the design now after printing the Left side the 2nd time. The 1st print flexed too much so I added ledges to the bottom & top. It does not really flex at all now. Not sure why I did not put those ledges in there to begin with. The 2nd print of the left side weighs 1.74oz & took 4 hours to print. I am expecting the right side to take 8 hours. I should have the printing done tomorrow. I have attached a photo of the 1st two test prints & screen shots of what the 8", 10" & 12" version look like.
IMG_9707_800x600.jpgY-AxisBackPlate_8inch_Rev26.JPGY-AxisBackPlate_10inch_Rev26.JPGY-AxisBackPlate_12inch_Rev26.JPG

[PyramidDave]

Prints came out pretty good for the 1st version, but was off by 1.5mm in centering the motor shaft hole. Now that I have the parts to play with, I can see a better way to do the bracing in the back. I could probably file that 1.5mm down, but may as well redesign this a better way before taking my printer apart to replace this. Everything seems to line nicely except for the motor hole. The Right side took 8.25 hours to print & weighs 3.5oz at 50% fill. Here are some photos of the 1st printing.
IMG_9709_800x600.jpgIMG_9711_800x600.jpgIMG_9714_800x600.jpg

[PyramidDave]

While working on this design, I published a y-axis back brace for the three i3v versions. There is a test print for each version that takes about 30 minutes or so to print & weighs about a .25oz. If someone with an 8" i3v could print the Y-Axis_i3v_8inch_TestBackBrace_Rev4_repaired.stl located here: http://www.thingiverse.com/thing:1302473 , that would tell me whether I have the hole patterns correct for the 8" version. I got the dimensions from Colin, so they should be correct. The attached screen shows what the brace would look like on the 12" i3v.
Y-Axis_12inchBackBrace.JPG

[cperiod]

The 8" offsets are correct, but inverted. If the back brace is printed flipped along the Z axis it's perfect. I assume Colin measures his braces from the other side of the board...

[PyramidDave]

The 2nd photo in the 1st message in this thread are the key dimensions that Colin gave me. If I understand what you mean, the test part being flat on both sides, it is not obvious which side goes where. The final part for the Back or Front of the Y-axis will be obvious with the Motor mount or idler mount in place.

Thanks for checking the dimensions.

[PyramidDave]

I redesigned the back brace & decided to use dovetail joints between them since the tongue & groove style joint did not print symmetrical. This is what the 10" version looks like. I plan to start printing the parts today. I made 2 versions of the inside brace. The other version only has the 4 holes at the joints, in case I do not need the extra support.
Y-Axis10inch_BackPlateAssembly_rev32.JPG

[PyramidDave]

I put the 4 parts together this morning and it feels quite sturdy. It has a little bit of flex at the ends, but that should disappear when it is connected to the wood frame & V-Slot. I changed the hole pattern to be more symmetrical than the previous photo & am going to reprint the back brace before the 1st test install on my printer. I am using Slic3r 1.2.9 with a Octagram Spiral fill for the top & bottom & 50% 3d honeycomb pattern infill. I really like the look of the Octagram Spiral on the faces.
Here are some photos.
IMG_9718_800x600.jpgIMG_9719_800x600.jpgIMG_9720_800x600.jpgIMG_9721_800x600.jpg

[PyramidDave]

I installed the new Y-axis backplate assembly today & fit like a glove. The sound seems more muted when the y motor is moving. I ran one 30 minute test print after leveling the bed & seems to work ok. I will get the files together to put on thingiverse in the next day or so. Here is a photo of the parts installed on the printer.
IMG_9732_800x600.jpg

[tonybuckley]

Sounds lovely! But unclear after reading the thread what is the problem being solved? So far my 8" i3v has been as expected. Very good!