A camera rig that tracks the Y and Z axes, for stable timelapses. Reuploaded because I couldn't figure out how else to enter it into the #PimpMyPrusa design challenge.

Prusa team sent my MK3 with stainless steel rods and sent me hardened steel ones to replace them. This left me with a few extra rods and bearings to use, so I came up with this Idea. When coming up with this idea, I had 2 main goals: 

• 1) Always be able to see the nozzle.
• 2) Stabilize bed movement for smoother timelapse

I am proud to say that this model manages to do both of those things as expected. The timelapses come out looking like they were shot on a Core-XY machine like an Ultimaker, where the bed descends during the timelapse as the print head does its thing. The bed doesn't appear to move in any direction but down, and the nozzle is always visible during the entire print to help spot issues through Octoprint. The camera may be mounted too low for some people, so I am leaving a link to my Onshape document at the bottom of this description for you to modify as you see fit.

Here is a benchy timelapse so you can see for yourself how it's supposed to work.
https://youtu.be/GEMzdQG6Z_A

I also have printed the spin vase by Devin Montes to test using as much print volume as possible. 
https://youtu.be/HStRvJ-0uu0
https://youtu.be/OSmlw1e6fmg

here is a space harrier
https://youtu.be/NZss6AdZipU

Note: The timelapses above were taken before adding the Y-Axis Brace, which significantly improves stability during Y-axis motion. Below are timelapses which demonstrate how much more stable it is with the Y-Axis Brace

Here is a timelapse printing the horn for the Echo Dot Gramophone. As you can see, having the brace makes Y-Axis motion much more stable.
https://youtu.be/lxtx13LV_5E

Here is a timelapse of the Kratos model on MyMiniFactory
https://youtu.be/D14ylNoziao

Cthulhu
https://youtu.be/R9q9A9i71V8

There are some important assembly instructions I should mention, or it will not work as well for you as it does for me.

NOTE: The Y-axis rod mount is tested to work with the R1 X-Axis Motor End. A version for R2/R3 has been uploaded but is based entirely on measurements of the model and has not been used on the printer yet. I don't think there should be an issue as I checked the models against each other, but let me know if you experience any issues.

Assembly:

Required Materials:

• - 2x Stainless Steel Guide Rods that Prusa sent by accident and were replaced with hardened steel rods.
• - 4x Roller Bearings
• - 8x Zip Ties
• - 6x M2x12 countersunk bolts and M2 nuts
• - the 3D printed parts
• - (optional) Some cheap LED bar I got on Amazon (I was unfortunately unable to find the same one, my order links to this one which is a different one than I got https://www.amazon.com/gp/product/B01H36HKCY/)
   

Part 1: Z-Axis Bar Mount

• 1) Unscrew the bottom left bolt in your print bed and remove the metal cylinder spacer thing.
• 2) Place the open end of the part onto the bottom of the bed frame with the hole facing up. Insert metal cylinder spacer thing into open hole.
• 3) Line up the spacer with the hole on your bed and threads below. Bolt through. Tighten as you normally would, the bed is still resting on the same metal spacer and not on the printed part.
• 4) Insert 2x M2x12 bolts and nuts in the side far away from the bed. Do not tighten yet. Do not insert guide rod yet.
   

Part 2: Y-Axis Bar Mount

• 1) Insert 4x M2x12 bolts and nuts at the bottom of the part.
• 2) Screw to X-Axis stepper motor with the M3 bolt that I didn't tell you you needed (don't worry, you should have a spare with your printer. sorry for not mentioning it ahead of time)
• 3) Optional: Insert that cheap LED bar, hopefully you got the right one. I found that facing mine towards the wall offers more diffuse light and helps keep the timelapse from looking over-exposed.
   

Part 3: YYZ Sled

• 1) Place 4x Roller bearings where the roller bearings go.
• 2) Place 8x zip ties in their zip tie runs and cinch them shut, BUT DO NOT TIGHTEN YET. If you tighten now, then your bearings will probably sieze on the machine and not roll smoothly.
   

Part 4: Putting it all together

Right now, you should have all of the parts ready, with nothing tightened. The guide rods should still be strewn about on the floor or wherever you keep them and the Y and Z rod mounts should be attached to your X-axis motor and bed respectively. If anything I just said is not true, go fix it or things are gonna turn out poorly (I know from experience)

• 1) Insert your longest rod into Y-axis rod mount. Do not tighten it yet. Position the Y-Axis brace on the underside of the X-Axis stepper motor and position the end of the rod to be just past the brace.
• 2) Slide the YYZ sled onto the Y-axis rod. Again, don't tighten anything.
• 3) Slide your shortest rod through the other bearings on the sled, and then into the Z-axis rod mount. We're getting close, but still no tightening.
• 4) Slide your bed all the way out as far as it will go. Make sure the Y-axis rod reaches that point. Don't tighten yet, thats the next step.
• 5) Home your printer before tightening. When all the parts are bunched up in the home position, tighten them. Start by tightening the Y-Axis Rod, then the Z-Axis Rod, and last the zip ties on the bearings. Note: do not overtighten the zip ties, they only need to hold the bearings in. They don't need to apply significant force to them.
• 6) Optional: The bottom of the YYZ sled has a tie point where you can put a zip tie or small elastic band to help control the cable connected to the Pi camera. I personally use a small elastic band, but I left the option for zip ties available. You could also forego this step entirely and just leave the cable dangling. Don't do it just cuz I put it there, do it because you think it's a good idea.

With that, the camera rig should be assembled and hopefully sliding smoothly. If it isn't moving smoothly, try loostening things and tightening them again.

And as promised, here is the Onshape document.
https://cad.onshape.com/documents/3e0346a171411ff39982a614/w/7177de8c2083548881992337/e/32668ee2e56e8e480a6aab65