A bunch of random questions on variations for Piper1 Piper2 MP3DP and MPCNC

Firstly, congrats on your work! I really like your approach for both MPCNC and the Piper projects and related work.

I have several questions and I am sure that you are way ahead on all of these, and any insight you provide will help!

  1. Has there been any attempts at using threadless screws such as Thingiverse #112718 #126537 #131034? It relies on friction, so if it doesn’t hold repeatability, more bearing and tighter clamping would help.

  2. I know Piper2 Enclosure version relies on the enclosure for stiffness. However, has there been any attempts at framing within a CNC cut box assumed square (of course cut by an MPCNC), for example using Thingiverse #27736 box generator? The box would be assembled and permanently glued/welded/cemented together along the teethed edged. The front side panel would also be used, but would have an access hole while also providing it’s part of the structure integrity, like piper2 front panel. This would eliminate alot of pipes, connectors, adjustments and weak points. Pipe mounts/anchors would be printed with exact spacing from corners/edges to ensure square. For example, on Piper2, the four z pipes would be anchored into each corner with 8 mounts. The printer would always be squared. For Piper 1, two horizontal pipes and two vertical pipes.

  3. Any tests or attempts at linking/syncing all three/four z-screws? I read that you had some problems with the steppers getting out of sync, possibly because of too much load. Independent steppers permit you to auto-level, but can get out of sync. It would seem simpler to level the base (rarely) and force all z-screws to be synced using a timing belt (or similar). You could probably also only have only one z-axis stepper motor by gearing it down, z-axis doesn’t need to move fast.

Following the piper theme, you could even use pipes as drives shafts and worm screws to gear down as you transmit motion. For example, 1x z-stepper > worm screw > long edge base drive shaft > two worm screws at each end > two 90 degree shaft > four worm screws at the base of each vertical z-screw.

I have been playing with the idea of drive shafts for transferring motion for many reasons, the mains ones commonly available materials, printed parts, low motion distortion, will work in higher temperature enclosures. The main disadvantage being the rotation momentum, which is not an issue for slower axis or proper gear down/up as required.

  1. Are there any versions of Piper2 that use 608 bearing X and Y sliders like the Piper1? I searched alot and didn’t find. I only found Thingiverse #3065538 “Piper 2 Bearing-less Short Gantries (PTFE Sliders) - 8mm, 10mm, and 12mm rods versions”

  2. In respect to the printed or Teflon sliders, why is almost every example I see using more than three contact points? A screw tightened C clamp with only three contact points (printed ridges or Teflon tubes) can easily be tighten as required as ridges get soft or worn. Any tests or prints that are adjustable three ridged sliders? Thingiverse #2661134 is an example of a printed recirculating linear rail that has three rows and thus universal. This could work also for piper and MPCNC and something that I will try eventually.

  3. The bolts in the MPCNC are quite massive for the strength of the plastic, even if infilled at 100%. Often, basic floor screws are the cheapest fasteners commonly available. I was thinking of modifying the MPCNC bolts to a hybrid of a printed hex nut with a small unthreaded hole and use floor screws as MPCNC fasteners by self-tapping into the printed pseudo-nuts. Also using a thick sacrificial printed washers to avoid the screw head digging into the plastic of the main parts, or just a metal washer, depending. Any thoughts, comments or tests done related to this?

I can only really answer #6, the bolts also serve as bearing races, and have more surface area to push against the plastic. If you use small screws you would need washers, steel bushings, and the longer screws get more expensive, and the small screws would much more easily deform the plastic…