Screw threaded telescopic platform (40mm,7 Segments)

####Screw threaded telescopic platform, 40mm deep, 7 segment version.

Note: I haven't had a chance to test print this version yet, and probably won't for a few weeks. Also, for this 7 segment version the resolution of the 3D model has been reduced as the 6 segment version was hitting the maximum size my computer's memory can cope with which massively extends the time taken to generate the STL files. On this model the spaces between adjacent vertices in the mesh will be about 1.5 times larger than those on all the models previously posted with 6 or fewer segments. This may have an impact on the appropriate clearance (see later in this description) to use when printing.

This version is 40mm tall when fully closed and ~200mm tall when fully unscrewed.

This object is a concentric series of threaded rings, each captive within the next ring out. The rings can be screwed up or down between two end stops positioned such that all of the rings, when screwed down, line up with each other to form a disk, or screwed up so that each extends above the ring directly outside of it to form a taller, cone-like structure.

Because these rings need to be fully captive 3D printing offers the easiest approach to creating this type of structure as all of the rings can be created at the same time in their final position, which avoids having to fit/attach one of the end-stops following creation as separate pieces with subsequent assembly. Note: The 3D models are set-up to print with the upper surface flat on the print bed. This gives a better surface for adhesion but should be remembered if it becomes necessary to apply an force to free up the rings; the rings screw out of the face that was printed downwards.

The point of this is to create an object that can be used support things in the way that, say, a pile of books might be used, but with a fully variable height (within its limits). This would have applications in, for example, DIY or modelling to temporarily support something in the correct position while glue sets.

I should mention that I don't know what the maximum load that these objects could support is (and it is likely to vary with print quality and the specific plastic (or other material) used , however the versions that I have printed in PLA have all been able to support my entire body weight so they are not inherently fragile. Note: plastics used in 3D printing (such as PLA) can fail suddenly by shattering so I would recommend that the consequences of sudden failure is considered in any application, and that if heavy weights are to be supported then the printed object should probably first be tested with a considerably (maybe ten times) heavier weight prior to its use in that application.

A smaller version of this object exists as an option for verifying the capabilities of a printer to create this type of object without wasting too much plastic on failed prints.

Specifically, Ideally each ring should be as close fitting as practical, but obviously if too close then the whole set of rings becomes one solid lump of waste plastic. This is largely down the clearance between rings (horizontal gap between the rings) designed into the 3D models, and the clearance that should be used will depend of the printer being used (how accurately/precisely it can print). To deal with this I have included 5 models for each version, each with a different clearance between the rings. The clearances included are 0.325mm, 0.375mm, 0.425mm, 0.475mm and 0.525mm. The clearance used in each model can be determined from the STL file names. Each STL file ends with "_CL" followed with some numbers and an underscore; replaced the underscore with a decimal point and take the result to be a number in millimetres and that is the clearance used in that file, e.g. "_CL0_475" refers to a 0.475mm clearance. (Note that the size of the 3D model depends on clearance, that is, the models with the larger clearance are wider than those with smaller clearance.)

It would generally be advisable to initially print the 4 segment example of the smaller version of this object to find out which value of clearance works with your printer prior to trying to crate a larger version as that will minimise the waste plastic that will result from failed prints.

The thread faces overhang and it is generally better to print overhangs with low layer heights. I have been printing these with a 0.1mm layer height.

Other details from the file names are, "S" is followed by the number of segments, and "H" is followed by the number of millimetres that represent the height of the base units.

I have previously posted optional end cap models for these 40mm versions. They are designed to press-fit together and into the ring structures and give a flatter upper surface to the central ring.

####Related Items

Screw threaded telescopic platform (20mm, 4 and 5 segment versions)
Screw threaded telescopic platform (30mm, 5 segment version)
Screw threaded telescopic platform (30mm, 6 segment version)
Screw threaded telescopic platform (40mm, 5 segment version)
Screw threaded telescopic platform (40mm, 6 segment version)

#####Update (22nd September 2019)

I received a comment form th008 suggesting that these would be easier to print if the clearance between the rings was larger where the from contacts the build plate. This would avoid any 'elephants foot' effect from gluing the adjacent rings together and make them easier to print. It tool some thought to work out how to do that without having to re-do the design from the start, but I figured that out and have now made that change. Specifically, where the form contacts the print bed the clearances between the rings is not 0.4mm wider, with that extra clearance tapering back to the normal profile within the first 2.5 mm in height. This change did indeed make these much easier to print reliably.