PET bottle PCO28 1810 thread standard models

Thread Design

This standardised thread is called PCO28 and is produced in two versions.

PCO28 1810 - the original standard (point of this article)

PCO28 1881 - the newer material-saving version with a shorter thread.

My problem was that on printable there is no model with a real matching PCO28 thread. This leads to the fact that all models here are not really tight and with those that are meant for liquids the function is not given. You only ever notice this when you read the comments of the first makes carefully, or after you have watered your flat with your own print.

The better ones could be sealed with teflon-tape, which is not usable for threads you have to unwind very often, or with a rubber sealing, which is the better, but not satisfying solution.

Most of the time, it's simply because the respective modeller hasn't thought about how the sealing of a PET bottle really works. For those interested, all the necessary information is available from the standardisation institution isbt - International Society of Beverage Technologists

For the sake of completeness, I have also uploaded the standardisation drawings as PDF files.

These drawings show, with a lot of information, how complicated these threads are constructed and what the individual components are used for. It is also clearly described here which surfaces are responsible for the sealing of the bottles.

The files that can be loaded here contain both the original modelled thread - as far as they are standardised - with all components, as well as extra variants optimised for 3D printing. the original thread contains 2 rings below the thread that are not necessary for modelling your own models.

The first is the tamper evident bead or locking ring, which probably nobody wants to use here.

The second is the support ledge, which is only necessary for the production of the bottle and the machine filling. Both can only be printed nearly accurate with support, which I always try to avoid. Also included are models where the vents are not included because they are only needed for carbonated drinks. They guarantee that the cap can be screwed on in a controlled manner without the pressure in the bottle suddenly blowing the cap off. For 3D printing, which can not achieve the necessary accuracy of surface the are highly contra productive.

As my models, the standard ends 5 mm below the support ledge; below this, every bottle manufacturer can shape the bottle as the client wishes.

Cap design

Interestingly, the caps are not standardised and can be designed by the manufacturer.

The models of the caps are probably much more interesting for you, as it is mostly a question of reusing an industrially produced PET bottle.

There are also several cap designs. Unfortunately I couldn't find a detailed technical drawing on the net and had to take the measurements myself using some samples and then adapt them to the printer.

One with vents, which meets the specifications for carbonated drinks, and another without vents, for which I paid special attention to tightness during 3D printing.

Both caps are tested on standard bottles as well as on the threads I printed myself.

However, only the cap without vents is pressure-tight and presumably only if they are printed vertically in PETG with the same print settings (no Prusa standard, but included in 3mf). 

Even if I have selected a layer height of only 0.1 (nozzle 0.4 mm), printing the thread at an angle (depending on the model for which it is to be used) is probably no longer pressure-tight.

In order to make it easier for you to use these threads, there are STEP files in addition to the usual STL and 3mf files.

My extensive test prints have shown that the PETG used also produces different results. I never succeeded in generating a working (fitting) print with Prusa Orange using the same gcode file - the caps always became conical (see picture) and did not fit.

I always had the best results with Prusament urban grey PETG. So testing your print in early stage of design is something you should consider.

Have fun modelling