Big model split into parts for 3D printing -> Strategies for creating gluing hints?

[haraldZXTDW]

Hi,

I have a big 3D model designed as a form, then thickened by 5mm into a solid and split into approximately 50 patches fitting into 25x25x25 cm boxes (the maximum size supported by the 3D printer). The following picture shows two such 25x25 cm patches:

Now I am looking for strategies for adding gluing hints to each patch. Do you have suggestions how to do this?

Regards,

[Oceanconcepts]

Is the concern primarily registration of the pieces, or keeping the curves in continuous alignment? My first thought would be to use sweep to make the edges into a kind of tongue and groove profile. This could be done as part of the splitting process if the splits are along a plane. Project-intersect in a sketch to get the splitting curve, then run a sweep profile(s) along the resulting curve to cut the pieces. Might need to allow some clearance for a glue line. 

[etfrench]

I like using a lap joint with locking pins.  The pins are just pieces of the filament.  You can either print the holes or drill them later.

[Drewpan]

Hi,

I recently watched a YouTube series by Adam Savage from Mythbusters that went through the entire

process of building a model for a current Computer Game by Bethesda called Starfield. Bethesda is a

huge Studio in video games just like MGM or Fox in Movies. You can find the series on YouTube here:

https://www.youtube.com/playlist?list=PLJtitKU0CAejiJisqHdCX4O-1-zJzfW36

The reason I bring this up is because one of the things suggested on this build was to design how you

are going to put things together as you go. While you say you will be using lap joints with pins, which may

be the only way you can do things for some parts, creating keys and holes and interlocking parts where

they can be done is more sensible when creating a large model. The model that was designed also had

3D printing constraints and also had to be modularised (ok the spaceship was meant to be modular so this

helped), the comment was made on a number of occasions in the video series that design includes trying to

work out what you might need later and designing it now instead of re-designing the whole thing later.

I know that this does not answer your question now, but it may help in the future. The series itself is a very

good way to see how professional model makers do things from concept to filmed scenes and how and why

certain decisions were made throughout the process.

Hope this helps.

Andrew

[haraldZXTDW]

Thanks for your suggestions. The Starfield build looks great but the model is much smaller and simpler (in the sense that it has no, or only small curved faces). A similar project is the 3D printed Lamborghini Aventador project on https://www.youtube.com/@lasersterling.

Lap joints and pins are an option but the material is quite thin (5mm) and large (each tile has an area of approximately 25cm^2). Lap joints are a great idea because I think that they are fairly easy to make: thicken the material on the cutting edges (=planes with a distance of 25cm cutting the model into 25cm^3 cubes) and then cut the joints into the thickened material.

I will also test the sweeping approach.

Generally my main concern is to keep the parts in place until the glue has set. Lap joints could help with this because I think that screw clamps can be used.

[Oceanconcepts]

Also don't discount making separate extensions on you model for use in clamping parts during assembly that can be removed later- if that can fit with your design goal. 

[etfrench]

If the parts will be sanded and painted, then you can add temporary braces to hold each piece in place with clamps.  You could also use temporary forms over the joints to force them to maintain their position.  Cauls are used in woodworking for this.

[haraldZXTDW]

@Oceanconcepts  suggestion of using sweeps brought me to the idea of using a chainsaw approach along the cutting edges (the one with the round corners is preferred because it works better with 3D print support):

I will checkout this too.

[Drewpan]

Hi,

I recently saw a couple of videos on YouTube, one was about the differences in the way people from

the West think about things compared to the East. The basic idea was that western people tend to think

with the object in mind where people from the east tend to think with the subject in mind. An example

is three fish swimming - west, a pond with plants and fish - east. A good practical example compared

various woodworking joins. West used standard mitre joints and lap joints and nailed or glued them

together, but eastern and particularly Japanese woodworking joints are often more complex and

interlocking. These eastern joints also tend not to use metal nails or glue but are pinned with wood. The

reason for this is that historically in Japan there was little metal of any quality and it was scarce so they

had to work out different ways of joining things. These interlocking wooden joints also worked very well

in a region prone to earthquakes and large temperature variations. I would recommend looking up these

joints as I did, the second video, to have a look as it was interesting and made sense in context.

The other people who have posted on this topic are sort of suggesting something similar here to what you

need. I presume that you are using lap joints to join two flat surfaces. This makes sense with this "western"

thinking. I think that you would be better trying an "eastern" solution, in that maybe instead of a flat surface

to glue with simple lap joints, maybe a simple interlocking "step" along the edges would help to make the

joins sit better and make gluing easier as then the parts would slide along but not apart. A two "step" approach

would even prevent sliding, so by glueing the edges, interlocking them and reinforcing the joint with a lap

joint it should sit nicely, not have a lot of movement and ultimately would be stronger.

Certainly worth thinking about. A very minor change along the joining edge would make this problem

much easier for you to solve.

Cheers

Andrew