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How do you join butted prints?


Erfolg
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I am producing a sub wing for a model. It is made from three prints.

 

My intention was or is to butt the sections together. At present i have two prints completed, and have noted that the joint is not perfect. In that there is probably a thou or so waviness. My intention was (and probably still is) to cyno the joint.

 

I then started to wonder how is this apparently simple task done on some of the commercial models. Do they normally print in a step/ locating tongue? I have thought I could possibly cyno some of the brim of-cuts to aid location and also gluing surface etc.

 

Yet again a lack of experience and common custom and practice is become apparent.

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If you print the plan as a PDF there is the option to include "crop marks" on the sheets, these will be a good guide as to where to align the pages. Cut one sheet to the crop marks then align it with the crop marks on the next sheet and tape into position and so on. It also helps to have an A3 printer which requires half the number of joins.

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I think Erflog is talking about 3d printing components rather than a pdf. I have added locating holes to both surfaces of my prints at the same diameter as the actual printing filament, then used small bits of filament to peg and align them together. I find this a better way rather than printing the peg in place

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Yep, I am talking about 3d PLA prints. Sorry about the confusion.

 

I have three of these which I intend to butt together at 400mm lg I thought that it could be a bit to tall for my printer. Now printing a 100mm lg section, I am thinking it could possibly be just about viable, although a very long printing session about  22 hours.

 

I think you can see that there is no overlapping on my arrangements. Or have I possibly mis-understood?

 

 

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Paul, I was not trying to cause an offence by a tautology. I can see from Rons image that a step of some type of step (however described) is beneficially  include in the 3d print design.

 

In future i will give some thought and consideration in how to incorporate the feature/concept into the design.

 

I am still not clear on what a pegged joint looks like?

 

In the mean time I am starting to cyno some bits of the brim to create an overlap on both parts being joined.

 

For me another example of common practice and methods that could be used in a model aircraft article for the RCM&E. I am sure that there is more than me that has a lot to learn.

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Erfolg

It depends on the duty of the printed component and the orientation of the print bead. A cyano joint is almost as strong as the grip between bead layers but of course is nothing like as strong as the bead in tension.

It follows that a simple cyano butt joint will suffice provided the two surface are in immediate contact but if you are joining printed surfaces that have their beads end to end then a significant overlap joint is required, indeed much the same as joining wood end to end.

Typically a shallow angle mitre but technically a 'finger' joint gives the highest strength.

FingerJoint.jpg.e4c044d8150a3f7a7514e2bd051384b8.jpg

It would not be the easiest thing to programme as it has to be a good fit! 😉

      

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I printed the 3Dlabprint Stearman, the fuselage had locating tabs between sections but the wings did not. You had to use slow cyano, get them lined up in the few seconds available then give them a quick blast with kicker, a job that really needed 3 hands. 

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Hi, Ron, the link to the Mightypeesh, is quite timely in that my next project is the production of WW1 wheels for the Fokker V29.

 

As yet I have not found the pegged link as yet, although I am now getting the impression the pegs go into the end face.

 

IMO there is so many aspects of 3D printing, design, aeromodellers experiences, and techniques  to draw on to produce a monthly article in the RCM&E. For many printing is the way forward with changes in supplies and products in the model trade.

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The linked video shows  locating features / tabs being used to aid assembly of 3D printed pieces. Due to the printing process resulting in one flat face, it's not always possible to print tabs where they are needed, so other methods can be used. The use of holes and pins as discussed above, or adding tabs by gluing. That latter method is shown at times 2:20 and 4:40 in the linked video.  Troy works so deftly, I do wonder what his bin looks like sometimes 😉

 

I have one of these printed out and am working up the courage to glue it together 😉

 

 

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Graham

 

The video has been reassuring, in that it shows what I have done and intended doing, once I had a problem was not totally a fudge, bad practice.

 

However i can see that incorporating registering, joint line at the design stage is much better.

 

Also the video reminded me that recognising that the methodology particularly of printing, should be approached as a different technology/processes. As a student I was taught that Iron Bridge although revolutionary, being made of iron, also had many features that were a reflection of wooden bridge practices. 

 

In my case, I realise that I could have easily added radius to the corners of many junctions, reducing stress raising features. My wall thicknesses in some places are to high. I have no idea of what common wall thicknesses are on fuselages etc. The video also highlighted novel control surface hinging arrangements, also notably is the undercarriage design features. Again as a student I was taught that heating up, drawn wire (i these cases piano wire) destroys the "properties that the processing history" have imbued. That the heating process is not only temperature dependent, duration is also important. That the oxidation colours are indicative and dependent on time and cooling process etc. In short soldering or brazing drawn wire modifies the structure. The video showed what can be done to avoid the phenomenon.

 

Yep a lot to learn, far more practice required and ideas to claim (as my own🙄).

 

 

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