Hello,
I would like to print the two halves of a cylinder that are supposed to be held together by a connection.
Everything fits in the drawing, but the two halves of a printed test cylinder do not fit together exactly.
What could be the reason for this?
The surface on which the support structure was located (I printed the parts upside down because a 30 mm support structure is required there, whereas the other way round a 100 mm support structure is required).
Kind regards
Proape
You have to design for printing, not for the CAD precision available.
Your drawing is very precise, a good thing, but you are not considering how things print.
Firstly, look at the centre if your print, that surface exceeds the way you drew it, likely the same reason the whole of that surface looks bad, it appears to be the underside of a supported print.
The design you have used to connect it at the edge is too small to do the job and doesn’t take the way FDM printers lay down filament into account.
That joint is weak, the way it is oriented makes it weaker.
Until you explain a few things, like:
It will be difficult to advise you on a solution.
Have you calibrated the filament and shrink?
The issue you have looks to be one of over cooling / under temp issue ,the filament in the print looks as if it hasnt melted enough to form a seamless bond, which i believe would cause excessive shrinking also layer shifting in the centre , when compared to the drawing , do you have a image of the sliced file ?
You can also link the your onshape file or a step file if you would like.
These are great questions.
Also,
Are you intending them to fit together using purely the joint or are you planning on using an adhesive? You might just need a locating feature.
Why are you printing it in two halves?
That’s a good question.
It replaces another part that I printed years ago, also in two halves. I can’t remember the exact circumstances, but I assume it was too difficult to remove the lamp first and insert the cable into the cylinder.
Why upside down?
Upside down because there is a smaller cylinder measuring 30 mm above the large cylinder measuring 100 mm, and because this way I only need a support structure measuring 30 mm instead of 100 mm.
The entire part has to be cylindrical.
How to design for printing?
I have ticked the option for calibration in the printing dialog.
A picture of the sliced plate of my test:
Zylinder test.gcode.3mf (169,6 KB)
I fit them together only by the connection.
Measurements
Other questions
I know you have answered some of this, I just want everything in the same place.
OK. I only ask because friction fitting is not the easiest thing to do in 3d printing. It can be done and is common, but it will take you to have a few revisions to determine how accurate you can make the printer.
There is the struggle of finding the odd balance between being able to move and having enough friction to hold it together.
The easiest thing to do in this circumstance is to use a mortise and tenon joint (variation of tongue and groove) then a few drops of super glue.
yes
yes
I made the diameter of the big cylinder 73mm and that of the small one 24mm, hoping that that will fit and that the small one is tight enough to hold onto the spiral cable.
no (see my previous answer)
how does that look like?
Give me a minute.
Here is a quick mockup. What makes that different from a tongue and groove is that you close the ends so that the joint is hidden.
A 0.2 mm to 0.3 mm tolerance is a good place to start. It looks loose in your CAD software, but once it is together it is fine.
Go simple.
The inside of this may not look the prettiest, but you will never see it. This uses bridges. It could be cleaner if you added some structure towards the top inside, but it is almost certainly not needed.
Change the orientation.
One side, face down.
The inside.
Use simple cylinders with small chamfers at the ends to make it easier to slide in.
If the holes have a 5mm diameter, make the plugs 4.9 or 4.95mm in diameter. You are making dowels and dowel holes. Make them slightly shorter than twice the single hole depth.
A simple mock-up.
LampCover.3mf (156.1 KB)
This took me two minutes to mock up; it will do the job just fine.
Ok, I know that from woodworking.
I wanted a self-locking connection. I had first printed a ring with a height of 5 mm, and the connection worked perfectly.
The connection is identical except that I have attached a male and a female connection to both parts. I also made the walls of the female connection thinner so that the male connection could be inserted.
The joint you just made will slip out, the end of the semi-circle will also need to be bigger.
Hold one first in your other hand.
The fist is bigger than the wrist, the hand bigger than the fist, each locks itself in.
In short, your male part needs a bell-end!
You should also have both one male and female on one side and then reverse them, one female and one male on the other side.
So each half has a male and female part to increase the strength and increase the chances they remain together.
I am offended with the lack of inclusive language
I’m afraid that joke has gotten almost as stale as “identifying as an Apache helicopter.”
I cannot confirm that; the ring holds together (well enough).
Luck is always good.
But, you only have fiction on either side, no compression force to restrict and add pressure to the make connection.
It will fail with some time and if you connect and disconnect a few times.
It should only be attached once and then never removed again.
The fact that it would not hold is not a problem, as I cannot join both halves cleanly anyway and my idea therefore does not work.
