I hope my question is not like broken radio that asked the same problem over and over again. so sorry for that, but I don’t know where to asked…
I tried to create modular box. As you can see in this picture below. All the hole on the corner of the box is the same size (3.5mm). On the slicer, I put the position of the box like in the picture. So, in my thought all the corner hole will be the same. I thought it wrong. 4 holes have different small size different. even one of the hole is very tight, my pin was broke when I tried to take it out. one of the hole have larger hole size and when I put the pin in it, the pin wobble because the hole is a little bit too big. the other 2 holes seems different small size also but still the pin can be put in and take it out without any problem.
here is the pin that I created for this box, I make the size smaller. The corner hole is 3.5mm and the pin I made is 3.3mm. I put up straight on the slicer when print it. it gives the same result better than printed it with horizontal position on bed.
When I tried the pin size 3.4mm, I have the hard time to push into the hole. it can be fit but with force to put in, so I didn’t tried to do it and change the size smaller.
Now… anyone can know why this thing can happend? I know that the size difference will be happend because of the printing result. But 4 holes with different small size in one object is confusing for me. and even confusing is the position of the holes are on the same level, so why there are a different for the printed result.
I use Sunlu PLA+ with 0.4 nozzle and 0.2mm line height on smooth plate.
You are experiencing tolerances. The machine has some and so does the material, so you can’t just make the pin 3.5mm, you have figured that much out.
But putting 3.3mm is 0.2mm of tolerance for two sides or 0.1mm, I suppose that is 3.3%, probably need closer to 5% tolerance to get a smooth fit.
Also, you probably want to chamfer the ends of the pins and or the holes in the box so they can start easily. This might allow you to use a tighter tolerance than otherwise.
When trying to get a perfect fit one would want to start with dry and calibrated filament.
good tips… I will try to chamfer the edge… back to drawing board than. before square, I tried round, but is not as strong as the square for the pins.
my filament is dried enough (i think) and I also calibrated my filament on bambu studio.
5% tolarance seems very high to me, but I will as close as possible.
but it still confusing why the 3.5mm holes have slightly different size. as you can see I have 3 pins to tried. all the pins have the same issue with the holes. I don’t know if the pins or the holes, but I tried different pins with the same hole, the result is the same. 1 hole too tight, 1 hole to wobble and 2 holes almost fit perfectly.
Well, best you can do is verify the original design is the right dimensions, then make sure you exported it in the highest quality possible (on fusion that is .step I believe). Then use the measure tool in Bambu studio to make sure that checks out and you don’t have a hole out of whack.
When that all checks out measure the dimensions of the resultant print, what are the actual differences in the hole size? Peg size? The will both have variance.
I think it might be due to the design, square peg in square hole with basic pressure fit, its not the best due to the perfect squareness that wont be in the result. And I’m not really sure of the fit you are after, stay in there for good, easy to remove and rotate etc… Material is big here, PLA is rigid, deforms and stays deformed, PETG is more elastic and works better for LEGO style fits though that doesnt seem to be what youre after here.
To put it this way, when you squeeze a toothbrush tube, you squeeze hard at first then gentle after, hence the line does not have the same thickness from start to end.
So that at where the seam is, there is more material there and it’s bulging in and out relatively to your part. Hence, it makes holes become slightly smaller or the part slightly larger at the seam.
In my experience when design tight fit parts, I’ll let some tolerance in the dimension in play according to the nozzle.
EG: 0.4mm nozzle should be +/-0.2mm tolerance, 0.6mm nozzle should be +/-0.3mm tolerance.
Sometimes to reduce the effect of seam, I choose random seam instead of aligned, but it would look ugly with pimples on the wall
3D printer is very much different from CNC machining when design the part. But still for CNC machined part, you’d need to have some clearance for tight fit parts as well, like 0.01mm or 0.005mm. Unless the part is friction fit and you heat up one part before press in then the clearance could be -0.001mm or depend on the expansion of the material when heat up.
Measure the holes with a caliper (if you design 3D models, you need one), don’t use the posts as a guide for the internal dimensions of the holes, you will never know wht’s dimensions are out, the holes or the posts.
The tighter the tolerances you want, the better the calibration of the filament needs to be. Temperature and flow calibration have to be the absolute best you can obtain. Fan speeds need to be played with too. That will help, but still will not eliminate the fact that the various other tolerances listed above still come into play.
There are also several (or more) posts on the forum about adjustments in the print parameters you can use to get more uniform hole sizes.
And last, although some people have good luck with the Sunlu filaments, I haven’t. I don’t like their PLA filaments, as I seemed to regularly have some issue with them. Uniform printing tolerances being one of them. I have one spool left of copper color, and it’s only been used for aesthetic prints. Once it’s done, I will use a different brand.
thank you for all the adviced… I really appreciate that…
at the end, I re-edit the pins to make it easier to put into the hole, and one of the hole still make the pin wobble, but at least 3 of them now fit without any trouble… I made bigger box with 12 holes and “only” 3 of them wobble.
it seems there is no perfect FDM printer… even this high advanced (they said) 3D Printer from bambu lab still need a lot of adjustment…
I mean I understand that it impossible to get the “perfect” printing result. but bought high advanced 3D printer or other middle range 3D printer will get almost the same result and do almost the same adjustment, only easier adjustment for (maybe) high end printer.
a lot of factor to be considered…
is 3D printer resin give more better result than FDM printer for printing small thing like this?