M4rty
July 17, 2016, 10:43pm
1
I have been printing since February 2016, so while I am still fairly new to the hobby, I am familiar with it and have solved several problems on my own.
The issue I am having right now and I don’t really know where to begin looking has to do with the sizes of multiple parts that are supposed to fit together.
I have about 3 small pieces that are supposed to fit into one larger piece, which I will then ABS slurry on so they stick. The problem is though that the pieces aren’t even close to fitting! Granted, the prints are small to begin with so we are talking about the parts being approximately 3mm too big to fit into the base piece. I have a dremel and I could start trimming, but I would have to do enough that I might end up exposing the infil, and parts just shouldn’t come out like this.
Now the obvious solution would be to just scale down the part sizes. While that would work for primitive shapes, one part is the shape of an arch, with a smaller arch in the middle that needs to fit into the base. Basically, the inside arch is too small and the outside arch is too big. I apologize if this is difficult to understand, communication is not my strong point lol
Here are my specs:
-Flash Forge Creator Pro
-300 Microns
- 20% infill
- no supports or raft
Garyg
July 18, 2016, 1:47am
2
Hi
When designing parts that fit together as an assembly, I usually use a 0.012" offset between the parts.
Depending on the printer used, as the filament extrudes, it squishes out a bit.
This causes parts to not fit together.
I no longer scale parts to fit together because all dimensions of the part like wall thickness change when
the part is scaled.
0.012" offset sounds like a very big offset, but after printing, it’s usually pretty close to fitting correctly, but slightly sloppy.
Some printers can get away with 0.010" offset or smaller.
I think you will need to make a few test parts with different offsets to see how they fit.
…
I hope this comment will help you.
Hi,
This are the tolerances I use when designing parts that fit :
Material ABS
.150 mm Clearance on all sides for a tight fit
.300 mm Clearance on all sides for a slide fit
.500 mm Clearance on all sides for a very loose fit
Hope this helps
cobnut
July 18, 2016, 10:41am
4
Hi M4rty, how big are the parts overall? Generally speaking fitting together becomes less of an issue the larger the parts themselves.
Do you have a vernier caliper? If not, it’s probably worth the investment (you can get very good ones for less than $20). With a caliper you can check the precise “real” size of a printed hole and/or object and get an idea of accuracy and then make appropriate adjustments. Calipers are also the best way to make accurate copies of real objects, so they’re useful to have lying around.
I have to say, I have a FF Pro and it seems to be very accurate; I’ve printed a number of items to fit (including a threaded nut and bolt) and they came out perfect.
Could you take pictures of your parts that are trying to fix together.Try playing with your model tolerances. Is the wraping or any issues with the layers. Try using a presice caliper.
We had a similar issue before. We end up printing out several testing parts with 0.01mm difference to find the best tolerance level of our printer.
Hi,
First of all, 300 microns is probably way too thick. 200 microns is usually standard for printing, and you should probably use 100 for small pieces. Have you calibrated the bed? Have you adjusted the extrusion multiplier? If you don’t want to do that, print at 100% infill and work from there. Good luck!
Sra1
July 19, 2016, 9:52am
8
agree with previous posts - try lowering layer height from 300 microns. Also try lowering print temperature, and increasing cooling. A combination of these 3 should solidify the plastic exactly where it was laid.
Also sandpaper works well. If the parts dont fit by 3mm, then rather than taking 3mm off one part, perhaps 1.5mm off both parts might be better. If you start exposing infill or otherwise compromising part integrity, then reprint and Increase the number of shells. Of course if you implement the suggestions above and in othe rposts, you wont need to take off 1.5mm - probably much less
M4rty
July 21, 2016, 1:40am
9
Hi!
So I have tried a few of your suggestions, and they worked pretty well! The main reason I use 300 microns is because I don’t generally print intricate designs, so quick prints are better for me than higher resolution prints. However, since these parts are so small, using 200 microns barely changes the time at all, but it definitely affects the size! That and tinkering with the offsets has allowed me to play with how tight the parts fit.
Thank you all for the suggestions, you were a great help!
Have you tried to calibrate the extrusion ratio?
