I have two gears to print for an agricultural grain machine. Since I still have the PA-CF spool that came with my X1C, I decided to print them with it. I bought a 0.6 hotend, dried the spool, and printed a Benchy to see how it would turn out, and it came out really clean. However, for the gears, I need to have precise dimensions, at least for the diameter of the shaft that goes through them. No matter how much I adjust the dimensions in my 3D software, I still end up with 0.2 to 0.3 mm more or less. I think I’m going to give up on reinforced filaments because I’m wasting time for not much gain and switch to ASA, hoping it will hold up.
Has anyone here experienced this kind of issue when printing with CF?
What’s the diameter of the hole? Can you just run a twist drill through it to open it up to the right size?
If you printed an object that’s 10cm across, that 0.25mm average error is only 0.25%, which is actually pretty darn good.
FDM printers cannot produce “tight” tolerance prints. Even if the printer could extrude exactly the right amount of plastic on exactly the right centerline to have the outer edge of the print line-to-line with the outer dimension of the design, the print is going to shrink as it cools and it won’t be on-spec anymore once it has.
PA filament shrinks quite a bit when it cools. Much more than the 0.25% tolerance error you’re getting.
ASA shrinks less than PA (or ABS which is why it’s a popular alternative to ABS) so you may have better luck. You can get ASA with CF if you need it for added strength.
Your issue has nothing to do with it being CF impregnated filament.
When I need tight dimensional tolerances on a 3D FDM print, I print the surfaces oversized and then I take them down on my CNC.
SLA printers produce much more accurate prints and usually don’t need any fancy tweaks or post-processing.
My diameter needs to be 16mm, but unfortunately, I don’t have the option to go over it again with a drill bit. Usually, when I print with PLA or PETG and need a relatively precise diameter, I always add 0.2mm in Fusion 360 to get the correct dimension, and it works well. That must correspond to the error you’re talking about.
This is the first time I’ve worked with reinforced filament and encountered this kind of issue. I’ve already printed gears on my SLA printer without any problems, but this one is quite large, and I don’t think my resin is strong enough for it to work. That’s why I switched to PA-CF, knowing that the original gear was made of polyamide.