functional parts w/ mounting holes

[dajay23D]

Wondering what everyone's doing for this or what's their solution. I find this to be quite challenging. Especially countersink and countersunk holes. They never fit a screw after it's printed and when i try to drill it out, you have to be very careful or the drills will catch the infill and split the part at times or completely ruin the hole. It would be nice if we can selectively choose full infill on a slicer. I think Simplified3D is the closest, but I don't think you can select the hole area or can you? It would be nice if we can create a diameter in the host software and then use the slicer to point in that diameter to select that's full infill. As of now, the only thing i can think of countering this is simply using plugs and then drill out the needed bolt/screw holes later.
The other problem is ABS warping. Functional car parts that i'm trying to print usually mean larger and require more infill which doesn't equal to easy printing. I thought I had ABS down until i started printing something that's 10" in length that's over 50% infill. I could try nylon or other more expensive materials, but ABS is cheaper. Has anyone ever tried to print a solid, 100% infill ABS block that's 10"? BTW, for bed adhesion, i've tried aquanet, kapton tape, blue tap, BuildTak, and ABS juice. Aquanet's the best so far for me. Bottom line, large parts still curl. Small parts, no problem.

[Xenocrates]

I print mostly in ABS. For the need for full infill around holes, increase the perimeter count, as well as the top/bottom count. If I acetone smooth them before drilling, I rarely have any issues with splitting it, although for holes I use brad-point bits rather than jobber (118 degree), and don't use the crap that is in most of the cheap assortments and indexes. I also tend towards coated bits, usually Ti-Nitride. I would also suggest that if you really want a quality hole, design the part to accept a heat set threaded insert for threaded parts, or a bushing of some sort for un-threaded holes. If nothing else, I would use acetal or nylon bushings rather than ABS for their improved wear qualities, and the better characterized behavior in the presence of thread lockers, lubricants, and particulate, especially since they can be replaced rather than having the reprint a large part.

As far as warping, using PEI, and an actively heated chamber, I rarely see a lot of warping, although I don't use 100% infill much. In my opinion, if you need a large part over ~60% infill, it may be cheaper to move to a better polymer or add in a strengthening filler such as glass fiber or carbon fiber, as you'll spend less plastic and time, even if the spool costs more. I've also had light-weighting hammered into me as a goal.

[IMBoring25]

I can't speak for other slicers, but Slic3r has a functionality called Modifiers that allows you to specify a second STL in the same coordinate system and treat it as a separate volume with its own settings, so you don't need 100% infill where you don't need it.

Yes, warp is a problem with ABS, especially at 100% infill, but not as much as with Nylon, actually. A heated enclosure does definitely help, and the hotter your setup allows it to get (within reason) the better. I still have too much PLA and too many electronics in the heated volume of my enclosed printer to go much over 40C, but it's still a big help. You can also do things with part design to minimize the warping issues.

ETA: In addition to the heat-set inserts, there are also multiple ways to add a slot or pocket for a nut. The slots leave an external hole and aren't as strong. The pockets require you to drop the nut in during the print.

[dajay23D]

Thanks for the responses. Wow, I didn't even know that Modifier feature existed on Slic3r. I would post this question on the Slic3r section, but seeing no one goes on there since last June, i'll post in here. This would potentially solve some of my problems. However, getting it to work is another story. I did some research and tried to use the Modifier, but it's hard to get it to work. I understand how it works, but half the battle is getting the part and the modifier to align. I'm using SolidWorks. From what I understand, in SW, i have to create pretty much a mold. A female and a male counter part or model. IMBoring25, have you used it much? It seems the feature only works on one plane. If i have multiples on different planes, then it's useless even if i got it to work.

[IMBoring25]

Well, this is a familiar-looking question that I already answered over on the RepRap forums.

http://forums.reprap.org/read.php?263,743819