ABS layer bonding

[davewlex 0]

I have an ultimaker 2 that I have upgraded to a 2+ with the ultimaker nozzle upgrade kit. I have been printing on this for some time before the upgrade and about 25- 30 prints after the upgrade. I hate to go into ABS discussions again, but I just am not sure what to expect when I do print ABS as far as layer bonding. I have a spool of Ultimaker grey ABS that I can get absolutely beautiful prints from. However these parts need to be functional. When I test these to see how strong they are, they always fail my test.

Here is what I typically do. I take 2 pairs of needle nose pliers and then give the parts a tug trying to see if they will separate. It takes a little force, but they still break apart in the layers at a point that I would say is really not good. I have no idea how much force I am appying, but it is certainly not more than an amount that would make the part useable. I use a plexiglass sheet that I place across the front of my machine as a door. I have been tinkering with the temps and considering a heat lamp aimed through the top to increase my internal temperature, but the big question is how strong of a part can I expect to achieve?? Is there just always going to be some weak layer bonding issues with ABS. The sample I am trying to print is a cylinder with 2.5 mm walls and solid fill. The diameter is around 30 mm.

I think my last print was about 245C with no fans and 30mm/s speed and 80C buildplate. I checked my heater block with the nozzle off at the internal heating portion and it seems ot be about 8-10 C lower than the machine says.

[gr5 962]

245C, 30mm/sec, no fan - that should be fine. Did that one fail also?

I know what you mean about the layer bonding.

I should mention (not related to layer bonding) that 100C is MUCH better than 80C. Parts stick better to the glass. MUCH better. Much less likely to get warping. But if your parts are very small 80C will work.

So it's great that you covered the front of the machine but you should also cover the top. I use those boxes you find next to the photocopier that hold reems of paper. Those boxes are perfect. No modification needed. No cutting. Just flip it over and put on top of a UMO, UM2, UM3. Leave a big gap at the back for the bowden. Combine this with a front cover and you should be able to get the air temp up to about 35C. Don't go above 40C because then the servos are starting to get into overheating range. I know someone who heats the air to 70C but he also has heat sinks and fans on each servo.

Anyway I find merely printing with no fan is plenty warm enough to get good layer bonding. But quality if parts I find is crappy if I don't use a little fan on overhangs and bridging so I usually compromise and run the fan as slow as it will go and still reliabley rotate. Around 30% on UM2 and 3% on UM3.

I'm surprised the block is *cooler* than programmed temp. These temp sensors can vary by 10C but usually they read cool (meaning the block is *hotter* than you thought). This is mostly because the wiring going to the temp sensor brings in some cooler temps.

It's fine to try hotter than 245C but beware if you leave ABS too hot for too long (e.g. 255C for 10 minutes not printing but sitting in nozzle) it will bake into a glue that requires some work to clean out (remove nozzle, flame, toothpick, etc).

[davewlex 0]

245C, 30mm/sec, no fan - that should be fine.  Did that one fail also?

I know what you mean about the layer bonding.

 

Thanks so much on the reply. Like I said, the print actually looked great. I had a small energy riser on the top of one part that formed perfectly. I had good bed adhesion and the layers looked good with no holes or any kind of underextrusion. It just seems weak when trying to pull it apart. I'm not sure if my expectations are too high and this is just the way it will print or if I can expect to get some functional usage out of an ABS printing. The part would probably be fine for a pencil holder or some kind of desk ornament, but if I was to build a device that threads into this or may be dropped or some kind of fixturing, then I don't think it would be sufficient. I know that my parts would be weaker than an actual molding or machined part, but what I am producing now doesnt even come close to something I would get from a stereolithography print or a polyjet. I will try enclosing the top and raising the temp about 10 degrees to compensate for my differences.

[gr5 962]

And raise bed temp to 100C to help you get to a warmer air temp sooner.