Holes appear to be squished in the Z direction

[Ace1992 0]

Hey Guys,

 

I apologize if this question has been answered multiple time, but I have been looking for quite some time now and could not find a solution to this problem.  I am having issues with the holes of the parts appearing to be squished in the z direction.  The hole in the attached picture is supposed to be 8mm in diameter.  As you can see the hole diameter in the X and Y direction is only .1mm off, but in the Z direction the circle is off 1.12mm.  At first I thought it was just the Z axis was not calibrated, but the overall Z dimension of the part is correct.  As you can see in the last picture, the overall part measures 21.45mm, and it is supposed to measure 21.5mm.  With it being off only by .05mm I don't think that my Z-axis needs calibrating.  I someone could please help me with this problem I would really appreciate it.  

 

I have an Ultimaker 2, printing with Colorfabb HT material, 100% infill, 60mm/sec, support at 60 degrees and .15mm gap between the support and part, 270 degrees print temp, and cooling at 30%.  I have great layer adhesion and no curling, so I don't think the temp has anything to do with it.  

 

Thanks,

 

Andy 

[gr5 2,099]

I suspect it's the top half of the hole.  I suspect this is normal for FDM printing because you are printing overhangs.  Usually I just design the hole to be a bit larger on the top or I drill it out after I print it.

 

One solution is to use PVA support but that would require a UM3 or major upgrades to your Um2.

 

Cooler temps help somewhat: more fan helps - make sure both side fans are at full power.  If you can lower the room temperature that won't hurt (put the printer under the air conditioner).  You can try lowering the nozzle temp a bit - maybe 10C.  But then you might get underextrusion so you could experiment.  You could lower the bed temp a bit but then parts are less likely to stick.  Some filaments print better than others.  Maybe try regular colorfab?  Or if you need high temp then try nGen (but with nGen I wouldn't mess with the temperatures -- just maybe try faster fan - maybe).

 

[Ace1992 0]

Hey Gr5,

 

Thank you very for the quick reply.  Currently I have the bed temp set to 100 C, and then I enclose the printer to keep the temperature inside the printer warmer.  If I don't use the enclosure then I will get layer split do to temperature change.  I am currently making my own E3D V6 mount, so I need the High temperature material, and to be honest this HT material is pretty easy to print. 

 

I have attached one more picture to hopefully add some more detail to my conundrum.  As you can see,  I have support materiel inside of the hole when I print it.  The pictures in my previous post were after I pulled out all the support material.   This leads me to the question of why does the support material let it "squish" that much.  Like I said, I have my support structures .15mm away from the structure, so in theory I should only get a .3 mm shrinkage. That little of shrink would not bother me at all.  It may be just the perfectionist in me, but I feel like I must be doing something wrong, because I know that these printers are awesome.  

 

Thanks,

 

Andy 

[gr5 2,099]

I don't think I've ever printed HT.  I certainly don't know it very well so I can't help you.  If it's splitting then it's indeed bad layer adhesion and you want to enclose the whole printer and lower the fan speed to maybe 30% but then the tops of your horizontal holes will sink down a bit.

[DF-Werkzeugservice 9]

I don't know which density and how many layers you are using for the dense support interface, but unless the density is maybe 90%+, keep in mind that - especially when printing in such a hot environment - your layers will also sagg a little through the support and the support interface itself can also sagg through the normal support.

When you are looking for perfect, I can make two suggestions:

 

1) design the hole for 7 mm and use a drill bit or even better a reemer to drill it out - will give you a perfect dimension and the printed 7 mm hole helps to get it into the right space

 

2) will be pretty much trial and error - design  the top half of the hole as ellyptic shape, modify the measurements until you get the desired result

 

+ I think on both ways you'll be able to print without support in the hole, which I assume is a pain in the ass to get out of there

[Ace1992 0]

Hey Guys,

 

Thanks for the replies and help.  Gr5, you had the right idea with increasing my fan speed.  I was afraid that it would start causing layer separation, but I has drastically increased the quality.  I just got a new roll of the HT in yesterday, so I am now messing with the print speed and the temperature a little more.  

 

@DF-Werkzeugservice:  Support material removal is not a pain at all for me.  I have spent quite a bit of time figuring out the best setting for this, and have found that .15 distance from part is just about perfect.  Most of the time, I just take a pair of needle nose pliers and twist and pull a little bit and the whole thing comes out.