Slowing down layer print time

I've been trying to print this (http://www.thingiverse.com/thing:523343), and am running into a bit of trouble. Whenever I try printing any piece that ends with a pointed tip standing up, it ends up getting warped. Here (http://imgur.com/SPfn0Ly) is an example. Five attempts, all the same result. As far as I can tell, the problem is that once the printer gets to the final few layers, it doesn't leave enough time between layers for the plastic to cool and set before it starts printing the next one. I've tried to adjust the minimum layer time when slicing the file, but it doesn't make much of a difference. While the print does slow down a little, it isn't enough to stop the warping. And I'm sure it's been slowing down, I've printed a few test cubes that are 1x1x1cm, and the minimum layer time does affect the print time a little, but not much.

I'm printing with a Flashforge Creator Pro, slicing with the Makerbot desktop software. The default minimum layer time is 5 seconds, and the software won't let me put the time any higher than 30 seconds. I've tried using that setting, but I am not sure if the printer is actually taking that long for layers. Does anyone have any ideas about what to do to increase the minimum layer time, or what else I could do to fix this warping?

Not sure about the Makerbot software, but I do know that Simplify3D can easy handle layer height printing settings. In S3D you can create multiply processes and assign a different process to different layer heights.

For this pointy of a model, the layer height setting won't make much of a difference.

The best solution I have found it to place a 10mmx10mmx10mm cube on the opposite side of the print platform. Scale the cube height to match that of your model. This will force the print head to move across the build platform, print the cube, then move back. The time this takes gives enough time to cool the print you want to look nice.

Give it a try and let us know the results. If I'm not clear, I can post a picture later, just let me know.

Quote:

---

Originally Posted by JohnnyV

For this pointy of a model, the layer height setting won't make much of a difference.

The best solution I have found it to place a 10mmx10mmx10mm cube on the opposite side of the print platform. Scale the cube height to match that of your model. This will force the print head to move across the build platform, print the cube, then move back. The time this takes gives enough time to cool the print you want to look nice.

Give it a try and let us know the results. If I'm not clear, I can post a picture later, just let me know.

---

You misunderstood what I was suggesting (I was not clear).. You can set up different processes for different layer heights in the model with S3D.


In other words:

1) From layer height (model layer height) 0 to 25 use Process_1
2) From layer height (model layer height) 25 to 50 use Process_2
and so on and on

Each process can have different settings, which of course includes print speed, temp, everything....

The great thing about S3D you can do this for each model on the print bed.

Here are 2 examples:

https://www.youtube.com/watch?v=9hw-6KTvZdA

https://www.youtube.com/watch?v=R4veZyRkGbQ

Quote:

---

Originally Posted by ServiceXp

You misunderstood what I was suggesting (I was not clear).. You can set up different processes for different layer heights in the model with S3D.

---

I perfectly understood your suggestion, I do this all the time in S3D.

However, my point is it will not solve the OP's problem. No matter how much you slow down the layer speed for the top 10-20 layers, you are still going to have too much heat concentrated in too small of an area. Slowing down too much can actually cause more issues because the hot end is in the area for a longer time period.

In my experience, the best solution is to move the nozzle away from that "hot" area by printing another object on the opposite side of the build platform.

In Cura I set minimum layer time, that makes the head bugger off somewhere else for minimum layer time - layer time seconds.

joynny v is right.
Even with active cooling for thin pointy things you're better off with a second print.

Rather than a cube - either print two different wings at the same time or two of the same wing. That way you not only end up with what you want - but also allow time for layers to cool.

I had a tiny rubber tube I printed recently and even with cooling I had to do two at a time to give the plastic enough time to cool between layers.

In fact slowing the print speed down for small prints actually makes things worse, as the heat of the nozzle itself remelts the layers - the slower it moves the more the previous layers stay melty.

Arguably you could maybe speed up the printspeed. But it's still not as effective as printing something else at the same time.

Quote:

---

Originally Posted by JohnnyV

I perfectly understood your suggestion, I do this all the time in S3D.

However, my point is it will not solve the OP's problem. No matter how much you slow down the layer speed for the top 10-20 layers, you are still going to have too much heat concentrated in too small of an area. Slowing down too much can actually cause more issues because the hot end is in the area for a longer time period.

In my experience, the best solution is to move the nozzle away from that "hot" area by printing another object on the opposite side of the build platform.

---

Interesting, Not sure why it works for me then.

PS: I don't think I suggested slowing the print down, quite the opposite. I've accomplished this by speeding up the print a bit, and reducing the nozzle temp. It worked well for me.

You know it just dawned on me, I wonder if material matters with the technique I used. I print in ABS primarily?

Slowing down print time usually isn't enough because the hotend never moves away from the part, you need something to force the hotend to move away so it has time to cool. A small secondary object the same height as the print will help a ton.

Thanks for the advice guys. I'm going to try JohnnyV's suggestions and put a scaled up cube on the build plate, as well as the other pieces that are tall and pointy. I'll let you know how the print goes.

Quote:

---

Originally Posted by ServiceXp

You know it just dawned on me, I wonder if material matters with the technique I used. I print in ABS primarily?

---

Yeah material can have a huge impact on parts like this. These type of parts tend to print easier in PLA, specially with an active cooling fan because the plastic hardens faster. ABS tends to need more time to cool because its extruded at a hotter temperature, so you get more warpage and melting in small narrow pieces.

If you have an active cooling fan, you can try setting to a moderate speed for the top layers when using ABS. This may eliminate the issue, however it will require some trial and error for each different model. I like to use the cube technique because its simple and works for virtually any model.