Friday, 28 February 2014

Temperature effects with PLA printing / RepRap News

I did a little experimenting with temperature and PLA printing last April (2013) when building the Rostock - and it looks like I totally forgot to post a blog article about it!

I found the pictures today, and you may find it interesting, so here is what I remember about the experiment and process -

Last year when I didn't manage to get hold of any Laywood for testing, I decided to see what effect temperature had on PLA when it's printed smoothly at a controlled rate. I randomly selected Blue and Brown PLA and also used Natural (clear) as a control as I was sure that would show more obvious external differences with a change in temperature.

First test was just a simple change from printing at 192 Degrees C (lower section) then changing to 198 Degrees C (upper section)


I thought it might be neat to try a gradient effect, this is simply a change in extrusion temperature by + or - one degree C every ~3 layers over about 20 layers. 

I tried the same gradual gradient with Brown, that shows up a gradual change from matt to glossy as the temperature increases. (camera can't really show it well)

This actually didn't work as I had imagined. it's better than the photo shows, the camera is not able to pick up the gradient very well and you also get a strange optical effect as you move around the object, quite interesting.

You basically get a more obvious effect with a sharp change in extrusion temperature, here above the matt bands are 190 Degrees C and the glossy are 200. 


The speed is also important for a good change, I found running at 80mm/sec or faster was about optimal for this PLA and a J-head MK5 Extruder nozzle.

A mixture of gradual temperature change over a number of layers and sharp changes produce some really nice finishes.


To help select the bands I did make a small script to post process the G-code, but sadly this seems to have gone missing from my files.

If I do any more with this process I may produce a more friendly program to allow shades and stripes to be drawn on the Gcode, unless anyone else wants to produce something to do that.

Printing in PLA - Just a temperature change - nothing else. (the model is custom MakeALot Bud Vase btw)

Purple colours also seem to work exceptionally well for this effect.

I also destroyed one of these vases at the time to see if the temperature made any obvious differences to bonding strength. I could not find any difference while splitting and ripping the different temperature printed areas.

Let me know if you try anything like this, or with other materials (it obviously works well with Laywood), I'm sure other translucent PLA's and even PET (Taulman t-glase or Coloutfabb_XT) would also show this effect too.

Next time I do this I'll also try out a single walled 'spiral vase' print with temperature changes, I imagine that should look very neat.

RepRap News - 

If you are in the US or can travel 14-16th March, do check out the 2nd Midwest RepRap Festival - Goshen Indiana - more info Here - http://midwestreprapfest.org/ Loads of fantastic people will be there for a dev packed weekend. Sadly I can't make the festival, life gets in the way of 3D Printing some times :(

Feel the Force young developer - Force Sense Resistors - 

Johann has done some great experiments using three force sense resistors to measure pressure applied to the build platform on a mini Kossel - RepRap Wiki page here and Johann's Blog info here. 

It would be neat if only one could be installed on the hot-end itself, but that's going to take a bit more work. These sensors are very simple to measure using a spare Analogue input, more info here.

Now all we need to do is print our own force sensors rather than buy them, conductive filament at the ready :)

Cheltenham Geeks - 

I'm doing another 3D printing night at Deep Space Works in Cheltenham Monday 24th March 7:00PM - if you want to come (it's all free) sign up on Meetup here - I look forward to seeing you and if you can bring a 3D printer, 3D scanner, projects etc. let Tom Howlett know via the comments on Meetup.

And anything you want me to talk about or demo, leave me a comment here.

Rich.

10 comments:

  1. Awesome post Rich - Love your work :-)

    I found a temp which works for my PLA but you've inspired me to experiment more with it.

    Just out of curiosity, how thick do you usually print your perimeters? I've seen a lot of 'vases' on your posts and they are very large on that rostock! Always wondered how thick the single-walled ones were?

    ReplyDelete
    Replies
    1. Thanks, and good luck with the further experimentation, it's an interesting area to explore.

      All the prints above were hollow but with two perimeters, (these were printed before 'spiral vase' in Slic3r) so they are strong and around 1.25mm thick using a 0.48mm J-head

      On 3DR I have a 0.3mm nozzle fitted and I run it fast at 0.15mm layer heights and also slightly under extruding, the single walled objects are more fragile, but print really quickly, wall thickness is about 0.4mm.

      Delete
  2. Cool post! I am guessing since you said there was no real difference in bonding strength, it is perfectly fine to run on either end of the spectrum. I will have to experiment a little as well.

    Thanks for the insight!

    ReplyDelete
    Replies
    1. Hi Sam, Yes with PLA usually anything over 160 is fine for bonding, temp and extruder speed/power also do some of the self limiting. I would go hotter with high layer heights (over 0.4mm) but typical layers of 0.15 to 0.3mm are fine at most temperatures.

      Not the same for Nylon and ABS, they do like it hotter.

      Delete
  3. I noticed that the temperature gradient also changes the width at these areas since you extrude more plastic. This is a great example of why PID tuning is a must. Many people blame ribbing in the prints on bad z axis rods pulling the carriage around. It could be as simple as a wild heat swing in the hotend.

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  5. That’s really interesting! It’s pretty amazing how changes in temperature can make a huge difference on the printout. I think I need to order some PLA filament now and try this experiment myself. Thanks for making a post about this. Kudos!

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