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How to print a very small model?

Posted by morgan76 
How to print a very small model?
October 06, 2017 02:22AM
Hello guys !!
I was wondering if someone can help me and give me some advice to print very little model?

Here is my trouble, I want to print part from chain, like bike chain, with this dimensions :

- Chain link : 14mmx5mm and 2mm diameter for the hole
- little cylinder : 2mm diameter intern and 4mm diameter extern

But it is horrible and the little cylinder just not print.

Oh and I print in ABS at 250°C hotbed at 110°C and print speed at 30mm/s and I use a raft.

thanks for helping me,
Morgan
fma
Re: How to print a very small model?
October 06, 2017 02:57AM
Do you have to use ABS? It is not the easiest material for that... I recently printed such small objects, but with PLA. And I used a good one (noname, translucide). If you have to use ABS, buy a *very* good one (if you can put your hand on Stratasys ABS, it is amazing).

A few advices:

1) print very slowly (30mm.s⁻² is a maximum)

2) insulate the bottom of your hotend, to avoid too much heat on the part

3) with PLA, use fan at full speed (you can increase the temperature to have better layer adhesion)

4) use slow accelerations

5) if you can, use a small nozzle (0.3mm)

You have to fine tune your extruder advance, to get the exact quantity of material. Do not just extrude 100mm and adjust steps/mm so you measure 100mm. After that, print a 20x20x2 cube, with 2 full bottoms and tops, and have a look at the top: you should obtain a perfect surface. If you have gap between filaments, increase the extruder ratio. If you have bumps, decrease it.

Also, if you can post a picture...

Good luck!


Frédéric
Re: How to print a very small model?
October 06, 2017 02:59AM
I had a similar problem a few weeks ago. I assume your litttle cylinder prints, but it is still too hot, when the next layer gets printed. Using a part fan is no option when printing ABS. You may try to print 4 or 9 cylinders at a time to increase layer printing time, giving the objects more time to cool down. My cylinder got little scars when the head moved from one to the next, and the connection to the hose wasn't airtight anymore, so this didn't help.
I reduced the printing speed as much as possible, and when printing, I reduced the feedrate in Octoprint as much as possible. IIRC the resulting print speed was about 5mm/s. Worked.
If this is still too fast for your cylinder, you may need to decrease the printing speed in the slicer settings. It looks weird, when you're printing this slow.
fma
Re: How to print a very small model?
October 06, 2017 03:07AM
I printed ABS for several years, before switching to PLA, and I always used part fan. But it was made of a tube (OD8,ID6), and an aquarium pump. It was blowing just a little, at the nozzle output. It does not make the part warp, and helps a lot on such small parts.


Frédéric
Re: How to print a very small model?
October 06, 2017 03:57AM
Ok thank you for your response both of you !! I will test again after my work with your advices.

I already try to print several part at the same times (about 10), so next try is decrease speed.

I use ICE FILAMENT.

Morgan
Re: How to print a very small model?
October 06, 2017 04:01AM
At the end, in 10 cylinder, only two was really print, one not bad and not not useful.

When I was looking the printing sometimes I don't saw the ABS get out of the nozzle at the start of the layer.
Re: How to print a very small model?
October 07, 2017 09:59AM
i am having the same problem for more than 2 months as i am printing a small part with fine detail. the thing i am testing now is getting more than one copy on the bed to allow the thing to cool down after every layer .

that thing with the tube is a good idea and it is the next upgrade i want to do but instead of a pump i ll use a fan. my nozzle is a 0.3mm and i am trying to get smallet width than 0.2mm . I think a smaller nozzle would do the job so much better but i to lazy to replace it for 0.05mm.

Anyway the infos written above were very helpful for me too. thanks guys.


RePrapPro Mendel 3
Duet 0.8.5 firmware 1.19
Re: How to print a very small model?
October 11, 2017 07:38AM
Just a different approach.
Its easy to think we can print anything but some times its worth stepping back. Especially as you could spend a lot of time and never get a good result.
If had several instances with similar problems and found its often simpler to use another manufacturing approach.
In this case you can try printing the cylinders with a nominal hole of say 1mm and then drill the centre to the diameter you want. However I start questioning whether I could really get a quality part, and look elsewhere for an existing form I can modify.
Not sure what your cylinders are for but small thin walled items like straws could be used or drill out some knitting needles.
Re: How to print a very small model?
October 11, 2017 09:44AM
* lower your hotend temperature, 250 °C is too high for small parts, normally ABS also is printable with 230°C (slow for sure)
* lower your bed temperature, go down as low as possible, depending on your abs, i`m gowing down to 98-102°C
* ensure that your per layer print time is at least 20 second, printing too slow is also not good for some hotends and getting too much radiant heat into the part.
so a combination of multiple objects and printing slow is the key
* what are the parts looking at the moment ?, what are the exact issues ?
* what slicer and settings do you print ? settings and a zipped gcode file would be good to analyze.
* print the parts on a podest which is at least 5mm high.this way the parts will not become an elephant foot and do not overheat that much while printing.

if you want to print such stuff more often i recommend you to switch to a small airbrush nozzle: (no stuff for beginners winking smiley )
airbrush nozzle have the benefit that the don`t have a flat surface for "ironing", which is an issue when printing small stuff (the lines will be pulled away), and less heat transfer.

Chri


[chrisu02.wordpress.com] Quadmax Intel Delid Tools
fma
Re: How to print a very small model?
October 11, 2017 10:10AM
What does an airbrush nozzle looke like?


Frédéric
Re: How to print a very small model?
October 11, 2017 10:19AM


either buying a merlin hotend or searching for a adapter to mount it on a E3D compatible hotend.

Chri


[chrisu02.wordpress.com] Quadmax Intel Delid Tools
fma
Re: How to print a very small model?
October 11, 2017 11:24AM
Nice! I will try to find E3D adapter... Thanks.


Frédéric
Re: How to print a very small model?
October 18, 2017 12:30PM
Hi,

I followed your multiple advice :

- Change nozzle to 0.2 mm
- Decrease speed at 5 mm/s in Cura

But is still no print sad smiley

In the attach file you can see my sol file and a picture of my print

It is really possible too print small part?

Morgan
Attachments:
open | download - chain.png (69.8 KB)
open | download - pict_chain.png (553.8 KB)
fma
Re: How to print a very small model?
October 18, 2017 02:46PM
It is strange that the cylinders don't stick to the raft...

Did you tune the extruder ratio? Just print a 20x20x3 square, et adjust this param until you get a perfect top surface. You should not get gap between wires (not enough plastic), nor bumps (too much plastic).

I also suggest you insulate the bottom of your hotend, to avoid too much heat on the printed parts. And you should try to increase a little bit the speed.

You could also try to find a tube, and cut it to make your little cylinders, instead of printing them... That's what I do for such simple parts.


Frédéric
Re: How to print a very small model?
October 18, 2017 04:11PM
can you zip and upload the gcode file ?
maybe also you cura settings (export)

Chri

Edited 1 time(s). Last edit at 10/18/2017 04:11PM by Chri.


[chrisu02.wordpress.com] Quadmax Intel Delid Tools
Re: How to print a very small model?
October 19, 2017 07:12AM
Might be worth a new software feature - min perimeter time.
With all those parts your layer time is going to be quite long so the feature wont help much.
But on the small cylinders the problem may be that each perimeter is causing the problem. How many perimeters have you set?

If you set the perimeters to 1 it should laydown all the perimeters and then return for the infill by which time the perimeter has cooled. Im guessing you have 100% infill already.
I usually try to avoid small items like this.
fma
Re: How to print a very small model?
October 19, 2017 09:08AM
I talked to Morgan in private (and in french winking smiley), and suggested to switch from Cura to Slic3r.

Cura makes an horrible job on the first layer, as it does not slow down small perimeters, and prints 1 wall of each perimeter at a time, which tends to rip it out when moving (at travelling speed) to the next perimeter... (I asked Cura devs to change that, but they don't want to).

I think this is the main problem, here. Slic3r should be better on this point.

Morgan will also try PLA, as it is easier to print.


Frédéric
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