Fine Calibration

I have had my printer since may. So-far its been totally fine for everything ive been doing.

However now im in an engineering class and were doing a project that requires rapid prototyping.
My printer can do fine for general things, but perfect parts just aren't coming out of it. My best parts are mediocre compared to others ive seen.
What can I do to get the quality I know is possible?

1.75 Filament
.25 nozzle
RAMPS 1.4
Slic3r 0.9.8
Ultimachine Black, or Natural PLA
Printing at 185-188C
No HPB

We are currently working on the project, so the sooner I can get it working well the better.

Thanks,
-Nick

Have you done ALL steps in the Calibration guide? (http://reprap.org/wiki/Calibration)

I've only been able to print accuratly after I nailed all calibration parts.

Personally, the things that affected the quality of my prints were:
- Poor spool holders causing too much friction.
- Idler not tighten properly.
- Bed not leveled.
- Not using fan when bridging.
- Printing too fast.

---

Cheers,
Franklin Dattein

There's a lot that goes into consistently producing great quality parts, but in my experience, 90% of moving to the next level is having well-aligned layers. There are a lot of things that need to be done to nail this down.

First of all, you need a rigid frame that doesn't move at all when the parts that are supposed to move do so. That means a MendelMax, Mendel90, Prusa i3, or something else that's rigid. Prusa 2s with threaded rods need to be well-braced to prevent side-to-side wobble when your X-carriage is moving.

Next, you need your machine's moving parts to be capable of fine, repeatable positioning. That means having good quality belts and pulleys. Forget printed pulleys and idler coverings if you want to achieve great quality. I'm partial to GT2 belts and pulleys because of their anti-backlash characteristics. Make sure they're fastened very taut so that there's no belt vibration when your X-carriage or Y-bed reverses direction. Also, don't let your stepper drivers overheat or you'll skip steps.

Next, you need to make sure that your Z-motion is consistent. This is hard to do with regular threaded rod, which can be hit-or-miss. Ideally you want real leadscrews, which ensure that every vertical movement actually moves the print head up by the same amount. You can tell you need leadscrews if your layers are generally well-aligned but have a consistent banding pattern where some poof out a bit. Make sure the nuts themselves are securely fastened to your X-ends!

Next, you need to make sure the same amount of plastic is exiting the nozzle all the time. That means buying good quality filament, which it sounds like you have, since Ultimachine PLA is excellent. You also need to get a high-quality hobbed bolt where the hobbing is consistent and the hobbed area is actually round, not slightly oval.

At this point, your machine is probably in really great shape. If you're still seeing layer consistency problems, check to make sure your hot end itself is securely fastened to the extruder body. I tore my hair out troubleshooting a problem only to find out that the hot end was ever so slightly wobbly in its mount.

Once your layers are aligned really well, just turn down the layer height and your flat walls will be truly flat and the individual layers will start to disappear.

I have a Prusa 2... How can I [easily-ish] beef up the frame.

I have GT2 belts & pulleys installed.

Steppers have skipped lately after I tried to adjust... just have to keep tweaking.

Leadscrews?... what exactly are these/where can I obtain some?


-Nick

There are a bunch of designs for Prusa-2-compatible braces: [www.thingiverse.com]

I don't have any Prusas so I haven't used any of them and I can't recommend a specific one, I'm afraid.

As for your stepper drivers, I'd say turn them up until the motors start to get warm-ish, and actively cool them with a fan (the steppers, not the motors). If your motor mounts are ABS, you can turn them up even higher until the motors get too hot to the touch. But that will also make them very noisy. This will ensure that your motors will not be skipping steps due to insufficient power for the speed you've specified. If they do still skip, it's because of the drivers heating up, so use a better fan or turn the voltage down a tad. Like I said, it's a bit of an art. You kind of have to keep tweaking until you get it just right.

Leadscrews are threaded rods made for linear motion, so they're straight and have fine, consistent threading. Not to toot my own horn, but I sell some nice leadscrews that use nuts that are compatible with your existing X-ends. If you end up with any leadscrews, not just mine,, you will need to adjust your firmware's z_steps_per_mm or Z rod pitch value because they will most likely have a different pitch from your threaded rods.

Same goes for GT2 belts and pulleys vs T2.5. You've adjusted your firmware for those, right? [reprap.org]

can you show pictures of what you mean by crappy parts?

Regarding lead screws, while they certainly do have advantages (speed) , in terms of print quality I think it's 100% possible to match lead screws using normal threaded rod.

1) Don't use m8, it's too thick and fights with your z-axis. Use M5/M6 which also has the advantage of a lower pitch.

2) Your couplings need to be really flexible in bending but stiff in tension/compression and torsion. Your rod must be perfectly concentric to the motor. I have had excellent results with 4.8mm ID fuel pipe. It's fibre reinforced so doesn't stretch, buy flexible enough to completely eliminate wobble. There is a visible slight wobble in my z-screws yet this is completely non-visible on the parts.

Good luck! Nailing the quality is the hard bit :p

jamesdanielv Wrote:
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> can you show pictures of what you mean by crappy
> parts?


I will post some tonight.

As best as I can describe:

My layers have these "inconsistencies". Its not necessarily wobbling X & Y, its just not looking good. Rather than each layer being nice & clean, there are some banding.

Would this be a result of bad Z rods?

-Nick

The shape of the tip of your nozzle can also affect fine detail quality. Can you post a close-up pic of your nozzle as well?

Edited 1 time(s). Last edit at 01/21/2013 12:36PM by Dirty Steve.

Dirty Steve Wrote:
-------------------------------------------------------
> The shape of the tip of your nozzle can also
> affect fine detail quality. Can you post a
> close-up pic of your nozzle as well?


What is the best type of tip to be looking for for the finest details, with say .35 or smaller?

I'm running a Wildseyed type hot end with a mig welder tip so changing my nozzle shape has been fairly easy.

From printing and testing with a .25mm nozzle and .1mm layers, I've gotten much better quality with a 'sharp' nozzle that is 3x the width of the nozzle hole. So for a .25mm nozzle, the tip is around .75 to 1 mm wide. See attached image.

I haven't gone sharper than this but I think a too sharp nozzle would cause other problems such as top layer finishing, not sure on that.

A blunt nozzle overlaps previous extruder passes too much, will 'smear' the exterior surface, and will pull up fill passes that are less than 100%

I had posted in the past asking about the profile of the tip of the nozzle but recieved no replies, so I found this out on my own from testing.

@xclusive585 I'd shape a .35mm nozzle to around 1-1.25mm at the tip with a file, or sand paper.

Edited 2 time(s). Last edit at 01/21/2013 02:45PM by Dirty Steve.

[dl.dropbox.com]
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[dl.dropbox.com]

I'm not sure but I think I read that PLA is not as good as ABS for small detail.

What does the tip of your nozzle look like? Top finishing should be much smoother than what your pics show.

[What does the tip of your nozzle look like?]

Top picture.... Wow i really forgot to add that...

Im not asking wether or not i can get the quality... ive gotten it before with a .35... now i need help with the .25 and layering.

-Nick

Edited 2 time(s). Last edit at 01/21/2013 06:53PM by N314.

[dl.dropbox.com]

Tip looks ok. I usually place a piece of 400 grit sand paper on my bed and move the nozzle back and forth a few times so that the tip is flat with the bed.