3D Printing: Oh, The Tuning We Shall Do.

After a while with the Ultimaker, a series of notes on the various things one can do to tune the 3D printing experience.

Some of this is specific to the Ultimaker, but most of it is not. Much of this is personal preference and, frankly, there is probably some stuff in here that is wildly sub-optimal. But, hey, it has worked for me and it worked better than it did when I started.

I.e. feedback and corrections are quite welcome!

First, a note on consumables. I have stuck with PLA (polylactic acid) exclusively. It is a plant derived material that requires a lower temperature and is quite thoroughly non-toxic (there are lots of articles about fume-venting ABS… not so with PLA). As well, when I screw up — which is often — the resulting garbage is biodegradable (however, I’m donating my “pile of PLA” to someone who needs input into a PLA scrap-to-usable-filament project).

PLA also doesn’t require — though it can benefit from — a heated print bed. ABS, the other common material, seemingly really does (though one can live without).

Thus, these tips are optimized to PLA.

These tips are also somewhat ordered in the steps that they should be done to maximize benefit. In some cases, that is because the earlier steps have a bigger ROI than later ones. In others, it is simply that the later steps really require the earlier steps first.

Upgrade to the Latest Software

See the discussion on this earlier post.

The same hold’s true for other 3D printers. You really want to be running the latest software [list of printers & corresponding firmware] as this industry is moving very fast.

In particular, the latest software goes way beyond just adding speed, it also adds much in the way of optimizing tool travel — extrusion head travel — to deal with the undeniable reality that is the physical world. Path lookahead. Acceleration curves. Etc…

This is being written on March 23, 2012 and I fully expect that the aforementioned article will have to be heavily edited by the end of April 2012.

This also includes not using ReplicatorG in your print pipeline. ReplicatorG can be quite useful for quickly adjusting a bit of STL, but it isn’t useful as either a slicing interface or as a printer driver (it can’t drive an Ultimaker at 250,000 baud, for example).

For slicing, Cura (formerly SkeinPyPy), Slic3r, or netFabb seem to be the current favorites. I’ve had great luck with Cura, though I really need to give Slic3r another go. A lot of people swear by netFabb, but, so far, it has completely failed to work for me (can’t communicate with the printer, even in the latest release that was supposed to be fixed).

Drop the Quest For Speed Nonsense

Unless, of course, your goal is to have the fastest printer on the block. If you are going that route, hey, all the more power to you. Hope you have a deep bank account, because you are going to need it to keep up with the unbelievable speed with which the technology is changing!

3D printing with the state of the art “filament squirter” printers like the Ultimaker are all about balancing the physical reality that is moving a the extrusion head about, squirting melted plastic through a really tiny hole, and dealing with the cooling properties of the plastic.

Go too fast and things like inertia, belt slop, and the limits of the machine start to impact print quality (i.e. circles will be ovals, etc..). Go for maximum speed and you can fully expect to be doing more “oh crap, it broke” maintenance work on your printer than going for reasonably fast.

With that said, going too slow is detrimental to print quality! Namely, if the slicing software uses extraction or, more primitively, quick acceleration to transition from points of extrusion across gaps of no extrusion, too slow of a speed will increase the stringiness.

For the Ultimaker, a base travel rate of 50mm/s is not unreasonable until you adjust the rest of the machine. 100mm/sec works well enough for most– but not all– prints once the machine is truly dialed in. Speeds of 150mm/sec+ are possible on a well tuned Ultimaker, but it comes at a cost of print quality and additional maintenance as mentioned before!

Tighten Those Belts Pt. 1!

As with most 3D printers, the Ultimaker’s motors can be loosened and moved a bit to adjust tension on the belts connected to them.

Loosen the motors and move them such that the connected short belts are tight. Do this immediately and plan on checking it periodically.

It is a dead simple adjustment and the results can be quite profound. In my case, I went from oval holes where walls and fill didn’t meet to solid fill/wall connections and very round holes. We are talking upwards of 1/2mm in accuracy improvement (which is really quite a bit when you add up all the 1/2mm inaccuracies across the print!).

We’ll get to part 2 in a second.

Use Two Layers of 3″ Painter’s Tape

(Unless, of course, you are using a heated bed.)

First, by using 3″ wide painter’s tape, it takes fewer strips to cover the print bed and, accordingly, that leads to fewer seams in the bottom of your printed objects.

Secondly, by using two layers, if you end up with super-adhesion to the point where the object won’t come off the tape, you’ll most likely end up lifting only the top layer and/or you can fit a thin bladed screwdriver under the object to gently pry it up without marring the acrylic print bed.

Two layers of tape is also more forgiving in case the head drags.

Note that a relatively fine flat metal file does wonders for taking blue tape goop off the bottom of printed models!

Level The Print Bed

First, adjust your print bed to be relatively level while all the adjustment screws are just below midway; i.e. the height adjustment screws screwed in more than not.

Then manually raise the bed until it just touches the extruder tip when it is centered on the platform. Now, back off a few turns such that there is enough of a gap between the bed and head that you can easily — a dime’s height — see the gap.

Next, set your z-stop switch to be triggered in this position.

By doing this, even if you were to adjust the height screws such that the extrusion head grounds out on the bed, there will be enough springiness in the height adjustment screws that it will be pretty forgiving. I’ve occasionally had goop buildup during a print that the head pushes out of the way by pushing down on the bed. No harm done. Not good, but no harm done.

Once that is done, time to level the bed. Start by putting the head in one corner and raising it until you can slide a piece of paper between the head and the bed, but there is friction.

Repeat with the other corners. Now, move the head to the middle and make sure it is still “one paper piece thickness” off the bed.

Note that this might actually be a bit too close! But we’ll get to that after the next point….

Always Prep Prior To Printing

First, clean the print surface. Remove any detritus from prior print runs. If you are printing really thin layers, it isn’t super-critical that you get ever last bit of skirt up, but all globs or large bits need to be removed.

Next, wipe down the tape with a rag soaked in rubbing alcohol. Give it a good scrub. This will remove any oils and/or other bits that prevent good adhesion.

Pre-heat the Print Head Regardless of whether you use a preheating function in the slicer or print driver, it is always a good idea to preheat the print head prior to starting the print. This will relieve an pressure on the extruder and will allow the temperature to settle.

Note that it is often the case that the extruder heater will be automatically shut down at the end of a print. If you are planning on printing again shortly, make sure to turn it back on!

Get to Know the Rhythm Of Your Printer

Nothing beats experience with a machine.

At this point, your printer should be tuned to the point that it can, at the least, produce a recognizable, usable even, print.

Slice and print a few bits of fun from Thingiverse and elsewhere. Don’t worry so much about calibration prints. Just focus on fun and/or useful stuff.

I started with things like trilego, Nautilus earrings, feet for my Ultimaker, iPod ear bud holders, and similar relatively simple models. Choose correctly and you can give away your printed tests to much amusement on the part of the recipient!

Now is also the time you might want to choose a somewhat more complex model as a calibration print. I chose a thick legged octopus as the outline is complex, but not crazy, while the level of detail is reasonable and the whole thing prints in less than an hour.

Why a calibration piece? Because, as you make adjustments to the pipeline, you can always slice this piece with your new parameters and send it to the freshly adjusted printer to compare with prior prints.

Besides, who doesn’t need an army of octopuses?

In any case, these initial casual prints will yield some very useful lessons. Focus on:

What happens when the print starts? Most software will extrude a bit of filament at the beginning of the print to ensure that the print head is clear and working. You’ll want to learn both what this normally looks like (to ensure the feed is OK) and such that you can remove the extruded bits before they dirty up your print!

What does the initial extrusion look like? That first layer of extrusion is absolutely critical (more on this in a second). If it doesn’t look like anything is coming out, try pushing down — gently — on the platform. If you start to see extrusion, consider lowering the bed just a bit. Or not; my first layers on thin-layered prints (0.1mm) are really really thin. Also, you can often adjust the first layer height in the slicing software.

Listen carefully to the printing process!! There are “normal” sounds, “hrm… I need to check up on that” sounds and “oh crap! pull the plug!” sounds. Listen closely.

A sure sign of “needs checkup” is if you hear any kind of grinding noise and/or dragging noises. Frequently, there will be bits of plastic goo that might blob up on the print head. These might come off doing the print and cause any number of issues. Similarly, the lack of adhesion on the initial layers may lead to part of the piece lifting up off the print bed, causing a noticeable change in tone as the print head has to push the lifted piece out of the way (this is another reason why the octopus is a good test — the legs tend to lift if the bed height isn’t correct, but they aren’t fat enough to risk damage to anything).

Note that it isn’t entirely uncommon to have threads of material that will stick up slightly and may potentially drag on the fan shroud and/or extruder. These aren’t typically problematic.

A skirt helps. A 5 revolution skirt is even better! In the Cura configuration interface, you can set the number of loops beyond the perimeter of the object that Cura will generate before printing the initial layer.

I highly recommend setting this to at least 5 for several reasons.

First, the very first bits that are extruded on a print often don’t stick or sometimes there is some filament sponge on the extruder. While the big slow skirt circles are being made, it is easy to grab any filament bits or lift anything that doesn’t adhere. Typically, by the end of the 5th loop, adhesion should be good and any sponge can be removed. If not, you aren’t likely to get a good print anyway and should start over.

Secondly, if one side of the skirt is either too thin (looks like a shiny transparent thin stripe on the blue tape) or not adhering whereas the other side looks good or is the opposite, it is a sure sign that your print bed is not level.

Finally, if your print bed is just slightly too high or too low, you can easily press down or lift up on it gently to adjust it on the fly. The skirts make it easy to see exactly which direction helps print quality and give you a moment to game the system a bit before the first layer is laid down. I’ve rescued many a print by gently pressing on one corner of the print bed (or adjusting the bed lifting screw) while the skirt was in progress.

Improve Your Printer!

First, belt slop sucks. It is the enemy of round holes and precise dimensions. Belt slop is what causes a print that is supposed to be 8mm on one side to be 8.4mm on that side. Slop causes the gaps between walls and fill. While the above recommendation specifically mentioned tightening the X-Y motor belts, you still want to tighten those really long X-Y axis belts, too!

So, print some belt tensioners! For the Ultimaker, I’ve found that the in-block belt tensioners from chasmaker work great. However, I started with the parametric belt tensioners from Owen that work quite well on the X axis (where there is enough clearance below the lower belt).

The belts should be tight enough that they are stiff to the touch and vibrate audibly when plucked.

You’ll want to re-check ‘em every now and then. The belts will stretch over time and the motors will move.

Secondly, the included fan shroud is lacking. It works, but you can easily upgrade by grabbing one of the many fan shroud designs from thingiverse. At the least, apply a bit of superglue to the joints to hold it together.

I ended up with a slightly smaller fan (the one that shipped with my Ultimaker pretty much disintegrated when I tried to mount it) and I designed a custom shroud for it. Works quite well! In fact, I printed the first version without the fan, revised it slightly, and then printed a much higher quality instance using the first shroud. There are many alternatives, though, and they are worthy of exploration.

Good cooling of the extruded material is absolutely key to achieving high quality prints, especially when potentially long bridges (spans of plastic over openings) are required!

Print a tool holder

I created a little toolholder that snaps onto the Ultimaker. It holds two 2mm allen drivers (of different styles), a pair of pliers, a pair of snips, and a flat head screwdriver.

This is pretty much the inventory of tools needed to prepare and perform most prints. I need to print another holder for the much larger wrench and allen driver that is occasionally used to clean the extruder.

Grab some different color filament! While I now have four 5 pound spools of filament — black, white, “natural”, and clear — along with ~2 pounds of silver that came with my printer, I’m likely going to order something like Faberdashery’s Rainbow Fun Pack. Having multiple colors on hand is actually quite handy.

When you switch colors, though, it isn’t just a simple switch in color. There will be a surprising amount of the old color left in the extruder. As well, you might find that the occasional bit of the old color will show up even after many mm of the new color has been extruded. This is particular true when switching to white where, obviously, any remaining pigment will be quite noticeable.

For a bit of fun, pull the filament in the bowden tube out a bit, cut it, and then load a different color into the extrusion motor. This will cause a piece to change color partially through the print. If you can figure out the math, you can even cut multiple lengths of different colors and have a many layered, colorized print, such as this awesome classic Apple logo!

Have Fun (but Give Back To The Community)!

This seems like a silly point in the list, but it isn’t. It really is quite easy to get wrapped up in trying to make the fastest possible prints or the perfect print or the most accurate print or fix bugs in the software or spend hours designing the perfect bottle cap or any of about a zillion other possible tasks.

Don’t forget to take a break from “making it work” and print some stuff just for the heck of it! I’ve gotten a lot of mileage out of printing various random “giftables” found on Thingiverse. Skull ear bud holders? Make great conversation starters and gifts. Nautilus earrings? My wife has given away a dozen pairs to friends.

At the same time, do try to take some time to give back to the community. Personal manufacturing is a self-bootstrapping revolution. By taking a moment to upload even an “I Made This!” image of something you made, maybe with a comment saying “Thanks!” or an idea, the author will be encouraged to upload more stuff. Similarly, if you design something, please share it if you can!

Similarly, with the software stack there is an endless list of things that could be improved. Taking a moment to file a bug or share ideas for improvement will help catalyze the much needed change required to make this whole thing truly accessible to all.



4 Responses to “3D Printing: Oh, The Tuning We Shall Do.”

  1. reimer says:

    Bill, what do you think of using silicone oven liners instead of the masking tape? Have not tried it of course but something like e.g. http://www.ptfesupplier.com/Silicone-Baking-Sheet-Liners-179.html

  2. Daniel says:

    Beautiful and brilliant write-up.
    I leaned some new stuff for operating my UM, thanks!

  3. Gregor says:

    Thank you for all the handy information!

  4. Phil says:

    Best article I’ve found so far on UM tuning. Many thanks!

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