MakerBot Industries

Printed bearing, nearly 608 size

This weekend I tried printing Rayraywashere’s ball bearing with mixed success.  The plastic spheres inside we pretty well fused to the sides of the bearing, which made for a difficult cleanup.  Although it got better with time, it was a laborious process.  Ultimately, printed bearings that rely on printed balls may not be the way to go for everyone.  Even if you can print it without fusing the balls to the bearing, there’s no guarantee the balls would be sufficiently spherical to work properly.

That ball bearing design got me thinking – if I could find a reasonably ubiquitous and cheap alternative to small printed spheres, I could make the entire design much smaller and probably significantly more reliable.  The photo above is rough draft/proof of concept for a printed bearing only slightly larger than a traditional 608 bearing.  Rather than printed spheres, it uses plastic pellets of the sort typically used as stuffing in craft projects.  I sorted through a lot of these and used only the most nearly spherical ones.  However, there was still a lot of variation that lead to the bearing getting jammed.

Later I emptied the plastic pellets and tried out small spherical 3mm plastic beads.  These have worked really well in this printed design.  To improve upon this design I intend to move the “bead filling gap” to the interior ring or change the ring system so that two rings will snap together and cover the filling gap.  Overall, I am very happy with this result.  I’m looking forward to actually installing a slightly smaller version into my Cupcake 3D printer in place of a 608 bearing to see how well it works.

I spent $4.00 for 1700 identical plastic beads, silver in color, 3mm in diameter.  It takes about a dozen of these beads to fill the bearing.  The potential savings are pretty self-evident.  The per-unit cost for each bearing is probably only about $0.05 or so in plastic and beads.  That’s pretty good compared to $2+ for commercial bearings.  The real test will be how smoothly they work, how well they work at high speed, how quickly they might wear out.  However, I think I may be on the right track here.

Any suggestions?

Dave Durant makes Skeinforge less spooky

Dave Durant has continued his series on how to configure Skeinforge for your 3D printer. ¹  Although Dave prefaces his comments by saying these are not necessarily recommended settings, he (again!) does a great job of going through each setting available in Skeinforge 033 and explaining why he is using that particular setting – along with suggestions of when those parameters may not be appropriate for your ‘bot.

Starting at ReplicatorG version 0020, the folks at MakerBot are also including a recent version of Skeinforge. w00T!!

I’ve been advocating moving up to more recent versions of skeinforge for months now, mostly because I think I can sorta figure out how to configure them. The older versions just make me go cross-eyed and confuse me. YMMV.

Since my last blog post was a bit (or more than a bit.. or even a LOT more than a bit) long winded and preachy, I’ll try to keep this one short. Below’s my notes on going through all the modules in skeinforge 33, the latest as of today. Note that this isn’t really “Dave’s recommended settings.” It’s more like, “where to start things, if you’re moving up from an old version.”

Bottom: This is new, as of version 32 or so. I’m not sure what it does but it seems to be the “bottom” parameters that used to be in the Raft module so I’m leaving it enabled and just taking the default values.

I think the “bottom” params in raft used to control how high the nozzle was at the very start of the print. Since I always tweak a Z pulley when I start printing, I don’t care too much about this one

Carve: Absolutely enable this. This one contains two of my Big 4 (or 5) parameters, Layer Thickness and Perimeter Width Over Thickness. Those two I care about, the rest I just leave as they are.

Chamber: Disabled. I think this is for heated build chamber. Like, if your bot was all enclosed in a temperature controlled environment, you’d want to enable this and figure out some reasonable values to plug in here.

Clip: Enabled. Clip is sortofa method that looks for parts of the print that are really close together and clips bits off, to keep too much plastic from being put down.

I’m very sure that the values you plug in here could be tweaked to get a little more performance out of your bot but I suspect it’s a 2% thing – good to learn if you really want the absolute best prints you can get but not really worth it for most people. I take the default values.

Comb: Enabled. I love comb. Comb rules.

Comb basically tells skeinforge to not let the extruder move outside the perimeter if it can avoid it. This makes a HUGE difference (in a good way) in cleanup times but does add to the total print time. Unless you’re really, REALLY interested in the quickest print you can get, just leave it enabled.

Cool: Disabled. This is an interesting module but I think DC extruders (which virtually all Makerbot people have) don’t play well with it.

Cool lets you tell skeinforge the minimum amount of time it should spend on each layer. If a layer is going to take less than that amount of time, skeinforge will add gcode to orbit around – aka: waste time – until that minimum is reached.

This is a great idea but unless you really have ooze under control, you probably don’t want to use it. If you don’t have ooze under tight control and enable Cool, it’s going to make a huge mess.

Also, if you do want to enable it but don’t have a stepper extruder, don’t use the Slow Down option. Slow Down tells it to drop the flow and feed rates down instead of orbiting – with a DC motor, the extruder will stall and you’ll get no plastic coming out.. Bad.

Dimension: Disabled. This is for “5D” stuff that’s not supported (yet??) on Makerbots. The 5D stuff, if I understand it correctly, are extensions to gcode that lets the extruder move faster on diagonals than it does on straight-X or straight-Y lines. Nice feature but not something Makerbots can use.

Export: Enabled. Not 100% sure what this does…

Some types of machines process the gcode in the firmware and one thing Export allows you to do is strip all the comments (stuff that’s user readable but ignored by the machine) out of the gcode. In theory, if you have lots of comments in the gcode and the machine isn’t very fast, stripping out comments will help prevent problems.

On a Makerbot, the gcode is processed by your PC (or Mac or whatever) so this isn’t much use for Makerbots. Leave it enabled, tell it to strip comments out or not – I leave them in but it doesn’t really mattter.

Fill: Enabled!!! I spend more time in Fill than I do anywhere else. More on this module later (next post?) but once you get your profile all nice and dialed in, this is pretty much the only place you need to be when you want to print something.

Fillet: Disabled. This is another interesting module that I don’t use very often. Fillet sorta rounds off sharp corners in the object, which can help if you’re suffereing from quality problems due to high feed rates.

Picture printing a perfectly square cube. There’s lots of “full power to X. Stop X! Full power to Y. Stop Y! Full reverse on X!” over and over. This can encourage belt-related issues like backlash. Fillet lessens these issues by rounding things off of a little.

In general, I’d say disable it for prints that require bolts and bearings and things – stuff that’s been measured out and has bits that fit together – and enable it for more organic-type object that don’t require precision.

Home: Disabled. This allows you to add a bit of custom gcode to the start of every layer. I’m sure there are good reasons why you might want to do this but I don’t think any apply to Makerbots..

Hop: Disabled. Not really sure what this does but I think it sorta tells skeinforge to add more into the Z increase at the end of a layer then drop back down for the start of the next layer.

Inset: Enabled. Another one I’m not to sure on but I think it controls tweaks on how to remove overlapping bits of the print that will likely cause blobs. I just leave this at the default values.

Jitter: Disabled. You know that extra little blob of plastic you sometimes get at the point where the Z goes up to the next layer? This module causes Z to move up in a different place on each layer, which spreads out those blobs.

Personally, I don’t get those blobs too much any more and they don’t really bother me anyway. I leave this module disabled but feel free to enable it, if you want.

Lash: Disabled because I haven’t gotten to mess with it yet. This seems to be about controlling backlash – that bit of lag you get when the X or Y steppers quickly start/stop/reverse. I suspect it won’t work well on a Makerbot but haven’t tried it yet.

Limit: Disabled but this is near the top of my list of things to mess with. Yet another module I’m fuzzy on but it seems to control the maximum feed rates of the gcode.

In particular, I’m eyeing the Maximum Z Feed Rate. If upping this value actually makes the Z stage move faster, it will go on my list of things to always enable – it should (might) help a lot with those blobs you get when Z moves up to the next layer.

If you want to enable this and see if you can make your Z blobs disappear, make sure to disable Jitter first.

Multiply: Enabled. Multiple is another one that rules. Enable it, set both Number of Rows and Number of Columns to 1 and skeinforge will automatically make sure your object is centered and on the platform. Very helpful.

If you want to print multiply copies of an object at once, you can mess with the rows and columns values – this is useful on small objects, since they tend to print too quickly and have heat problems. (which Cool would also help, if we had stepper extruders or well-controlled ooze)

Oozebane: Disabled. Oozebane tries to limit ooze (the extra strings you have to clean up post-print) by shutting the extruder off a little early. It can also turn the extruder on a little early if you have lag between when the machine is supposed to start and when it actually starts.

Probably very useful but I think it’s tricky to configure correctly and don’t use it.

Preface: There’s no enable/disable on this one. Take the defaults.

Raft: Enabled, even if you don’t want to print rafts. Actually, I’m not sure this always needs to be enabled now, since the temperature settings moved to a different module – they used to be in raft.

I just leave it enabled anyway. If you don’t want to print a raft, just set Base Layers and Interface Layers to 0 instead of disabling it.

Speed: Enabled. Two more of the Big 4 (or 5) settings live here: flow rate and feed rate.

Splooge: Disabled. Yet another module that I’m not to sure on. Seems related to oozebane.

Temperature: Enabled. This is where you can tell skeinforge to use different temperatures for different parts of the object. Note the Cooling and Heating rates in this module – if you use different temperatures for different parts of the object, these control how long skeinforge will orbit between the different parts. (I use the same temp for everything because I don’t want it to orbit)

Tower: Disabled. Another good (or at least interesting) module that I don’t use. Say you want to print ”I I” standing up. Tower tells it to print multiple layers of one leg then drop back down and print multple layers of the other leg.

This is useful because you’ll have a lot less ooze between legs but beware using it on objects that have small legs – using tower on objects like that will encourage heat-related problems which, IMO, are worse than ooze.

Unpause: Disabled. I think this tries to bump up your feed rate a bit to compensate for processing delays on complicated objects.

If you have problems printing things like bolt holes or other feature that have lots and lots of little turns in them, you can try enabling this. Beware having your feed rate times the Unpause “Maximum Speed (ratio)” being higher than your maximum useful feed rate, though – if you speed things up too much, your print will end up worse than before.

Widen: Disabled. Yet another module I’m not sure of.

Wipe: Disabled. This one’s good if your ‘bot has a toothbrush. This lets you send the bot to some particular position at the end of every layer so the extruder nozzle can get cleaned off.

If you set the Wipe Period to some big number, it should do this only at the very start of the print, before it does anything else. If you’ve got some sort of brush mounted in your bot, this is useful for auto-cleaning up the test extrusion.

That’s it!

Next up: Creating a new profile…

Thanks Dave!

1. Photo courtesy of Great Beyond [↩]

Rocketboomer Ellie stopped by the MakerBot Botcave to chat about innovation. It’s so great to see Rocketboom still going strong, they inspired me to get into video in 2004!
Two of my friends, fashion designer Diana Eng and artist Marius Watz are also in this video! Awesome!

Naked pull-less cord

I had a wildly productive Saturday morning this last weekend. ¹  I tore through my honey-do list as if it were made of paper. ²  For those of you unfamiliar with the concept, a honey-do list is a list of things your spouse gives you to fix, take care of, or generally address.

The way our list works is that my wife can add anything she wants to the list and I can ignore it all week long.  Come the weekend, I put forward a good faith effort to resolve as many of the things on the list as I can.  There’s no need to knock them all out, just make a dent.  My wife likes this system because she knows whatever she puts on the list will be taken care of one day.  I like this system because I know there’s a finite number of things, and I can do whichever ones I want whenever I want.  We both like this system because we can see the progress being made on things that need to be done around the house.

One of the things added to my list last week was to get a new pull for our kitchen mini-blinds.  The cheap plastic pull had broken or come off at some point and my wife wanted a new one.  The only requirements were that it “just work” and not be ugly.  No problemo.

I designed a simple cylinder with a hole in the top and knocked it out in clear PLA in 6 minutes flat.  For those of you who don’t print in PLA, it tends to hold its heat and stay malleable longer.  This is a mixed blessing.  On the one hand, the cylinder walls were so thin that they weren’t fully cooled before the next layer was put down, making the next layer up squish the lower layer slightly.  (This can be mitigated with any number of Skeinforge tricks such as the Cool or Orbit settings or using Multiply to create more than one instance at a time.)  The result was a slightly twisty, sculpture-esque tower.  Although the gloppiness of the molten PLA obscured the hole at the top of the cylinder, the part was still so hot that I easily widened the hole with a pair of pliers before it had a chance to cool.  This made for a very easy installation. ³

Printed PLA pull

I was fine with using this as a proof of concept, to make sure I had the basic design down, but my wife liked the twisty nature of the pull and that’s what we have on our kitchen mini-blinds right now.  One of the coolest things about this fix is that I was able to design and fabricate a fix faster than you could yank a part off a shelf, all without leaving my house.⁴

Bonus real conversation:

MakerBlock: Wow, honey.  You were totally right to insist I purchase a MakerBot last year!

Mrs. MakerBlock: <eye roll and grin>  Yes, I’m very glad I insisted you purchase a MakerBot.

1. At least, wildly productive for me. [↩]
2. Which, in fact, it is. [↩]
3. Step one: Untie knot in mini-blind cord.  Step two: Thread new mini-blind pull onto cord.  Step three: Tie knot in mini-blind cord. [↩]
4. A MakerBot might not necessarily be the best fix every home repair.  However, it is the best way to get me to start working on a home repair.     [↩]