Archive for the ‘3d printing’ Category

Printing resonators

Saturday, September 21st, 2013

I've been designing silicon resonators for the past year. So a few months ago, I sketched up stylized versions of the two I've worked most on and printed them out. Here are four of 48 MHz resonators them hot off the printer.

I showed them off at work, and the marketing/sales people liked it enough to buy me a few spools of filament to keep cranking them out.

Funny enough, the printed resonators made it into a recent article about SiTime here and here.

Really printing printers this time

Sunday, July 14th, 2013

The title of my last post was intended to be figurative. Yet here I am with a second printer on my desk. No instructions or a bill of materials this time around, just some photos to work backwards from and a Google Group.

It's not something that I would necessarily recommend doing unless you're slightly nuts and have some spare time on the weekends. But now I have about 6x the build volume and can print 3x as fast. And Deltas just look incredibly cool - My wife calls it the Spiderbot.

It's all open source and on GitHub, with the main development here and my fork, with some custom parts and modifications, here.

Printing PLA on frosted acrylic

Friday, May 3rd, 2013

Updates:
(1) The adhesion problem described in this post caused by the filament. You get what you pay for. I only use Diamond Age (high quality, every color under the sun, expensive) or Printrbot (local, cheap, good) filament now. Skip the random vendors on Amazon.

(2) Printing on unheated, frosted acrylic is a bad idea. The roughness combined with the lack of thermal expansion makes over-adhesion a very real problem.

(3) If you have trouble printing on heated glass, something else is wrong in your system. If no heater is available, use blue tape from Amazon or Printrbot.

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The adhesion between my PLA and heated glass bed suddenly degraded about a week ago. Before then, adhesion had been fantastic running the extruder and bed at 185C and 60C, respectively. I was using borosilicate glass from McMaster-Carr mounted on top of the heater PCB with clips. Two other things changed in the same time frame that might have led to the adhesion problem: I started using colored PLA filament from new sources (Amazon and 3D Printer Hub) and I started running the air conditioner.

The sudden degradation in PLA-glass adhesion has been reported by other people (e.g. here, here and here). I'm not sure exactly what caused it in my situation (build up on the glass? moisture in the PLA? black magic?) but I found a better alternative to heated glass in the process of debugging. I tried a few things initially that didn't solve the problem that are worth mentioning.

First I tried modifying the bed temperature (60C -> 90C) and obtained a slight improvement in adhesion but prints would still fail quite frequently. Next I tried cleaning experiments. For the first month I had been using nail polish remover (acetone + lots of other crap) and was concerned that contaminants might be building up on the glass. So I consulted the forums and tried cleaning the glass with hot water and detergent, vinegar, lemon juice, isopropyl alcohol and acetone (separate experiments). None of them solved the problem and I was starting to get frustrated with glass.

So I started looking around at alternative bed materials. Many people use kapton tape or blue painters tape with good results, but I like having a continuous and smooth printing surface. Polycarbonate has also been reported as working, but it scratches more easily than acrylic and is more expensive. The main problem with acrylic seems to be that it bonds too strongly to PLA even when unheated, but I remember seeing that sandblasted or frosted acrylic can give the right level of adhesion. So I picked up a 6" x 6" x 1/8" piece of acrylic from Tap Plastics and frosted it by hand with 400 grit sandpaper.

The frosted acrylic solved my issues and has a few significant advantages over a heated glass bed with just a few downsides. The advantages are that acrylic is incredibly cheap ($1 for my piece), it can be refinished using sandpaper in case it gets dirty or scratched, it can be easily drilled rather than held in place with clips, and it doesn't require any heating (faster prints, one less variable to control).

The first disadvantage is that you can't print ABS anymore, but I have no interest dealing with warping and rafts so this wasn't an issue. The second disadvantage, perhaps more significant, is that you no longer have separate control of first layer temperature and adhesion. So far this hasn't been an issue, but I can imagine a scenario where good first layer adhesion required a higher than ideal temperature which would cause other issues.

The main risk seems to be that the adhesion might be *too* good, although this hasn't been a problem with my first few prints on the acrylic. I also bought a sheet of HDPE while I was at the store; it is more chemically stable than acrylic and I haven't seen anyone write about trying PLA + HDPE so it's something that I'll try out in the next week or two as an experiment.

Printrbot insulator sleeve

Friday, May 3rd, 2013

A few weeks ago I started a print and took the dogs out on a walk. When I came back, there was a huge blob of PLA attached to the tip of the extruder because the first layer had not adhered to the bed. The filament gunked up the red insulation boot and I cut off the contaminated portion. Unfortunately this made it slightly too short to cover all of the hot bits, so I started looking for a replacement.

Printrbot does not sell individual replacement boots and finding a generic source seemed like a much better solution than contacting them for this one random part. After a bit of searching I found a 1/2" silicone coated fiberglass insulation sleeve that is similar (although not identical) to the sleeve on my printrbot LC. It is slightly looser than the stock sleeve but works great and 5 feet of it is about $20. I'd consider ordering the 3/8" sleeve in the future to have a slightly tighter fit if I ever run out of my 5 feet, although there is some risk that it'd be too small. It would be nice if printrbot sold their insulation boot separately but this will do.

(update: I contacted printrbot and they included a replacement sleeve with another order that I placed. Fantastic customer service!)

Printing printers

Monday, April 29th, 2013

I bought a printrbot LC kit about a month ago. I had been toying with the idea for a long time, but was spurred on by seeing a 3d printed cat toy that a friend made and realizing that there are relatively inexpensive printer options ($500-600) out there today. At that price it is relatively easy to justify; if my only options were the $2k monstrosities from MakerBot then I would have never purchased one.

So far I've been having a lot of fun and am very happy with my printrbot LC, which I would highly recommend. I occasionally wish that I had purchased the LC+ rather than the LC (200 mm vs. 150 mm of travel along each axis) but it hasn't been a significant issue so far.

You need a reasonable amount of mechanical, electrical and computer skills for assembly and setup. CAD experience is also helpful for designing things. My wife thinks I'm crazy and would never build one herself. You can buy preassembled printers, but there's something to be said for knowing how it all fits together so that you can tear it apart to make modifications and debug issues.

There are a few absolutely essential upgrades:

  • fan, fan mount and three-point bed leveling system. The fan addresses PLA oozing and makes bridging work incredibly well. The leveling system is necessary to get good consistent adhesion. All three of these things are included in the LC v2 (currently shipping) whereas I had to purchase them after the fact.
  • glass bed and clips. I separately purchased the 0.125" x 6" x 6" piece of borosilicate glass from McMaster-Carr to use as my bed. The glass is rigid, hard and chemically inert so easy to clean, and provides good adhesion to PLA. The first thing that I printed (after Mr. Jaws of course!) was a set of clips for holding the glass in place. I taped the glass to the PCB heater for this print, and there was a noticeably amount of sliding around.
  • wall-mounted filament spool holder. I mounted a toilet paper holder onto the wall in my room and it is absolutely perfect for holding a 1 kg spool of filament. It is a much better option that the lasercut spool coaster and spool options from printrbot in that the spool can never slide off yet rotates easily.
  • filament guide. I'd also highly recommend replacing the built-in wooden idler latch with one that has a built-in filament guide. My extruder used to occasionally skip if the incoming filament angle was off-axis; the built-in guide solves this problem.

The glass clips have worked quite well, although the combination of the clips and the leveling bed design effectively reduce my y-range from 150 mm to 110 mm. I will probably design modified clips in the near future.

Adhesion between PLA and the glass bed has generally not been an issue. I've printed with natural, red, black and white PLA to date. Only the black PLA has sub-par adhesion, requiring that the glass is squeaky clean and that both the extruder and bed are hotter than normal (e.g. 185/60C typically, 210C/65C for black filament). 1 kg of PLA costs about $30. I've purchased spools from from printrbot, Amazon and 3D Printer Hub and haven't had any issues.

Regarding extruder temperature, I'd recommend running M303 to automatically tune your PID settings if you have a printrboard with Marlin firmware. I use a set of 5 mm calibration cubes and a frog to check print quality whenever I've modified anything.

One other tip - rather than trying to fine tune the z-limit screw, I've found that using the "Z offset" parameter in Slic3r is much easier way to adjust the degree of first layer squishing. This does not affect the need for the bed to be level, just removes the need to mechanically fine tune any constant offsets. For leveling, I follow the standard procedure of putting a sheet of paper between the extruder tip and bed and adjusting the thumbscrews on the bed to yield a constant and light amount of rubbing between the paper and tip across the bed.

I've come across a lot of useful links. Here are some of the better ones that I'd recommend checking out: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Here's a video of my printer chugging away:


fetishroom