Archive | March, 2013

Filament review: Conductive ABS from Repraper

26 Mar

Filament review: Conductive ABS from Repraper

I'm working on a really great 3DP project but I will have to wait a little while before I can tell all the details. However - in this project I'm making some really cool touch-sensors with 3D printing and I thought that I'd share my experiences with the "Conductive ABS" that is sold by Reprap-Walmart (Repraper.com) and numerous others sites.

1. It's all the same

It may seem as if there are multiple vendors for conductive plastic, but in reality it's just a single, chinese company. I bought mine from Repraper.com and I suspect that most of those selling Conductive ABS are getting theirs from the same source. They all have the same spool, so it's easy to spot just this. This means that if you see Conductive ABS in a RepRap webshop, they most probably got this and all their other filament from china/reprapper.

2. It needs very tight temperature control

This plastic is difficult to print with. The main reason is that to be electrically "conductive", it contains a lot of carbon. This narrows the useful temperature area. On my printer (Ultimaker) I had to use 230-240 degrees. I suspect it will be similar for any other Reprap or other 3D printer. Anything less than this and the print delaminates (click the image above to see this on the cylinder to the right). Anything more and you also got a plug. Since I got my Ultimaker (a year++ ago) I never had a plugged extruder. While printing with this material I had 8 plugs and it's a real hassle to fix.

3. It's soft

This makes filament grinding a major issue. Took me forever to figure out exactly how much pressure to use when feeding the filament into the Bowden. Because of this, it's also next to impossible to print with retraction, so keep that in mind when modeling.

4. It's probably not too well mixed

I can't really prove this, but it seems that since most of my prints failed due to contaminations in the filament. I must have done maybe 20 attempts at printing the same model (12 cm tall & tube-like). Only one of these succeeded. This makes me suspect that some bits of this filament isn't too well mixed so that when a bit of almost pure Carbon come along, there's no way you'll manage to push that through (see #3...)

5. There's a better solution...

While it's conductive, you can't really print circuits with this material since the resistance is much too high. If you just print the same model with normal PLA or ABS and then use Conductive ink to paint it, you'll get the very same effect. No need to over-do things, is it?¨

So to sum this up - try to avoid this material unless you enjoy dismanting your printer. It is certainly conductive and small prints can probably print without a problem. Just don't think that this is as easy as other materials. It's annoyingly hard. If you know of alternate providers of 3mm conductive plastic, I'm really keen to try them out so please post a comment below.

PS: I should also mention that the color-changing filament from Reprapper.com only changes color BEFORE you put it though the printer. I got the purple-to-pink filament and after printing, it's impossible to make it purple again. Would have been fun - if it worked.

My first PCB - a DS1307 based realtime clock

14 Mar

My first PCB - a DS1307 based realtime clock

The last months at Bitraf has been quite hectic in terms of workshops & activities. First there was a soldering workshop that I helped put on, then a PCB design workshop and that was followed by a PCB etching workshop. I also organized our third 3D Printer Meetup there. Peter, Trygve and Carl at the hackerspace has now gotten my dad's old Roland CNC to drill all the required holes in a PCB based on the Eagle files, so it's really possible to make nice things at Bitraf these days.

My first PBC, an RTC for Arduino

When an Arduino looses power, it's clock will always start in 1970 when it gets power again. For a client project I'm working on, I needed the correct time after a power outage. It was easy to find several RTC's online and they all cost something between $5 and $10. My problem was that getting it fast would be expensive and I happened to have the most used IC for this purpose. The DS1307 used in most of these modules is about a dollar each and the remaining components are not much either. Here's the Bill Of Materials along with links to where I bought them:

1 x DS1307

1 x 32.768 Crystal

3 x 10k resistors

1 x 104 capacitor (0.1 uF)

1 x 2032 battery holder

2 x 6-header pins

All together this is about $2 in parts, even for a very modest volume. Not shabby and I highly recommend both TaydaElectronics (Thailand) and Spiratronics (UK). Both are great shops that ship quickly to places in Europe and I use them a lot in addition to ebay.co.uk.

Designing it

I looked online, but couldn't find something that others had made that was "free to use" and I had an idea: why not make it plug straight into one of the header rows on the Arduino? That way it would be real plug-and-play since both power and the analog pins used for i2c are on the same side. Above you can see how this turned out - it plugs right into the Arduino Ethernet shield.

I looked up the reference design and looked at how others had done it before and then made a first go in Eagle. After a couple fails (I forgot to "fill" with ratsnest + had counted the pins incorrectly) I got a couple nice looking PCB's.

Making it

The etching went really well and with all the helpful people at Bitraf, it's not hard to get this right. I drilled this one manually, but I'll definitely use the Roland CNC as soon as we have a good way to cut consistent PCB sizes. Here's how it looked after cleaning with Acetone:

I didn't have the required clock crystals, but I got these from Spiratronics in just 3 days. Today I soldered it up and plugged it in. Guess what - it didn't work... I looked over the PCB with a magnifier glass and cleaned up some excess solder along the traces and it still didn't work. Bummer. I went online and looked at how Adafruit did theirs and then it struck me - I had put the IC on the wrong side of the PCB.

Using it

After doing this, it worked like a charm! I used the Adafruit 1307 library and it works just as I hoped. I'll definitely make a couple more of these for other projects and so can you! Below you can find the Eagle schematic + board and here's the final stencil to use for the etching.

See more pictures of the PCB etching process on Flickr

Printrbot Jr Heated bed upgrade

12 Mar

Printrbot Jr Heated bed upgrade

I was so happy when my Printrbot Jr heated bed kit arrived, but it works far from optimal. I didn't expect to be able to print any bigger with this upgrade, only to enable ABS printing and maybe sticking the first layer down a little easier. Instead, I actually got less space to print on despite the huge 6x6 heated bed PCB. The problem is where the heated bed is positioned. Here's a video highlighting the problems with this $65 kit.

It's not set to be centred on the 6x6, but rather towards the far Y-edge of the platform. The result of these misplaced holes is that I'm actually loosing 1,5 centimetres print area along the Y-axis since the print head may hit the bolts holding the PCB heater.

Another couple things that make me suspect the kit have been made in a hurry, is the metric machine screws that should hold the PCB in place. These are too short to reach through both the PCB and the plywood. The instructions are also unclear about the need for an extra PSU. It says that you should not use the "laptop power supply" that came with the printer. Mine didn't come with a "laptop" PSU but rather a huge 300W ATX supply. I assume this is good enough to drive both the printer and the bed.

Kapton

I also bought a nicely cut 6x6 sheet of Kapton tape. I love the quality of it (feels thick and solid) but I can't get over the fact that you can buy a 100 feet roll of 6" kapton on Ebay for less than the price of a single sheet from Printrbot. Given that you have to manually cut off those nicely rounded corners to make the sheet fit between the bolts that hold the PCB, it's even less of a value. If there was holes cut for these, I could see the value but I think I'll just pick up some 6" kapton and place it next to the 20" kapton I use for the Ultimaker.

The above probably makes you think that I'm not too happy with my purchase, but that's not the case. For it's price, the Printrbot is a really good kit and I dig hacking my printer to make it better. The fan-holder I added helps immensely on the quality of PLA prints. My next upgrades will be some belt tighteners and a better suited industrial PSU that I can fit beneath the printer.

I really feel that all the Printrbot's I've seen have some unpolished edges that could be smoothed quickly. If Printrbot / Brook want's to stay in the 3DP business for a long time, he should look to companies like Ultimaker, RepRap Pro and Makergear. They don't churn out lots of new products, but rather listen to the customers about what must be fixed for the existing kits to be really good. Printrbot is on the right track by adding necessities like fan holders, belt tighteners and this HBP kit.

I think it is now time to polish the three kits (LC, Jr & Plus) to perfection. There's no better advertising then happy customers that has a printer that "just works".

grin

 

3D Printer meetup #3

09 Mar

3D Printer meetup #3

Last weekend, I organized the third 3DP meetup in Oslo together with @kefir from reprap.no. Quite a good turnout of people and 14 different printers there. My two favorites were the Adapto printer that is using pretty much only parts that are avilable in normal hardware stores. How's that for RepRap? The other favorite were the two Rostock printers being built by two AHO-students. Very cool to see these in "real-life" and I could even help a tiny bit so that was fun as well.

The next meetup should be some time in May and I'm REALLY looking forward to see Johan's DuoHex machine! It has one of the smartest RepRap designs I've ever seen, using Hexagonal rods to drive a dual extruder design. Below is a short video showing the different machines at the event and here's some nice pictures that Kjetil took.

Meetup Pocket Sign

08 Mar

Meetup Pocket Sign

My brother is thinking about going back into the signage business and as he would start up his own company, he'll need to build himself a network. My favorite way to connect with people and communities these days is Meetup.com - a website that help you host meetings with ease. So - I set out on a mission to help people remember my brother and what his company delivers.

I've long wanted to do something with the neat little 1.8" LCD screen I picked up from Adafruit some months back and looking through their site I found that they also have this neat Lipo charger as well as slim, matching batteries. What if I made a small LCD-sign that he could drop in his pocket? I ordered the components and started modeling.

About a week later, the parts arrived and I modified Adafruit's example file a bit to load images one by one from the SD card beneath the screen. That gave me a simple, but effective slideshow. All my brother needs to do is to to change the contents is to make some BMP images and dump them onto the SD card. Easy!

After a few iterations I came up with this case. The part containing the battery is not the slimmest, but it's also meant to go inside your shirt pocket. I could have made it slimmer, but then I would have to sacrifice battery time. With it's 1300mhA battery pack, it lasts 2 hours on one charge and charging it takes a little less than an hour. I could have saved a little space by skipping the proto-board that lies in between the electronics and the battery, but it made mounting things and getting the USB-port right for charging. I might remove that if I do a next iteration.

The part that is visible on the outside of the pocket is much slimmer and it looks like the red and white Meetup.com logo. It took quite a bit of fiddling to get the case right. I learned that by slanting the print 28 degrees while printing, a lot less cleanup was required.

The supports came off really easy and printing the parts like this actually made them much stronger and easier to glue together in the end. I usually use PLA plastic for all my 3D printing, but for this I used ABS since it can be grinded and polished (PLA can't). Towards the end of the project I didn't quite get the time required, but it was a fairly polished thing I gave away. It took me 4-5 evenings to make this project and I think it was worth it. I could of course have bought a CD or something from a shop, but this was a personal gift that (as far as I know) nobody has. Much more fun!

Here's a shot of junior showing off the final sign and if you want to make your own - grab the files on Thingiverse and components from Adafruit.