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Archive for July, 2015

22
Jul

Me & 3D, printing that is…

I decided to build a 3D printer a month back. Right after deciding that I’d never have any use for one.

A friend pointed out with all the Arduino stuff that I do, a 3D printer could be a valuable asset for doing mounts, panels, widgets and doodads. Especially the latter two.

At the Maker Faire in Vancouver last month there was a glut of 3D printers. Oddly I didn’t see any of them printing anything. I know why now. It’s a black art. In other words, you just don’t take one out of the box, plug it in and start printing. Sure there are some that imply this, but when I’ve talked to the owners of the same, they all admit there is some “tweaking” to be done.

Since I like building I thought I’d rather build one. My second reason was that if the thing broke, at least when I built it I’ve had a good idea of how it worked so I could fix it. As it turns out that was a good idea.

3D Types

There’s two main types of 3D printers, both available in various configurations in kit form. The first is the standard Cartesian models. In these types, normally, the head moves X & Y and the Z (height) is a table that moves up and down.

Then there’s the Delta. These work within the Cartesian plane but can’t be confused with one because they have three arms that do all the moving. The printer bed is fixed below the three arms in a triangular tower. These are designed for speed and a bed that does not move.

Lastly there are machines that use Polar coordinates. You have to see one of these in action to marvel at how it works. They are fairly rare at this point.

Kossel

The local makers that I’m a member of is selling a Kossel 3D kit and since I knew beans about 3D printing, I figure I’d be a good test for the kit. In other words I went into it blindly and completely unarmed.

This is what the kit was supposed to be like after it was assembled:

Kossel 01

Unfortunately many of the parts in my kit were printed incorrectly and I ended up rebuilding it a couple of times after one of the members graciously reprinted some of the parts for me. As a gag I sent them a photo of what my build was going like:

Kossel Turbo Encabulator

That photo was hanging on the wall at the Maker Space for a while…

Kit

I’ve built plenty of kits in my life, but this was more of a box of parts than a kit. The “assembly” manual was a PDF online that actually refers to the same “delta” printer but it has different components so, you can’t really follow it 100%. And since you don’t know what’s going to be critical and what isn’t, failure is almost guaranteed.

Thus, you have to build one, to know what you really need to pay attention to. I learned the hard way and even with help from one the most astute members in the group, I hit brick walls. Hard. A lot.

As it turns out, building the kit is the easy part. Calibrating it is a nightmare. For a number of reasons. The least of which is because no one seems to be able to explain the calibration process in simple terms. They kind of know what has to be done but they don’t seem to have a procedure for doing it.

Calibration

The really VAGUE “how” is you find dead center on the bed, measure some distances on your printer, you put that in the firmware (Marlin), you send that to the printer. Make sure it always goes back to dead center. If not, you adjust the values again, re-upload the firmware, retest, until it does.

You use software like PronterFace or Repeatier to control the hot end.

Once the middle is found, you setup the height of the print area. More firmware update.

Next you measure the gap at four points on the bed. One by the X, Y and Z towers, one dead center. The gap is a piece of 20b bond paper you use as a feeler gauge. All four POINTS MUST BE EXACTLY the same “drag” on the paper. If it tears the paper, too close, if it doesn’t touch the paper, too far away.

I found a web site that kind of describes it. Check the May 30th, 2013 and Dec 22, 2012 for the info. Read them both.

Delta Calibration

Using PronterFace I managed to get mine “flat” in less than one hour. That’s huge. But it only worked that way because I modified my printer. To do the “gap” test, you adjust the top end stops higher or lower, each one at a time, until things work. And if you change one, it does tend to affect another. I used a 3mm screw like this:

Kossel Adjuster

So you home the end, run it down to the bed, check the gap, and adjust the screw to raise or lower the hot end. I was using less than 1/8″ of a screw turn to tweak mine at the end of the adjustment phase. But it’s a major easy way instead of trying to move the end stop switches up or down by .1mm or less.

When you finally get the bed “levelled” you breathe and think you’re done. Ha. No way.

Next thing is to set up the extruder to give the right amount of PLA, and then finally, print something.

I assure you that if you print a 30mm x 30mm square it will not be. Measure it with a digital micrometer. Either the X or Y will be out. For sure.

Back into the software you go and adjust one of the numbers in DELTA_DIAGONAL_ROD. Of course when you do this, well, you have to go back and adjust all the gap points at the towers and in the middle again.

At some point in all this you’ll get close. Maybe even exact. Now you can print! Maybe…

Slic3r

The objects are in STL files and you need to “slice” them into layers for your printer to print. And I’ll tell you there are a LOT of numbers in the Slicer software that you need to set. No one can tell you what those numbers are, so you get ballpark numbers for a start.

On my printer I’m not running it at max speed. I run it about 60% of max. And it runs just fine. To me speed isn’t as important as a reliable print. Other guys want to print maximum speed. If you’re doing a coarse print resolution that might work. I use a depth of .24mm for the first layer, .3 for each layer after that.

Heating the hot end and the bed is another thing. I run my hot end at 210, first layer at 215. That’s where it’s the happiest. The bed is heated to 50c for PLA and I use some Elmers Glue Stick to LIGHTLY coat the print area. It sticks REALLY well so don’t add too much!

So my printer works very nicely now and I was testing some glues to glue PLA pieces together the other night. Two different kinds.

PLA Glue Test

The glue on the left doesn’t work well at all. The Crazy glue sticks! So I printed a Minion and glued him together.

PLA Glue FrankenMinion

Kind of looks like a FrankenMinion but he’s stuck together quite well. Next I printed some feet and a base for the little guy.

PLA Glue MinionFeet

Finally I glued him to the base.

PLA Glue Minion W Feet

And yes, he’s supposed to be bent over like that. Because this is not just a printed thing, it’s my

PLA Glue Cellphone Holder

Cellphone holder…now how cool is that…

21
Jul

Nixie Clock Kit

Apparently I have an affection for clocks. Of all types. The latest is is a bit of a throwback to when I was.. ah.. a lot younger..

Specifically a nixie clock. Nixie tubes are those cool looking neon tubes with numbers inside:

Nixie

The tubes take 170vdc to “light” up a number so there’s a bunch of leads on the bottom of the tubes. Digits 0 to 9, two decimal places and an anode. Appearing in the mid-1950’s, they fell out of favour in the late 70’s but were still being made in Europe and Russia. For a while any way.

Now that no one makes them any more, they are becoming more valuable and the driver chips for them even more so although there is a Russian knock off that’s around. None the less a search on eBay will turn any number of sellers of them (usually in Europe someplace) and of course all manner of tubes. Some removed, some NOS (new old stock) not to mention a slew of different types.

My favourite Nixie have always been the IN-14’s. Large, easy to read, I like them. My first “digital” voltmeter, a Heathkit IM 1202 used Nixies:

IM1202 front1

Used it for twenty plus years before going to LED. Kind of wish I still had it…

I decided that rather than design one, I’d start with a kit. of course my idea of a kit and what others idea of a kit is can be vastly different. When I think “kit” something like Heathkit or Tamiya comes to mind. Lately my “kit” experience has been quite different. More like a box or bag of parts and an online PDF.

There’s a number of different companies producing Nixie clock kits and I chose PV Electronics in the UK for one reason. I liked the concept of an easy to replace Nixie tube because I know they don’t last forever. PVE sells on eBay and I ordered one of their kits. It arrived in short order consisting of some PCB’s and a bag of parts.

At least someone had the forethought to put a URL on the parts bag so I could find the assembly manual online.

Thus armed with a PDF I started to assemble the kit. At the same time a letter shows up from the eBay seller with a fuse part inside. Apparently it was missing from the parts so it was a good thing I’d delayed a few days before starting to build the clock any way. Now that’s what I call support. Rare indeed.

My 55 year observation is there are people who can write assembly manuals and there are people who shouldn’t. To their credit PV Electronics falls right in the middle. The information is in the manual, but it’s not organized in the best way that’s going to walk you through the build. I.e. the parts are on one page, the result on another, and no outlines on the result picture to show you the area you’re working on. Nope. Just a R12-R28, R32-R34 XYZ resistor and your PCB should look like this.

Considering the quality of the PCB and the parts, the assembly manual was a bit of a downer. But at the same time, not all that surprising.

I spent considerable time examining the silk screen of the PCB looking for where the parts go.

The resistors are metal film types and if you can’t read the colour codes or have access to a resistor tester you’re up a creek.

Hence right off, this is NOT a kit for a novice in my opinion. Certainly it’s one thing to know how to solder but to get this kit working I had to do some trouble shooting for defective parts. Parts that I have replacements for and know how to trouble shoot. Whereas a novice would be up that creek again…

The complete assembly took me just over 3 hours. Mostly spent flipping back and forth on my iPad reading the PDF.

At the end of it, I fired up the clock and it worked. All Nixies were perfectly. But one of the RGB LED’s was missing the blue component. I traced it to a faulty RGB LED. I replaced that and the clock worked as it should. But I have these components in my parts bin so not a big deal for me.

The heart of the clock is a PIC chip. Which means it’s a software clock. It is adjustable. How accurate is it? Compared to the lowly DS1307 or the more robust DS3231? No idea. No pun intended but time will tell.

The kit does sport a serial port so you can connect up a GPS to it, program in the offset to where you are and it will compensate. This is the route I took. I got one of my GPS breakout boards that I use on some of my Arduino projects and wired it, via a jack, to the Nixie clock board. It works absolutely flawless. Even if you forget the GPS chip when you move it around (I took it to some meetings to demo it), the Nixie will tell you when it hasn’t sync’d in a while. I plug in the GPS and with seconds, it’s running perfectly on time again.

Also some of the parts have changed since the kit was done in Dec 2014. A 15pf cap was replaced with a 33pf cap. No doubt to help with the software clock. There was supposed to be a piece of paper in the parts bag that told me this. Keyword was “supposed” to be. I never saw one if there was.

The “super” capacitor has changed value so if you go looking for the one in the assembly manual you won’t find it. You’ll find one that’s physically identical but a different value.

That’s one of my pet peeves with kits. If there are substitutions, update the assembly manual. Simple. Do it.

Here’s a shot of my completed build.

IMG 0214

And

IMG 0213

Thats right, there’s LED RGB lights under the tubes that you can create custom hourly colours with.

I still really like the concept of the tube sockets but I’d say it’s a kit aimed at more experienced builders.

My brother looked at it and I got a “cool” thumbs up from him. He loved it…