Designing reprap circuits to be printable Pt1- DIP chips as replacement for Surface Mount

Special note: A printable circuit will not be more efficient, or smaller or easier to make or use. Making printed curcuits is more an exercise given the ojectives of self replication. Using the SM electronics from makerbot or others will probably always be an easier method. Designing circuits for printing is alot of work for not too much advantage apart from getting closer to the theoretical replication point. This design will be similar to the Gen 2 electronics(I crimped the old chips from there), only as a single large board for extruder and motherboard each as per the 3rd gen.
circuit
Anyway, now that we've thrown any idea of ease of production of simplicity aside, on to the semi-pointless exercise.

I've been working on gathering together a list of parts for the motherboard and extruder board that are DIP(through hole) as well as SM(surface mount). The current boards work ok (though my extruder board is currently experiencing huge problems, for some unknown reason. Which is what put me down this path) but some of the parts are only listed as available for SM. Usually in the SOIC design. The ATMEGA chips all come in some sort of DIP version, but others do not or there is some slight variation in the name.

The reason I'm looking for DIP over SM/SOIC is because printable circuits should be the objective within the short and long term future for the project. The exact spec for solder printing hasn't been released yet by Adrian (one of his final yr students worked it out, but the needs of marking rules meant he couldn't release the report immediately), but looking at the closeup photos from the blog post I'd guess that the channels are all at least 2mm wide(guessed from the grain in the photos, seem to be about 4 layers across). It's always safe to double to needed precision on a real machine. Thus the best resolution would be about 4mm (DIP chip spaces are often around 8-9 mm, leaving us space for channel seperation). This is too fine for SMT but fine for most DIP parts. Thus DIP is the way to go for printed curcuits until we get the quality way up.

I was originally just going to design the circuits themselves as stl's, but ran into the obvious troubles with replacement chips.

Solder would be used for now as the curcuit conductor. The problem of high resistance in solder is an issue, but for now I'll ignore it.

The biggest problem (and in fact was the reason they went to SM originally a year ago) is replacing the A3949 chip. The old L293D chip has a much lower amps capacity than the A3949 chip(it would blow up constantly, and was a constant headache in my machine last year, due to it's low ampage capacity) and needed an additional logic chip. The only way out of this problem that I can see is either replace it with a LMD18200 chip(which is the same as a L293D chip, just higher capacity for amps), or to essentually expand the entire L293D chip out with transistors, and do the same with the logic chip. It is essentually a large array of diodes and mosfet(dmos) or other type of transistor chips(we would need 4 for the chip, and 4 more for logic control of one motor at least). These would take up alot of area, but if we are only using one of them, it wouldn't be especially difficult, just time consuming to build/print.

Anyway, the list thus far for the extruder board, which is what I'm working on(I'm 90% sure it's my RS485 that's not working properly, but can't figure out why not). Things like resistors and capacitors I assume can be very easily replaced and are not listed.

Note: 4 stars(****) indicates it's the exact same chip,or is the same chip, just with a different sizing spec

Current chip used replacement chip/original chip
ATMEGA168 ATMEGA168****
SN75176A SN75176AP****
7805 7805****
NIF5002N (5003) TIP120
A3949 LMD 18200 or L293D expanded chip (add logic chip as well)

Chip by chip issues:
7805- This is the voltage regulator, it tends to generate heat. Hense they may need a heatsink. However, this appears to be a component that is very common and is not made by just one producer. The reason for this is that some parts need 5V, some parts need 12V.

NIF 5002N(there is some confusion here, since NIF5002 are whats on the board and spec, and whats supplied with kits, but 5003 is what described on the wiki page) these are made to take 42V and 20 amps(though the website for the chip on onsemi.com says they can only take 2 amps, not 20. Can someone please look into this. http://www.onsemi.com/PowerSolutions/product.do?id=NIF5002N , the spec seems to match the chips I got from makerbot, as well as the photo on the wiki. Are these the same chips? if they are, then they can only take 2 amps, not 20 and the wiki has a minor type). The TIP ones replacing it can only take 60 V and 5 amps. Plus there seems to be a slightly different design basis, given that the NIF's have 4 connectors, while the TIFS have only 3. Can someone see if there has been any major design change based on this. As far as I can see, the basic design is unchanged from the PWM board. The NIF's main advantage is the removal of a resistor(on the signal section) and a diode(on the power) from the board. They also have some sort of safety advantage, though I'm not sure if this is really part of our system (I've managed to blow my heater circuit by accidentally contacting it with the thermistor, hense why i'm trying to figure out a way to produce this system)

A3949- As stated above, this chip gives by far the biggest headache. Apart from expanding the old Gen 2 chips outwards, I don't see an easy way to get around the problem. the A3949 chip is a great chip given it's high amps and inbuilt processing etc, but is only available as Surface mount, and is too fine to be fited in a printable circuit. The LMD18200 is pretty expensive, and expanding out the L293D chip with higher amp parts would be annoying.

And now...a brief update

Apologies readers, but the project has been on the backburner for a little while, but no longer. Just a quick update before things get crazy with the posts here. I'm currently unemployed (damn mining collapse) but have made the reprap my job for the next few weeks. So the designs will be coming thick and fast soon.

Updates are:

The Perth hacklab is definately getting extremely close to coming about. Go to our website at http://hacklabperth.org for my details. When it gets going, I plan on being a major part of the groups educational segment. I'll be working on the reprap group, and the arduino microcontroller group.

The thingiverse site is filling up with data pretty quickly with plenty of stuff, among the most promising is a lasercuttable high power electric motor. It's a first generation, but as a proof of concept it's great.

Simon Kirkby is doing some great stuff with his makerbot, and is currently the main person doing actual major printing in perth given I've been a little distracted with an Extruder re-design. Him and I are going to work together on more R&D work on the reprap system. Our current next major project looks to be experiments on running larger bore extruders and seeing the effect of them on both build speed and strength. After that it's parallel heads time.

I'm currently doing alot of messing around with using resistors as heating instead of nichrome wire, since this is alot safer than nichrome. More info soon.

The 3d scanner design I had as my last post will be updated with a version 2. If anyone wants to have a look at it, please give me any ideas on it's improvement. I prefer zero overhang designs which are millable and printable, but any ideas are welcome.

As always, if anyone wants to make a post, email me and I'll get back to you ASAP.

-Peter "letsburn00" Hillier

Printable parts for a 3d scanner

A basic method is described for how to produce a basic 3d scanner was described on the instructables website a few years ago. It has popped up in the forums a million times, and there are some programs out there that will do a similar job.

3-D Laser Scanner - More DIY How To Projects

The basic needs for this method are described essentually as

1. The object itself. (you're got it if you want to scan it right?)

2. A laser pointer (cheap and easy to get)

3. a wine glass or something similar (cheap and easy to get)

4. a webcam or something you can use to make a movie file (relatively easy to get and cheap these days)

5. The image processor program (this uses matlab, but the comments include references to the david 3d scanner, which is freeware. You can also use the blender apparently. There is someone doing their PHD on this topic, hopefully a full integrated program will do this in future, but for now these programs work)

6. A rotating turntable. (this one is more dificult than they make it in the video)

Given this method has already been described, I figured I'd design up a turntable system that is reprap printable that you can put the object on, then follow this method to get some good 3d scans. Every part that is printable contains absolutely zero overhang, but is all smaller than 10cm by 10cm by 10cm. I know the reprap can print overhang, but in order to also make this machine producible by milling and the makerbot I did it this way. A side effect is that it is probably bigger than it has to be.

The electronics to run it is basically just the old DC motor drive curcuit. The motor I left a hole for was sized for the same motor we used in the extruder. While designing it, I didn't include a spot for an encoder piece or for it to be bolted in, so it will just fit relatively loosely into it's slot and push against the wall when it's driving the motor. I know you can get the motor without an encoder, and in this case it's probably not needed. I'll write up some code soon, which will simply be the gen 2 DC motor tester program for arduino with some minor modifications so it just goes up to speed and stays there.

The basic method of design is: DC motor drives a small gear, this gear drives a larger gear (which runs slower than the DC motor spins). The Larger gear has a rotating table on top of it that you can place your object to be scanned. The large gear rests on a bearing that allows free rotation. I used m8 bolts and nuts to keep everything locked into place

I've delierately designed the entire thing so that everything has relativey low needs for quality. For instance, the m8 holes are actually 82mm instead of 80mm. That said, before any printing is done, I recommend people who are better at designing look over things. The part I'm most worried about is the gears. Each are just simple triangle gears and probably can be fixed to work better.

And onto the design pictures themselves!

Now this is how it looks in a pretty exploded view

If you're confused, below is more detail and each part pointed out

Ok, got that? I've uploaded the 5 printable parts to the reprap site. The non printable parts are

1     6cm m8 bolt

3     3cm m8 bolts

5     m8 nuts

1     m8 bearing (the same size as used in the reprap)

1     DC motor driver, of the same size as gm3. I designed the machine based on the one I got from bits from bytes, not being aware that some others have encoders.

I hope that this design can be used and improved by everyone. Having a usable, printable turntable should make 3d scanning a bit easier with less work needed by the analysis program.

-Peter "Letsburn00" Hillier

Reprap prints electronics and new reprap projects

For those not following the reprap blog, the reprap has printed it's first electronics. One of Adrian bowyers undergrad research students has printed a reprap opto-endswitch using a combination of both plastic and standard store bought solder(as opposed to expensive low temperature solders previously thought required). The final result were able to have the remaining components stuck into it easily with a standard solder heater (and no new solder needed to be added).

The part was pretty quickly put into the machine that made it, meaning that electronics circuit boards are now officially in the list of parts that can be self-reproduced and/or self-healed depending on how you see it.

Perth Hacklab

At the first reprap group meeting, there was a discussion about whether a hackerspace was possible in perth and if anyone wanted to look into it. Long hair Peter (As oppsed to Curly hair Peter) offered to look into a spot. Looks like another group has suddenly formed and beated the reprappers to the punch.

Currently it's all at a somewhat embrionic stage, but if you scoot over to the website at http://hacklabperth.org/forums you'll find a small discussion that has appeared on working out the details. As well, there is talk about creating a logo for the hackspace if you're artistically inclined.

-Peter Hillier

PS. On a personal reprap note, I've managed to wire up my extruder and get it producing a stream of plastic. The current difficulty is mostly around getting the extruder to stay hot enough(current experiment is to clad the whole thing in fire cement. The reprap software for some reason tends to freeze up whenever I have both the heater and the extruder running at the same time.