Its a very Rosie Xmas…

February 26, 2010

We live in a very small world  these days.  On the 22nd, I ordered a bunch of parts for Rosie from a couple of companies in LA, and 4 stepper motors from a company in England.  They all arrived three days later – even the motors.  It seems like not so long ago sending something overseas was a huge undertaking, and you never quite new how long it would take.  No longer!  Coming home from work today was a little like Xmas morning!

So all of the fasteners, studding, bar stock, bearings, belts, and motors have arrived.  There was a slight problem with one group of washers, so I have to deal with that, but otherwise the orders all look complete.  The last two parts printed successfully, and I have cleaned the support material out of about half the 34 parts that needed cleaning.  The support material is soluble over several hours in a heated detergent bath.  I’ll clean the rest tomorrow and cut all the studding and bar stock to length.  The printed parts will need to soak overnight, then dry, so I am probably still a couple of days away from assembly. That probably works out OK since I need to wait on the new washers and on the laser cut parts.  Soon, though!  The BOM is almost complete for the mechanical construction.

I just realized that the motor shaft does not have the double flats that the drive gears have.  I’m going to have to make a custom gear and print it out.

Right now, though, time for sleep!

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Rosie Gets Ready…

February 25, 2010

So this is a pretty big day…  By the time I post this, all of the Reprapped parts will have been printed.  The fifth plate of 11 finished this morning, and the last plate of two small parts was printing when I left work. Tonight I brought the first five plates home and cracked all the parts off, then sorted them by whether or not they would need to be put into the solvent bath for a final cleaning.  Of the 98 printed parts, 63 needed no additional work, 2 are printing, and 33 need further cleaning.  I picked as much of the support material off as I could (messy, messy job – wear safety glasses!) and the rest will get dissolved out.  That will probably take the whole day tomorrow – not much to do, though, just stir the parts in the bath now and then.  Here is a picture of the fifth plate:

The last two parts to print had problems in the STL files that it took awhile to fix.  Otherwise they would probably be on this plate.

Tomorrow my order from McMaster should arrive, and the bearings shouldn’t be far behind.  That is good news.  I’ll be able to cut all of the bar stock on Friday, and hopefully start mechanical assembly this weekend.  It also gives me a couple of days to finish cleaning the printed parts, get them dried out, and get everything organized for assembly.  Can’t wait!


Rosie Picks My Pocket (Again…)

February 21, 2010

I swear, I’m spending more on postage on this project than I am materials. After spending the entire evening  trying to find the right stepper motors from a supplier in the US, I finally settled on a UK distributor.  They had 4 quality motors available that are perfect and relatively low cost.  In fact, the Reprap site listed the B-version of the motors as proven, but they are double shafted.  The A-version, identical except for a single shaft (which is better) is now available from the same distributor.  The cost? Including postage, less than the cheapest equivalent motors I could find in the US.   So the motors are now waiting on airfreight delivery from across the pond.

Wrote an email to a laser cutting house tonight, also.  With a little luck, that will get done this week.  Also fabricated the opto-endstop flags:

They still need to be drilled (I have to find some metric bits), but they came out pretty well.  I’m glad I went with the heavier flashing stock.

Well, once everything on order arrives, I will cut all the bar and studding stock to length, and I should be ready for mechanical assembly.  The only mechanical parts that I haven’t got in the pipeline are for the extruder, which is fine since that will probably be the very last part built – even after the electronics.  That bit is a little complicated and is going to take some time.

OK, time for bed.  Rosie has kept me up long enough for 1 (um…. 2) days.


Rosie Picks My Pocket

February 21, 2010

Well, definitely committed now.  Placed an order with McMaster-Carr for all of the fasteners: nuts, bolts and washers.  Adding up all of the fastener part counts from the Mendel BOM, there are 1188 required for the build.  Of course when it says you need 17 of something, you wind up buying a bag of 100, but at least they aren’t too expensive.  I plan on advertising the extras for sale on the Reprap site to recoup some of the cost, though, so that will help.  I also bought all of the studding (threaded rod) and plain rod I need on the same order, as well as the drive belts.

I also ordered the 50 (!) bearings that are used in the Mendel from VXB.com.  They provide a custom Reprap kit with everything you need, which makes ordering from them very convenient.  Fortunately the individual bearings cost < $1 apiece, so the total came to less than $50.  (I will  post an accounting of the cost once all of the parts and materials have been procured. So far it looks like it is going to come out right around the $500 the Reprap site claims.)

For the thick sheet stock that makes up the print bed, electronics supports, etc., I found a piece of nice, flat, 0.22 inch thick cast acrylic.  That works out to 5.6 mm, and the spec calls for stock 4 to 6 mm thick, so that is just about ideal.  I’ve decided to bite the bullet and have it laser cut (at a local shop) from the .dxf files provided on the Reprap website.  It is a little extravagant, but should look much cleaner and more professional than what I could do with a bandsaw or fretsaw.

The thin sheet stock can be pretty much anything as long as it is optically opaque to infrared, is less than 2 mm thick, and is stiff but can be bent.  You can use the aluminum from soda cans, but I bought a small piece of galvanized flashing that is stiffer and should last longer.  It will be a little harder to cut and bend, but not unreasonably so.

Another run of printed parts is complete!

There are only 13 parts left to print and I’m hoping they all fit into one build.  We’ve found a couple of problems with the STL files, so I’m going to be spending some time this weekend trying to repair them.  Once the printed parts are done, and once everything I ordered yesterday arrives, there will just be a few mechanical parts left to purchase (the stepper motors and some extruder parts).  I’m excited to start the mechanical fab and assembly.  Its my way of procrastinating on the electronics buildup 🙂


Rosie’s Bones…

February 17, 2010

Over the long weekend John and I were able to get about 2/3 of the printed parts completed.  I’m going to try and include some pictures in this post if I can figure out how (I’m new at this blog thing).

The RepRap bill of materials (BOM) says there are 95 printed parts required for the Mendel.  Of these, we have successfully printed 64, plus 4 jigs/tools, and one optional cable clamp.  Only 31 to go, although it may take a few days to get back in the schedule again.  No worries – it isn’t like I don’t have lots to keep me busy.

OK, pictures…

Hmmm, not quite how I planned it…  I was going for side by side.  Oops.

Clamps and brackets and gears, oh my!

The whole process of 3-D printing is amazing.  You have to construct the parts in a CAD (computer aided design/drafting) package and then create an STL (stereolithography) file which describes the surface of the piece as a bunch of triangles.  This gets turned over to the printer software which figures out how to draw the piece as many thin layers, with each layer partially or fully overlapping the previous one to build up a complex 3-D shape.  In more complex printers (like the one used to print these parts) a special filler material is used to help support holes, overhangs, and other structures that would otherwise not build properly.

So this is what I am trying to build – a 3D printer or stereolithography machine.  Stereolithography is the formal name for this process.  Rosie won’t be able to create parts that are quite as detailed as the ones shown here, but they will still be pretty good.  Good enough to build another Mendel (“Astro”, maybe?) and maybe good enough to create something nobody has ever thought of before.  Very cool!


Rosie’s Roots…

February 16, 2010

The blog was a bit of an afterthought, so I should probably bring things up-to-date.

First: Rosie?  Take a look at the About page for a complete explanation – the robot that will result from this project has been christened “Rosie” in honor of the Jetson’s mechanical marvel.

Exactly what I am building?  The RepRap site lists two machines: the original, Darwin, and the updated version, Mendel.  I am building a Mendel.  I am also going to use the Generation 3 electronics.

In the interest of full disclosure, I have to admit I know almost nothing about electronics.  Sure, I can talk about Ohm’s law and resistors and capacitors, and I can even describe the general workings of a microprocessor.  But build anything practical?  Nope, not really.  So this is going to involve a lot of learning – from how the circuits operate to how to program the processors to how to solder teensy-weensy SMD (surface mount device) components to a circuit board.  Oh, and making circuit boards (but more about that later).

The mechanical part of this project I’m pretty comfortable with – no stranger to nuts and bolts.  Procurement may pose some issues as the RepRap project has its home at Bath University in the UK and all of the dimensions are in the metric system.  Why the US has to be the only industrialized nation that uses English units (which even the English don’t use) is beyond me.

What have I done so far?

1) I’ve started trying to learn about electric circuits.  This has taken the form of working my way through the book “Make: Electronics” by Charles Platt.  Pretty simple stuff at the beginning, but soon moves into basic switching and digital circuits.

2) Started putting together the toolkit.  I think I have all (or most, at least) of the mechanical tools I need, but the electronics tools are a different matter.  So far I’ve purchased a number of basic items and am trying to choose a good soldering station.  That said, much of the soldering is surface mount, so I need to decide if I am going to try and hand solder all the parts or use reflow soldering for the bulk of the work, which means procuring a hot plate, skillet, or toaster oven.

3) Started buying electronic parts.  I purchased three Opto-Stop kits from MakerBot.com, as well as the bare motherboard.  I also took advantage of the automated Bill-Of-Materials generator on the RepRap site, which saved me at least an hour (maybe more).  Most of the parts came from Mouser.com, with a few from Digikey.  As far as cost goes, about 1/4 of my outlay so far has been on postage.  The overall cost has been pretty minimal, although I’ll keep a tally of the receipts as I go and post a summary from time to time.  A couple items of note:  I discovered that one of the capacitors listed on the website is obsolete, and had to figure out an alternative.  Also, I discovered that the NEMA-17 stepper motor identified on the RepRap site is no longer made.  It might be possible to find them somewhere, but I was unable and am trying to identify a good alternative.  When I get it figured out I will post what I use.

4) I still need 4 additional boards – the three stepper motor controllers and the print head controller.  These are supposed to be available from MakerBot, and I am on the email notification list, but from the info I’ve gleaned from the message boards I’m not encouraged that they will be available anytime soon.  I’ll leave this for now and work with the electronics I have and do as much mechanical assembly as possible, then reevaluate the situation.  I’d rather not go into etching my own circuit boards, but if that’s what it takes, that’s what it takes.

5) One of the very cool things about a RepRap machine is that it can make parts for other RepRap machines.  There is a series of parts that can be machined, laser cut, or 3-D printed which provide much of the custom joinery, alignment, etc.  Ideally, if you can find another person with a functioning RepRap, you can wheedle (or bribe) them into making a set on their machine (this takes several days – the printing, not the wheedling, which may take weeks).  I have the very good fortune to work for a company that has a commercial 3-D printer that occasionally has some idle hours.  They have graciously allowed me to make use of that printer with the help of my co-worker John.  My thanks go to to both the owners of the company and to John for their assistance.  (I don’t feel comfortable, unfortunately, saying who I work for because I don’t think they want potential RepRappers bugging them to build parts.)

I think that about brings things up-to-date.  Tonight I’m going to order some soldering supplies on the internet (I spent an hour at Fry’s this weekend and couldn’t find what I wanted) and we will be off to the races.  The printed parts are about 1/2 complete, so I’m hoping I can get serious about the procurement of the mechanical parts soon.  Stay tuned.


Universal What?

February 16, 2010

Universal constructor, that’s what!  A machine that can create a copy of itself out of materials it finds in the environment.  They are commonly called von Neumann machines, but that is a misnomer – the vN machine is actually the design approach used by most modern computers.  John von Neumann preferred the term “universal constructor” for a machine capable of self-replication.  He was referring specifically to cellular automata (Game of Life, anyone?), but the concept is the same.

The science fiction genre is rife with references to universal constructors – from the Terminator movies to the nanoscopic “gray goo” of Michael Crichton’s  novel “Prey” – pretty nightmarish stuff.  The flip side of the replicated coin, however, is on-demand fabrication.  Imagine a world where all you have to do is press a button and say “Earl Grey, hot” or “grande iced three shot half caff no-foam peppermint skinny latte” and “bzzrt!”, instant gratification.  The cost of items would be reduced to the cost of energy and raw materials (most of which could be recycled).  Production and transportation costs would be a thing of the past.  The ultimate service economy. You can argue all day about whether this would be a good or bad thing (what would all the people put out of work do?) but I prefer to imagine a world where people have the time to live full lives, travel, help others, and discover new truths. If that sounds a little Star Trek-ish, well, guilty.

So what is this blog going to be about?  I’m embarking on a journey outside of my comfort zone to build a RepRap Mendel machine (www.reprap.org). Briefly, a RepRap is a 3-D printer that costs less than 5% of what common commercially available units cost.  The RepRap project (I encourage you to visit the website) is dedicated to the development of a true universal constructor – one that can create a copy of itself.

What’s the motivation? First, I want to learn more about electronics and robotics (my late seventies engineering degree was sorely lacking in these areas – maybe because analog computers were still state-of-the-art).  I’ve always learned best by doing, so I was searching for a project that would push me, but leave me with something useful at the end.  My spouse, practical to the end, lobbied heavily for a dusting robot (like Rosie from “The Jetsons”) to complement the Roomba she covets.  That’s probably a little out of my league right now, but the name Rosie has a nice ring to it.  Project Rosie has been born.

Engineer I may be, but I’m an analyst by trade and by the time this little adventure is over I expect to know a lot more about my craft than I know today.  In the end I’ll have a device that will allow me to start Phase 2 of the adventure – but that is a story for another day.