Challenges ahead

Quoted here to start things off.

The winner of the PM interim prize will be the inventor who can make a 3-D printer that can demonstrate the following:

* Print at least three different materials, including one that is usefully electrically conductive.
* The ability to print electronic circuit boards.
* Print beds† must be of a material which may be reused with minimal refurbishment for at least 20 print cycles.
* Maintain a total materials and parts cost under $200 and that 90% of the volume of the printer parts be printed.
* Demonstrate a build volume of the printer above 300x300x100mm in order to insure that items daily utility can be printed.
* The capacity to print a full set of parts for a complete replica of itself within 10 days unattended save for clearing no more than one printer head jam.
* The ability to print autonomously without a PC attached.
* Uses no more than 60 watts of electrical power.

The first point always annoys me, as i'm always envisaging the early experiments of extruding solder into plastic channels, and circuit boards need three things (other than parts on them)
1. Rigidity to hold parts from excessive movement where possible, though flex is usually used only as connector cables.
2. To be able to withstand constant temperature variations and vibrations.
3. Able to have a method of connecting more than one layer to another.

I'm reminded of this article last year
condutive ink.

It is possible now to use silver ink/paint, it is very expensive and corrodes easily, and solder ability. Such is the nature of silver.


The next point

Quote

Maintain a total materials and parts cost under $200 and that 90% of the volume of the printer parts be printed.

Just going through the list of what cannot be printed.
Most electronic components (all counted as one)
Some sensors (Opto endstops could be replaced by reliable contact switches)
4 x Stepper motors
Extruder barrel
Extruder nozzle
Extruder thermal barrier
Heated bed
Nichrome wire
Power supply
Belts (though I have noticed that we may move away from belts over rack and pinion drive)

That alone may bring the total number non printable items to 5-10%, and i'm sure i've forgotten some stuff.

Quote

The capacity to print a full set of parts for a complete replica of itself within 10 days unattended save for clearing no more than one printer head jam.

This is possibly one of the most challenging parts, a reliable extruder, though I believe that it is possible, and just have either a huge reservoir for fluid type materials, (epoxies, silicone etc) or a way of cleaning the filament before it enters the extruder.

My last point I want to poke at is,

Quote

Uses no more than 60 watts of electrical power

I would say that would be darn near impossible, considering the power of a normal incandescent light bulb of 75 watts, chopped into 3, using a 1/3 for the heated bed, 1/3 for the nichrome wire and 1/3 for the steppers.
I know from my tests that the steppers alone would take over half of that power, and the nichrome wire would take about 12 watts, and I haven't taken into account how much the actual electronics would consume.

I thought of a couple of other things i'd like to see happen, but I cannot recollect what those ideas were, doh!

Edited 1 time(s). Last edit at 01/28/2010 01:50AM by Grogyan.

I remember a couple of tore ideas.

1. All non replicatable must be able to be made without the need for special equipment like a lathe. A drill press and bits, vice are a couple of examples of tools which are easy to come by.

2. To be able to demonstate that the printer can swap tools by itself.

3. Demonstrate it can use all 4 tools in a single build.
The fourth tool being a light drill for drilling and/routing.

4. That it can dance the funky chicken,
Or play a tune with its motors once build has finished. Empirial march comes to mind.

My Mendel uses 36 watts just by being on with 3/4 of the steppers enabled (default) and with the extruder heater off. With the heater turned on (from cold start) it goes up to 59/60 watts. This is measured using a Kill-a-watt electricity meter connected between the electrical plug and the ATX power supply. Also, ATX power supplies are generally not very efficient.

Yes. Light bulbs are very inefficient.

Solder and silver paste are not the only ways to obtain conductivity. My team is currently developing a printhead to lay wires into a part. However, solder/silver paste (might) be needed to join the wires to each other.

> That alone may bring the total number non
> printable items to 5-10%, and i'm sure i've
> forgotten some stuff.

Which means there's almost no space left for bolts, bars and other hardware. Requires more plastic to build then and raises the production time of one machine... this point will be very tricky IMO.

> The capacity to print a full set of parts for a
> complete replica of itself within 10 days
> unattended save for clearing no more than one
> printer head jam.
>
> This is possibly one of the most challenging
> parts, a reliable extruder,

Probably one of the easiest parts on this challenge. A geared pinch wheel extruder can/will do it for plastic. For the other stuff I'm sure we'll come up with something.

> My last point I want to poke at is,
> Uses no more than 60 watts of electrical power
> I would say that would be darn near impossible,
> considering the power of a normal incandescent
> light bulb of 75 watts, chopped into 3, using a
> 1/3 for the heated bed, 1/3 for the nichrome wire
> and 1/3 for the steppers.

Leave out the heated bed and it becomes possible.

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FiveD Firmware fork (supports Arduino Mega): [github.com]
reprapsource.com

>> Which means there's almost no space left for bolts, bars and other hardware. Requires more plastic to build then and raises the production time of one machine... this point will be very tricky IMO.

The original analysis on the 5-10% implied the only solution would include a thermoplast extruder. Also the "by volume" seems disingenous; to meet the criteria, I waste cheap material to print out several quick and dirty large empty boxes to pad my overall volume of printed material.

I believe the % volume clause for this reason alone may require modification.

I believe the rules may require modification to get to the real intent - the ability to quickly create additional machines for low cost; I'd suggest changing the % by volume to: "With an existing working machine, US $1200 ($200 shipping/handling/tax surchange reasonable?), a bill of materials, instructions, and 60 days, 5 new working copies can be constructed by a team of 3 people with minimal training (assume some ability to solder, use simple tools, etc.), spending no more than 4 hours each day, at a site identified by the panel as the 'test location'. Could be predetermined or witheld, as the contest administrators choose, predetermined allows more ability to judge third party component availablity and shipping costs - locally vs remotely.

Tweak the numbers to change the different priorities of cost vs. time vs. training vs. man-power.

While I think it would be admirable to build the machines without leveraging existing mega-factory complexes, the microcontroller alone indicates it probably won't occur for some time; so rather, use the existing manufacturing world to its full potential to the advantage of the project rather than adding arbitrary constraints.

joaz Wrote:
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>
>
> > My last point I want to poke at is,
> > Uses no more than 60 watts of electrical power
> > I would say that would be darn near impossible,
> > considering the power of a normal incandescent
> > light bulb of 75 watts, chopped into 3, using a
> > 1/3 for the heated bed, 1/3 for the nichrome
> wire
> > and 1/3 for the steppers.
>
> Leave out the heated bed and it becomes possible.
>
Rapman without a heated bed pulls about 40-50 watts.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Which means there's almost no space left for bolts, bars and other hardware. Requires more plastic to build then and raises the production time of one machine... this point will be very tricky IMO.

The structure could be created without all of the large supporting bolts.
A large portion of the mendel design can be easily designed to fit withing the constraints outlined for volumn. Their minimum volumn is just over 11"x11"x3" or so. If you really deconstruct the mendel design into some creative structures, it could be made from pieces which "snap" together but are entirely printed and still retain quite a bit of strength. Like so, cut the top and bottom of the printer in half. Split these 2 halves into further halves along their widths. Then do the same with the bottom 2 halves along their lengths.

In the end you would have 6 pieces which make up the "frame" of the printer. Obviously there would need to be holes for attachments and the z/y axis...

The herringbone structure demonstrated a means of getting by without some of the bearings.. it could be expanded to provide the track upon which the x axis rests. By that I mean embed the rack portion into the printed surface and when the wheels turn they move it one direction or the other by the appropriate amount.

I think that with the structures demonstrated so far on the blog, it is possible to remove the belts entirely.

Just doing those things will remove a huge portion of the non-printable hardware.

By snap together I mean using a latch mechanism or double hing mechanism.. the pieces would fit together (i.e. raised lip on one side and matching groove on the other) and then you "pin" or latch the pieces to make 1 strong support.

I don't know how thick it will need to be to be strong enough or how long it would take to print. I will have to design it up and give it a try.

I hope my ramblings made some sense.

Oh.. and by the way.. I am looking for a team to join.

Edited 1 time(s). Last edit at 01/28/2010 10:42PM by cephdon.

I haven't been on here for a while for a large variety of reasons, but I'm currently working on 3 designs that could all be useful in decreasing non-printed materials and costs, depending on how well they work.

The first and closest to being in need of physical testing is a linear bearing and rail system using recirculating ball bearings. I've sized it to use 6mm diameter balls, as they are the non-printable component (unless someone out there with a reprap would like to prove me wrong, I don't believe that a precision 6mm sphere is within the capabilities of the current system). Why 6mm? 6mm precision, smooth, polished, biodegradeable plastic balls are sold by the thousands in your local sporting goods store as Airsoft ammunition. The basic models for a first run are just about ready for this, but I don't have a printer. Expect to see them popping up on the forums this weekend.

The next is a rotational ball bearing, also using non-printed 6mm balls. It won't, obviously, be quite as nice as a skate bearing, but I bet I can design one that works.

The last one is a 100% feedstock/printable tube roller bearing design. the primary design will be based on using cut sections of the feedstock as rollers, but it could just as easily be redisigned to use whatever size teensy cylinder a reprap can produce accurately is.

I wanted to chime in on the volume bit as well: What exactly do they mean by volume? A nema 17 stepper motor doesn't displace all that much water, you know, whereas a thin-walled printed box can displace an awful lot if it's watertight.

I also have had some ideas about printheads that I've tossed out and fiddled with before but never been able to really follow up on. I did a good bit of experimenting with a piece of oak as a thermal break. I don't actually know how hot I got it, but I was able to easily push a piece of ABS through a welding nozzle by hand while holding the oak it strapped to with my bare hands. The ABS was smoking at the time, the wood was not. I believe that the thermal transition zone can be gotten down to almost nothing by using a wood thermal break.

I'd definitely be interested in joining a team out there. I don't have too much to offer, but I've got some free time and a student copy of SolidWorks to play with.

I think that the first place to attack the lowest hanging fruit for the biggest change, and I think that this is to replace the fasteners (at first some, then all). Some sort of strong snappable fastener is going to really get things moving and once we get the problem solved, it will reduce the non reprapable parts by a huge amount.

I think that Adrian and the Prize people sorted out the GPL/BSD prize kerfluffle very nicely. Take a look at the prize page this morning.

"All technology developed by participating teams becomes open source under a GPL
or BSD license. Therefore, the winning team will have to have published at least
some of their innovations more than 12 months before the deadline.

"(Note that the RepRap Project itself is licensed using the GPL, so any entry
derived from that is constrained also to use the GPL. Any entry not derived from
the RepRap Project can use either license.)"

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Corwin Wrote:
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>Why 6mm? 6mm precision,
> smooth, polished, biodegradeable plastic balls are
> sold by the thousands in your local sporting goods
> store as Airsoft ammunition.

If I understand this right, you have a pretty cool idea for how to get rid of the ball-bearings, although I have a suspicion that Airsoft amunition as common in the ROW as in the US.

I think that the decreased durability of the bearings is an acceptable cost.

@Anton: I share your supsicion about how common airsoft ammo is outside of the U.S. Fortunately, anywhere you go steel balls are less expensive than bearings - the design doesn't care what material they are, and can be adjusted to fit slightly different sizes of ball. The quality of the bearings and whether the difference between them and commercial all-metal bearings is an acceptable tradeoff remains to be see, I think.

Airsoft balls are available in New Zealand, however I don't trust that they will be robust enough to last.

It may be an idea to come up with a design that doesn't need bearings at all.
From the demo videos that Ed posted, it tends to make the printer a lot more noisy