new acrylic front plate!

08/22/2009

I went to town on our new Universal Laser Systems VLS6.60 laser cutter and made a new front for my makerbot:

I made the opening larger and took away the big M in the center so I would have easier access to the inside of the machine. The lower section is engraved with a bunch of diagonal lines and three makerbot Ms with patterns inside.

It was cut from 1/8th inch acrylic.

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Makerbot Vs. Dimension SST 1200es

08/20/2009

The Industrial Design department at the University of the Arts in Philadelphia (of which I am a part) just moved to a new building with brand new facilities, including a new shop. I guess it was time for an upgrade because almost every tool in the shop is brand new and we now have a Universal Laser Systems laser cutter (new favorite) and a Dimension SST 1200es 3D printer.

This particular Dimension printer happens to utilize fused deposition modeling and it prints with ABS plastic… So of course, having recently completed my Makerbot, I had to do a little comparison. I printed two objects (both of which can be found on thingiverse.com); a stormtrooper head and a dodecahedron. One thing to keep in mind when reading this is that my particular Makerbot is not up to the highest printing quality yet, so there is definitely room for improvement. First, the prints (click pictures for ultra large versions):

QUALITY
Obviously the Dimension wins this round. Printing at 0.245mm (0.01 inches) per layer, it trumped my 0.35mm per layer Makerbot prints. The XY resolution is definitely higher on the Dimension, and the plastic extrusion in general is more controlled and precise. If you are looking for tolerances rivaling what the human eye can perceive, the Dimension is what you are looking to print with.

The big difference is that the Dimension prints support material in addition to the ABS plastic. This means that crazy overhangs, objects within objects, etc. can be achieved. (The folks at Makerbot designed their printer to be compatible with multiple print heads, so some time in the future the Makerbot will be printing support material too)

TIME
The stormtrooper and the dodecahedron were printed at the same time in the Dimension; they took roughly 1 hour and 40 minutes to complete. The Makerbot had the stormtrooper done in 25 minutes and the dodecahedron done in about 16. Add an extra 5 minutes or so for setup between prints (which is a pretty conservative estimate) and you’re still talking less than half the print time (~46 minutes).

But wait! The Dimension prints support material as well, so the storm trooper and dodecahedron must go in a vat of solution for an additional hour. Bringing the print times to:
Dimension – 2 hours 40 minutes (assuming you didn’t have to wait for the solution to get up to 150 degrees and you grabbed the prints out of the printer as SOON as they were done– an idealized situation).
Makerbot – 46 minutes.

EASE
Those of you familiar with the Makerbot know how many settings there are to tweak just to get the bot to print something decently coherent. Skeinforge is not the user-friendliest software package ever made, and it takes some getting used to. The Dimension comes ready to party and, spare a few simplified parameters you might need to change, you can hit ‘Open File’, select your file, and hit ‘Print’.

The physical preparation is similar for both; the Dimension has a plastic tray you must snap into place, while the Makerbot has a build platform you must snap into place.

The Dimension is the easier of the two to use, however…

TWEAKABILITY
After learning the ins and outs of the Makerbot, I was taught how to print something on the Dimension. There is a drop-down menu for the density of the object you are printing; the options are something like ‘Sparse’, ‘Dense’, ‘Minimum’, and ‘Maximum’. To which I replied: you can’t even set the object density as a percentage from 0-100?

The Makerbot lets you tweak EVERY little detail, while the Dimension gives you almost no options. You don’t even have the ability to turn the support material off!

Things you might not realize can be tweaked on the Makerbot: layer thickness (.01 inches and .013 inches are your only options on the Dimension), feedrate (speed), flowrate (extruder speed), object density, wall thickness…

PRICE

Dimension SST 1200es: ~$30,000 (for just the printer, excluding plastic, support material, and build trays)
Makerbot: $750
Dimension obviously capitalizes on every opportunity to charge money; the plastic (which is almost identical to that used in the Makerbot) as well as the support material is housed inside a case that slides into a slot on the printer. Though I don’t know the price of a case off the top of my head, I know that it works out to about $5 for every cubic inch of plastic. A 5lb reel of ABS plastic for the Makerbot costs $50 or $60 (depending on the color)  and will last you at LEAST a few months of printing regularly.

Do keep in mind that you are paying $30,000 for the ability to hit the ‘Print’ button and walk away. This is crucial in many work environments (because it eliminates the need for a dedicated staff of technicians, which some printing technologies require).

WHAT THE INDUSTRIAL DESIGN STUDENT THINKS

Speed wins out over quality most of the time when designing things. 0.35mm per layer means that you can see how an object feels in your hand; ultra fine detail is not always necessary. 46 minutes versus 2 hours and 40 minutes is a HUGE difference!

The Dimension would be clutch in the engineering field because of the tolerances necessary, but as far as designing goes… I’ll take my $29,250 and sacrifice a few fractions of a millimeter.

No offense to Dimension, though. You make nice printers.

The Makerbot Process

08/11/2009

I wanted to write up this post for two reasons; one, to explain a do-it-yourself 3d printing platform to those new/curious, and two, to provide a solid explanation for those interested in purchasing a makerbot (a pretty hefty investment for most). Forgive me if some of this is rudimentary… I wanted to paint as complete a picture as possible.

SO. The Makerbot is a fused deposition modeling (FDM) printer (follow the link for more information on the process). All you need to know right now is that it prints plastic in a layer-by-layer process.

The printing process can be broken down into two major steps: computer software pre-processing and actual physical printing. I will limit this explanation to the Makerbot specifically.

First, a 3d model is designed in pretty much any 3d modeling software program. When it is finished, the model has to be processed before the 3d printer will understand it. Since the Makerbot prints layer-by-layer, the model needs to get sliced up (among many other things). The software run by most Makerbot users is currently Skeinforge, which happens to be totally free and open-source.

Skeinforge contains all of the settings for the user’s particular Makerbot– from speed, layer thickness, and extrusion temperature down to the exact distance the plastic extruder turns on before laying down a path (in fractions of a millimeter). These settings can (and must) be edited to get the most out of the printer. The 3d model is chopped up into thin layers by Skeinforge, and the output is a set of instructions that a machine can understand and use to build the model. The instructions are in a language called GCode. Since Skeinforge knows the details of the particular Makerbot, it tailors the build instructions to get the most out of the printer. When the instructions are compiled it lets you view them layer by layer. It uses lines and arrows to show you precisely what the printer will be laying down. Here is an example window from a build I did:
skeinview

GCode is a simple language used by computers to control machinery. Most lines in a GCode program are literally just “move here” and then “move there” and then “move back here.” It controls other aspects of the machinery as well; a CNC router, for example, has a milling bit and the GCode might tell the bit how fast to spin. In the case of the Makerbot, the GCode controls the position of the build and the speed and temperature of the plastic extruder.

The prepared GCode is loaded into a program which will communicate with the Makerbot. The program Makerbotters use is called ReplicatorG. ReplicatorG specializes in reading GCode and translating it into Makerbot language. The Makerbot itself has its own program on it which specializes in turning ReplicatorG-Makerbot-language into physical movements.

Setting up the Makerbot to print is very easy. You have to put either foamcore or acrylic on top of the build platform, which snaps into place on the bot. Once ReplicatorG is open, you can jog the X, Y, and Z axes so that the print head is positioned a fraction of a millimeter above the center of the platform. When all is ready you hit the “Build” button!

So to give a brief overview, the process can be summed up like this: 3d modeling -> conversion to GCode (Skeinforge) -> printer setup (ReplicatorG) -> print!

From a designer’s point of view, the process is quick and virtually painless… When iterating and prototyping a design, the first thing you notice is how little time you actually spend designing. Having access to a machine like this is invaluable.

it prints!

08/07/2009

So the makerbot is finished and it works. I will be posting a bunch in the near future on how it works, etc.

Extruder Controller

07/03/2009

I finished soldering the extruder controller, which controls the plastic extruder.

The plastic extruder does two things: it heats, and it pushes using a motor. First it heats; then, when the temperature is right, you feed plastic filament (3mm thick plastic rod) into it and a motor turns, forcing the filament down into the heater. This process is covered in the post on FDM.

The extruder controller is a board with an arduino built into it; it is the brains of the plastic extruder. It handles the signal from the thermistor, which is a temperature sensor built into the plastic extruder. Using the information from the sensor, it is able to regulate the temperature of the extruder very accurately.

extruder controller

Stepper Drivers 2+3

07/03/2009

Solder paste arrived and all of the stepper drivers are done.

stepper drivers, completed

Optical Endstops

07/02/2009

I am waiting on solder paste, but in the meantime I soldered all of the optical endstops because they don’t require the hot plate reflow method.

The printer has a stepper motor for each axis- X Y and Z. Each stepper motor runs along a metal rod. A problem that might arise is this: how does a stepper motor know when it has reached the end of the rod? If it goes too far, it might damage some of the hardware, or maybe even the motor itself.

…Which is where the endstops come in. There is an optical endstop for each end of each axis (two ends per axis times three axes equals six endstops). It works by shooting a beam of light into a light sensor. As long as the light sensor detects the light, everything is fine and it sends a signal equivalent to OK.

However, the printer is constructed in such a way that when a stepper motor reaches the end of the axis, the beam of light is broken. As soon as the light sensor stops detecting the light, it sends a message out. The motherboard interprets this message as STOP.

Pretty clever, right?

endstops, completed

The black component with two rectangular sections (NOT the RJ45 connector) is the sensor. One of the rectangular sections contains a light and the other contains the sensor. Putting anything between those two sections cuts off the beam of light.

Stepper Motor Driver #1

07/02/2009

The first part I constructed was a stepper motor driver. This is a board that controls one stepper motor (there are three stepper motors in the printer). It converts the power to the appropriate voltage and current, and translates the signal from the motherboard into a signal that a stepper motor can understand. As you will see in the pictures, it contains two ethernet (RJ45) jacks. This doesn’t mean the board understands ethernet signal; it is utilizing the ethernet cable because it is more convenient and organized than soldering a bunch of wires individually. The makerbot electronic components all communicate with each other using ethernet cables.

I soldered the first stepper motor driver together. It came like this:

stepper driver unassembled

tiny components

There are a whole bunch of tiny components, which are too small to be soldered using a regular soldering iron. Instead, I used a method called hot plate reflow. A solder paste is first applied to the bare pcb board; it is a thick gray paste which, when heated sufficiently, turns into hard metal. After the paste is applied, tweezers are used to place all the components in the right places.

The board, components in place, goes on a hot plate. Since the solder melts at a lower temperature than the board itself, the hot plate doesn’t damage the board. When the melting point of the solder is reached, it all pops and becomes hard metal, effectively soldering all of the components into place.

hot plate in action

The larger components required a typical soldering iron. Finished:

stepper motor driver #1, complete

Unfortunately the solder paste I used wasn’t the greatest, so I am waiting on some higher quality stuff in the mail. I ran some power through the stepper driver and the appropriate LED lit up, but it remains to be seen whether it is fully functional or not. Fingers crossed…

Makerbot!

07/02/2009

I have received a MakerBot kit.

printer, as shipped

laser cut parts

the electronics come in the form of small bags with heaps of microscopic components:

electronics in bags

…and so I begin.

Printing Technologies

05/20/2009

So there are currently ten posts covering eleven different printing processes. In order to learn them better I decided to summarize them all in my own words, which I hope are easy enough to understand (feedback is greatly appreciated, both conceptually and grammatically). Here is a list of all of the types I have covered and their appropriate links. I have also categorized them so that you can see some of the underlying technologies/similarities/differences.

SLA – Stereolithography
SLS – Selective Laser Sintering
FDM – Fused Deposition Modeling
LOM – Laminated Object Manufacturing
3DP – 3-Dimensional Printing
Inkjet and MultiJet Printing
SGC – Solid Ground Curing
JP – Jetted Photopolymer
DMLS – Direct Metal Laser Sintering
LENS – Laser Engineered Net Shaping & DMD – Direct Metal Deposition

The following websites were extremely helpful in researching:

http://www.custompartnet.com/wu/additive-fabrication
http://www.efunda.com/processes/rapid_prototyping/intro.cfm
http://home.att.net/~castleisland/home.htm
http://home.utah.edu/~asn8200/rapid.html

…as well as manufacturers of these technologies, whose pages are linked within individual posts.

What I have found in doing this research is that many of the processes are very similar, but deal with slightly different materials. They vary in speed and quality, and it seems that if you are familiar with all of these technologies, there will always be one that stands out for a specific application. I will be constructing a map soon that I hope will shed light on these subtle differences and help to analyze cost and speed in addition to accuracy, tolerance, etc.

Laser Engineered Net Shaping (LENS) / Direct Metal Deposition (DMD)

05/20/2009

LENS and DMD are the same technology. LENS/DMD is used to print parts out of metal using a print head (as opposed to the DMLS process). The print head moves in all three axes. A laser is focused through the print head and metal powder is injected into it. The powder is sintered as it exits the head and is put down on the model.

An inert shroud gas is used inside of the print head to shield the metal from oxygen (so that it sinters correctly and can be controlled more accurately).

from http://home.att.net/~castleisland/lens.htm:

These technologies have been utilized to fabricate and repair injection molding machines, and to create specialized parts for aerospace applications.

LENS/DMD is limited at the moment because support structures would have to be made out of the same material as the model, which makes them difficult to remove afterwards.

Advantages?
• The printed objects usually have desirable metallurgical properties and are completely dense.
• Can be used not only to fabricate but to repair parts (something DMLS is not capable of doing).

Disadvantages?
• Severe overhangs are an issue because of a lack of a different material for support structures.
• Objects usually require some post-print machining.

Direct Metal Laser Sintering (DMLS)

05/20/2009

DMLS is identical to SLS, except that the machine sinters metal powder instead of plastic powder. The model does not require a finishing stage.

According to custompart.net, DMLS is capable of printing steel alloys, stainless steel, tool steel, aluminum, bronze, cobalt-chrome, titanium, and ceramics.

One of the most common uses for DMLS is “rapid tooling,” which is the production of specialized tools that go in machines; these tools may be specific to one application in one machine and therefore aren’t produced in mass quantities. The cost of traditionally producing one of these pieces (by CNCing, casting, etc.) is extremely expensive and wasteful in comparison to printing it. DMLS has proven successful for making these sorts of parts.

Moldmakingtechnology.com has an excellent article on a 2003 collaboration between two companies (Morris Technologies and Extreme Tool & Engineering) testing the pros and cons of using DMLS to make molds. They were somewhat disappointed with the results.

Advantages?
• No waste is generated and little energy is used, as compared to traditionally machining an object. This is great for prototypes and one-offs.

Disadvantages?
• In Morris and ET&E’s test, the mold they printed had a considerable amount of warpage and required additional machining, as well as polishing. Bottom line: not a good solution for moldmaking.

Solid Ground Curing (SGC)

05/20/2009

SGC was a process developed by Cubital Inc. of Israel. The technology is no longer being produced, as Cubital Inc. no longer exists (though Objet Geometries Ltd. of Israel retains intellectual property of the process). I have included it here because it is an interesting and unique approach to printing.

SGC uses photosensitive liquid in a layer by layer process, however the main difference is that it exposes an entire layer at one time.

Before the process can begin, a series of plates must be printed. Software splits the CAD model up into thin layers, and each layer is printed (2-dimensionally) onto a plate. The plate acts as a mask; any model cross-section is transparent while the rest of the plate is opaque.

The machine first sprays a layer of photopolymer into the working area. The first printed plate is loaded right below a UV lamp; a shutter opens and the entire plate is exposed to the photopolymer at once. The cross-section that was exposed hardens the photopolymer, and afterwards the uncured photopolymer is sucked up by a vacuum.

Next a layer of wax is put down over the unexposed area (evening out the bed) and the entire layer is milled so that it is completely flat (all of the excess material from the milling stage is vacuumed up). Another layer of photopolymer is sprayed on, the next plate is loaded, and the process continues.

At the end the model is contained within a block of wax, which gets melted away. No other post processing is necessary.

efunda.com has a nice illustration of the process (it is fairly difficult to explain):





This method failed because of high acquisition and operating/maintenence costs.

Advantages (while it existed)?
• Very fast and decently accurate (though not as accurate as SLA).

Disadvantages?
• Produces a lot of waste.
• Expensive in comparison to other methods (for both material and operation).

Jetted Photopolymer (JP)

05/20/2009

JP printing is identical to InkJet printing, but instead of using thermoplastic, it dispenses photosensitive liquid. The print head contains a UV light; after a layer is put down, it is cured with the UV light. This eliminates the need for a separate curing process and is very accurate.

Advantages and disadvantages are similar to Inkjet printing.

Inkjet and MultiJet Printing

05/20/2009

Inkjet printing is almost identical to FDM, however the plastic is held in a liquid state inside of the machine before being dispensed. As soon as the print head dispenses the liquid plastic, it cools and solidifies on the model. This process makes for very smooth finishes, however the print time is slow.

The print head on most inkjet printing machines consists of two dispensers; one for the thermoplastic, and the other for wax that acts as a support material.

Another feature typically included in this technology is a plane milling stage. Between each layer a plane is rolled over the model, cutting extraneous material off of the top layer. This ensures that the layer is precisely flat. This has something to do with the slow print speed.

This method sees some of the smallest layer thicknesses of any of the technologies: as small as 0.0005 inches per layer.

MultiJet is indentical to inkjet, but with many print heads simultaneously dispensing plastic. 3D Systems manufactures MultiJet machines (though they call them Pro-Jet) which have several hundred nozzles.

Advantages?
• Very accurate.
• Smooth surface finish.
• Supports are wax and can therefore be melted away.
• Quick print time for MultiJet.
• Milling stage means better accuracy.

Disadvantages?
• Slow print time for Inkjet.
• Supports must be melted– a separate process in itself.

Three Dimensional Printing (3DP)

05/20/2009

The name is a bit confusing, since it doesn’t give any insight into the process, but 3DP is the term used to describe  Z Corp’s technology, which they employ in their line of ZPrinters.

The machine uses a bed of powder and a print head. The print head dispenses a plastic resin which binds to the powder and solidifies it. It spreads on a layer of powder with each new print layer.

Like SLS, the unsolidified powder stays in the workable area so support structures are unnecessary.

Z Corp’s claim to fame on their printers, though, is their ability to color the resin as the machine prints. This means that one model can be printed in any combination of colors; it is even precise enough to print text into an object. Taken from the Z Corp website:

In addition, it can print moving parts the same way that FDM can. The quality of the finished models is rough compared to other technologies, though the parts can be machined afterwards.

Advantages?
• 24-bit color system…
• Prints moving parts.
• No supports necessary.
• Relatively fast printing time.

Disadvantages?
• Rough finish.

Fused Deposition Modeling (FDM)

05/20/2009

FDM is gaining ground in the printing world. It is arguably the most “printer-like” of all methods; it consists of a moving bed (Z-axis) and a print head (X-axis and Y-axis). The print head has a heating element in it; thermoplastic is forced into the print head, melts, and is squeezed out, not unlike toothpaste. The bed is usually cooled so that the plastic hardens soon after being placed down. Again, this is a layer by layer process; some systems can print layers as small as 0.178 mm.

From custompart.net:

Since it is squeezing out spools of plastic filament, there are different types of plastic available to print with. ABS is the most popular; if you are not familiar, ABS plastic is what LEGOs are made of. It can also print PPSF and PC plastics.

Stratasys, the developer and leading manufacturer of FDM technology, offers FDM systems that not only print parts as large as 36x24x36, but print moving parts. The machine can differentiate between separate objects within a CAD file, allowing you to print, for example, a system of gears that works right out of the machine. You can print objects within other objects, etc.

Support structures are necessary, but the print head contains a second element for extruding support material. Stratasys’ FORTUS systems (expensive) contain a bed of water soluble liquid that you place the models in after they print; the liquid disintegrates all support material from the model.

Advantages?
• ABS plastic means durable and functional models.
• Several different material options.
• Prints moving parts.
• Separate support material with removal system.

Disadvantages?
• Slow print time compared to some other methods.
• Rougher surface finish than SLA.

Laminated Object Manufacturing (LOM)

05/20/2009

LOM uses a laser, but the material and process greatly differ from SLA or SLS. It is based on the idea of laminating material; that is, building up a model sheet by sheet with adhesive in between each sheet.

On the side of the bed is a roll of paper with adhesive on one side; at the start of each layer, paper is rolled over the whole bed and heated so that it adheres to the previous layers. A laser traces over the cross section of the model and then cross hatches over all of the extraneous material so that it can be removed later.

At the end of the process the model is contained within a block and you must brush off all of the cross hatched parts (which break off in cubes as a result of the cross hatching… see the picture below). The finished material is described by most as “wood-like.” It can be further machined like wood, though the model has to be sealed through whatever means in order to prevent moisture damage.

AZoM.com has a nice visual description of the process:

LOM machines have also been created that laminate plastic or metal sheets using the same process.

Advantages?
• Cheap materials.
• No support structures are necessary.
• Larger working area than most RP technologies.

Disadvantages?
• The excess material can be difficult and time consuming to remove.
AZoM.com says that it has problems producing good bonds between layers, and that it has difficulty producing hollow parts.
• However cheap the material may be, it generates a lot of waste compared to other methods.

Selective Laser Sintering (SLS)

05/20/2009

Selective laser sintering is similar to SLA. It uses a laser, but instead of photosensitive liquid, the laser heats a bed of thermoplastic powder. It sinters the powder, fusing it into larger chunks, again in a layer by layer process.

A roller first rolls a thin layer of powder onto the bed; the laser traces a cross section of the model, and when it finishes the bed moves down one layer and the roller rolls another layer of powder on.

From custompart.net:

To speed up the sintering process, the whole workable area inside the machine is heated up to just below the melting point of the plastic. This way the laser does not need to be as powerful and can move quicker through each layer.

Advantages?
• This method uses material similar to thermoplastic, so the models are rigid upon completion.
• A major advantage is that support structures are unnecessary; since the unsintered powder isn’t removed until the model is finished, it provides support.

Disadvantages?
• This process is not as accurate as SLA. Since it is difficult to control exactly how much powder gets sintered, models often come out grainy or with excess plastic on them.
• The models are also porous, so some sort of varnish is necessary to seal and strengthen them.
• The workable area must be cooled down when the model is finished, which, according to some companies that use SLS technology, can take up to two days.

Stereolithography (SLA)

05/20/2009

Stereolithography is the oldest and one of the most common methods for printing. It prints by using either one or two lasers focused at a pool of photosensitive liquid. When the laser(s) focus on one point at the top of the pool, the liquid solidifies. This happens a layer at a time, each layer being typically about 0.1mm thick. Each time the machine goes to print a new layer, the bed moves down and more photosensitive liquid is poured in.

When the model is done printing it goes into another machine to be cured under an ultraviolet light.

From efunda.com:

So what are the advantages?
• The machine is very accurate and the vertical step size is small. This is good if you are looking for exact specifications.

Disadvantages?
• The models can’t be handled straight out of the printer, as they need to be cured first.
• Support structures must be printed depending on the specifications of the model, but because of the nature of the machine the supports must be made out of the same material as the model. This means that you have to cut them off manually after curing, which can leave artifacts (I have a first hand experience with this one).