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— urbantick

March, 2014 Monthly archive

Over the past few years printing three dimensional objects has become widely popular with new tools now becoming available at low costs ready to use. Whilst 3D printing has been around since the 1980s only now have consumer gadgets found their way onto the market.

Most of the models currently available are using the extrusion technology where the material is liquefied and then added layer by layer where it hardens keeping its new shape. Such printers like the RepRap series, the cube or the MakerBot are very popular. The main drawback with this is the limitations in accuracy and roughness of the surface finishing.

An alternative is the Form 1 which uses Stereolithography (SL) technology. This process is based on photopolymer that is cured using a laser resulting in very high accuracy and smooth surface finish. It requires, however, a cleaning process to finish off the model after the printing.

Image by urbanTick / The Form 1 printer is after plugging in and filling up ready to use. It comes neatly designed and is operated with just this one button.

The Form 1 is produced by FormLabs which came out of a Kickstarter project. They managed to secure plenty of funding for the proposed product and have stated shipping about a year ago in early 2013. We have no finally managed to get hold of one of these cool machines and be able to play around with it testing various builds and models.

In short, it works great and is very easy to handle. Basically out of the box, poor some photopolymer in the tray and your good to go. The software to send the 3d object to the printer can be freely downloaded at FormLabs. It loads .STL files places them in a virtual cube representing the build volume (125 x 125 x 165mm ) of the printer.

A good place to start for 3D models is either on shapeways or for free on thingiverse. Both are community based platforms to share 3D objects. Users can comment and upload images of their own builds for each of the objects. The discussion often gives hints and instructions if it is a more complicated project.

Once loaded in the software the object can be rotated resized and moved if other objects need to fit in beside. The software also helps with the support structures. These are important during the building process both for the stability of overhangs, but also to secure the object in place during the process.

Image by urbanTick / Printed parts hanging down from the build platform of the Form 1.

The Form 1 creates the object upside down. They each hang on the built platform and grow out of the tray with the liquid photopolymer. The laser is located in the bottom of the device beneath the tray with has a transparent bottom. The fancy transparent orange hood of the Form 1 blocks in the laser beam in case it goes off target. It is save to operate the device on your work desk.

Once all the digital objects are in place and each has their supporting structures the model is sent to the printer. After the data is transferred, the printer can be disconnected. Very handy, you can prepare the model on your laptop, once ready plug in the printer and upload the model. It will start working straight away on the first layer and once the upload has completed the computer can be disconnected, and the printer runs the object independently. Time to prepare the next batch.

Simple small things will require an hour or two, bigger and more complex objects can take several hours. Time ask depends on settings such as kind and density of support structure and resolution and layer thickness. The Form 1 offers three resolutions 0.1mm, 0.05mm and 0.025mm. While some extruder based Machines will also print at 0.1mm or 100 microns the SL technology will produce a still smoother overall finish. The difference between the three options really is marginal if considered for rapid prototyping.

Image by urbanTick / Cleanign tray with the required tools and cleaning containers.

Once the printing is complete, the objects have to be taken off the build platform and washed in 90% alcohol (isopropyl alcohol) to get the uncured resin off. To get the object off the platform, a scraper tool is necessary. This task is still quite fiddly. It often sticks very well, and with other objects on there too there is little room to manoeuvre. Getting the alcohol here in the UK to soak the parts can be tricky. If your lucky the chemist down the road will sell 70% isopropyl alcohol. It too works, takes a little longer soaking times. Online it can be expensive, and Amazon does mainly 99.9%. Boots in the UK will do something similar 90% ethanol mix, surgical spirit. Seems to be working too, but again a bit stronger than recommended.

Once soaked and washed the parts can be taken out and its time to free them from the support structure. They can easily be broken off or cut with a sharp little tool. FormLab includes all the necessary gadgets including tweezers, scraping tool, pincers and a large pack of rubber gloves to handle the parts during this after the print process, very convenient.

Image by urbanTick / Smooth surfaces and a perfect fit are the characteristics of finished parts using the stereo lithography of the Form 1.

Parts coming out of this process are smooth and detailed. We have been working with clear resin producing some nice semi-transparent objects. FormLabs also offer grey and white resin that can be used depending on the design or further use of the model.

The accuracy of the finished models is pretty good. Lego pieces, for example, do fit with the original parts, so that figures can be extended or attached to objects. We printed this saddle for Lego figure to ride a HexBug for example. The material is quite sturdy once completely dry. We have printed some bracelets from it. What is much more difficult are movable parts. Individual chain links work well, but large pieces often get stuck at one end. Not sure how this can be improved in the model or has maybe to do with the printer setup.

The handling of the digital model in .STL format, setting up the print and printing is all straightforward and extremely simple. The cleaning process, however, can be a bit of a struggle and requires some getting used to. It can also get messy especially if you have a build that failed because it might have not correctly attached to the build platform and fallen off. The handling of both the cleaning liquid and the resin have to be done carefully and both, in their liquid form, need to be disposed of as chemicals, your coal chemist might take them. All this makes the process quite a bit more challenging than the extruder alternative. It requires more planning and greater care. Based on this some comparisons between the two processes of SL and extrusion have often rated extrusion more consumer friendly and easier (e.g. popular mechanics).

However what you get from SL and the Form 1, in particular, are beautifully detailed and smooth objects with a very high standard finish.

Image by urbanTick / Polyhedron sphere printed on the Form 1. Model can be downloaded from georgehart.com

Beyond the process of printing itself of much interest is the wider process of production including design. This is really where this new technology and the available tools become interesting. The ways the possibilities might change existing chains of production to the point where some goods are manufactured in the end users home. A lot of research is currently being undertaken, e.g. at MIT in collaboration with Hyperform. Of interest will also be strategies to integrate options for prototyping in existing workflows and an increased combination of digital and physical prototyping. So there is a lot of material to explore now that the printing works.

edited, 2017-11-14. Minor edits and updated links

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