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3D printing challenges explained

From: Mark in Denver

Rough example in ABS, showing emphasized artifacts, not from ShapewaysBelow paragraph on the process from the Shapeways website.

As you can see the process is involved (not quite as intense as some other ways but still a few steps). The material is acrylic plastic, if you use Plastruct or Pro Weld with a light coating over flat areas and such you should be good for “knocking down” or melting top ridge lines.

The process really can’t eliminate that though I think shapeways is seeing about possibly more advance equipment (the one machine alone runs about 60grand!).

I have in past emailed shapeways about the way they make the parts as to orientation.. they pretty much indicated (and this does make sense) that they orient the parts on the program so that they can get the most number of parts in a single run. That means if one day you have only a few parts then they might lay a frame upside down and help keep the majority of it horizontal (a good thing) on the other hand if a lot of parts, they have to orient it standing on end.. then you get the horizontal lines along the main length of a frame (or part) (a bad thing). I have no say on this as a modeler..

I asked if I can do anything on MY part when I create the parts as to orientation, XYZ coordinates etc.. they said no.. when they get the file..they try to “pack it all in” on a run and that means if it takes up space they re position it,same as if you make acity if you can’t spread out you go up. Do keep in mind that this same process is used for the majority of products now a days thatare going to be injection molded.

The process is meant for RAPID prototyping.. a hands-on , feel what the finished product is going to belike as to assembly, size, weight, moving parts etc. In industry, everyone knows that the final “mass produced” goods aren’t going to have “horizontal ridges” on it, so that isto be expected and accepted. So this with shapeways is kind of “pushing” a bit of what the process was originally intended to do andcan do as to making something a “finished ” product.

I figure it a fair trade as it can save a great deal of time and accuracy when doing some things. This just has to be understood when purchasing these parts.  If you read the process they are pretty good on getting rid of any “residue” from the support material and all. If you need to, you can use a dishwashing soap to give it a good cleaning (same as when you prep a paint job on a injection shell). I hope this helps, like I said I try to create my models so that they are in parts not only for easy customization, replacement, painting, etc, but also so that hopefully on the orientation makes the ridge along a easy to reach and sand edge or UNSEEN area.


From the Shapeways page:

UV Curable Acrylic Plastic
Perfect for small high detailed models like miniatures, model trains, computer generated characters and alike due to the fine quality of the finish, thin walls of 0.5mm in Frosted Detail and 0.3mm in Frosted Ultra High Detail, in both settings we can achieve feature details of 0.1mm.  The material is quite strong, slightly flexible and heat resistant up to 80/176  degrees C/F.

Printing process
The printing process used is Multijet Modeling (MJM). Molten plastic is deposited by print head onto platform in layers through several nozzles, essentially a large print head that sweeps across the build layer. As the heated material jets onto the build plate, it instantly solidifies. Afterwards, each layer is then cured, or polymerized by a wide area UV lamp after deposition. The next is applied and layers of thermoplastics builds up.

For overhangs, a support structure of lower-melting wax is constructed that is removed later by being heated. This method of hands free support removal allows for highly complex, and delicate applications. The products are printed on an aluminium tray. When printing is ready we place the aluminium trayin the freezer. After that, we get the models from the tray and put them in a basket. That basket we place in an oven to melt the wax away. After the oven we put the basket in a ultrasonic bath with oil to remove all wax rests. After the oil bath the product are really greasy, so we put the basket in another ultrasonic cleaner with water to flush all leftover oil away. Then we dab away the leftover water on the models.

The pros of this technology include build speed virtually independent of part size or quantity. This means that whether a person submits one part or 10, they will all print in almost the same time.

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