Printed 3D Models Refinement
One of the problems that all fans of FDM 3D printing is ribbing of external surfaces. Since the technology itself is based on the successive application of plastic layers, this effect can not be avoided. You can, of course, make it less visible by increasing the vertical resolution of the printer (ie, applying thinner layers), but you will not be able to completely get rid of the ribbing.
We are always searching for smoothing methods for the finished models. The emphasis was placed on two features of thermoplastics: the ability to melt under the influence of high temperatures and soften when contacted with the appropriate chemicals.
As a rule, heat treatment does not give good results – it is quite difficult to regulate surface heating, and this leads to a boil-up of plastic, subsidence or simply the emission of toxic fumes. Nevertheless, this method can be tried on monolithic models from PLA-plastic.
Chemical processing is more promising, but it also entails certain difficulties. In addition to technological problems, the problem of reagents is urgent – different plastics react with different solvents. If acetone perfectly dissolves ABS plastic, then it almost has no effect on PLA-plastic. With limonene, everything is exactly the opposite.
The main methods of chemical smoothing still revolve around ABS plastic because of its high popularity and low cost of suitable solvents.
A typical solvent for ABS plastic is acetone. Good dissolving power makes it possible to use it as an adhesive for component parts of ABS models, although usually a homemade mixture produced by dissolving in ABS acetone is used for this. The same glue (only a more dense consistency) is often used for repairing stratifications or cracks.
Along with increased aesthetics, an important factor in developing methods of smoothing is increased strength.
Makeraser is a combined tool, intended, among other things, for surface treatment of models
Not surprisingly, first 3D artists were armed with usual brushes with a natural nap (synthetics can dissolve) in attempts to smooth out their models. However, processing with a brush is a time-consuming task, and even requiring a certain skill. After all, softened plastic is easily deformed by the brush itself, that is, the hairs will leave a trace on the plastic, which may not even level before the acetone evaporates.
An attempt to create a special tool for manual processing became a device called Makeraser. In fact, this is a simple felt pen with acetone filled tank or glue, and it has integrated scraper for removing models from the platform. From a practical point of view, this tool is better suited for bonding model parts or applying ABS/acetone glue on the work table usually just before the printing to combat the twisting of the lower layers.
Dipping into Acetone
A more promising and simplest method is immersion in acetone. Diving the ABS plastic model into the undiluted acetone for about 10 seconds is sufficient method to dissolve the outer layer of the model. The time may vary depending on the quality of the original model and from the acetone concentration. Since the sale of pure acetone may be regulated, it is possible to use a technical solvent.
After aging, the model must be kept on fresh air until the acetone evaporates. The process can take about half an hour.
Although this method is fast enough, it is difficult to regulate the process. If the exposure is excessive, the model will simply begin to dissolve, rapidly losing small details. In addition, it can lead to the of stains on subsequent models dipped in the same acetone.
A more controlled process is the treatment with acetone vapor.
Perhaps, the most effective method of obtaining models from ABS-plastic with a glossy surface. This method requires placing the model in a container with a small amount of acetone at the bottom. The model itself should not come in contact with acetone, so the model should be mounted on a platform, or suspended from the surface of the solvent. When installing on a platform, the properties of the stand material should be taken into account. Wood is a bad choice for this task.
Perhaps, the most effective method of obtaining models from ABS-plastic with a glossy surface. This method requires placing the model in a container with a small amount of acetone at the bottom. The model itself should not come in contact with acetone, so the model should be mounted on a platform, or suspended from the surface of the solvent. When installed on a platform, the properties of the material should be taken into account. Wood is poorly suited for this task due to porosity: the bottom surface of the model is glued to the wood, and it will be difficult to separate it. The best option is to use a metal stand.
It is advisable not to use wood as a platform
After placing the model, the container must be heated to raise the temperature of acetone. Acetone evaporates slowly. It should be borne in mind that boiling of acetone is not recommended, as this will contribute to the accumulation of condensate on the model and it is not good.
The time varies depending on the temperature of the acetone. Thus, boiling can last only a few seconds, while experiments with a medium temperature require up to 40 minutes of aging. Fortunately, using a transparent container, you can determine the readiness of the model “by eye”.
As with dipping, the model must be ventilated before solidifying the outer surface, avoiding unnecessary physical contact.
The thickness of the walls of the models should be taken into account. The shell must be thick enough to withstand the imminent loss of the outer layer.
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