Share

Thermal Masking Technology

The Thermal Masking Technology was developed in the Ilios Workshop to address the issue of costly SLA solutions in order to produce a final result. The technology uses already proven and simple methods, combined in an original way to produce the final 3D model layer mask for exposure. By using thermal masking instead of traditional ways such as DLP projection, LCD masking or Laser drawing, the manufacturing costs are cut almost by a factor of 10 since no complex electronics nor optical assemblies are required and the result can yield sharp layers with very high contrast.

Thermal Masking Technology has been implemented in our Ilios Nano SLA 3D printer which combines a low cost print platform with the below described technique. As a result the printer although has lower specifications than other SLA 3D printers we manufacture, is very affordable as well as safe to use in educational institutions, DIY workshops and other fields where an entry level SLA system is needed under a low budget.

How it works

There are 3 main aspects of the technology which make SLA 3D printing possible. First one and perhaps the most important is the VAT glass coating which is what masks UV light upon exposure. The second aspect is the thermal print head which interacts with the coated glass surface and determines the resolution of the exposed layer as well as the print speed. Lastly since the technology uses heat, it is important to control the cooling of the glass surface during and after exposure to ensure that the masked surface stays visible long enough for the UV light source to cure the SLA material before moving on to the next layer.

VAT Glass Coating

The coating of the glass surface is done within the Ilios laboratory and is a mix of a Black Opaque heat sensitive pigment which when exposed to heat becomes transparent and a specific clear coat which protects the pigment during long print cycles and ensures the coating remains on the glass surface for long periods as well as protects it from scratches.

The VAT is assembled in several layers to ensure the correct light exposure, cured resin detachment and sealed environment free of leaks. Additionally the VAT accommodates the Heated Print Head which runs over the back surface of the coated glass during prints. In the Ilios Nano SLA 3D printer the VAT is small enough to produce adequate model sizes and covers almost all of the heated print head when masking each layer. This also saves space in order to make the 3D printer as small as possible and lower costs during manufacturing.

As seen on the above image, there are 3 layers covering the top and bottom parts of the glass surface. The top section is identical to most SLA solutions except for the protective film used in Ilios products which ensures easy detachment of the model during printing and is a very good replacement of the traditional PDMS coating which normally tends to deteriorate after a limited amount of prints and repeated exposures on a single area.

The bottom side of the glass surface is coated in the heat sensitive mix and comes in direct contact with the heated print head during 3D model printing. A single pass of the print head is enough for the mask to appear within seconds and remains on the surface long enough for the SLA resin to cure.

As seen on the image, the coated surface has excellent contrast characteristics and no light is bleeding through the layer, which is common among DLP and LCD techniques which cannot fully block stray and surrounding light sue to low contrast specifications. This problem however is eliminated as the coated surface is completely opaque and blocks all stray light, providing only the needed sections for layer curing.

As a side effect of this technique, software supplements such as Anti-aliasing are not required since the thermal dissipation within the coated surface and the glass itself smooths out any pixellation while stopping it from progressing due to good glass thermal characteristics.

Although the coating is used on a glass surface on the Ilios Nano, the same coating can be applied to any transparent material and yield the same effect as long as the surface is resistant to prolonged heat exposures and does not deform. This is also one of the main reasons glass is used in our products instead of cheaper replacements.

Alternative materials can be used in a case where replacements are needed on the VAT without exchanging the entire assembly as the coating will deteriorate over long uses, which however is highly affordable to manufacture. The coating can be applied within minutes and installed on the existing VAT.

Thermal Print Head

In order to apply a controlled layer of heat on the VAT surface, a heated print head is used. The same heated print technology is used in devices such as Label printers and other printers with a thermal paper coating. As the thermal print heads are highly affordable and are simple in controlling, this allows the core of the Thermal Masking technology to be affordable as well and provide reliable as well as tested components to ensure a voxel dense layer is exposed each time.

The resolution of the heated layer is directly determined by the resolution of the print head used since the actual coating on the VAT glass surface contains very fine particles of the opaque heat sensitive pigment and can achieve theoretical resolutions as dense as the particles themselves. In our Ilios Nano SLA 3D printer a 300dpi print head is used, which allows feature sizes of up to 84 microns based on the available build area. This resolution is more than enough for producing quality entry level SLA prints as the heated effect smooths out any imperfections and produces a sharp layer for exposure.

Since a traditional printing technique is used, the layers are sent to the 3D printer as image data and no additional connections such as HDMI or VGA are needed. The layers are prepared within the Ilios 3D Suite like with any other SLA 3D printer we provide and then sent to the Ilios Nano for printing. Additionally, the print cycle itself is very similar to the Ilios Photon 2 3D printer as well as the Ilios HD Kits and utilizes most of the functions such as VAT protection, Viscous Mode and other features. Besides the exposing part of the printer, the remainder of the assembly is very similar to any traditional SLA 3D printer although manufactured in a much more affordable way to provide the price at which the Ilios Nano is currently available.

Cooling

As the Thermal Masking technology uses heat for masking each layer, it is important to provide a controlled environment for the coated surface. If the coated surface is not cooled between each layer, the masking surface will dissipate heat slowly, remaining on the surface until cooled to its pigment changing temperature.

To control the temperature of the coated surface, a Fan is used, which is enabled and disabled during the print cycle. The air is channeled from the exterior of the printer and is supplied to the VAT surface when needed. This part of the print cycle also can slightly alter the print speed (by a factor of 1 - 3 seconds) depending on the room temperature, although this effect is only noted in extremely hot environments and a typical room temperature will provide a steady print speed.

Advantages

The most notable advantage of using Thermal Masking is the price of production. Parts are easily available and cost much less than alternatives such as DLP projectors, LCD assemblies and UV Laser gantries or Galvo actuators. The amount of components used is less since there are no additional lenses, mirrors or additional optical components. The most expensive component used during Thermal Masking is the print head as the rest of the assembly has minute costs and complexity.

Disadvantages

As with any technology there are benefits and compromises. In the case of the Thermal Masking technology, the print build area is mainly limited to the size of the Thermal Print Head used. Since in our Ilios Nano 3D printer we use a very common print head, its size is limited. Larger print heads are available, however require more accurate components to move and control. As the build area increases, so does the price, which however is much more affordable than other alternatives.

Besides the build area, the resolution is also determined by the print head used. A 300dpi print head will produce a feature size of 84 microns on the Ilios Nano. A 600dpi print head would yield double resolution of 42 microns. Once again the price is increased as the resolution increases, which however is much smaller than other alternatives.

Summary

As the technology of Thermal Masking has just been invented, there are many ways of improving it as well as scaling it up in the future. The Ilios Nano 3D printer was specifically designed to be manufactured affordably not only because it uses the Thermal Masking technology but because it utilizes much more affordable components. The SLA 3D printer is 90% 3D printed and uses components such as encoded DC motors, affordable spindles and other parts which when combined produce an affordable package. The accuracy of the Ilios Nano does not represent the full capabilities of the Thermal Masking technology and can be implemented in much more accurate assemblies to produce much more detailed results at a 10th of the price of traditional SLA 3D printing products. With funding and more research this could be the optimal technology to use in future 3D printing products and has great potential for expansion and alteration.

Written by Demetris Zavorotnitsienko

You have no rights to post comments. Please Login or Register

Supported By