Designing a Resin 3D Printer Part 1

Having seen the amazing detail that a resin printer can produce and the need to be able to produce printed models with this high level of detail for the college i am currently attending. A resin printer is the way forward.

The basic principal essentially is that a layer of uv or daylight resin is cured layer by layer in a certain shape to create 3 dimensional model. How this is done varies greatly. There is different methods of delivery the curing light to the resin, also how the mechanics works, how the build plate functions etc.

Curing System

Now i will explore the standard methods of how the resin is cured.

Such as:

  • UV Laser
  • DLP Projector
  • LCD Photomask

UV Laser

This system uses a laser beam to trace out a 2 dimensional shape, like a FDM printer except using a laser. Unlike a FDM printer this process is extremely rapid since the laser is moved using a galvo system used in most uv laser based printers. Galvo system is a set of mirrors each attached to their respective galvo motor orientated in the xy. The rotation of the mirrors reflect the laser in the desired direction. Problem with  Galvo system is it is expensive and very technical. Lasers are inherently dangerous also.

DLP Projector

This system uses the light image from DLP projector to cure the resin. The benefit of using a projector for curing is that the image is displayed at once. This allows for faster layer curing speed. The setup is easier in comparison to a uv system and cheaper. It is a proven technology with many diy setups using this due to the ease of building this setup.

LCD Photomask

This system uses a lcd screen to control the light image displayed to the resin. This possibly could be the future of resin printing as lcd panels are abundent, cheap and the resolutions of these displays are improving constantly. The problem with this technology so far is the fact that standard lcd have a uv filter in built which makes it unsuitable for uv curing. There are resins that can be cured using the normal range of wavelength outputted by a lcd screen. But the selection of these “daylight” resins are low.

Which will i choose

For this project i have decided that a DLP projector system is the easiest to implement and considering that cheap DLP projectors are easy to come by.

 

Build Platform

There are two standard methods of how the resin model is manufactured.

Such as the:

  • Bottom Up Method
  • Top Down Method

Bottom Up

With this method the build plate which the resin adheres lay just below the surface of the resin. The resin which is contained in a ope top container. The curing light hits the top of the resin, this cures a layer which is adhered to the build plate. For the next the build plate is lowered further into the container of resin and then this layer cured. This keeps happening until the model is built up. Problems with this setup is that the model size is limited by the size of the resin container also resin can be meniscus which means it will have a curve at the top. This adds inaccuracy to the prints. The benefit of a bottom up  is that it is simple, cheap and can be rapid.

Top Down Method

With this method the curing light shines through the transparent bottom of the resin container. The build plate for the first layer lower to the desired distance from the surface of the bottom part of the container. As each layer is cured the build plate moves away from the bottom surface. An inherent problem is the sticking of resin to the container surface. There are a large range of methods of preventing this. Firstly some kind of layer of material prevents this such as PDMS or Teflon sheet for example. A lot of machine use a peeling mechanism which essentially peels off each layer. There also a number of ways this is done as well.  The benefits of this method is accuracy. Since the layer is being produced at the bottom of the container there is no meniscus effect and the force of the build plate squeezes resin between it and the bottom surface of the container. Another impressive benefit is that model is not limited by the size of the container. The z axis height of the model is only limited the z travel of the build plate. Major problem as stated is the adhesion of resin to the container, but there are clever ways to resolve this.

Diagram of Build Method

bottom up vs top down

What build platform method will i choose

I have decided to go for the bottom up method as this is the industry standard for resin printing. Initially i was hesitant about going this direction due to the adhesion problems, but from research i found a solution which i will go into detail later on.

Preliminary Design combining DLP and bottom up methods

I have sketched rough design of how these two will be combined into a functional printer. This only to give myself a rough idea of how it will come together and will probably be changed.

DLP Resin Printer Diagram

DLP resin projector

You can see from the diagram how the container is designed and how it overall works. In the diagram a mirror is used. This is not essential as you can place the projector under the build container, but is a good way to make the machine more compact. For my first prototypes i will most likely just have the projector underneath for simplicity sake.

Another Rough Sketchup Model of a possible design layout

Sketch Up Designs.png

I will use sketch up to quickly rough out ideas. Next i will create of a number of designs and choose from the best for the final design. But as this happening i will be testing a unfinalised prototype in the mean time.

To be continued

 

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