Overview of Resin 3D Printing and Calibrating the Print Platform with the Creality LD-002H

Updated 12 January 2022

Resin 3D printers are an immensely powerful tool in the hands of a maker and they have never been more accessible. This will be a rundown on this technology, contrasting it to filament 3D printing and an explanation of tools whilst teaching you to general methodology to produce great parts from them. One of the best Resin 3D Printer is the LD-002H UV 3D Printer which we will use to further demonstrate features of a resin printer, the tools you are provided with it, and exactly how to home and level the printing build platform.

By the end of this guide, you will be ready to pour the liquid resin into the resin tank of your 3D printer and start a print. All the resin I use is quality and has been made from Creality. Contents to this guide are as follows. 

- Overview on Resin Printing

- Resin 3D Printing VS Filament 3D Printing

- Creality LD-002H Compared to the Earlier Model

- Explanation of Tools that Comes with Creality Resin Printers

- Leveling and Homing Build Platform

After this guide, the next step to check out is the tutorial How To Complete Your First Resin 3D Print. This is an overview of the workflow to produce a resin 3D print and you can follow through, step by step, to do just that. With that under your belt, the guide Preparing a Computer Model for Resin 3D Printing is your next port of call. That is going to dive into the best slicing software for resin 3D printing and give you a whole bunch of tips and tricks to produce your own custom 3D resin components. The final guide worth mentioning here is Finding Optimal Layer Exposure Time for Perfect Resin Prints which will do exactly what is stated. After having a leisurely stroll through these guides, you will have all the information you need at your fingertips to produce stunning printed models and functional components with this technology. 

If you want a guide on how to Replace your FEP Film, Print with Multiple Colours on a Single Resin Print, or Colourise 3D Printer Resin using Alcohol Inks and Pearl Ex Powder we have the tutorials for you. As always if you have any questions, queries, or things to add please let us know your thoughts! 


Overview on Resin Printing

Resin Printers create models using the principle of photopolymerization. That seems like a complicated word but really it just means the printer is curing liquid resin with light (in the case of these Creality printers a UV light). This is done layer by layer, with each layer stacking on top of each other, to create a 3D Model. Typically, DLP (digital light processing) resin 3D printers have a vertically moving build platform (on which the 3D printed object is formed), a light source, a light mask, and a resin tank. Resin 3D printers can form an object normally or upside down, but usually, they are formed upside down. On timelapse photography, it really looks as though the object is being pulled out of the tank.

So the object is pulled out of a resin tank (also called vat), which holds liquid resin, by the vertically moving build platform. The build platform bounces up and down slowly extracting the model, layer by layer, out of the tank. The build platform is attached to a lead screw which raises and lowers the platform and out of the tank.

The print bed sandwiches a layer of resin between it and the FEP sheet. Now an FEP sheet is a transparent sheet of non-stick plastic which is found at the base of the tank which allows each cured printed layer to peel off after curing. FEP stands for Fluorinated Ethylene Propylene. This process happens many hundreds of times to create a model. Thus the FEP sheet is a consumable, losing its non-stickiness like a non-stick pan that has been used too many times. But instead of resulting in bad cooking, it results in bad printing. If you think you need to replace your FEP sheet check out this guide here to know for sure.

Beneath the resin tank at the base of the machine is a UV projector that projects the images up to the bottom of the tank to cure each layer of resin. Before the light can get to the resin tank there is an LCD screen it must travel through. This screen produces a mask for each specific layer so that the UV light will only cure the necessary sections. As each layer is exposed (potentially thousands of times for a single model) and certain screens will last longer than other screens. See the image below for all the features being talked about labeled on a cross-section of a 3D resin printer. 
 

Cross Section of a DLP UV Resin 3D Printer

 

Creality printers have many different slicers programs that can work with them. Slicing software creates files that the projector can use to cure each layer precisely. It is akin to providing a recipe for an expert chef to follow. A critical factor with upside-down resin printers is the print adhesion and supporting structures. These are set up to prevent a part from falling down due to gravitational pull and are removed once the print is complete. These support structures are created in the slicing software. An example of a model being sliced with supports can be seen below in the free Chitubox Software. I would recommend using Lychee Slicer and have created a comprehensive guide for it found here.

Chitubox Example

 
Note on the Resin. These machines work with photopolymer UV curing resin. This resin cures into a hard plastic when exposed to UV light and is a powerful solvent. Because of this, the resin is a liquid and not like ABS or PLA filament used in FFF printing which comes in large rolls. Parts are not suitable for food or children's toy applications and it can be a skin irritation when not cured fully. Gloves, Eye Protection, and masks are definitely a good investment. You will also want to place the acrylic cover on top when printing, not only to trap the fumes and allow them to be caught by the carbon filter but also to protect the resin in the tank from curing by latent UV light.

Resin and recommended PPE 

Once the model has been printed and removed from the print platform it will require extra processing. You need a way to clean the components as they will be covered in a layer of uncured resin and also because the curing done by the printer is not enough to fully cure the components. I would recommend using isopropyl alcohol (IPA) in a spray bottle to clean the model. Then allow the IPA to fully evaporate off your components (for best results). Keep the run-off IPA and when it becomes fully saturated you will need to dispose of the resulting solvent mixture as hazardous waste. Most waste disposal areas will accept IPA even if it has been contaminated with UV resin.

Once it is fully washed of uncured resin you can then cure the pieces. The most abundant source of UV light is right above us during the daytime and you can simply leave your models out in sun for a couple of hours to fully cure them. To get faster and more consistent results use UV lights or a UV Curing Machine. See below for images of UV LED Strip that you can create a DIY curing station with and the Creality Wash and Cure Machine.

UV Lights and Cure Station 


Resin 3D Printing Vs Filament 3D Printing

Resin printers can work at an order of magnitude finer than fused filament fabrication (FFF) printers. An excellent contender in the resin printing landscape for makers is the Creality LD-002H 3D printer and an excellent filament 3D printer is the Creality Ender 3 V2, see below for images of these printers. Resin printers can produce layer heights as small as 30 microns. Because the layers are significantly finer you get a part that looks more like an injected plastic part. You can also get resins nowadays that produce components that are comparatively as strong as filament ABS printed parts. These machines are faster than FFF printers. If you want to print multiple parts at the same time, instead of a single part, so long as the same height there is no time penalty. Currently, resin printers have smaller overall build areas than filament printers of the same value but there are some huge maker-level resin printers in the horizon.

Resin Vs Filament Printers

Resin 3D printers use fewer moving parts than a fused filament fabrication 3D printer. This is good for maintenance, resulting in less overall maintenance than filament printers, but there are some sections that will require attention. First, the FEP film layer is a wearing part that will need to be replaced. As the film has the print pulled from it many thousands of times this is not surprising. The UV LED and LCD masking screen are also parts that will need to be replaced eventually as they will slowly get darker over time.

Resin printers do require extra processing after printing. Supports are done in a similar way to fused filament fabrication. So make sure there are no unsupported islands or large overhangs. However, keep in mind that print is occurring upside down so if there was a large bridging section instead of the area sagging they would instead bow upwards. You can hollow out models and create internal structures in a similar manner to filament printers as well.


Creality LD-002H Compared to the Earlier Model

Now I have been printing with the earlier design the Creality LD-002R Resin Printer for a while now, so allow me to make clear the differences and similarities between this older model and the newer LD-002H.

Worth noting both printers have air filtration through the activated carbon filters. Both also have indicators in the tank to tell you how much resin has been put into the tank and provide fully customisable settings in the user menus. The two printers can be seen in the image below, aesthetically at a glance, the only real difference is the colour shift from orange to red for the acrylic cover. Everything structural that should be made from metal is and it results in very sturdy, heavy-duty products. They also both have very satisfying On/Off buttons.

Creality Two Excellent UV Resin Curing 3D Printers 

The major differences between these two printers are as follows:

  • The LD-002H printer has a build area of 130mm x 82mm x 160mm high. This means the horizontal axis area has increased by approximately a third from the previous model. 

  • The LD-002H uses a 2K monochrome display instead of an RGB display for the masking screen. Due to the monochrome screen having fewer layers, thus letting more UV light through, it drastically reduces curing time from ~12 seconds a layer down to ~2 seconds. This will decrease print times (particularly when you consider a single print can have thousands of layers). A monochrome screen also results in an increase in the longevity of the screen's life by up to 400%. This screen is also a higher resolution which means your printed models will be more defined.

Explanation of Tools that Comes with Creality Resin Printers

Along with the Creality LD-002H 3D printer or Creality LD-002R 3D printer, you will receive a number of extra tools and supplies in the box. This will go through the purpose of these. 

Worth noting here as we are unboxing the printer Creality is a little sneaky here and basically disguises the Build Platform inside the foam packaging so make sure not to throw this out until you get that platform out. It does mean it is very securely packed and won't get scratched so can't fault Creality there. See below for an image of most of the tools that come in the box.

Some of the Tools that come with the printer
 

Below is a list and considered explanation of what each of the tools is for and how they are used of everything that comes in the box when you purchase a Resin Creality printer.

Sharpened Metal Spatula: Used for removing a 3D print from the build platform by sliding it underneath the model

Plastic Spatula: Very useful to help clean the FEP sheet and remove unwanted cured resin if it is floating around the tank

Soft Bristle Brush: Good to gently clean the parts and models in combination with IPA.

Strain Filters: Good practice is to keep the uncured resin in a sealed container. If left out in the air for too long it can affect the print result. These strain filters make it easy to pour the resin out of the tank back into a container whilst not letting cured resin contaminate the good resin. 

USB Stick: This is what we will use to bring the files from the computer to the printer. These USBs also already have models on them so if you just can't wait to print something you can just plug the USB right into the printer and start. I would highly recommend leveling and homing the Print Platform before starting.

Allen Key: There are three Allen keys that you can use to effectively pull the entire resin printer apart. The most important one at this stage is the smallest size which we will use to correctly level and home the Build Platform.

Print Platform: This is what will be printed on. Has an exposed aluminum surface that has been treated with light scuff marks to improve adhesion. The top of the print platform is tapered to help resin fall off. This can be found tucked away in the foam. Try to keep the raw metal print side smooth and unscratched. A scratch-free surface will create better prints.

Resin Tank: This tank (or referred to as vat) comes with a FEP sheet already installed on the bottom, and has clear resin level markers on side of the tank. Do your best not to scratch the surfaces of the FEP sheet.

Spare FEP Sheet: This is an FEP sheet film that sits at the bottom of the tank with instructions on the back on how to install it. You will not need to use this at this point as there is a FEP already installed on the Resin Tank. If you ever do here is the special technique I use to keep it taut. See below for images of an Uninstalled FEP, Uninstalled Tank, and installed Tank.

What and Where A FEP Goes
 

Manual: Comes with Specifications of the machine, a warranty card, and instructions.

Power Cord: Plugs directly into the machine

Safety: The Creality LD-002R 3D printer came with gloves and masks but the LD-002H did not. Make sure you have safety equipment on hand as it will be needed. The goal is to prevent resin from making contact with your skin and stopping any fumes from getting inside you. Keep PPE nearby as it only takes a small lapse in concentration to end up with a resin spill.


Leveling a Print Platform of a Resin Printer

The very first step for setting up any Resin 3D Printer is to level and home the Print Platform. The goal here is to make sure the print platform is perfectly flat in relation to the surface of the LCD screen and has a zero point exactly where the top of the FEP sheet is. This guide will focus on Creality Resin Printers but this process is basically the same for all resin machines. The process is as follows and there is an image further below showing this process.

1. Remove the Tank by unscrewing the two large thumbscrews knobs on either side of the Tank. You can do this without lifting the print platform mount.

2. Plug in your machine and using the touch screen raise the print platform mount to the halfway point. You can find this option by clicking on the Tools button then the Manual button. Press the Triangle symbols to move the mount (you can move this manually by spinning the coupler manually).

3. Now attach the print platform to the print platform mount. Unscrew the large thumbscrew know which is onto the top of the mount and slide in the build platform. Then screw that thumbscrew finger tight.

4. Place a normal A4 sheet of paper over the screen where the tank was, it is okay to leave the screen protector on at this stage. This is to emulate the height of the FEP Sheet. Some printers come with a special calibration card that you can use instead of paper.

5. Around the edges of the build platform are four Allen Bolts each in a slot hole. Unscrew them so that they are all loose with the Allen key supplied.

6. Having done this tap the Home button (represented with a house symbol) on the touch screen. This will bring down the build plate to the level of the LCD screen surface. 

7. With it resting on top of the A4 sheet, push down just lightly and evenly on the build platform. Whilst doing that slowly tighten all the bolts bit by bit going around in a circle. 

8. With that the printer has been correctly homed. Now we can tell the build plate to go up and out of the way. You should also pull off the protective surface ontop of the LCD screen.

9. Reattach the tank which will have the FEP already installed from the factory. Take note of how tight the FEP sheet is, is effectively like the skin on top of a drum.

Step by Step to level the platform
 

Now, all we need to do it fill it with some fresh resin (say the 2/3 mark), plug in the USB stick with files, and press play because your resin printer is ready to start printing.

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