Category: Troubleshooting

How to Make a Silicone Mold Out of a 3D Printed Piece

If you have a 3D printer and want to create multiple copies of an object, or if you want to cast your 3D printed piece in a different material, you might want to make a silicone mold out of it. Silicone molds are flexible, durable and easy to use.

What You Will Need:

  • A 3D printed piece that you want to make a mold of
  • Silicone rubber (you can use either tin-cure or platinum-cure silicone, depending on your preference and budget)
  • A mixing container and a stirring stick
  • A mold box (you can use any container that is slightly larger than your 3D printed piece, such as a plastic cup or a cardboard box)
  • Mold release agent (such as petroleum jelly or spray-on mold release)
  • A knife or scissors

Step 1: Prepare Your 3D Printed Piece

Before you make a mold of your 3D printed piece, you need to make sure that it is clean and smooth. You can use sandpaper, files or other tools to remove any rough edges or imperfections. You can also paint or prime your 3D printed piece if you want to improve its appearance or durability. However, make sure that the paint or primer is completely dry before proceeding to the next step.

Step 2: Apply Mold Release Agent

To prevent the silicone from sticking to your 3D printed piece, you need to apply a thin layer of mold release agent over the entire surface. You can use petroleum jelly, spray-on mold release or any other product that is compatible with silicone. Make sure that you cover every detail and crevice of your 3D printed piece. You can use a brush or a cotton swab to spread the mold release agent evenly.

Step 3: Place Your 3D Printed Piece in the Mold Box

Next, you need to place your 3D printed piece in the center of the mold box. The mold box should be slightly larger than your 3D printed piece, leaving some space around it for the silicone to fill. You can use any container that is sturdy and leak-proof, such as a plastic cup or a cardboard box. You can also use hot glue or tape to secure your 3D printed piece to the bottom of the mold box.

Step 4: Mix and Pour the Silicone Rubber

Now, you need to mix and pour the silicone rubber according to the manufacturer’s instructions. You can use either tin-cure or platinum-cure silicone, depending on your preference and budget. Tin-cure silicone is cheaper and easier to work with, but it has a shorter shelf life and may shrink slightly over time. Platinum-cure silicone is more expensive and sensitive to contamination, but it has a longer shelf life and does not shrink.

To mix the silicone rubber, you need to measure the correct ratio of part A and part B (usually 1:1 or 10:1) and pour them into a mixing container. Then, use a stirring stick to mix them thoroughly until they are well blended and have no streaks. Be careful not to introduce any air bubbles into the mixture.

To pour the silicone rubber, you need to slowly and carefully pour it over your 3D printed piece in the mold box. Start from one corner and move across the surface in a thin stream. Make sure that you cover every detail and crevice of your 3D printed piece. You can also tap or shake the mold box gently to help release any air bubbles trapped in the silicone.

Step 5: Let the Silicone Cure

After pouring the silicone rubber, you need to let it cure for the recommended time (usually between 6 and 24 hours) at room temperature. Do not disturb or move the mold box during this time. You can also place the mold box in an oven at a low temperature (around 60°C) to speed up the curing process.

Step 6: Remove Your Silicone Mold

Once the silicone is fully cured, you can remove your silicone mold from the mold box. Carefully peel off the silicone from the sides of the mold box and gently pull it out. You should be able to see your 3D printed piece embedded in the silicone. Then, use a knife or scissors to cut along the edge of your 3D printed piece and remove it from the silicone. You should now have a perfect replica of your 3D printed piece in silicone.

Congratulations! You have just made a silicone mold out of a 3D printed piece. You can now use this mold to cast

This post wrote itself over the weekend. I was printing a bracket for my wife. Estimated print time was about 32 hours. Before I went to bed on Saturday, I checked the amount of filament and realized that I needed to change spools in order to be able to finish the print.

M600 to the rescue. So far so good. Simple task, just press M600, let the nozzle get out of the way. Take out the old filament, put the new filament in, press resume. Good to go then I can go to bed.

When I did so, I pressed the button for one of the macros that I created, “Extrude new filament through Bowden tube.” As soon as I did, the machine started to home itself. Now I’m in trouble. You see, because of the size of the bracket that my wife needs, I had to use up pretty much the entire bed. What this means is that when the machine homes it would come down on top of the already printed material. I had to e-stop the machine. Now what? Well, I measured the height of my print. Dropped that much material through the table in Cura, then printed the rest of the print. When I glued them together I ended up with a tiny seam. But a little bit of primer over the seam made it disappear.

Then I removed the homing sequence from my macro.

I saw a user in a forum asking for help with bridging. They were trying to create a large print that had many bridging features that were intended to be straight across and ended up being droopy.

When someone asked what they had done already, they responded with “I slowed down my speed to help the bridging out.” In most cases, this is the opposite of what needs to happen. If my print has a lot of bridging features I typically speed it up. If you think about the mechanics of what is happening here, heat is being applied the entire time that your nozzle is extruding. So, the longer something takes with heat being applied to it, the more it will sag as a result.

Your printer is supposed to be able to create a solid outline on the bed of your printer. Sometimes, though, your print will have little gaps in it and it will look like Morse Code. Most of the time that I see this, it is the result of a user having changed something regarding their extruder. Their gear may have worn out and they replaced it, they changed filament or nozzles and forgot to calibrate their e-steps, or their extruder is starting to fail.

For troubleshooting, first make sure that everything is mechanically sound. Take a look at your extruder gear and make sure it’s not missing any teeth.

Once you have determined that everything looks good, calibrate your e-steps.

Sometimes I print parts that have a top surface that look like a riverbed. There are valleys and branches going all across the surface of the part. This is usually a result of the nozzle being too close to the bed. Mechanically, there is too much filament coming out of the nozzle for the amount of space between the bed and the nozzle. When this happens the filament flows into other areas of the print and creates these valleys.

In short, your nozzle is too close to the bed if you have this. Adjust the height or redo your bed level.

Some 3d printers end up with rough top layers. One thing that you can check if this happens to you is the rate of filament flow. Filament flow is affected by a couple of things, the most common issues are:

  • Flow rate setting in slicer. I normally set my flow rate to 105% – 110% for the first few layers, then turn it down to 100%. If this is set too high then your printer is adding more filament than you might need, resulting in a rough surface.
  • Extruder calibration. Run a simple extruder calibration to double check that you are extruding the amount that you think you are. If you are overextruding, you might be causing problems for yourself.

Although there are a couple of things that can cause parts to curl, I have found that it is usually related to the environment that the printer is in. If your parts initially print good layers, and then the print curls up away from the bed I would initially start to investigate whether the printer is in line with an HVAC vent or in a very drafty area. Ideally, put it in an enclosure.

A lot of times I’ll see someone asking for help online that goes something like this:

“I just changed the bed on my 3d printer to XYZ, bought a new extruder from LMNOP brand, updated my retraction, temperature, and speed settings, and now nothing works. How do I fix it?”

My advice to these folks is almost always to back it up a bit. What ends up happening is that they change so many things all at once that it’s impossible to tell which configuration change or setting change was the one that threw everything off.

I recently turned on and homed my 3d printer, only to find it grinding against the side shortly afterwards. Here is what I found. I did a quick check of my limit switches (seems to be a common cause) and found out that they are good. It turned out not to be necessary for me, but I could also have checked the voltage to the motors.

What it turned out to be was that the cable that provides power to the hotend fell down in front of the limit switch. Then when I homed it, the axis wasn’t able to reach the limit switch. The fix involved a quick zip tie of the cable harness to make sure it didn’t happen again.

After a while, things wear out on your printer. One item that is often overlooked is the connection on either end of a Bowden tube. If the teeth that hold the tube in place aren’t doing their job correctly, the tube can move back and forth as the extruder extrudes and retracts filament. The result of this is that you can end up with zits and voids in your final print.

To fix this, replace the fittings on either end first. If it still happens, replace the tube too.