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8 Essential Design Rules for Mass Production 3D Printing

If you're designing a 3D printed product for mass production, here are a few things that you really need to consider to make sure that you're reducing your cost and getting the best possible product out of your design.

1. Avoid Thin Walls

First of all, make sure that no wall has a layer thickness less than 1 mm. A standard FDM printer nozzle is 0.4 mm, and in order to make sure that you have a nice reliable wall, you want to be able to use two nozzle widths, which is 0.8 or up to 1 with side extrusion. So make sure that every feature of your part is at least 1 mm in width to ensure that the nozzle is creating a good quality vertical wall.

In the vertical direction, you can go a little bit smaller than that based on what your layer height is, but generally, just assume that you have a 3D pixel size of 0.4 mm. So make sure that you're going at least 1 mm thick to ensure that it's reliable and strong.

Virtual diagram showcasing orange lines where your walls should be extended to on your 3D Print.

2. Reduce Overhangs

Avoid horizontal overhangs on a part that has a single arm sticking out the side. We have to put support underneath it. This both causes that area that is supported to be slightly deformed and creates a lower quality appearance. It also adds on additional labor of having to post-process that part, whereas a part without that overhang could go straight into a box and ship out the door, which is way more affordable. The way to avoid overhangs like this is to just go ahead and put a chamfer underneath it, and we have a whole video talking about this particular topic.

Virtual 3D Model showcasing points of overhang

3. Simple First Layer

Make sure that the first layer of the print is as simple as possible. Avoid sharp corners, don't put text on the first layer. When the first layer is going down on a print bed, you want it to adhere reliably and well, and in order to do that, you want it to be as simple as possible. You don't want a lot of detail, and you want to get as close to basically a perfect circle as you can. Again, we've discussed this in another video in quite a bit of depth of how to optimize and the direction to go, but just eliminate as much detail as you can and make it as round as you possibly can.

Chart depicting three different 3D print first layers ranging from worst to best, left to right.

4. Round is Better

With that rounding is very important. Make sure that you round or fillet every vertical edge of your part. The reason for this is it will improve the print time of your part because sharp edges with the nozzle of the printer moving around cause it to slow down and speed up because it has to go to the corner, basically stop and change direction. If you round that outer corner, the nozzle is able to travel through it like a car going around a tight turn. If a car had to go to a turn, stop back up, and then go the opposite direction, it would make the lap a lot slower. But if you round that corner, the nozzle is able to fly right around the edge. It's able to print faster; it creates a better-looking part and is just more efficient overall.

Photo showing how rounded edges create smoother transitions with 3D prints

5. Avoid Cavities

Do not put cavities into your part. This is a vestigial idea from old manufacturing methods. Everyone is used to trying to remove material from parts, but 3D printing doesn't have this issue because we're able to fill in large volumes with a honeycomb structure, which makes the part stronger. You can actually make a fully solid large cube with all six walls enclosed and have it be an enclosed volume that you could never make before. And do remember that this is a different type of process. If you want more strength, add more volume. Historically, everybody's used to cutting out material, but by cutting out material, you make thin walls. When you're printing those thin walls, they can be weak. In addition to this, remember that the layer lines do exist and don't create thin features that can cause the layer lines to unzip. We don't want those stress concentrations. Go for a thicker, chunkier part to make sure that you have the strength that you need.

photo shows two different 3D printed products, one with cavities and one without.

3D Printed model showcasing an interior honeycomb structure for additional support.

The red object on the left has a honeycomb structure infill printed for extra support (as seen below) whereas, the green object on the right displays massive cavities which are not as supportive for the product.

6. Textures

This is a good time to remember that there are layer lines. Design for the layer lines. Put a texture on your part, and that will hide the layer lines. Don't push for higher resolution; that'll increase your cost. Apply a texture either in CAD or request a texture to be applied by us where we can digitally add a little bit of noise to the outside of the part so that it no longer shows the layer lines.

7. Compliant Features

If you have a high tolerance feature, make it compliant. Don't attempt to go for a really high tolerance center hole in the side of a block. This can create a lot of extra cost because it has to be very carefully checked, and often times you have to compensate for material shrinkage and other sorts of factors. Instead, design the hole to be compliant. Give it some flex features, either make some cutouts on the edge and make it a little bit smaller or use options like grip fins to allow it to grasp the part that has to be inserted into it.

8. Minimize Bed Contact

Minimize bed surface contact. In order to mass-produce a part with 3D printing, you don't want to have people have to pull your part off of a printer. But if it's a pyramid with a big old wide base that fills the entire print bed, it's going to be very difficult to not remove it manually. If you can design it to have a minimal contact surface on the first layer, then it becomes "ejectable", where our machines can automatically remove them and then move on to the next part. It also eliminates the surface defect of that first layer looking different from the rest of the part. So design your parts to sit on an edge at a 45° angle. If you're making an electrical enclosure, instead of printing it broadside down, turn it at a 45° angle, and now you can mass-produce it very quickly, very reliably, and almost everything will be in the correct plane to where it's all very strong.

This 3D virtual model shows the most ideal way to minimize your bed contact when 3D printing.

Final Thoughts

To summarized everything discussed, with just a few rules in a single statement: make your part thicker, make it rounder, and minimize the first layer contact area, and avoid supports as much as possible. Those are the main things; otherwise, you're going to end up with a part that is really thin and looks like some kind of terrible injection-molded part that will end up causing problems in the 3D printing process. You cannot put a square peg into a round hole; printing is a different process. You have to design for that process; otherwise, you will be disappointed with the result. So hopefully, that was a good summary of all the kind of main things to be aware of when designing for FDM. You want to make sure that you have these principles in mind when you're designing your part to make sure that it's fully optimized for mass production.

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