Understanding Design for Manufacturing (DFM) is critical to a successful build, even during the 3D printing phase. The right design with the wrong 3D printing materials will lead to poor results. There are several kinds of 3D printing materials available, each of which uses a unique manufacturing process. However, PLA is a common choice, because PLA is widely popular as a material for amateur printers, and its production price is relatively cheap.
The following guidelines should be followed when designing parts to be printed in PLA, using PLA for prototype design, or determining whether PLA is suitable for your design.
When to use PLA
PLA (polylactic acid) is a biodegradable material made of corn starch, which is suitable for early prototyping of simple geometric parts. It is suitable for quick form checking, but should not be used when high resolution printing is required. The melting temperature of PLA is about 130 ° F, so its use in high temperature environment or mechanical function is limited.
PLA is one of two common FDM printing technology materials, and the other is ABS. The main difference between the two is that PLA uses a rigid support system while ABS uses a soluble support system. This means that the structure (such as overhang) to be supported during printing in PLA will be rigid and needs to be removed by hand (usually with pliers) after printing. This can lead to rough surfaces, and if the wall or feature is too thin, it usually causes the part to break.
DFM of PLA
As mentioned earlier, DFM is also suitable for 3D printing, although its strength and stiffness are much lower than DFM in machining or injection molding. Please remember the following rules before clicking "Checkout" after obtaining instant quotation from the wonderful platform of virtual TV:
Rule 1: 45 ° design
FDM printing can support itself, with a maximum angle of 45 °. When the angle exceeds 45 °, PLA will add a rigid support to prevent sagging during printing. You may want to avoid this situation because the support material will not only increase the cost, but also produce a rough surface finish after removal.
Also, it is important to note that for any slope or curve on the PLA, you should expect to see steps on the surface. Because of the low resolution of this material, you cannot snap to a gradient surface.
Rule 2: Minimum wall thickness of 1.5 mm
In PLA, wall thickness is critical because low resolution printing usually fails without a solid support layer. Therefore, it is recommended that the acceleration should be at least 1.5mm, but preferably larger.
In addition, since PLA uses the process of melting plastic and then cooling layer by layer, there is always a risk of warping. To minimize the possibility of warping, high or long walls should be supported or ribbed to provide rigidity. This also applies to posts or pins.
Rule 3: 0.4 mm offset of interlocking parts
Any interlock components need to be offset. You never want to design an inch pin for an inch hole. Especially for PLA, we recommend a total offset of 0.4 mm. For cylinders, the clearance is 0.2 mm on all sides or 0.2 mm on each side of the square.
Rule 4: Carving>Relief
It is often necessary to brand or label your products. Although PLA is not good at capturing small details, there is a best practice to meet this demand - sculpture, not relief. The main reason is that the relief is usually very thin, which will lead to poor support during the design process.
For relief, it is better to go deep into the design of 0.2 mm or so, and use at least 16 point bold font to ensure that the label is printed clearly.
Rule 5: Brass insert>thread
For low resolution materials, thread design is never a good idea unless you have a high pitch. In most cases, it is better to use heated brass inserts. Due to the low melting temperature of PLA, a simple soldering iron will help to slide the plug-in into the designed through-hole relatively easily.
Key points
When you start the product development lifecycle, it is great to use PLA for prototyping, but as with any manufacturing process, it is important to understand the design requirements of the build process. Although it may be the cheapest option among available 3D printing materials, if you choose it instead of the more appropriate option, you may face the risk of printing failure. More importantly, you can learn from the prototype. On the other hand, if it really suits your needs, or if you design these guidelines for the first prototype, it can bring huge cost savings before you move to higher quality printing options.
