3D printing of drill holes, threads and hinges

Drill holes are indispensable for many components. This applies to both conventional and additive manufacturing. The small but subtle difference: In 3D printing, thread inserts can be printed directly. The printing of drill holes is always recommended if the printed material does not permit subsequent processing by drilling because it is too brittle or too thin-walled and mechanical processing would lead to defects or even rejects afterwards. If holes are to be printed, precision and feasibility are directly dependent on the direction of the print. Holes that lie horizontally in the installation space of the printer always become somewhat oval due to the production process, while holes that are to be produced vertically can be made with sufficient roundness.

Important to know:

In 3D printing, very tight tolerances in the hundredths or thousandths of a millimeter range cannot be produced during printing. A 2.0 mm hole is usually made as a 1.8 or 1.9 mm hole - the reason is that material is always applied during printing. Special attention should be paid to the tolerance deviations to be expected when printing hinges or fits. Hinges from 3D printing can be printed without any problems, but a tolerance value must be included for the bores. This ensures that the cotter pin, which ultimately connects the two parts of a hinge, also fits into the hole. For fits that require the tightest tolerances between the bore hole and the cotter pin, it is essential to observe the following during design:

• Press fits without clearance: specify bores 0.1 or 0.2 mm larger.
• Clearance fits: Specify holes larger than 0.2 mm

In general, the following applies to holes in 3D printing: the larger the hole, the more reliably you will achieve a precise result. The minimum size of a drill hole must not be less than 2 millimeters. From about 5 millimeters, the printing of drill holes in additive manufacturing is possible without any problems.

Example:

In the case of the housing shown below, the drill holes would have been too small. For this reason, threaded inserts were used. Images: Visualization and printed component.

Threaded connections allow components to be joined permanently, reliably and, above all, detachably. Threads can also be easily created in 3D printing, provided certain properties are taken into account. In general, a thread can be printed, whereby the larger the thread, the easier it is to print.

Threads from M5 onwards can be implemented well in 3D printing, and threads from M8 onwards can be printed without any restrictions or compromises. In case of doubt, we recommend printing only the core hole and manually recutting the actual thread afterwards.

Depending on the starting material, printed threads may suffer losses in the area of stability. Ideally, therefore, threads in 3D printed components should be implemented from a combination of printed core hole and thread insert. This enables maximum precision and functionality even without costly reworking.

Important to know when it comes to thread 3D printing:

• The larger a thread, the easier it is to print.
• Starting from M8, threads can be realized in 3D printing without any problems and usually without reworking.
• For small threads, just print the core hole and re-tap the thread afterwards.
• By using a thread insert in 3D printing, maximum stability and functionality can be ensured for threads.
• Even with careful manufacturing, most threads, especially smaller or fine threads, need to be recut.
• Re-measuring the threads with test gauges is possible, but deviations due to printing tolerances must be taken into account.

We would be happy to advise you in detail in a personal meeting on the specific requirements when it comes to threads in 3D printing.

The production of internal channels with sophisticated, intricate geometries is one of the great advantages of additive manufacturing. What cannot be realized with conventional manufacturing methods can be achieved in 3D printing with sufficiently adapted design. When manufacturing channels, however, it must be taken into account, especially when printing in a powder bed, that the powder must be removed after printing using compressed air. This is not always possible with particularly small or strongly intertwined channels. The length of the individual channels must also be taken into account in the design - the longer a channel is, the more critical is the removal of the powder.

Here, we recommend a conical design of the channels with a small opening and a channel that becomes larger towards the inside. This ensures thorough removal of powder in many cases. Transparent materials are also advantageous when channels are to be printed. This makes it much easier to see adhering powder in internal areas.

Please contact your Solution Partner before placing an order, especially in the case of tolerance-critical components, components with channels or if you do not have your own experience in 3D. It may be necessary to align components in the installation space separately in order to ensure the desired precision. We will be happy to advise you on this in a personal meeting, without obligation!

As an alternative to classic, mechanical hinges, so-called film hinges are available in many cases. Film hinges do not have a folding mechanism, but are made of a deformable, fatigue-resistant material. Film hinges are best known from the lids of shampoo bottles or similar everyday objects. Very impact-resistant, low-fatigue plastics such as PP or TPU can be considered as materials for film hinges. For film hinges that are not frequently bent, PETG, PA12 or PA11 can also be used. These materials are particularly recommended if workpieces are to be bent into shape only once. A practical application here would be, for example, promotional gifts that are to be printed flat and folded for use (folding boxes or similar).

When 3D printing hinges, it is important to note:

• Classic, mechanical hinges with a cotter pin connection can be printed if the appropriate tolerance adjustments are taken into account during design
• Film hinges without a mechanism are easier to print but, depending on the material, are not always suitable for frequent operation.

We would be pleased to advise you in a personal meeting on our possibilities to realize threads, drill holes and hinges economically, quickly and precisely. Just write us a message or give us a call right away! We are already looking forward to realizing your printing ideas in the field of "3D printing parts joining" soon!

_{This blog is machine translated, for the original text please change language to: German.}

Read more All about the design of additively manufactured parts:

• Design guidelines for additively manufactured SLM metal parts.
• Topology Optimization
• The optimal part without 3D printing errors