10 things we usually redo in startups’ CAD models before manufacturing

Oftentimes, we are approached by startups to develop nodes for the existing solution or prepare the item for manufacture. In this situation, customers typically send us their 3D models of the upcoming products which is the most transparent language for us. So we are quite happy to receive them from a client, as they relieve us from the long-hours-discussion burden.

As it naturally occurs, the scope of work may become much larger than it was expected, if 3D models contain gross mistakes. In the worst case scenario, if errors are not fixed, further product development process is not feasible.

This article speaks about the commonest failures in client’s 3D models and possible ways of eliminating them before turning to a manufacturing company.

1. Interferences between parts

The interference between CAD assemblies should be examined with the built-in utilities. Even if an assembly appears to be perfect, there could be internal component interference. One object being superimposed on another is referred to as interference. This occurs when two parts are being assembled and one component "fits" into the other. For example, you accidentally create a shaft with a diameter of 50 mm and try to fit a bearing with an inner diameter of 45 mm onto it. The software will let you put the parts together, but it might prevent you from doing any analysis until the error is fixed.

An illustration with the interference between parts is provided below.

2. Places for wiring, hydraulics, pneumatics are not worked out

When building devices from the clients' models, there might be issues with wiring because models do not allow additional space for it. Once the wiring is built up and connected, it might turn out that the board with it does not fit in the enclosure.

In the model with hydraulic or pneumatic wiring, the client might forget to consider the maximum bending radii of the wires. It may seem that there is enough space for the wiring while using the CAD program, but that is only at first glance. Because of wires’ rigidity and the potential for damage, we will not be able to bend them as shown in the image.

The picture shows a device enclosure where the wire built in by a client could not be fitted into the enclosure.

3. Treating sheet metal improperly

The improper treatment of sheet metal is the following common misstep. When working with sheet metal, designers may not consider the bending radii. If the entire piece is built incorrectly, we should rework it, as the size of the facets changes after the metal has been bent.

See the example below.

4. Building in basic parts incorrectly

Oftentimes, clients use basic parts incorrectly. The simplest example is the use of bearings. Bearings can support 3 types of load: radial load, axial load and their counterbalance. For each of these, a specific type of bearing is used which can take a specific load. Clients frequently place a bearing of the necessary size without taking the bearing load into account. If it doesn't stand up, we need to redesign the assembly and choose new parts.

Axial, radial, and angular contact bearings are different types of bearings that can sustain axial, radial, and combined loads. From the outside, it is challenging to determine which bearing is in front of us, as in the figure below, but their internal design and cost are different.

Similar-looking bearings can vary in cost by several times.

In table 1, we have compared the cost of 15x32x12 bearings.

5. Production-aware design

When designing a part, it’s necessary to assess the equipment that will be used in the production process, the level of precision the part requires, and the available technology. The client oftentimes omits to consider this. They visualize the final product and transfer it into a CAD program. When it comes to realizing the idea, they are staggered by the cost.

Designing a product requires taking production costs into account.

Two similar parts are shown in the illustration below. The only distinction is that the first part’s interior corners are rounded.

A slight design change leads to a significant difference in manufacturing cost. The first part can be made for $100 on a milling machine in a few hours, whereas the second one will require an electric discharge machine that will take about a day to produce and will cost us $1000.

6. Model parts cut into one another in the end positions

When 3D modeling vehicles, robots and devices with moving elements, it is a regular mistake to design the device with the wheels facing straight. When the suspension and moving element nodes have been designed, the design of attachments, enclosures and other ancillary components is initiated. This leaves the suspension in a neutral position: wheels pointing straight ahead, shock absorbers unloaded. As a result, we often find the elements cutting into one another when simulating the operation of the transmission or steering wheel.

See the example below.

7. Checking assemblability

When designing a device, it is necessary to check the individual parts and assemblies for assemblability at each stage. It happens frequently to receive a model of a finished product only to discover that it cannot be put together in the actual manufacturing process. The model may show that the assembly's parts were put together by passing through one another and fitting it together, however, this might turn out unworkable. This can be seen in the illustration below. 

The figure illustrates the customer’s model in which the yellow part was solid and welded. It needed to be fixed into the red part. However, this was not possible because the welded finished part would not pass through the red part's holes.

We had to separate the yellow part into components and rework the assembly.

8. The model files are not sorted out

All components, assembly parts in the CAD system are numbered, instead of being sorted out into folders. This is not a good way to approach the stage. It is preferable to make distinct folders for purchased parts, metalware, etc.

There was a case when our client was horrified to learn how much manufacturing his product actually cost. Some parts could be made only by punching and it would be necessary to develop a tooling. After talking to the customer, we found out that stamped assembly parts could be purchased because they were mass-produced and therefore had a low price, not commensurate with the cost of piece production.

For convenience, it is preferable to organize the assembly's components into folders. Fasteners, for instance, will be in the "Metalware" folder, while items that can be bought and do not need to be made separately will be in the "Purchased" folder.

The image below shows a breakdown of an assembly into folders as an example.

9. Adding exterior components

Although not adding body parts, interior items, building models to the model is not erroneous, it is very helpful. This will make it easier for the contractor to grasp the size and scale of the design you are creating.

10. Shipment

When designing a product, the designer takes into account a variety of factors, including assembly, material availability, safety aspect, and much more. It is also important that the gadget can be transported. Say, we have already developed a model, the technologist has confirmed that we can make it, the materials have been purchased and we can start making it. However, it's essential to think about where we'll eventually install the device and how we'll get it there.

If our device is 1000x1000x1000 mm in size, it will not pass through a standard doorway, which is typically 600–900 mm. It might be worthwhile to include wheels if your device is heavy so that it can be moved.

It’s crucial to keep in mind not only the manufacturing process but transportation of a device as well.

Conclusion

This article addresses the most common errors in 3D models that we encounter over and over again. The labor cost for the job will increase if none of these errors are fixed. The price of product development process and delay to market will increase as a result.

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