3D Modeling & CAD for Motorsport: Bends
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Bends
06.50
| 00:00 | - The ability to bend bodies is one of the key advantages of sheet metal CAD modelling and is a very commonly used manufacturing process when working with sheet metal. |
| 00:08 | Using bends enables us to add strength and structure to sheet metal, creating relatively lightweight, strong and low cost parts, all of which are important factors in performance automotive applications. |
| 00:22 | In CAD, the bend tool allows us to bend the sheet metal body around a sketched bend line. |
| 00:27 | Although the actual sketch line doesn't need to extend across the entire part, the resulting bend line will be projected across the full part. |
| 00:36 | This is because you can't just bend halfway into a sheet as it'll cause the material to tear or deform. |
| 00:42 | Let's jump straight into a simple example so we can explore how all this works in practice. |
| 00:47 | We're going to create a basic formed sheet metal part with a few bends. |
| 00:52 | Let's start with a square base body, 100 x 100 mm with a 20 x 20 mm square cut out of the top corner. |
| 01:00 | Now we can extrude this 5 mm thick and convert it to sheet metal like we discussed in the previous module. |
| 01:07 | Let's make a sketch on the top face to define our bend lines, starting wtih a vertical and horizontal line from the corner of the cut out section across the part. |
| 01:16 | Now we'll add another horizontal straight line across the part but not the entire way and then another line off this on an angle to the bottom edge. |
| 01:25 | So now it's time to start using our bend tool, remember S on our keyboard brings up the search function, all we need to do is type in bend and hit enter. |
| 01:35 | Otherwise you can find it here in the create dropdown menu. |
| 01:39 | The first selection we need to make is our stationary side. |
| 01:43 | This is the face of the part that we want to remain in the same position for this operation, and what the preferences like bend angle will be referenced to. |
| 01:51 | We'll choose the top face for this. |
| 01:53 | It's important that we choose the face that our bend line sketches lie on, or we won't be able to select them. |
| 01:59 | Once we have our stationary side selected, we can choose our bend line. |
| 02:02 | Notice that we have four options here, as we have four sketched lines. |
| 02:07 | And although two of the sketched lines don't cross the part completely, like we discussed earlier, the bend lines do project across the entire part. |
| 02:15 | We'll select one of the lines from the corner of the cut out, rotating the model to get a good view of the details. |
| 02:22 | We can quickly change to bend angle, flip the bend to the other side and change the bend line position preference which moves where the bend starts relative to the bend line. |
| 02:32 | Notice the relief for this bend and how it changes with the bend line position preference. |
| 02:37 | Reliefs are incisions or cut outs along the side of bends that are needed to prevent the part from tearing or deforming when the bend is applied. |
| 02:46 | OK so let's add another bend using the other line from the cut out section. |
| 02:51 | Now we can see that the corner relief comes into play and in this case, the bend relief is no longer a factor. |
| 02:59 | We have the ability to override our sheet metal rules if we wish to change the bend radius or relief shape and size, as long as we consider the implications that this might have on manufacturing. |
| 03:12 | For example, causing the part to split when bent at too tight a radius. |
| 03:16 | Our bend tool allows us to make multiple bends at once and we can change the preference for each bend individually so they don't need to all be the same. |
| 03:25 | If we tried to add another bend using the other horizontal line we can see our feature fails as this would cause our body to self intersect as one bend crosses another. |
| 03:35 | We could however add in a bend using the diagonal line to bend up the corner of the part in either direction. |
| 03:43 | So let's finish up with this example now, if you've been following along, save your work as we'll be pulling this design up again in an upcoming module. |
| 03:52 | At this point, you've hopefully picked up the importance of considering how a part will actually be made in the real world and that our sheet metal rules are there to help us avoid making bends that could cause our part to fracture or distort. |
| 04:05 | The reality is though, even when sticking to these rules, it's still very easy to design a model that would be extremely difficult, if not impossible to produce. |
| 04:14 | If we consider the process of actually bending a sheet metal part on a bending machine, when we're making multiple bends, it's possible that we might not be able to complete the bend at the desired angle without the part contacting the machine. |
| 04:29 | Most sheet metal benders have movable sections to help with this but the geometry of the part and the order of the bend operations needs to be considered when designing. |
| 04:38 | If you think back to the design fundamentals section of this course, we talked about tolerances and the variation in the final part when compared to our intended dimensions. |
| 04:49 | With each bend, we're introducing more potential for variation. |
| 04:53 | For example, if we're designing a sheet metal bracket and we have two critical features like mounting holes with multiple bends between them, what's the potential variation we might expect to see in the location of the holes? Will this prevent the bracket from being mounted? Can we reduce the number of bends, change the orientation of the bends or maybe slot one of the holes to give more tolerance. |
| 05:15 | Adding to this, generally when designing, fabricating and bending sheet metal parts by hand, we'd measure out and mark the location of our bends. |
| 05:24 | So a big advantage of designing our parts in CAD software, is the ability to add features to locate bends when manufacturing like breaks in the straight edge of a part making a corner or small indented cuts. |
| 05:37 | In some cases, the corner reliefs on the flattened part may help locate the bend. |
| 05:42 | If we can avoid the manual measuring process, that's one less potential chance for error. |
| 05:47 | Lastly, keep in mind that sharp internal corners are stress risers so we want to avoid this if strength is a primary concern for the part we're designing. |
| 05:58 | In summary, the ability to bend the 3D body is one of the key advantages to modelling sheet metal in CAD. |
| 06:05 | By sketching straight lines on our sheet metal base, we can use the bend tool and select our stationary side and then bend the sheet metal body around the bend lines. |
| 06:13 | We have the ability to create multiple bends at once, reducing the number of features in the timeline and naturally saving time. |
| 06:22 | The form of each bend can be adjusted individually by changing the various bend parameters available to us. |
| 06:29 | We can also choose to modify and override our sheet metal rules to change the bend radius and reliefs. |
| 06:36 | As long as we consider the implications this will have when manufacturing our design. |
| 06:40 | Some forward thinking during the design stage can help us design parts that are easy to produce and function as intended. |
