3D Modeling & CAD for Motorsport: Step 5 - Post Processing
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Step 5 - Post Processing
06.21
| 00:00 | - CNC milling a complex part like this from a relatively large piece of billet aluminium is going to require a skilled operator an expensive machine and a lot of machine time so naturally it's going to be an expensive undertaking. |
| 00:15 | We've analysed our model, worked with the machinist and made a prototype, all in the interest of proving the design and being sure it will work before manufacturing. |
| 00:25 | The manufacturer will complete the CAM or computer aided manufacturing work for this project as this requires an in depth understanding of the machine and machining process. |
| 00:35 | All we need to do is send them a step file which is easily created using the export function under the file tab. |
| 00:42 | The last piece of important work remaining from our end is creating the technical drawing. |
| 00:47 | It could be argued that this isn't required since the manufacturing process will use a STEP file from the model and we've discussed the details with the machinist. |
| 00:56 | But if we want to be certain we're going to get exactly what we want, then supplying a technical drawing is ideal. |
| 01:03 | It will also allow the manufacturer to check their work based on what we specify as the critical dimensions as this is the standard practice in a professional environment. |
| 01:13 | We can use the part's drawing template we set up in the course for this with two sheets to capture all the information clearly. |
| 01:20 | The first sheet will have 3 orthographic projections showing the top, bottom, front and driver's side of the valve cover with the breathers. |
| 01:28 | We'll also have an isometric view for a 3D representation. |
| 01:32 | It's good practice to show the overall width, height and depth dimensions on the technical drawing, especially for a billet part so the manufacturer can quickly understand the stock size required. |
| 01:44 | On the bottom view we'll show the horizontal and vertical linear dimensions to all the mounting holes from the central mounting hole. |
| 01:52 | Where on the top view we'll show the size and spacing of the spark plug holes as well as the diameter for the mounting holes and the counter bores. |
| 02:01 | That will cover our key dimensions for sheet one that can be used by the manufacturer to check their work. |
| 02:07 | But we'll also include a note to support these. |
| 02:09 | This will be a tolerance note saying that all tolerances are +/- 0.1mm unless otherwise stated, rather than adding this to every dimension. |
| 02:20 | We'll also add a flatness tolerance of 0.1mm to the flange mounting surface as it's critical this is a nice and flat surface for a good seal and to prevent stressing the part when it's bolted down. |
| 02:33 | We also need to specify the threads of the breather ports with a note saying tapped for -10 AN ORB. |
| 02:41 | As well as the thread for the coil mounts as M6 x 1. |
| 02:46 | Finally, to finish off the first sheet, we'll add a material specification table, showing the material, stock size and grade requirements. |
| 02:54 | The second sheet will be focused on communicating information on the o ring groove so naturally the scale will need to be a bit bigger. We'll use a break view of the bottom of the valve cover and then a section view through the middle of this. |
| 03:09 | This view shows a cross section of our o ring groove but it's still quite small so we'll use a detailed view of this area to scale it up and then add the critical dimensions being the depth width and corner radius. |
| 03:22 | We can do the same for the depth of our counter bore mounting holes as this couldn't be clearly shown on the first sheet. |
| 03:29 | The same tolerance note can be included along with a note stating this o ring groove is designed for a 3mm high temperature o ring. |
| 03:38 | Finally after saving our drawing file, we can export it as a PDF and send this along with our STEP file to the supplier. |
| 03:45 | Again, the CAM work will be done by the machinist but in this case, Bruce of Five13 Fab actually did this through the Fusion 360 manufacturing workspace so let's quickly look over some of the details to show what goes into a part like this. |
| 04:00 | Multiple setups were used, starting with facing the top of the material stock to ensure that it was flat when bolted down, preventing any stressing or distortion of the part. |
| 04:10 | The bottom and inside of the part was then roughed out using adaptive roughing operations, removing the majority of material up to around 0.2 - 0.3 off the final face of the part. |
| 04:22 | This was then followed by various finishing operations using a 10mm bull nosed cutter. |
| 04:28 | After this, the part was flipped back over and a similar roughing and then finishing process used to finish the top and the outside of the part. |
| 04:37 | Finally, the part was fixed to an angle plate so the breather ports could be machined and tapped. |
| 04:43 | With the finished part on hand and looking awesome, it's always worth doing some checks of our own to make sure we're happy with the finished part before risking any damage installing the part. |
| 04:54 | As much as we'd like to retain the raw machined finish, the fact is that this will not hold up to the abuse of a racecar engine bay. |
| 05:03 | With the excessive heat as well as spilt fluids like coolant and oils, the surface finish would only last a few events if we're lucking before staining and being scratched up by tools during maintenance. |
| 05:15 | The valve cover was then sent away to be hard anodised black which is very similar to regular anodising but produces a thicker oxide layer with more chemical and wear resistance while also preventing discolouration with heat. |
| 05:29 | This is a common finish used on motorsport grade parts like high end monoblock brake calipers which see extreme temperatures and abrasive conditions. |
| 05:39 | Finally we can fit the part for good and appreciate our hard work. |
| 05:42 | In our case, the SR20VET had just had a refresh and is almost ready to go back into the GT86. |
| 05:50 | When the new setup is tested on the dyno for the first time, we'll be sure to keep an eye on things, making sure there are no leaks and retightening the hardware after some use. |
| 06:00 | If there are any modifications needed then now is the time to update the CAD file while it's still fresh in our mind, just in case we ever need to use it again in the future. |
| 06:10 | If you've followed along with this worked example and made something similar for your own car, we'd love to see it so feel free to post it in our member's forum. |
