Aluminum Dash Trim Fabrication - GTi MacMini

From March 18, 2005. Sorry these updates are slow in coming - I’ve had a ton of emails to answer (thanks to everyone for their questions and information) and a lot of site issues to deal with. I’ve got a few more detailed photos of different portions of the install up my sleeve, so keep an eye out for more posts! This post will go into a little detail on the fabrication of the aluminum bezel that surrounds the Xenarc 700tsv monitor and OEM climate controls. I’ve had more than a few questions about this, so hopefully this will get some of you going on your own projects. As mentioned in the previous tech post, I originally wanted the MacMini to live in the dash with the monitor and climate controls, but space simply wouldn’t allow it. By the same token, I also wanted to leave the OEM cup holder in place (it usually lives above the radio) for the sake of convenience, but this also soon proved to be a problem…

So, I’ll start at the beginning: The first thing to do when trying to make a large component fit in a small area (like a 7″ monitor in a double DIN-sized opening) is to take it apart and remove as much stuff as you can that is extraneous or unecessary to the project at hand. In the case of the Xenarc monitor, this meant opening the case of the monitor, removing the built-in speaker, reversing the orientation of the power led, removing and relocating the infrared receiver for the remote control and doing away with the front of the case entirely, including the buttons on the front bezel (all these functions are now performed via remote control). This gave me a flat surface to build trim on top of, as well as reduced the overall size of the monitor significantly.

The next step was to mount the monitor in the opening left me by Volkswagen while still retaining the climate controls and their housing. This is the point at which the cupholders got removed from the equation, sorry to say. There is really no extra material to cut out and still have the climate controls mount securely to the subdash in their original location, so with the monitor resting on this structure, there simply wasn’t enough height to allow the cupholders to still fit. Unfortunately, about half of the opening where they used to reside is now occupied by the last 5/8″ of the monitor. In the end, though, I feel like the amount of aluminum that is blank above and below the monitor worked out well stylistically, so I don’t miss the cupholders too much…

To mount the screen, I built a back brace out of 1/2″ acrylic that was pre-drilled, countersunk and screwed to the OEM subdash radio mount, then two-part epoxied for good measure. The monitor (with its back casing still attached) was then epoxied to this brace as well as to the surrounding subdash area. The epoxy I used for this, as well as for many of the iPod dock installs I do is made by 3M and is used for factory automotive assembly. It is called Duramix, for those who may be interested, and is specifically designed to adhere plastics together. It is rather expensive, and requires a special “gun” to apply, but is extremely strong and fast-setting. It is usually available at autobody supply stores, if you’re lookng for some to solve a problem.

Mounting the monitor’s case to the subdash in this way will allow for easy monitor removal if any issues arise with the screen sometime down the road, although I am happy to say that it has performed flawlessly up to this point, and provides not only a single VGA input for direct connection to the MacMini, but also two composite video inputs for extras such as a PS2, PSP, (fingers crossed)PS3 or a rearview camera to be connected and switched to via remote. The rearview camera is definitely coming in the near future, as I had one on my last car and really found it useful (and somewhat fun).

As mentioned above, I also removed the infrared eye from the monitor’s front bezel and relocated it so as not to have to drill any extra holes in the aluminum dash trim I fabricated. If you look closely in shots of the dash, you can see where it has been located near the top corner of the black trim surrounding the aluminum bezel behind a small beveled hole I drilled in the factory dash trim. The monitor is signal-sensing for power and auto-detects the MacMini’s resolution, so I really never use the remote, but I wanted to have access to the screen’s menu system, power and source selection for future upgrades and unexpected occurrences (you might want the screen turned off if you get pulled over, for instance).

Once the monitor was mounted and wired, the subdash radio mount was reattached to the car’s subdash, the climate controls remounted and the fabrication of the aluminum bezel begun. I started by using double-sided trim tape (3M again) to adhere the factory climate control trim to a piece of 3/8″ MDF. After rough-cutting the places where holes were going to be with a jigsaw, I used an inverted table router with a 1/4″ flush-trim bit to copy the OEM openings and outside dimensions into the 3/8″ MDF. I then unstuck the OEM piece from the MDF and had a perfect copy of the original climate control trim that fit perfectly. I then measured the screen’s actual display dimensions with a micrometer and used sticks of 1/2″ MDF brad-nailed to a larger piece of 1/2″ MDF to create a jig for the monitor opening. Again, I rough-cut the opening with a jigsaw and cut it out on the router using a 1/4″ bit to get a solid jig for the opening to be used in making a one-piece jig for the entire dash trim.

Once the monitor opening jig was cut down to fit perfectly in the dash (with the climate control jig below it), I used cyanoacrylate adhesive to glue the two together and brad-nailed this two-part jig to another solid piece of MDF, 1/2″ this time. After pre-cutting and routing, this gave me a solid jig that had all the climate-control openings as well as the monitor opening and the exact outer dimensions that the final aluminum piece would have. This piece was then detail-sanded by hand (to make sure the openings and corners were perfectly square) and then copied (I used double-sided tape again to adhere the jig to the raw acrylic) using the inverted router into a piece of 1/2″ clear acrylic to function as a jig for cutting the aluminum. It would have been possible to cut the aluminum using the MDF jig, but you have to spray lubricant on the router bit while you cut the aluminum, and I have had experience with the MDF softening during this process, resulting in a non-square finished part, which is simply a waste of time. So, I always make acrylic jigs for any parts that will ultimately be cut from aluminum.

After one more test-fitting and detail sanding to work out any flaws in the jig, I traced the jig’s pattern onto a raw piece of 5/16″ aluminum plate and pre-cut it (slowly, and wearing safety goggles, I might add) using a jigsaw with a very new and sharp blade. Precutting usually takes about 30-45 seconds for a part like this in MDF or acrylic, but pre-cutting the aluminum took 25 minutes. It’s not something to do quickly, as the jigsaw can easily bounce out of the material and damage the aluminum or any of your many body parts… The acrylic jig was then double-sided taped to the pre-cut aluminum and cut using the inverted router with a new 1/4″ spiral flush-trim bit while a co-worker (thanks, Anthony) sprayed Kent silicone lubricant onto the bit constantly (it took two full spray cans of lubricant to cut this part). It is important to note at this point that the aluminum was initially stuck backwards to the jig to allow for the next bit - a 45-degree chamfer - to cut completely through the aluminum while still having a surface for the bearing to ride on, finishing the machining on this part with a bevel all the way to the inside edge of the monitor opening for cosmetic reasons, as well as to allow full functionality of the touch-screen interface. For the next four hours, I hand-sanded the inside of this bevel starting with 80-grit sandpaper and working through 120, 180, 220, 280, 320, 400, 600 and 1000-grit sandpaper to reach a polishable surface. I then used a pneumatic die grinder with a polishing head and a block of blue jeweler’s rouge to polish the aluminum bevel to a mirror finish. The last step was to “brush” the surface of the aluminum dash bezel horizontally to mimic Volkswagen’s OEM dash trim in the GTI337, 20th Anniversary GTI and R32. This is a slow and tedious process, but it is very important to make sure all the lines left are perfectly parallel and horizontal.

All of the other aluminum parts in my vehicle (the iPod and trackpad plate, the port and flash reader plate and the ring around the boost gauge) were all made using the same technique of using seperate jigs to make a complete one-piece acrylic jig that was used to cut the aluminum parts. They were all then hand-sanded, polished and brushed in the same manner.

I hope this gives some ideas to those out there looking to do something similar to their vehicles or anyone interested in the process of fabricating one-off parts without needing to take a trip to the local CNC Machine-equipped shop for some CAD work and machining fees. Please check back frequently as I will be detailing some more aspects of the install in the coming week, and seriously thanks again to everybody who is emailing with requests, info and questions. It takes a little while for me to answer them all, but I enjoy it all the same…

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