360 Recreate Challenge Front Grill Frame

I decided to replace my stock front grills with Challenge grills because my stock ones were beat up and had a lot of broken plastic. Challenge grills were the obvious choice so I located a pair on eBay for about $150 each. Silly me, I didn't check the part list. There's a frame required, besides the grill, to seal up the cooling duct for the radiators. (parts 39 & 40 in the diagram below)

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Checking parts online found that these frames are (naturally) ridiculously expensive. About $500+ each. Spending another $1000 on my car is of course a pleasure, but sometimes I'd rather just keep my money and do something else.

I decided to reproduce the parts and 3D print them instead. I found one grill frame for sale on eBay for $80 that was beaten up and broken but it would serve as a model just fine. It's a large part with about 15" at the maximum dimension.

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After digitizing the dimensions and importing that data into Fusion 360, I had a solid model.

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After printing, this is what I had:

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Unfortunately, my printer is only capable of a maximum 9" dimension so this is a 60% scale model. I'm getting a much more capable printer in about a month (Prusa XL) that can print it in full dimension, in Nylon, which will be usable as a replacement part.

I wrote an in depth article on the entire process: https://www.ferrari360.org/2023/06/ferrari-360-front-challenge-grill-frame.html

 

I was already getting the printer for other reasons (ordered it last year), so this is just another part to print. I'm kind of a do-it-myself kind of guy so I wouldn't want to send it out. Besides, if I did get it done from one of those printing companies and the part didn't fit just right, I'd have to do it again. By printing it myself, I can tweak it to make it fit nicely and not have to worry about a two week and $100+ (?) lag.

As for milling, the geometry of this part would make it difficult to mill. I could probably do it by mounting the blank in the indexer, then doing multi-sided milling using the indexer as both the hold down and rotational platform. That works pretty well but is a pain to design. 3D printing for a part like this is the way to go. In nylon or another tough material, it would be far more resilient than the original fiberglass part, and probably lighter too.

The original part I purchased on eBay had three of the five mounting points broken. I had the same thing on my stock grills. I think the bumper flexes pretty well when the car is bottomed out, or hits a wheel stop in a parking lot. The problem is the grill frame and the stock grill are inflexible and instead of moving, they crack. Making the frame out of a more pliable material will likely last longer and follow the motion of the bumper instead of just cracking and breaking. At least that's my theory.

(I used a Prusa MK3S+ to print this. My new printer is the Prusa XL.)

 

There's another guy in Australia that made some grills already. I'm making the frame. At this point, I'm making two, a left and a right, for my car.

See the thread https://www.ferrarichat.com/forum/threads/front-challenge-grills-nice-or-not.677402/#post-149139043 for details on @rizzo308's grills.

 

The frame is required if you want the cooling duct to be sealed. Without the frame (the grill just covers the opening), air will spill out of the cooling duct and bypass the radiators. The frame takes up about a two inch gap between the grill and the radiator ducts. While this probably doesn't matter puttering about town, I think a risk of overheating would occur if the car was driving in a sporting manner.

 

You could cut the fins out and it would probably fit just fine. I considered that too, but my existing stock grills are in rough shape with broken attachment points. The material is very brittle too, so it can't be repaired.

 

Finally managed to print a full sized Challenge Grill Frame in nylon. It's been quite a road to figure out how to do this successfully, without warping or other issues. The biggest problem is that the part isn't flat. It needed supports and in nylon, that can be a royal pain. To solve the support problems, I searched for a combination of materials that would result in the supports being lightly held so that the entire support structure would pop off after printing leaving zero post printing work to restore the surface that would normally be heavily scarred by the supports.

The combination: Essentium HTN and Amazon Basic PETG black. The PETG support structure sticks great to the bed sheet and the HTN sticks very well to the PETG but when cold, the PETG doesn't stick at all to nylon and just pops off. A miracle of material science! To anyone who has printed 3D before, they know what I'm talking about but to everyone else, this all sounds like Greek, or Geek.

Essentium HTN is a high temperature nylon that will function at 200C (about 400F). No part on a car, with the exception of parts in the combustion flow path like headers and cats, ever gets near that temperature. It's an extremely strong and tough material that exceeds the original in every category except weight. The weight is about the same, around 150 grams.

HTN sands easily and since it's not temperature sensitive, it can be worked with machine tools. This part requires no finishing since it's an internal part but for anything else, it can sanded and even polished to a high sheen, or painted with automotive quality materials and processes.

Here is the frame in the printer. Note the support structure, the more black plastic, under the part.

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And here is the bottom of the part after it popped off the support structure. Note what's left on the printer.

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So now I have the design, the printer, and the method of printing. Now all that's left is fitting it to the car. For that, I have to take off the bumper again and for that, I need help. That will take a few days to gather.