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Yogi, 3 things...

1st, DON'T use acetal, its impact resistance is poor. With things like suspension arms, it's best to use a flexible material & allow them to flex, they'll last a lot longer. Typical example of this is the Tmaxx - really bendy & floppy, but pretty much unbreakable. The best materials would be polypropylene, polyethylene, nylon etc.

2nd, 2D drawings are sometimes better for CNC routers as they're easier & quicker to generate, & being less complex, are less likely to confuse the machine (Don't have anything else running on the PC at the same time either, particularly antivirus, auto-updates or screensavers).
The way to get 3D objects from a 2D drawing is to use layers in the drawing. dedicate each layer to a specific tool with a specific cut depth. The only time you really need 3D is for cutting curves in the Z-axiz (Up/down-ways). Doing it this way also means you can use cheaper end mills/slot drills/router bits rather than ballnose cutters. What software is the machine running?

3rd, if you're not already aware, any profiles need to be drawn as "Closed polylines", so the machine knows if/how to offset the tool. Otherwise it will cut "on the line" & do it in a random order, treating each line as a separate cut, rather than a continuous profile (If that makes sense). Of course, you can calculate & allow for tool offset, but it's one more thing to remember & cause problems if you don't, or get it wrong.

Hi Eddrick, thanks for the pointers. I agree that flexibility helps. As for acetal, my research indicates that acetal has quite a high impact resistance and very good mechanical properties. This is Iten Industries description of acetyl (but typical of what I found):
"Key property advantages of general purpose acetal include a high modulus of elasticity, high strength, rigidity, and dimensional stability. The material also exhibits a high natural lubricity, a wide useful temperature range and good electricals. It also exhibits excellent resistance to moisture, gasolines, solvents and many other neutral chemicals. Other characteristics include low coefficient of friction, good bearing properties and a high resistance to repeated impacts and makes it ideal for close tolerance parts and electrical insulators requiring high structural strength at above normal temperatures, or in high moisture environments. As an engineering plastic, acetal has many applications where it out-performs metals."

PE is quite good, its used in tupperware! I haven't tested it but I would have thought it was too soft for a swing arm. I had also considered nylon, which is cheaper than acetal. I just checked comparisons of acetal and nylon, and I think got things a little backwards, nylon seems to have a higher impact resistance than acetal, so nylon might be a better choice anyway.

The 2D line drawing I've got down pretty well. I do all my drawings in adobe illustrator and then export out as a dxf file. g-code is processed through cambam and I cut with Mach3. The picture below is a test cut of Ligier chassis plate I made from aluminium composite panel. Its a 3 mm sandwich of polyethylene with 0.21 mm aluminium skin, which makes it really light and stiff, but its too thick really for a chassis (it needs to be about 1.6 mm). But its fairly easy to cut and was a good test to see how far out my copy is.



But saying all that, the fox arms might not be needed. I see on Tamiya blog he has a list of upcoming models, of interest is the "Nova Fox". What that means is anyones guess really, but I could see a re-re fox as its quite a popular car.

updated info from tamiyablog

58577 Nova Fox
The driving force of 80s off-road buggy boom revives as “Nova Fox”! Racing 2WD Buggy that was released in 1985 will be finally resurrected. Durable ABS resin monocoque chassis with built-in RC mechanism in the frame. Sealed gearbox, 4-wheel independent double wishbone suspension with rear drive dog-bones. One front, two rear CVA damper with sufficient travel. High drivability by front ribbed tires and rear oval blocks with gold plated wheels.

very interesting!

Intriguing ... I guess we're looking at a fairly faithful re-re, maybe with a few tweaks & definitely bogus decals... "Nova" though? Tamiya couldn't afford the licencing fee on the word "The"?

I should have known really - any time I buy and fix up an old car, there's a high probability Tamiya will re-release it - it's a conspiracy I tells you



ps - Anyone thinking of getting one should be aware that I will be referring to this car as "The Faux" from now on

Re: acetal - I might be thinking of something else then....
Re: polypropylene/polyethylene - the scratch-build 1/5 petrol car I did had suspension components made of polypropylene, & they were surviving 70mph+ impacts whilst the radio was playing up! (More than can be said for the hardened steel shafts & gears!).
Yes, it's floppy/bendy, but that's what you want, to avoid breakages - it's like in-built damping effect to reduce shock-loading on the parts.

Chassis looks good! I was going to convert my mill to CNC, but lack of time & finances have prevented that happening. To be honest, for the things I'd like CNC capabilities for, one of those desktop routers might be a cheaper, easier option.

I've got a copy of Mach3 but haven't tried using it yet. I found the Pacer software for work's smaller CNC router much easier to use than full-on 3D milling software. Haven't investigated what the bigger router is running yet

eddrick wrote:

Re: acetal - I might be thinking of something else then....
Re: polypropylene/polyethylene - the scratch-build 1/5 petrol car I did had suspension components made of polypropylene, & they were surviving 70mph+ impacts whilst the radio was playing up! (More than can be said for the hardened steel shafts & gears!).
Yes, it's floppy/bendy, but that's what you want, to avoid breakages - it's like in-built damping effect to reduce shock-loading on the parts.

cool, I'd hadn't really though about polypropylene, I might look into as its bound to be a lot cheaper. Did you machine or mold it?

Chassis looks good! I was going to convert my mill to CNC, but lack of time & finances have prevented that happening. To be honest, for the things I'd like CNC capabilities for, one of those desktop routers might be a cheaper, easier option.

I've got a copy of Mach3 but haven't tried using it yet. I found the Pacer software for work's smaller CNC router much easier to use than full-on 3D milling software. Haven't investigated what the bigger router is running yet

Thanks, I bought a desktop cnc machine as I needed to router 3 and 6 mm MDF for work. I was getting bits laser cut initially, but over time that is an expensive way to go, so I needed to look for a cheaper solution and turn around time was also an issue.

I ended up buying TS-3080-H80 with a 200W motor (I had a tight budget otherwise I would have gotten a bigger motor), and it ended up being only $1150AUD including delivery. It is a cheap chinese one but for the price overall it was pretty good. I was looking at building one, which would have cost at least $800 and probably taken me a few months. The body is quite solid, but the electrics and motor will eventually be upgraded, plus a set of limit switches wouldn't go astray either. The manual was chinese-english and not really worth the effort of reading. It only took an hour or so of googling to get the right profile file for mach3. The cnc machine also come with a bunch of pirated software, but I ended up buying a Mach3 licence, adding $145, but it just seemed safer. Googling for cnc software though gives you lots choices for software though, almost too many.

I've been testing cam bam to make g-code, and for 2D stuff its been great. You get 40 uses as a trial, and I'm only half-way through that.

So far I've blown 1 x capacitor and about 5 power box fuses, probably from driving it too hard. I think I blew the capacitor when I was trying to cut too much 0.8 mm aluminium too quickly.

The machine also have a forth axis, but I am a long way from learning how to setup that one up!
My next step is to start learning 3D with Rhino3D, they have a free beta version for macs, otherwise its another pricey software purchase.

The polypropylene was machined. Polyethylene has similar properties & is usually cheaper (I just use polyprop cos I can get it cheap through work)

HI!... Don't know if this helps or not but this guy is selling a bunch of FOX parts :

windsor.kijiji....Z502393869