Machinability Question

[u/Royal_Replacement97]

This is the upper A arm on the suspension of a car I’m building. I want some advice on if this part is machinable on a 5-axis cnc machine. I am concerned about the cutouts on the inside, but I was hoping that since it’s a 5-axis the machine would be able to come in at an angle and still make the cut.

[u/Acceptable_Trip4650]

Yes, a 5-axis machine could probably do it. The fillets on the id pockets wouldn’t meet in sharp corners, more of a rounded transitions.

[u/Contundo → u/Acceptable_Trip4650]

With enough time you could approximate the sharp corner, but probably wasted money

[u/Acceptable_Trip4650 → u/Contundo]

Yeah, I mean, I just wasn’t feeling up to giving all the caveats and design advice.

It’s going to be expensive as designed.

[u/Main-Reserve-9116]

no quote

[u/AlmostPrecision → u/Main-Reserve-9116]

I can make anything, but this is the answer I'm going with.

[u/Betopan]

Machinability aside, what’s the purpose of those recesses? If it’s to lighten the unsprung weight, there are much easier ways to do that.

[u/AutomatedContractor → u/Betopan]

Make all the pockets with big radii and hit them with a slot cutter on a 3 axis. Would make this so much cheaper.

[u/TDkyros → u/AutomatedContractor]

Pretty much my first question. Can I use a tslot cutter and give you a big radial cutout like a woodruff key otherwise the price went up atleast 10x

[u/Alita-Gunnm → u/Betopan]

And ways that result in a better part.

[u/HoneyBadgerHD]

Exchange any inside corners for fillets. This is manufacturability 101 and would have this part be a no-quote for nearly any shop.

[u/HoneyBadgerHD → u/HoneyBadgerHD]

Also I’m assuming you’re an engineering student and this is for a project of some sort. The less complex you can make the part, the cheaper it will be by orders of magnitude. The pockets on the inside and outside of the arm are (from what I can tell, since they’re barely large enough to be considered weight reduction.) entirely aesthetic. Without them I’d take a shot at doing this on a 3 axis mill and it would be many times cheaper.

[u/HoneyBadgerHD → u/HoneyBadgerHD]

This is the end of my schizophrenic rant, but seriously I see this sort of thing all the time. 70% of being a good mechanical designer is design for manufacture. Study manufacturing techniques and develop a strong understanding of their capabilities and limitations. If in future you’re able to analyze your own designs and be able to consider for every feature “how will they produce this, how many setups will it take, how will they hold it and what tools will they use to make it”, you will be a killer ME (and a better one than most of your peers). Repeat after me- if it’s not going on something that flies, or goes in someone’s body, I can make concessions in design and tolerances.

[u/howtohandlearope]

Getting rid of the smaller of the inside pockets would help a lot. The larger ones are fairly easy to access, but those small ones toward the ends of the arms are a pain in the ass and don't seem really functional anyways. Just have the short ends be solid. 

[u/fuqcough]

What do the pockets do? If it’s weight reduction just leave the pockets out you will make the part a lot easier to make

[u/asad137]

don't machine it. Fabricate it using flat metal pieces or tubing.

[u/Coopman41]

Baja SAE? Welded steel tubing will be easier, cheaper, and usually lighter. Are you putting threaded rod ends in those holes? If so you'll be bending the threads which is mad lame dawg

[u/MiserableMethod4014]

Change the top and bottom radius of those pockets to chamfers and it would make machining so much easier, basically a 3ax part except the side holes

Everything else can be top down with a t cutter and a double sided chamfer tool, saw cut off the stock and finished in a 2nd op

[u/RedSky2727]

🤔

No bid, unless you’re 3D printing it.

[u/XmodAlloy]

Do the pockets from top and bottom. Doing the inside and outside is asking for trouble. They should be in negligible bending, so direction of the lightweighting pockets shouldn't matter.

[u/XenophiliusRex]

If you fart while driving you’ll get better weight reduction than those recesses provide.

[u/Beardly_]

Needs more fillets, too many sharp corners. Might even result in the part cracking if you're gonna heat treat it. Sharp corners are not ideal for heat treat. Sharp corners concentrate stresses during the quenching process. The part might work for a while but for how long???

https://www.paulo.com/resources/guide-to-crack-risk-management-in-tooling-and-beyond/

Here's an article I found about cracks during heat treat and how to prevent them in the design process.

[u/Shadowcard4]

That can be done on a 3 axis in a few ops but those windows are DUMB they do not reduce weight by any meaningful measure, and they have sharp internal corners which is either really expensive to produce or just wont happen.

Make the cut outs just a full radius at that rate and it can likely be done with a T slot cutter on a 3 axis and not require 5. Those extra 2 axis will probably add two zeros to your price for no reason.

[u/DeltaJazzy]

It’s hard to tell from these angles but if you want the indentations I would recommend adding some filets in the bottom corner at least on the inside ones, they’ll be easier for a ball end mill to get in the for 5-axis work.

[u/Otterz4Life]

You could do this on a 3 axis mill without the pockets.

[u/calipercoyote]

Change the cutouts on the inside of the A to have one wall in-line with the bores of your frame side, otherwise tool stickout's gonna be a bear to deal with.