Scrap rates due to distortion during milling of aluminium alloys

Rav2019 · Dec 17, 2019

Interested to know what are the scrap rates mainly due to machining distortion during milling of aluminium components and also would be interested to what procedures are implemented to control this.
Thanks

AARONT · Dec 17, 2019

Zero if you plan for it.

Rough everything then finish everything. Problem solved.

Ox · Dec 17, 2019

Senior Project.

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Think Snow Eh!
Ox

DMF_TomB · Dec 17, 2019

Rav2019 said:
Interested to know what are the scrap rates mainly due to machining distortion during milling of aluminium components and also would be interested to what procedures are implemented to control this.
Thanks

.
machine distortion ? not likely unless machine flimsy. many parts if cold rolled and not annealed when machined as soon as unclamped they go bong or warp, 60" part can easily curl over 0.100"
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sure you can rechuck at lower torque and take semi finish cuts but often it will easily warp some more. some parts sag from their own weight so where or how supported matters too. point is when rechucked to not distort it when applying torque. soft foot or clamping against uneven surface can cause part distortion as you apply pressure
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i have also seen parts straightened in a press and the next day it warped back a bit. just saying warpage the metal often needs time to think about it.
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usually easier to get metal annealed or stress relieved. often its done more than once for example after milling and before grinding.

Milland · Dec 17, 2019

Ox said:
Senior Project.

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Think Snow Eh!
Ox

Has that feel. Also, terrible laziness to not even offer any significant context as to part, machining processes, etc.

DMF_TomB · Dec 17, 2019

its a learning curve. new person almost always surprised that parts can warp when unchucked. they can also distort from temperature changes.
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try recording things like amount of distortion per 100 parts, usually find it not a if it will distort, only how much it will distort and i have seen it can change the next day or needs time to think about it

Ox · Dec 17, 2019

Milland said:
Has that feel. Also, terrible laziness to not even offer any significant context as to part, machining processes, etc.

Well, if it's a study, then it is "in general" and no actual trouble part exists.

???

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Think Snow Eh!
Ox

DMF_TomB · Dec 17, 2019

it is true some machines at high feed rates often do not exactly follow programmed path. thats why usually finish cuts usually not at very high feed rates.
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see that often if doing dry run refollowing something already machined but going at much higher feed

Booze Daily · Dec 17, 2019

My scrap rates go up when I get distorted.

Rav2019 · Dec 17, 2019

Thanks for the responses,

From experience, the scrap rates for aluminium alloys has been higher than any other alloys, hence the question to see if this is common and if the rates are higher.

Many thanks for the contribution

DMF_TomB · Dec 17, 2019

Rav2019 said:
Thanks for the responses,

From experience, the scrap rates for aluminium alloys has been higher than any other alloys, hence the question to see if this is common and if the rates are higher.

Many thanks for the contribution

6061 T6 is common and it common to see warpage. if annealed its tensile strength is lower but if making jigs and fixtures it often doesnt matter the lower tensile strength. thus many buy jig plate or 6061 T0 (annealed)

Milland · Dec 17, 2019

Rav2019 said:
Thanks for the responses,

From experience, the scrap rates for aluminium alloys has been higher than any other alloys, hence the question to see if this is common and if the rates are higher.

Many thanks for the contribution

If you want real help you have to provide more information. Are these parts cut from solid stock (plate, bar)? Are they from castings, fixtured and finish machined? If so, sand, diecast, ?? What alloy, is it heat treated?

How much material is coming off? What are the critical features, where are you getting non-confirming dimensions? Are you holding the parts in a way that contributes to distortion? Cutting mostly from one side of a piece?

Et cetera.

macds · Dec 17, 2019

I tend to work from t651 plate when I can.

Usually big parts (30x15), and tolerances are usually right loose.

I dont find much warpage\movement aside from temp changes.
Could be my machining approaches.
Im super anal about rough, rough, semi, semi finish, finish.

But most of what Im doing in 6061 is visual, and not tight tolerance.
What I'd do to work with 7075. But I cant talk customers into it

Comatose · Dec 17, 2019

Usually if I get distortion, it was a flattish one-off that I lazily threw on parallels and cranked down the handle to "yeah that'll hold."

The rate's gonna totally depend on the part, the process control, the fixturing, the toolpath and the required tolerance.

A lot higher when you're working to machinist tenths rather than carpenter tenths.

DMF_TomB · Dec 18, 2019

usually get no scrapped parts from distortion or warpage.
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sure you might need to design fixture better, plan on rechuck often and take semi finish cuts to remove warpage
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usually when allowed it better in the long run to have part stress relieved or annealed before machining to get much lower warpage. literally might get 10x or more warapge if part not annealed or stress relieved.
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obviously if part warps 0.100" and you only allow 0.020" for finishing you wont remove all the warpage. and if warped 0.100" and you machine 0.100 and when unchucked it warps .030" more after finish cuts that could be a problem

DMF_TomB · Dec 18, 2019

barbter said:
You quite often cite stress relieving for ally as a suitable process.
Do you do this, and on what parts?
Yes it obviously can be done, and is occasionally done on *some* parts.
In all my years, I've never seen a part where we had to do it.
And with EVERYTHING being cost critical nowadays, the added lead-time and process cost is best avoided and would only be an absolute last resort.
IMHO.

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many places send all metal for stress relieving before machining. its part of engineering design for manufacturing. parts precut send to heat treat by the hundreds every day. most likely it doesnt cost that much cause its done in bulk.
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i have seen 5 foot part not stress relieved warp 0.100", but when annealed before machining, warpage usually less than 0.005" after roughing. it cost much more to not have it annealed, normally.

Ox · Dec 18, 2019

I've never heard of stress relieving alum.
At what heat range is this done?
It doesn't trump the temper?
And then - if you need to re-harden, aren't you just back to square one?

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Think Snow Eh!
Ox

macds · Dec 18, 2019

I dont do "stress relieving" per se.

But, if I have something I dont want moving around (and have the time, and its a picky enough job), I'll do a low temperature aging cycle.

Ill see if I can find the whitepaper I based the process on.

Stardard stress relieving will ruin the temper, from my experience.

Scrap rates due to distortion during milling of aluminium alloys

Plastic

Stainless

Diamond

Diamond

Diamond

Diamond

Diamond

Diamond

Titanium

Plastic

Diamond

Diamond

Hot Rolled

Titanium

Diamond

Diamond

Diamond

Hot Rolled

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