Remove equal amounts of material from both sides of the plate, or anneal and straighten after machining.

What temper is the finished product supposed to be? If it doesn't matter, consider stress relieving the piece before machining. You may have to rough machine the piece, then stress relieve before finishing. This will take some tests to see what works best.

GA

Liked your post.

>80% material removal sounds like a poor design.

Poor design?? What if I need an alum cap in the shape of a cylinder about 2in od x 4in long with a uniform wall thickness of .062 all around? I'd use standard 2in bar stock and hog out more than 80% material. How's that a bad design?

Bad? Yes.

You turn 80% of the bar into scrap.

YES! It my well be poor design, consider the myriad of other methods of manufacture.
I've had no education as a mechanical engineer yet I can think of at least 3 other ways to make your hypothetical aluminium cap without wasing 80%.
Spend 80% extra effort on the design just once and then save on every part you make. That's the whole point of design!
You only opt for milling and throwing away 80% when all else fails.
Anyhow it's self evidently poor design as it has created a problem, even if it's ony due to poor material selection, which is of course part of the design.
So other than a poor grasp of processes and material, the design is great
QED
Del

i agree with terraman in regards to his scenario

some of you guys appear to be assuming that there will be a run of 10,000 such parts in which case an extruded design would probably be chosen , however if there was one off such tube as described by terraman then ripping the guts out of solid bar would be the method of choice in Aluminium.

If it was steel however you would probably use a heavy wall hollow bar and weld a cap on the end.

There is a greater range of sections available in steel compared to Ali .

what we need from the OP is desired temper and corrosion qualities their client is asking for

Other than Mr.Impossible, you guys missed my point. Let me try again. A few months ago we completed some tooling for a turbofan test pylon (...a short wing to attach a jet engine to a plane). The pylon's framing members are all machined from SS and Alum raw material. More than 70% of material is removed to produce these complex, light weight, but strong components. This is not "bad" design!! This is necessity! These are one-off components with stringent structural requirements. Welding is not permitted and producing forgings to save on machining time is not cost effective. Machining from solid ingots is the best option when you consider the requirements, economics, lead time, etc. Waste material is at the bottom on the list of concerns (...it's recycled anyway!). There are many examples like this on this planet. So...your statements about what qualifies as good design is flawed and narrow minded. We have no idea what the OP is producing, what it's for, and what his requirements are. To say that the design is crap because he needs to remove 80% material...whatever!!

You fail to recognize that the OP has not given even the remotest indication of the part's function or requirements.

Don't take offence if we don't jump on your band wagon.

You could make this part, whatever it is, by any number of methods.

Many years ago, we dip brazed Al parts that could never be machined from a solid part. They are still in orbit, as far as I know. Many other methods are available today, as well.

No offense taken. No band wagon to jump on. Just voicing my opinion. I recognized very well that the OP presented little info. It's you and Ron that claim his design is poor without knowing all the facts...not me! ;-)

Point taken.

Cheers.

I accept your point that the amount of material removed alone does not make this a bad design. You're forgetting though one critical point that I suspect ronseto thought was so obvious that it did not have to be stated. What confirms to me that this is a bad fabrication design is that the part does warp. 100% of the material does not meet the customer's specification. If the customer insisted on this fabrication technique then our OP may be able to recoup some cost and face when giving the customer the bad news. If the OP chose the machining approach then they should count this as a lesson learned and try another approach.

'...What if I need an alum cap in the shape of a cylinder about 2in od x 4in long with a uniform wall thickness of .062 all around?...'

Seems like something you'd want to spin form.

*This is comment and not suggestion.

*Removed aluminium can be recycled at low cost.

*M/c cost for aluminium is comparatively lower

How much coolant is being supplied while milling?

Part of your problem is the material. 5083 is not intended to be a machining alloy. It's intended for welding. You can machine it but you need to stress relieve before final machining as mentioned.

maybe they want a higher tensile class

without assuming thats what the OP is aiming for what is a machineable grade that also has high tensile strength and temper ?

( the surface hardness in 5083 is probably what is causing the warping )

stress relieving after rough machining as mentioned above is one way

If the OP only needs to manufacture one off and has already done so its possible that piece can be salvaged by clamping it down to a steel plate , stress relieving it and check his tolerances after that to see if its scrap or within spec

( assuming the annealed state is acceptable to the customer )

It is because thermal stress.Try some suitable cooling process.it may work.

My experience on this ,I used to for a fabrication shop manufacturing stinter's and mangles for textile machines.3 mtr long,90x90 MS angles were required to be welded back to back,with a 8mm spacer .This was done to match our German principals specifications .Our observation was the rails used to get twisted afted welding ,and we had no option but hammer them to make them stright.We tried G clamps but what came our rescue was an adler fan cooling while welding.This reduced ot hammering effeorts.We lerned this through our expirience .

Other option is (suggested) can it be facbricated ?

Here is what I would do:

1. Drill holes in a tight pattern and a depth which would stop too much heat being generated in one area or all over the plate at one time.

2. Mill the now already weakened plate the way you would if solid. The heat transfer will not be continuous but restricted to the holes outer rim, less 'meat' to transfer heat across plate.

3. Keep coolant flowing while milling. You knew that, just sayin', bloody Germans.

4. Do the 0.9mm in the second last run.

5. Do the 0.1mm in the last run and bobs part of the extended family.

Never done this because I would not waste 80% of anything to end up with something that could be molded. One of? different story, go for it.

Good luck, Ky.

He could get back to us but it's early days.

Not harsh at all, very informative, Ky.

GA

Good comments

I think you hit the nail on the head (also in your other post). He may also not have a choice in the material selection. I suspect the design comes from his client. 5083 is typically used in marine and military applications so that in itself might be a design requirement. As you said, we have little to go on so it's all speculation.

I agree, we have had similar issues just skimming the surface of a relatively thin cast aluminium piece - when released from the mill it warped, and all we were attempting to do was to remove small casting imperfections from the surface.

The stress in the surface can be a killer!

Many complex parts for modern aircraft are milled from billets with most of the material being removed as the most economical way for them to be fabricated at present...... perhaps 3D printing will change this.

A friend was involved in programming the milling machines to do this, and yes the billets wold have been specially treated beforehand to avoid this problem.

Also all the 'waste' material is returned for re-processing.

I am working like engeneering in Aerospace industry. If you need solution send better contact. Hi Libor

Do as much metal removal as possible with a band saw or water jet. Final machining should be done with a very sharp end mill, slow feed, and lots of coolant. If part is not flat enough, Blanchard grind after machining.

Part of your problem is related to the use of the AlMg alloy. If your customer doesn't care, you might consider switching to a 6000 series such as 6061-T6.