Flatness on MIC-6 Alum Plate

[chancey]

Can anyone help me come up with a reasonable, manufacturable, flatness tolerance to call out on Mic-6 Cast Alum plate that is 16" x 22" and 1" thick? From the manufacturer I believe it is close to .005" but they talk thickness and not flatness. I am figuring on .003 but the flatter the better. Any ideas? Thanks in advance.

 

[unclesyd]

We bought a lot of Al tooling plate from TCI Precision, formally TCI Aluminum, for use in building in house machines and I don't remember any question of parallelism or flatness. Looking at there brochure I see smaller numbers (0.0002") than I remember.

As you gave no desired dimensions I would give them a call and see if they can cover your requirements.

http://tciprecision.com/machine-ready-blanks/capabilities/Duplex Milling

 

[SincoTC]

A long time ago, I bought twenty pieces of 1" MIC-6 tooling plate, about half the size of your parts. They were all within .005" on thickness with a good surface finish, but most tapered .002/003 end to end, I used them for moulds and selectively paired them so the outer faces were nominally parallel and the moulds worked fine and didn't flash.

I never could quite rationalise the taper on the piece length with the stated overall tolerance on the whole plate. I understood that at that time they fly-cut the entire plate (12ft x 6ft I think) and then cut the required pieces, so if there was any minute dishing of the cut face caused by the verticality of the cutter spindle, how parallel your piece was depended on which part of the plate it came from and its orientation. However, it was a long time ago and this process may have changed.

It is a great material though, but has completely different characteristics from the more usual wrought tooling plate so make sure that it fits the bill. I had one mould fail when the operator forgot to fit a support pillar, when he ran it, the mould only flexed a few thou and flashed near the centre, on the next cycle it snapped like a carrot!

Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

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[unclesyd]

Excuse my error in stating the you gave no dimensions for some reason I was think big plate when writing my response and not reading the OP.
All other comments are still applicable.

 

[argusengineering]

chancey,

In any design the question should not be "what is the reasonable, tolerance?" but "which are the design requirements?" and apply the tolerances accordingly.

For a 16" x 22" size plate the +/-.005" tolerance can be considered reasonable.

Tudor Agapescu

http://www.argusengineering.net

 

[chancey]

Good point and I understand what you are saying. It was a base plate for a indexing fixture I was working on and I just wanted to be as flat as I could without getting outrageous. I am not used to working with such big plates. I try to understand the processing abilities as much as possible. Mainly not to ask for something that is not possible or going to cost a lot of money to make.

 

[unclesyd]

Here is one list of tolerances for the two types of Al plate, cast an rolled.
This company is also one of several that can give you CS plate to some very good tolerances.

http://www.interlakesbases.com/dial_plates.php

We purchased several machine bases from these people where we had the top plate ground flat and parallel after fabrication and stress relief. Slightly more expensive than a home built but well worth it as all you had to do was find a flat floor to put it on.

 

[chancey]

Thanks to everyone. All good comments.

 

[ornerynorsk]

Flatness is 0.005 total, thickness is +/- 0.005 for the approximate size of plate you described.