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Gr 2 Ti plate part with tight parallism and flatness tolerances...

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gregormarwick

Diamond
Joined
Feb 7, 2007
Location
Aberdeen, UK
I am quoting a plate part, ~350mm sq. It has one square corner, but the opposite two sides are tapered outwards and blend tangent to a large radius.

Finished thickness is 12mm +/- 0.2mm, but parallism and flatness are both to be held at 0.05mm

BOM calls out to start with 13mm plate, but we can do whatever with that.

I'm thinking to start out with a waterjet profile, do the ancillary machining and send it out somewhere to get finished to thickness, but what process for Gr2 Ti those tolerances?

TIA Gregor.
 
Stay away

gregormarwick said:
I am quoting a plate part, ~350mm sq. It has one square corner, but the opposite two sides are tapered outwards and blend tangent to a large radius.

Finished thickness is 12mm +/- 0.2mm, but parallism and flatness are both to be held at 0.05mm

BOM calls out to start with 13mm plate, but we can do whatever with that.

I'm thinking to start out with a waterjet profile, do the ancillary machining and send it out somewhere to get finished to thickness, but what process for Gr2 Ti those tolerances?

TIA Gregor.
Click to expand...
STAY AWAY
14 by 14 inch titanium plate,.472 thick,.0019 flat and parallel.This would be tough to do with a mild steel plate that was stress relieved and flipflopped many times on a magnetic surface grinder. You would need to remove about .020 inch per side from your 13 mm titanium plate wilst keeping it flat and parallel.I put in aproxamate inch numbers so that myself and others might more readily give it more thought.It is possible that there are specialty shops that can grind titanium plate with vacuum chucks.If you do this job ,please post the results.Edwin Dirnbeck
 
how you going to hold ? many plates will bow up when put in vise just from the vise clamping pressure. even when clamped to table if already bowed and you force down to table as soon as you release clamps it will bow back up. cutting forces and push part away and when cutter is gone part deflects back.
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literally you can spend a large amount of time dealing with a small amount of warpage
 
I work with CP2 all the time, pretty stable stuff. they give you .008 on the thickness so thats plenty to do the flipy flopy a few times to dial it in. In some instances instead of clamping in a vise and having the part bend, I will toe clamp it in deiffent sections and take down to final thickness by just moving the clamps at stops in my program. 12mm is still decently thick enough not to warp that much
 
Either double-disk grind the stock before doing any further work, getting quotes from materials suppliers who do that as their business. Or start with 14mm and do the flippy/floppy bit on your own equipment.

Unless the quotes were ridiculous I would sub out for DD grinding over trying to machine to thickness in-house.

Here's a company that does DD grinding, but no idea of size limits or cost: Surface Grinding - Birmingham Stopper You can search for other options, even a US vendor may be workable. Machine-Ready Blanks and Contract Machining - TCI Precision Metals
 
Thanks for the answers. We declined this, but I'm going to continue to ask around so we have some solutions for next time.

I really don't have any intentions of trying to machine this to thickness, even if I could find a way to make it work it would be too time consuming to be worthwhile. I'm looking for a dependable subcontract option.

Milland said:
Either double-disk grind the stock before doing any further work, getting quotes from materials suppliers who do that as their business. Or start with 14mm and do the flippy/floppy bit on your own equipment.

Unless the quotes were ridiculous I would sub out for DD grinding over trying to machine to thickness in-house.

Here's a company that does DD grinding, but no idea of size limits or cost: Surface Grinding - Birmingham Stopper You can search for other options, even a US vendor may be workable. Machine-Ready Blanks and Contract Machining - TCI Precision Metals
Click to expand...

I have very little knowledge of grinding, but isn't this part much bigger than typical double disk work?
 
gregormarwick said:
I have very little knowledge of grinding, but isn't this part much bigger than typical double disk work?
Click to expand...

It depends who does the work. The US source I mentioned can do it, I have no idea if the Birmingham co is able to do something that big. Perhaps they have Blanchard machines that could do one side at a time, but a DD is a better bet to give parallel faces when done.
 
I never ran titanium, but I did aluminum and stainless on my blanchard. You just block in the parts with steel so you don't toss them off the chuck. I had some big steel rings that I used to make a border, then filled in with smaller pieces of flat bars or whatever was handy.

If the plate is bowed to start, you have to shim the underside so it doesn't push down, and it would probably take a flip to hit the tolerance- but it's not particularly difficult to blanchard grind non-ferrous plates to that tolerance, just a little bit of a PITA to get it blocked in so it stays put. "Straight" edges help...
 
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