Machining from center or zero corner

[Bill1]

There is a big debate in our shop about machining from center of the block or using zero corner as the machining pickup. Please give me your input.

BILL1

[lakeside]

most of the time I us part center if the drawing is symmetrical(it can be a lot easier to check location in program ie. bolt holes. If the part is Asymmetrical then I program from the location on print

[ajl6549]

Use the same zero as that which most print dim's come from

[Geof]

If the part will be flipped for machining both sides always use a location that is accessible from both sides; a through hole or something.

[One of Many]

The first part of that debate should be to question where is the stablest tooling point coming from for the operation at hand. Either in this operation or a previous one, but not leaving out anything that follows.

Secondarly, how well can you position the part to maintain the tolerance per print using a chosen point as it relates to other datums and critical references, given the variances included in each individual part.

Point being, look ahead a few steps in order to use what is available to your advantage and group tighter toleranced call outs as programmed paths to avoid nesting errors in the tooling used or in process of design. This also reduces the concerns of fixturing repeatability if the machine is capable of better resolution required than human interference in moving a part from one setup to another.

DC

[Stu_M3]

I always work from the centre of a die set when mould making as it halves any errors you might make. it makes it easy to mirror your programmes and also removes the possiblility of errors due to blocks being slightly out of square or having different stock on them, nothing is ever perfect! but it is possible to work in a way which minimises any build up of errors.

[Toolmaker96]

Most moldbase companies no longer match grind the outside of the bases. Therefore you should always indicate your zero corner pin/bushing hole when machining your A & B plates. This will eliminate any possible mismatch at parting line.

[Bud Guitrau]

Things may have changed since I was cranking handles, but when I was on the bench, almost all of my mold work (and everyone else's in the shop) was done from center, whether it was a mold base or an insert. This made almost all math, programming and machining operations much simpler, producing fewer errors. ie: laying out a 16 cavity mold from center requires only two numbers which are used in both the X and Y, needing only + or - designations.

Even when handcranking mold pockets through the A & B plates, it was much easier to flip them over, tram them in and recut the pockets from the opposite side to remove any taper. Location could easily be verified by measuring from the insert opening to the outside of the mold base, but now I learn from Toolmaker96 that:

Most moldbase companies no longer match grind the outside of the bases.

This is new to me and sad to hear, as I've been off the bench for a number of years, but if this is the case, it sure makes things more difficult than they should be. I might be an old dog, but rather than learn a new trick, I'd pay extra to match grind the mold base. Everything about mold base work is so much easier from center. (IMHO)

Bud

[Tebis]

I'll use leader pins/bushings or something like that to align my plate and pick up the center of one those bushings to center,but I have to be carefull and make sure where the offset is and the double check with another bushing to make sure i get the same reading,If not, I start over.

[spider]

we do core and cavity cut files from center of mold, and then after we finish cut, we put in the toolingballs.


It all depends, The less manual input, the less chance of a mistake. If your doing plats via manual xyz input, then it would be wise to go from center (because most of the time it's cymetrical) However if you get solid files, it would probably be better to stay at the work corner so you can eliminate somebody punching in the wrong number when moving, and to eliminate setting up the plate wrong way.....