Origin

[Tony]

Hello,

As I am continually looking better Machining stratagies,(I from Cave Don't know Grammar) !!! I was wondering where most of you

put your Origin? Mine is 95% of the time top of the stock and center/center.

Some Dies are off the edges...

A friend of mine where he works always sets his at the Bottom of the work piece center/center that way it's easy to check

your Z on irregular shapes and such.

Are there any other advantages?

As always thank you.

[ 07-31-2001: Message edited by: Tony ]

[kathy]

Tony,

It all comes down to maintaining a part datum relative to your stock.

If I am machining a complete part out of a piece of stock that is clamped to the table, I set my X,Y Zero at the lower left of the stock so that the numbers are positive. If the stock is thin (.125 or thinner), I specify the tool (Z) zero to the top of the table, which is the bottom of the stock. Otherwise I use the print datum, which could be at the top or the bottom of the stock. If we pre-machine a finished edge or face, I will use that as my setup datum. When hold material in a vice, it’s best to use the back fixed jaw as the Y datum.

For my panels, I always set the tools to the top of the panel, which is the bonded surface. This is because of our table. I will set the X,Y Zero to a known feature on the panel because of existing features i.e. potting, embedded fittings, in the panel. Since I machine both sides of the panel in the same Mastercam file, I will leave the default C’Plane , the UCS, at the panel print datum, and setup 2 C’planes’ for the two setup’s. At the first setup, I will generally drill three tooling holes in the off-fall to index my panel on when I flip it over on the machine!

Hope this helps!

Kathy

[Chips Ahoy]

Tony, I guess the origin could be anywhere on your part as long as you are compensating for the difference in your program. Usually you would determine the origin of your part by your blueprint. Most round parts are normally centerline origin and block type parts are located off of two sides. The two sides being X0 & Y0 on a verticle mill. This gives you exact locating everytime. I always use the top of the finished part to be Z0 on a mill and on a lathe it would be the face of a finished part. Hope this info helps. Rick

[Scott Bond]

Hi

"As I am continually looking better Machining stratagies"

The basic logic of my system is to set my own defaults my way,then every move I make is to programm to them. I let the part drive the set up.

When programming for my friends I make it their way.

When programming for our team here ,I find that by being consistent; I am easer to follow.This makes my completed work get to the pallet faster with less mistakes.

[ 07-31-2001: Message edited by: Scott Bond ]

[cadcam]

Tony it sounds like a mold thought.

if you talk wtih me or sctto bond when it comes to molds we like to use center of the block to make sure cavitys line up.

now as for the bottom thought it matters on what the insert block is to some times i use the bottom to define the part hight.

[Guest]

As far as part datums go, the position should be dictated by the part and the machine setup. Program Zero can be anywhere and by using fixture offsets, the machine can figure the rest. For example, a toomstone of multiple parts can have a z-zero at the centre of the table, the bottom or top of the workpiece, or even if you choose for some daft reason, leave z-zero at the machine origin. If you would like to use the same tool length offset for an A-Load B-Load setup, choose the centre of the table (centre of rotation) and then do the math to figure where the differing levels for the top of the workpiece would be.

Getting back to my point, the type of business that you are in also will have a foctor on the placement of the program zero. Should you need to reduce setup times (as in a job shop enviroment), I might suggest to use the bottom of the part, lefthand corner closest to the machine as program zero, by using fixture plates ball locked into the machine table (at known positions) the work zero can be directly input into the control without measurement - only a verification would be needed to ensure the night shift hasn't buggered the machine again... The other advantages of this type of a system is that the fixtureplates can be manufactured and assembled offline by a skilled machinist and then put on a CNC machine with semiskilled labour and then run by not-so-semiskilled operators .

Having said all this theory, I have always programmed zero where I felt like it. No rhyme or reason, just picked a spot that felt right. Z zero was always at the top of the part so that the not-so-semiskilled guy could ignore the z-depths of the program and set up tools that would inevitably crash into the top of the part and destroy the first two pieces when we can't figure out why the first one was wrecked. The moral of the story goes that 5 more minutes to setup things correctly in the office can often save Hours of machine time and thousands of dollars in displaced tooling costs!

Good Luck

[cam-eleon]

I tend to look at the drawing that is supplied and pick the same datums if at all possible.

[Guest]

Gooday,

Definitely a moldmaker strategy. I programmed for molds ten years and found center,center,top of part - was the easiest setup. If the top of the part was difficult to touch off, because of its surface shape, I would use a support pillar similar to the height of cavity or core for my Z Datum.

Good Luck

[Bill]

For molds, I always use center, center and as for Z it generally is the highest flat surface of the core and the lowest flat surface on the cavity. If there isn't a good flat surface (big enough to pick up from) I will use jo blocks referencing the top of the blocks.

[Will Slota]

When I set the work origin for a part on a mill I usually (90% of the time) use the immovable fixture locations to establish my origin. Then if the stock is sawed big or is not necessarily flat it doesn't matter. I always set Z from the bottom; 1) if the tool breaks in the middle of a "part" I don't have to try to "touch-off" of something that isn't there anymore... 2) for consistency.