Setting the Origin for Machining

Setting the Origin for Machining

The WELmill software guides you, step by step, through setting the origin for machining. This must be done with care before machining commences.

Below is an outline of the process.

Secure a billet of material to the mill table with a vice or some other suitable and safe system. Mount the first cutter in the milling head.
Shut the mill door.
Start the spindle rotating and set the speed to its lowest.

Using manual axis control, bring the tool down until it just scratches the top of the billet.
Click "Done" to zero the Z axis.

Using manual axis control, move the tool until it just scratches the left-hand end of the billet.
Click "Done" to zero the X axis.

Using manual axis control, move the tool until it just scratches the front of the billet.
Click "Done" to zero the Y axis.

Lift the cutter clear of the billet. The exact position does not matter: the WELmill software keeps track of where the tool is in relation to the origin just located.

Switch off the spindle.

Setting the Origin for a Pointed Cutter
The Z origin position is set as described above. Because the diameter of the tip of a pointed cutter is zero, the X and Y origin positions are set by bringing the point of the cutter directly over the top, front, left hand corner of the billet.

Tool Radius Compensation
When the position of the origin is set, as above, to the top, front, left-hand corner of the billet, WELmill automatically compensates in the X and Y directions for the radius of the cutter: this can be seen in the X and Y co-ordinate readout on the manual control screens.

Alternative X, Y, Z Origin Position
While the X, Y, Z origin is usually at the top, front, left hand corner of the billet, it does not have to be there. The X, Y, Z origin can be in the centre of the top of the billet. This is particularly useful if the billet is large and the cutter is pointed and therefore has a tip diameter of zero.

The design shown above is to be 3D engraved by a 45 degree router cutter (the blue lines are the path followed by the tip of the cutter). The X, Y, Z origin is on the top surface of the billet at the intersection of the two purple lines. The tip of the cutter is placed on this intersection when setting the X, Y and Z origins.

Please note that the NC code must be prepared so that the cutter can move negatively in X and/or Y as well as the more usual positive movements.

A "centre of the work" X , Y, Z origin can also be used for a non-pointed cutter, for example a slot drill. However, because WELmill compensates for the radius of the cutter, the centre of the end of the cutter is not placed over the intersection of the two purple lines in the picture above. Instead, the periphery of the cutter is aligned on the left of the vertical purple line to set X and aligned below the horizontal purple line to set Y. It touches the top of the billet to set Z.

Alternative Z origin position
While WELmill directs you to touch the end of the tool on the top of the billet to set the Z origin, you can, if you wish, touch the end of the tool on the bottom of the billet - or rather, on the surface on which the bottom of the billet is placed. It is essential that the NC code takes account of this, ie that Z co-ordinates are positive and not, as is usually the case, negative. This strategy is useful when doing 3D machining as it ensures that no point on the top of the part is left uncut because the top of the billet is uneven: the height of the billet must, of course, be slightly greater than the height of the part.

Take Care!
If 3D machining is being done with a ball-ended cutter, the cutter will cut into the material on which the billet is standing. This ensures that the profile of the part is completely cut. It is essential that the billet is standing on some suitable thickness (at least equal to the diameter of the cutter) sacrificial material which will not damage to cutter. It is likely that the cutter will need a safe, clear space all round the part. Plan work-holding with great care!

Important
At no point in this process should the X, Y or Z axis hit an end stop. If this does happen start the process again from scratch.

3D Machining Tips
Accuracy of Machining
Billet Size and Working Envelope
Code File Header Information
Measuring Offsets
What moves - the milling head or the table?