Milling

The milling of the wax mold is done with the modela player 4, that is part of the software suite for the Roland mill SRM-20. In this section of the week I use the failed well plate as the example, because for it I documented this part the best.

For milling it is necessary to define the size of the model we are going to mill out. For this piece of the well plate, the size is 150wide and 88mm deep and 37mm thick, it was necessary to rotate the piece 90 degrees on the Z to have it properly aligned for the program. Without this alignment it would assume the piece was 88mm wide and 150mm deep.

It is also necessary tell the program where the origin is expected to be, for this piece the origin is expected to be in the bottom left corner.

At this part of defining the job, we define the margins for the piece, as my model was pretty exactly the size of the waxblock I had made this part of my model, and as such left 0 margin, otherwise would be a good idea to have it on automatic.

Here you define the depth of the wax block,

It can be useful to define a slope to be milled, the real benefit of this is that not all milling bits are the same size, so with the smaller bits you will have collisions with the waxblock. Using the sloping moves the edges outwards so that the milling bits do not collide with the piece when going in deeper. Slope can make using the cast silicone mold trickier to use.

In this part you can define the size of the wax block, and let the program calculate the room for sloping and margins.

Now that we have the model and the wax block defined for the program, it is time to program the cutting we need to make, it is done in couple stages, roughing is the initial run of the piece making the large scale cuts. Finishing is the run for making the final details in great precision.

Then we tell the program that the run is from the top down

Also it is crucial for the machine to know the milling bit it is using for the job. In this case I am using a 3mm flat headed milling bit.

By default here you tell the program that it uses the milling bit selected earlier, on the whole surface of the model and that it goes 37mm deep. If it is necessary you can set partial jobs, useful if you want to run only part of the model for example with this model, for example speeding up the finishing job by defining more precisely where the head needs to run for the finishing.

Here you define the kind of path the milling bit will make, if it moves only left to right along X, or back and forth along Y and mixture of both. different paths can produce different results and some milling machines can favor an axis, so switching from X to Y can improve of lower the quality on some machines.

Finally you can then define the different speeds used in the milling.

• XY speed, dictates the main cutting speed, in this case we move 20mm a second.
• Z speed, this dictates how fast the milling bit is pulled up or lowered down, can effect the time it takes to make the piece if the head needs to move up alot. In this case we use 10mm/sec.
• Spindle, this is the value how fast the milling bit rotates, and is dictated by the milling bit settings. In this case we use 7000 rpm, if this value is too high or too low it can effect the quality of the finished product.
• Cutting-in amount, the thickness of the each of the cutting layers. if you try to cut too much at a time, you can snap the milling bit, or if you set this too small the cutting will take forever. Here we cut 1mm layers at a time.
• Path interval, this dictates how much the cutting head moves for the next line. if this is too small it takes forever to cut, if it is too big the result is not proper. Here we use 0.6mm to make sure the cuts made look neat.
• Finish margin, the level of detail, it is a good idea to leave this as is, and let the finishing run then do the final details. Here it is 0.2mm leaving bit extra material on the piece for finishing run to clear off.
• Stay at hole bottom, if you are drilling you can specify for the bit to stay down a bit longer. In this case we dont use it.

It is possible to name the cutting program you just specified, if you need to make number of programs it helps to name them.

then you can run a simulation to see how well the program you made performs, this lets you see if you defined the model, and the program right.

You can also see how long the run would be, and I wasnt joking doing the run properly can take ages.

In this view you can see the run path of the program you defined, gives a cursory idea if you got it right.

Once you run the simulation this is the view you can get of the piece you are making.

If you define the run depths properly you can define that the final finishing run of the piece is done only where it is needed, in this case at the very bottom of the wells.

here you can define the location of the origo of the milling bit for the program.

This defines the thickness of the material and how far up the milling bit should be pulled when moving around to the next cutting place. In this case we move th bit up 1mm off the wax when the head needs to move to make a new cut elsewhere.

This window verifies the machine you are about to use to cut

In this window you finally initialize the program you have prepared, before you run it, it is time to use the normal control view for the mill to set the origin.

Now altough we have told the program where the origin for the piece is, the machine is still clueless. so use the normal vPanel you have used before to set the milling bit into the physical origin for the wax block

When setting the physical origin point, remember that the point the machine uses as the origo, is the middle point of the milling bit.