In this tutorial you will be introduced to stock models and boundaries, learn how
to clone a toolpath, and see how to create a rest machining or rest roughing
toolpath. The first toolpath we created was used to rough out the majority of
the material from our stock. We are now going to tackle the remaining areas of
excess stock on the part using a rest machining toolpath. Let's rename our
first toolpath as "Roughing" to help us identify it later and then look at the
remaining stock on the part. Autodesk PowerMill has the capability to build a
model which represents the stock material left after each machining
operation, called a stock model. Stock models can be referenced by subsequent
machining operations, producing toolpaths that are as efficient as possible,
continuously cutting material whilst minimizing any fresh air cutting.
To generate a stock model, again we can create one either from the explorer tree
or the stock model ribbon tab. Create a stock model, let's call it "Stock Model"
and leave the rest of the settings as default. The stock model is initially
empty so we need to add toolpaths to it, in order to build up the stock image.
Add the roughing toolpath either via the right-click menu or from the ribbon.
Note that the toolpath is now in the stock model list.
Calculating the stock model will generate the stock image. Items in the
explorer tree can have their visibility modified by using light bulbs. Let's hide
the roughing toolpath to see the stock model more easily. By default the stock
model is wireframe but can be shaded for better clarity.
We can also view the rest material by selecting the option to do so.
Hiding the model makes this easier to see.
Reshade the model.
Our stock model can now be used as the reference for subsequent operations. Although we could
create a rest machining toolpath in the same way as shown previously, in this
instance we're going to clone a toolpath instead. If we revisit the roughing
toolpath settings we can create a clone directly from the toolpath settings
form. By creating a clone we obtain all the settings of the previous operation
allowing us to change the minimum number of options. Because we made edits to the
toolpath a warning informs us of this case. Choose OK.
Some of the values you want to keep, others will be changed. Let's rename the toolpath as "Rest Roughing".
From the tool area, let's change to our 20 millimeter end mill. In the limit
section we will define a boundary to limit the toolpath to stop it working
down the sides of the part. Select the last icon for the
user-defined boundary. In the graphics area select the bottom surface of the
part and then press the insert model icon to create a boundary. Accept to
close the form. This boundary is active and so will be used for the toolpath.
In the model area clearance section we will check the option to rest machine.
Note a new section appears in the form to define the rest parameters. Since we are
using a smaller tool and we are trying to remove the material left by the
previous operation we will adjust the step over to be 10 millimeters and the
step down to be one millimeter. In the new rest section we can choose our reference.
Rest machining can reference either a singular, previous toolpath or
a stock model, the latter of which has the advantage of effectively allowing
multiple toolpath references. Two key settings to change here are the
"detect material thicker than" and "expand area by" settings. The detect material thicker
than setting tells PowerMill to ignore rest material that is thinner than the
specified threshold. This helps avoid thin regions being rest machined
such as those caused by cusps from the previous toolpath where the benefit of
a second cut is negligible. The expand area by setting will expand the rest
areas measured along the surface by the distance specified. We will set 0.3
millimeters and four millimeters respectively. The final option we will
modify is to switch off the unsafe segment removal tool since this tool is
center cutting. Hit calculate to generate the toolpath.
This toolpath will will take longer to calculate but the toolpath produced will be efficient
saving overall machining time. We can add this new toolpath to our stock model
and calculate it. Once calculated we can save the project again to complete this tutorial