DMP Mill assignment
You are asked to machine a part that looks like the shape below. You will receive a print for the part with appropriate dimensions. The goal of this project is for you to gain an understanding of the basic operation of a mill and how material can be machined with accuracy. For grading, you and I will measure the completed block against the print.
You will find the knee mill will be set up with a 1” diameter end mill mounted in the quill/collet and a vise is mounted to the bed of the knee mill table.
I will create this project live in addition to our Technician Marlowe is available for questions during your creation of this project. Everyone will have an evening to create the part, you may select another student to partner with for the project, every student will create a part.
My recommendation is to understand the overarching concepts about creating a shape on the machine. On the outside, the vertical mill appears very simplistic, do understand that this machine is almost 200 years old and has some very advanced capabilities.
Below is a legend of a typical vertical milling machine, also called a knee mill.
Order of Operations for machining with space for notes:
The steps below are meant to remind you of the operations, make notes as necessary and ask questions. This is all new to you.
Everything is based off one datum, one starting point, x,y,z 0,0,0
Begin by cutting a block of 20pdf high density urethane foam that is approximately 3.0”x7.0”x4.0” using hand tools. Tolerance is +/- .25
Mount the foam material in the vise attached to the knee mill (vertical mill).
Using the x y and z handles, maneuver your tool to the top (z) of the foam material and zero the indicator on the appropriate handle. Remember the diameter of the cutter, remember the machine backlash.
Using the x y and z handles, maneuver your tool to the left side (x) of the foam material and zero the indicator on the appropriate handle. Remember the diameter of the cutter, remember the machine backlash.
Using the x y and z handles, maneuver your tool to the front (y) of the foam material and zero the indicator on the appropriate handle. Remember the diameter of the cutter, remember the machine backlash.
According to the print, create a block that is 2”x6” 2” tall. This is so that you warm up with the machine operation AND it creates a block for the additional steps.
At a depth of 1” from your z-zero, apply an inset .250” in distance around the perimeter of your block.
At a depth of .50” from your z-zero, apply an inset .50” in distance around the perimeter of your block.
Touch off with paper: The traditional old school method involves holding a piece of cigarette paper (rumored to be exactly 0.001″ thick) on the workpiece and gradually lowering the cutter until it starts to catch the paper. Add another 0.001″ and you are at zero! Not having any cigarette papers, I used standard laser printer paper. I cut a 1/2″ wide strip so I could hold onto one end from a safe distance, and waited for the cutter to grab. In my case, I got a grab at 0.010″, not 0.001″, but at least it was a nice round number and pretty repeatable.