Programming a Part

Today we will start with the programming of a part. This image is scanned from "Applying AutoCad 2007" by Terry T. Wohlers, page 670 L2 problem 36. After drawing part in AutoCad it must be saved in .dxf format as this is the only format that Lcam can import from AutoCad. A word about Lcam. Lcam is the program that controls the table and lets you edit the program for the separate layers (cutting tools) needed. You notice the drawing is of a 3d part. It has profiles on both sides as well as other contours . This will entail having to index the material(add 4 holes) so that we can flip the material over and work on the other side. Lcam is also a DOS program and as such I will not be able to show the controls using screen captures. You think you got slow computers? On one table i've got a 486 25 the other is a 486 100. Being a DOS program table speed is controlled by processor clock speed.




Here is the 2D screen capture of the same part. In another post I'll go through AutoCad and some of the shortcuts I use to make a file. Notice that it really is nothing more than circles, arcs and straight lines. There is a control in Lcam that will allow you to Sort the drawing to make it one piece, for now we will forgo that and keep them separate parts.

This is the first 4 layers of the program. The entire first side that needs machining. First we put in 4 index holes that gives us the ability to index the part to the table when we flip it over to machine the second side. Next the .3 holes are cut, then the .5 couture is cut. Then a .050 hatch is machined to drop the height down to the main body height. If you look at the part head on you will see that it has three height planes. Machining down 50 thousands finishes this side of the part.

Now we need to run the next layer which will put in 4 index holes into the table. Insert 4 pins into those holes and then flip the part over and place onto the guide pins. You do have to check and see if the part flips along the x axis or the y axis. Many times it will help to turn on all layers so that both mirror images are shown.

Now remember that the red layer is the part and as you look at the drawing. The next layer, after index and mounting, will be a .050 hatch, then the center will be cut out using a 1/8 inch mill and finally a 1/4 inch cut out. The material call out is .150 aluminum.

Now many times the cad operator has not an idea of what material is in stock at the time. Since it would take 2 months to get material in it was decided to use .250 instead. Another layer was added to hatch the first side down .1 inch and all layers on the first side must also be changed to follow suit.

Welcome

First posts are always the hardest to do. My name is BJ and my job description is CNC Router Table Operator. The Company that I work for is responsible for replacing aircraft interiors with custom made (customer requested) configurations. After approval and final design any parts that are not available have to be made. This is where I come in.
The machine that I use is a computer numeric controlled router table. Specific a Larkin Model 600. Table size is 76 by 144 inches. Usable space is 74 by 100 inches.
Dependant on the part needed I maybe cutting aluminum, composite (prepreg layups, carbon fiber ), plastic, nylon, phenolic, wood etc. Most parts take about 30 minutes from load , mounting, cutting to finished product.
Another name for the procedure is rapid prototyping. If it can be drawn it can be cut. If it can be modeled and a tool offset programmed it can be made. The job itself is quite interesting and challenging. Along with creative, stimulating, and exasperating. In future posts I will go over the actual procedure from start to finish along with cad work and programming. I hope that I'll give a good over view of the subject and be able to answer any questions posed.