This entry kicks off a series of posts that record my building of a starter CNC machine. Using OpenSCAD, I had previously explored various alternatives for size and materials. See Modelling a Starter CNC. I found that eventually settling on only one set of dimensions, materials and configurations can be surprisingly difficult, because of the many alternatives. However, the selected design appeared to embody the best trade-offs between needs, performance, budget, and my ability to build the machine given the tools that I currently possess.
By following these posts, you might be inspired to build your own machine, as well as learn from some the pitfalls that I find along the way.
Settling on the Design
The picture above shows the design with the dimensions that will be used.
The base, the X axis frame is 39 x 26 inches. The Y axis, which holds the table, is about 27 x 18 inches. The Z axis, on a column to raise it above the other two axes, is about 18 inches.
The table is 36 x 13 inches and the Z axis can reach about 95% of it. In addition, because the machine is not enclosed, if workpieces are greater than the platform size, theoretically the work can extend beyond either end or toward the front.<< more >>
Designing a do-it-yourself (DIY) CNC machine is an interesting challenge, solved by navigating the thicket of desires, needs, abilities, and, of course, budget to arrive with a machine that presents the best mix of all of the above. By modeling the parameters, you can explore the space of possible configurations that might best match a reasonable course of action.
Generally speaking with machining, the best machine is always the next size larger than what you have. By definition then, the best machine is always slightly out of reach. I cannot hope to solve that problem. However, I expect to create one that will be a sufficiently good test bed to create some good work and gain some experience. This post is about designing an effective machine, not the best machine.
A few years ago, I became interested in robotics, automation, and the practical implementation of intelligence in real-world objects. Having a software background (hedge funds) but lacking experience with the creation of real objects, I had little idea how machines were put together, the forces involved in movement, and how to actually make real things.
So, in the last few years I have learned to machine manually, taking a number of excellent classes on machining and CNC at the local community college. And, I bought and rebuilt an old South Bend lathe from the ground up. My current equipment is fine as far as it goes, but I find that I am still astonished at how long it takes to make a prototype.
Finally, I concluded that it is past time to move to the next step and start using CNC equipment.
The Modeling Process
Using OpenSCAD, one can create each part that would be used. By using a combination of parameters and fairly standardized parts a<< more >>
Dimensioned Drawings with OpenSCAD
OpenSCAD is an open-source program used to create 3D objects. Part of its appeal stems from the form of input to create the objects. Unlike some other 3d programs such as Blender, the means of input is essentially a written program that specifies the objects, placement, rotation and other features. By creating a small program, the object can come to life with full control of the characteristics of the object from a text level. That means less messy tweaking on the screen with the mouse and fudged dimensions.
However, suppose that you would like to go into the workshop and create your new creation with manual machining equipment? You quickly run into a problem: A lack of an annotated engineering drawing.
This program represents a first pass at enabling dimensioned drawings. While by no means complete, useful work can be performed with the modules included here.
The approach uses a top view in OpenSCAD with all of the dimensioned lines and text on the xy plane. Combing multiple views of your object in various projections and translations with dimensioned lines overlayed on a plane just above your object will give the illusion of a dimensioned drawing.
The image below shows a portion of the previous image, still primarily a top view, but rotated to break the illusion of a flat drawing.
Dimensioning Elements Available
A number of elements must come together to implement dimensioning. There must be lines, some with arrows, and some without. Written annotations must accompany the lines to provide dimensions and other written descriptions. In addition, there are a number of conventions associated with annotations and a partial implementation of such functions are included.
Getting Started<< more >>