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 >>
The South Bend lathe is complete. There is nothing like getting a new piece of equipment, taking it apart and putting it back together again to develop an appreciation for it.
This post covers the final results of painting and assembly. We will start with the headstock and motor, move to the middle, the carriage, and finally look at the tailstock.<< more >>
Cleaning the Apron and Carriage came somewhat later in my process after I was able to clear some room. For those not familiar with lathes, the terminology can be confusing. Ultimately, the point of the carriage is to position a cutter relative to the work and enable the cutting to take place. work. It moves on the bed via gearing. The carriage consists of several components: the part that moves back and forth on the bed is the saddle. On top of the saddle is the cross-slide. On top of the cross-slide is the compound which enables other positional movements of the cutter. On the side of the carriage is framework that hangs down in the front. This is called the apron.
Here is the saddle upside down with the apron still attached. The cross-slide and the compound have already been removed. It has been cleaned to a degree, but not fully disassembled.<< more >>
This post covers painting the South Bend Lathe that was torn down in the previous post. After going through the process of cleaning the lathe down to the bare metal, it is very satisfying seeing it progress back to functionality. Like the teardown, it had to be done in stages because of the space limitations in my workspace. However, I rigged up flat areas in the workshop that could hold quite a few little pieces.
All the pieces took several coats. I also cut the paint slightly with a fluid designed to slow the drying process a little. The purpose of that was to help eliminate brush strokes.<< more >>
I had been interested in getting a lathe, and an old friend of my Dad's decided that he no longer needed his. It was perfect timing. Not only was it functional and reasonably sized for my workspace, it was also a little bit of history.
Being used to the cycle of electronics that rapidly progress from latest-and-greatest to junk, it takes awhile to adjust to idea something more than sixty years old and expect to do some viable work with it.
A Little Maintenance
Ok, it did have some grease and dirt on it, and a little rust too. I concluded that it needed some cleaning. Once I started using it, I realized that I probably would never go back and really clean it up. So, refurbishing up front seemed like the way to go.
What follows in this posting and in some following postings are some of the pictures associated with the process. The reason I document this, is for a couple reasons. First, it is intrinisically interesting for those who like machinery, but, also, for someone else who takes on this task, you might get some ideas of what lies ahead.
My approach was, first of all, to try to do no harm. So, if something seemed fairly difficult to get apart, I wanted to avoid damaging it if at all possible, and would try to err on the side of caution. Second, I would try to clean off the grease and grime, and save the original paint if I could. Third, if I was going to paint anything I wanted to match the original color as well as I could.
Finally, I was hoping to be able to put it back together correctly.<< more >>