The screw drive of the standard rotary table has a lot of benefits in this 4th axis application. There are a few limitations in the area of backlash (controllable) and rapid speed (not really necessary.)
With small mills like the Taig and the Sherline, weight (mass) is a required parameter to consider. Most rotary tables are designed to have a lot of weight as part of their design. It adds stability for normal machining. However for miniature CNC machining, it is undesirable to abuse your drive system with a lot inertial mass to start, stop and reverse perhaps up to a hundred times a minute.
The winner in my selection is the Sherline 3700-CNC rotary table with motor mount. At $320 it is not the least expensive of my 4th axis schemes but I think it is the best in this case.
First point is the weight. At 8 pounds it is heavy enough and when you look at it, you see it carries no extra weight in a heavy case or mounting system flanges.
Second point is it is specifically designed for CNC operation internally (Sherline says in the worm housing) as well as the included #23 motor mount and coupling.
Third big point with me is the drive is 72/1 turns. Some rotary tables are 40/1 (yuk!). At 72 turns and 1/4 stepping, each step is 0.00625 degree. (Sherline uses 1/2 stepping.) A 90/1 would have… Continue reading
I am investigating very intently the world of very small CNC machining. I am looking at small items such as mold machining for model parts and jewelry sized items using very small milling bits and high speed spindles. Actually I should call it CAD/CAM/CNC. It is far more than running the CNC mill.
I also looked at micro machining but that is a very high tech world that is still outside the needs and abilities (and machinery) of the personal machinist. It is truly amazing what can be done in the very tiny micro machining. I am not going there.
What I can do using my Taig CNC Micro Mill and a +10,000 rpm spindle is overwhelming. My recent Christmas ornament project is what has driven me into this investigation. The fantastic finish in wax that I was able to obtain actually surprised me. The Taig is a truly capable machine in this precise machining task.
I have now found web information of other, higher speed spindles added to the basic XYZ Taig movement. The Taig non-linear bearings and ways actually are up to the task for precision machining. I have many hundreds of hours of operation on my machine and it is still holding the performance line.
For now I consider myself “good” as far as machinery needs. I also have the appropriate software for CAD/CAM. That may change but not for quite some time. I will be adding a forth axis very soon, but other than that, I am comfortable.
I have the HB2 for larger projects and I will use the Taig for my miniature machining. I hesitate to use the word “micro-machining” but I am thinking it within my own definition.
I will also continue in my mold making and casting of components. I will definitely… Continue reading
A visitor to this blog named Bob Warfield left a comment about a post he made in his blog HERE. Bob is also the creator or progenitor of machine shop “Speeds and Feeds” software called GWizard. It probably isn’t fair to call it just a Feeds & Speeds as it does so much more.
Bob told me he was known for The CNC Cookbook Blog as well as anything. So naturally I had to dive in and take a look. Sure enough there was Bob standing there grinning and holding plate with pumpkin pie. You’ll probably have to scroll way down to find him now (and the pie). This CNC Cookbook is a great place to read and study about the “science” of rotary machining.
I like a guy that doesn’t hide his face from his peers and customers.
I perused carefully everything I could find on that web site. Where was this when I needed it!? Of course always the skeptic, I had to figure out what was the “deal” going on here. The biggest question for any CNC machinist (well at least for me) is how hard can I push feeds and speeds and what are the reasons. It would seem obvious that this sort of program would have been offered long ago. But… it is a very complex subject. Tool manufactures are of course going to shade any such tool program toward their own products.
Bob admits it could be done with a spread sheet and in fact that is how he started. When I first started CNC machining I eventually found the safe speeds for the kind of work I usually do, but it had taken a lot of effort. I could have built a spread sheet myself but the effort would have kept… Continue reading
A local person here in Frisco asked if I could duplicate this part (the black one). I don’t usually like to take on outside projects as I have enough of my own. This part looked interesting. It is part of a tripod bracket for an expensive, but what the owner called a “toy” gun. Actually is is a very sophisticated collector item.
As can be seen in the photo the bracket had the tab broken off. It is a very nice injection molded aluminum casting but the crystallization left it vulnerable to breaking where it did.
I was going to make a duplicate by manual milling. That’s the rotary table setup in an earlier post. I changed my mind and decided to do it with CNC milling.
I had to first very carefully measure the part in every detail then make a 3D drawing in Rhinoceros (Rhino) You can see the screen capture and a couple of output pictures.
I converted the drawing to two G-Code files with RhinoCAD, one for top and one for bottom.
I did a test run in oak then made the one in aluminum. I used my Taig CNC mill running mist cooling. Overall size of the part is rather small, about 1.5″ x 1.5″ x 3/8″
I’m not setup for doing anodizing and I have never done any. I have studied the process and it can be done in the home shop. The new part really needs to be anodized like the original, but that is not my “thing” right now. That’s all I need is another skill to master. 🙂