diy 4th axis rotary table in stock

About 3 years ago I bought a cheap rotary table that I converted by taking off the handle and replacing with stepper motor. I used thrust bearings and whatever I could think of to minimize the backlash but it was a big FAIL. The internal worm gear mechanism was so sloppy that backlash was measured in degrees. Its been sitting on the shelf collecting dust. Since then I found out about Harmonic Drives and what high end CNC/Robotic systems use for rotational axis. A new harmonic drive is big $$$$ so eBay to the rescue. The gear head I used is planetary but made by Harmonic Drive Systems so it is very precise. It’s simple and just the right size for my small cnc. Since the stepper motor, gecko drive and gearhead was bought off eBay, it wasn’t that expensive. Under $150. I had upgraded my mini lathe to a bigger 5″ 3 jaw chuck. The 3″ chuck wasn’t being used anymore so I put it on the gearhead.

Tombstones correspond to Fixture Plates on a mill.  There are many different shapes and sizes of Tombstones available for 4th Axes.  Here’s one I’ve shown before from a big horizontal milling setup:

I was reading an article about Tombstones in the Tormach blog recently and it got me to thinking about how Tombstones on VMC’s can make a job more profitable.

Tombstones are par for the course on Horizontal Machine Centers, but they’re seen a lot less often on Vertical Machining Centers.  Perhaps it’s because they’re just built into a lot of HMC’s at the factory whereas you have to set one up using a 4th Axis on the a VMC.  The question for this article is how to get a handle on their value?

There’s an old saying that you’re not getting the most return out of your CNC Machine until you have fixtured a job up so that every square inch of the table’s accessible area is being used to make parts.  Put as many parts as possible down for each setup, in other words.  Relying on just a single machining vise, for example, can mean a lot of available table area is wasted versus putting two vises on the table (so you get 2 parts per setup), or two double station vises (so you get 4 parts per setup).  It’s all about how many parts the machine can “chew” on for each setup.  The more the merrier because your setup time divided among all the parts will invariably be less on a per part basis.

Now consider a tombstone like the one pictured above.  It’s like having 4 smaller tables available.  In fact the width of the tombstone is 4″and the length is 13″, so counting all 4 sides, you get 4 x 4 x 13 = 208 square inches.  That’s actually 22% more area than the travels suggest would be available on the table.  So,  for about every 4 parts we can fit 1 part gets a free ride.  That’s not bad!

In addition, we can machine 3 faces on each part.  Ordinarily, that would take 3 setups which would be a lot more time consuming.  Pretty cool, eh?  Depending on how much additional setup time is required for this arrangement versus just using the table, we’ve probably made our job more profitable.  Perhaps by quite a bit.

Suppose we had a tombstone that was a full 18″ long to match the Tormach’s travel.  Yes, we might need a big fixture plate so the 4th axis and tailstock have room on the table, but that’s doable.  With the same math, we’d get 4″ x 18″ x 4 sides = 288 square inches.  Dang, now we’ve got 68% more available area and we’re really starting to cook with fire.  68% more parts each time we press the green button get finished.

Suppose we create our own “Tombstone” with a piece of 1″ thick cast iron.  We can go 2″ if we want it to be more rigid.  Now, let’s further assume it is the width of the table’s diameter, which for the 8″ 4th axis is 7.9″.  We’ll mount it dead center of the axis, make it a full 18″ long, and use the two sides.  Our total area is now 7.9 inches x 18 inches x 2 sides = 284 square inches.  That’s almost as good as the earlier tombstone example, and gives us 66% more area.

What if we have a triangular tombstone that just fits in the inscribed circle of the table?  No problem.  The math says each of the 3 faces of the triangular tombstone will be 6.84 inches, so we have 6.84 x 18 x 3 = 369 sq inches.  That’s 116% more area than on our table–twice as many parts per run.  Winner, winner, chicken dinner!

When you look at it this way, it’s not hard to see how a 4th axis with tombstone can increase the available area for parts in each setup and make available more faces of the part to be machined.

For round parts, and for many things that go ’round, lathe tooling is where its at.  After all, it’s optimized to do workholding along a rotating axis.  Hence, it’s very common to mount lathe chucks on your 4th Axis:

All the same ideas that apply to which chuck to use in a lathe work for 4th Axes on mills.  Years ago, I put together a chart that has been useful to me in turning work and we can refer to it here too:

“Repeatability” applies to the ease with which you can remove a part and put it right back into the chuck in exactly the same position so you can continue machining.  It’s a big factor to consider, but typically isn’t as important for 4th Axis work as it is for turning.  When turning, for example, you often have to swap a part end for end, or you may have to take an existing part and put it in the lathe to rework some aspect.  With a 4th Axis, you will often just stick in a piece of raw material, in which case Repeatability is not a factor.  Hence the ubiquity of the relatively non-repeatable 3-jaw chuck for 4th Axis work.

Turning between centers happens fairly often with a 4th Axis just because you have to make sure you’re supporting any part with significant overhang out at the end too.  How much is significant?  I was taught 3 or 4 diameters was about a much as you want to hang off the chuck on a lathe before you start looking for more support.

Collets are really nice for turning work (hence the ubiquity of the old Hardinge Lathes and their 5C collet system).  They get high marks on just about every aspect.  It’s no coincidence that the original Haas 4th Axis had a 5C indexer:

I never would have guessed it, but Geof on CNCZone says the following 4-axis mill set up was able to machine these aluminum bars to length, ensure the faces were square, and drill and tap a hole faster than he could do it in a lathe.  You can imagine each of those 4 parts being a 5C spin indexer and suddenly you fit quite a few more parts on your 4th Axis.

I’ve written at more length on Stallion’s Trunnion fixtures in another post.  They’re very slick, but you need to make sure they solve the problem you need solved for your 4th Axis.  In particular, the access to the part is going to be limited to the access you can get form a vise.  As such, you’d be looking to use a Vise on your 4th Axis largely because it is super easy, familiar, and to gain access to 3 sides of the work rather than just the top in a single setup.

Workholding and Fixturing are always an art that it pays to learn well.  I’m always on the lookup for clever setups and fixtures and you should be too.  The 4th Axis opens whole new avenues for fixturing and setup.

So I tried another blank, taking the opportunity to dial in the accuracy of my axis. For some reason, my Z was too low, so when the CNC roughed out the pen, it was already at or a hair below the finished diameter. For grins, I went ahead and engraved it, though the engraving was much thinner than I had planned. I packed it quickly with coffee and CA and turned it down. Yup, the engraving turned off here and there.

The Next Wave CNC 4th Axis gives you the ability to create precisely turned spindles or columns with intricate carvings and designs that wrap around the circumference of your work. The 4th Axis easily bolts to your existing bed and rotates with the help of its own dedicated stepper motor, providing the cutter with access to all sides of your project. It can be mounted parallel with the bed, or Machined from solid aluminum stock, the Next Wave CNC 4th Axis is built to last, and comes complete with a high quality Nova Precision Midi 4-Jaw Chuck, which firmly grips both round and square stock.

In a four-axis CNC router, there is an additional rotary axis (A-axis) that allows you to do rotary cutting and indexing for making cylindrical/round parts.

PRO4896 CNC uses a PRO rack and pinion system with linear guides to guide the X and Y-axis machine movement. Y-axis is driven by two stepper motors to prevent it from racking.

Avid provides many upgrade options for the PRO4896 CNC. The Rotary Axis attachment is the one you need to achieve fourth axis capability on this CNC router.

Their post-processor uses inverse time feed rates that prevent the production speed from slowing down during programs with combined linear and rotary motion.

The rotary axis is highly versatile, it can be mounted to the PRO4896 CNC router parallel to the X or Y-axis and can be recessed to the machine to help maximize the workpiece diameter.

The 49" rotary axis used in the Avid PRO4896 CNC router can be mounted with a maximum workpiece length of 34" if mounted parallel to Y-axis, and 28" if mounted parallel to X-axis.

Avid CNC"s post-processor for rotary control is available for all the Ventric software products and for the Autodesk Fusion 360 software. It can be downloaded either directly from the Avid CNC website.

They also have detailed instructions on assembly, different mounting options, and the electronics of the rotor axis. It is available on the website and in the user manual.

Avid offers various accessories like a leg kit, auto Z and corner finding touch plate, proximity sensor kit, composite nailer, dust shoe, plasma kit, and a rotary axis.

The chuck and tailstock of ShopSabre"s 4th axis system don"t come attached to a frame, so each can be mounted on the worktable in different configurations.

ShopSabre 23 has a wide list of accessories like the 4th axis kit, braille kit, computer mount, digitizing touch probe, laser sight, tool measure switch, tabletop, vacuum pump, warning light bar, and wireless pendant.

GDAE10 6040 CNC router is the best budget-friendly 4-axis CNC router on this list. It comes with a rotary axis that can be attached along the Y-axis to attain 4-axis control.

The fourth axis control in GDAE10 6040 CNC is achieved through a rotary system with a 3-jaw chuck and a tailstock. It comes with a belt, tailstock, rotary axis, and five wrenches.

There are a lot of videos on youtube on cutting different materials using GDAE10"s 4th axis, you can refer to them to get a visual idea of its operation.

The 6040 CNC router has a large user base because of its low price. It is a great introductory 4-axis CNC to many people trying to come into 4-axis CNC machining.

The iQ CNC router machine can be upgraded with the Laguna Fourth-Axis Attachment for achieving 4-axis control. It helps you machine complicated designs.

The 4th axis attached to Laguna iQ can work on workpieces having a length ranging from 12" - 26" and a maximum diameter of 7" depending on the optional table size you opted for.

You can use 4-axis G-codes generated from any G-code generator directly on Laguna iQ through a USB flash drive and iQ CNC can operate without a computer.

Next Wave CNC"s Shark HD520 is a popular choice among small businesses and many woodworkers. It can do 4-axis machining with a 4th axis rotary system installed in its work area.

The Shark HD520 CNC can be upgraded with the Shark Standard 4th axis rotary system. The rotary system provides 4-axis machining capability to your HD520 CNC router.

You can place the 4th axis driver board on the controller slot by facing the pins out of the box, then you"ll have to tighten it with provided screws to hold it in place.

The 4th axis post-processor can be downloaded from the Next Wave CNC"s website. These post-processors are used to process and convert designs and toolpaths to CNC readable G-Code.

In most cases, a 4-axis router kit is used to achieve 4-axis machine movement but to control this additional axis you"ll need to have a 4-axis compatible controller.

To put it in a simple form, the standard 3-axis together with the A-axis gives you a 4-axis setup. A-axis is the rotational axis that turns the workpiece.

4-axis machining brings in a great deal of flexibility to your CNC machining process, enabling you to create some of the complex designs that otherwise would not be possible.

4-axis CNC machines are costly because there is a lot of research and development going into building all these machines. You require 4-axis supported controllers, software, and CNC machines to do 4-axis machining.

Also, 4-axis designs require a high precision system to design those models. To make high precision systems you need to use a rigid machine built with well-calibrated electronics. As there are more moving parts in the machine, the operating complexity increases, and a lot of support systems are required to keep the machine running.

In 5-axis machining, two rotational axes operate separately to rotate the workpiece in many different angles with respect to the cutting tool. The machine may utilize either A-axis or B-axis with the C-Axis to achieve this feat, all these are rotational axes.

In 4-axis CNC machining only one rotational axis is there, but with 5-axis machining you can achieve two rotational axes that can operate independently. It brings in a great deal of flexibility in your CNC machining.

Yes, due to the advanced system, a 4-axis CNC requires specialized software to control the movement of the fourth axis. It requires CAM and control software that supports 4-axis machining. To control the machine properly, the software must understand the geometry of the 4th axis and how it relates to the other axes.

Small Milling Machine CNC Control system: $18,385M400 3 axis with 1Kw AC Brushless Yaskawa servo motors and drivesMedium Milling Machine CNC control system: $22,175M400 3 axis with 2Kw AC Brushless Yaskawa servo motors and drivesLarge Milling Machine CNC Control system: $25,760M400 3 axis with 4.4Kw AC Brushless Yaskawa servo motors and drives

Small Slant Bed Lathe CNC control system: $15,450T400 2 axis with 1Kw AC Brushless Yaskawa servo motors and drivesMedium Slant Bed Lathe CNC control system: $18,795T400 2 axis with 2.2Kw, 2.2kw w/brake AC Brushless Yaskawa servo motors and drivesLarge Slant Bed or VTL CNC control system: $21,597T400 2 axis with 4.4Kw, 4.4 Kw w brake AC Brushless Yaskawa servo motors and drives

Auto part set, Auto tool set, 3D contouring, 4th and 5th axis machining, Available in OEM configurations, Professional Installation with Service & Training and DIY CNC kits for both new machines and retrofit upgrades.

CENTROID Boss series II retrofit customer testimonial"The quality and workmanship of the CENTROID equipment was outstanding and very professional. CENTROID was able to custom tailor the control to allow us to continue to use our rotary milling arrangement as before and even expanded our capability. The short story is that we ended up with a four axis CNC mill for less than half the cost of the three axis Haas. This includes the work that was done by our staff."