Name Required. Mail Will not be published Required. You can follow any responses to this entry through RSS 2. You can leave a response , or trackback from your own site. Net Blog is powered by WordPress 5. Home Buildlog. Stepper Driver Arduino Shield ». The board uses low cost socket mounted stepper drivers. These are easily replaced if ever damaged without any rework to the PCB.
A compatible relay driver is planned that also fits this socket. This will allow up to 2 relays to be controlled per board. These are controlled via the set and direction pins associated with that axis and uses the existing terminal blocks for that axis.
This is perfect for a spindle on a CNC router or assist air on a laser cutter. There is an integral cooling fan for the stepper drivers. It mounts directly to the board and has a dedicated power connection. It is mounted high enough to allow heatsinks to be mounted to the drivers. This will allow the drivers to run at their full potential of 2 amps per coil.
There is a 1 amp 5V switching power supply on board. This will not get hot like a linear regulator due to the voltage drop from the motor supply. This can optionally be 3.
All other items on the board are 5V — 3. The resolution of the drivers can be independently set via rotary switches. The resolution is selectable between full step, 2x, 4x, 8x and 16x microstepping. These and the control connector are flush mounted to one side for easy bulkhead mounting. The board has a dual pattern for the control connector. With that in mind, why not think of that Tombstone in the 4th Axis as being all about creating more addressable table surface area?
Now consider a tombstone like the one pictured above. So, for about every 4 parts we can fit 1 part gets a free ride. 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? Perhaps by quite a bit. Our total area is now 7. 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. Winner, winner, chicken dinner! 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:.
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. 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. Perhaps the biggest shortcoming of 5C collets is they only allow for parts of relatively limited diameter. This can be overcome by turning things on their head. Consider this setup:. 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. In particular, the access to the part is going to be limited to the access you can get form a vise. Note that on a big Horizontal Mill tombstone, you may mount multiple vises on 4 sides of the tombstone and even more than one on each side. That creates a lot of capacity! Workholding and Fixturing are always an art that it pays to learn well.
The 4th Axis opens whole new avenues for fixturing and setup. The first 3 Axes are the familiar X, Y, and Z. The A and B axes are potential 4th Axes. Then you can simply refer to is as such in G-Code.
Rotating the 4th axis to the 90 degree position might be done as A90, for example. With most controls, 4th Axis coordinates get all the tricks regular coordinates have available. So, for example, you can use Absolute or Incremental Coordinates. And, if you there are 4 parts on each side, you might also have 4 sides times 4 parts or 16 work offsets. With those 16 work offsets, you can create 1 part program in your CAM software, set it up as a subprogram , the set the work coordinate, call the part subprogram, set the next work coordinate, call the subprogram, and so on, to make all 16 parts.
Part Zero is, of course, the origin, when programming your part. When 4th Axis programming, it is often convenient to have a part 0 on each indexed face of a tombstone, for example. That way you can use Work Offsets as described above. That makes sense for 4 axis CNC indexing. But, when doing continuous 4th axis machining, it might make more sense to have the axis the 4th spins on be 0. Choosing part zero for continuous machining will require that you be very familiar with your CAM software.
Instead, you will use one of 2 kinds of software to help. In essence, you program the work on a flat XYZ plane. For example, you might create some sort of text engraving. The 4 Axis Wrapper Software will then transform that g-code so it is wrapped around a cylinder of a particular diameter. Wrapper Software can be useful, but clearly it has many limitations.
We have a lot of readers who are interested in the details and even in building their own 4th axis. To create a 4th Axis basically requires that the axis be well mounted so it can spin, and that there be some means of controlling that spin via g-code program, preferably with as little backlash as possible—backlash is the enemy of CNC.
The mounting process is not unlike mounting a spindle. Typically there will be a shaft between bearings. I suppose you could even contemplate sleeve bearings as opposed to precision angular contact bearings, although the latter are standard industry practice.
Tapered roller bearings can also work reasonably well for a 4th axis. Perhaps the simplest low backlash approach would be a Geneva Mechanism.
The drawback is that 4th Axis Continuous machining is impossible because the Geneva Mechanism has a fixed set of stopping places. Hence can only be used as a pure indexer and not a true 4th Axis. Hobbyists are often taken with the idea of using a Rotary Table. The worm gear mechanism of most rotary tables has a fair amount of backlash. They require adjustment often to keep the backlash out.
You could use a timing belt just like the kind that are used for the X, Y, and Z axes on a mill. Even a linear axis has the further reduction of the leadscrew. This approach is doable, but you need to pay close attention to the resolution of your stepper or servo motor lest you wind up with not enough accuracy positioning the axis. There are other advantages too. One neat thing about this style is it allows fairly high speed operation of the 4th axis spindle.
Enough so that with the proper timing belt ratios you could use it as a lathe headstock and attach the tooling to your mill spindle. See my write up on this neat combination 4th Axis and Mill-Turning gizmo …. Suffice it to say they offer nearly backlash-free gear reduction—perfect for this application. For a long time they were really cheap on eBay as they were Industrial Surplus and nobody knew what they were good for.
Unfortunately, the word is out so you have to look carefully to find a deal. Nevertheless, one with an appropriate ratio would make a sweet 4th Axis. There are many more odd mechanisms that eliminate backlash and perform the reduction function.
I wanted to mention one more since Haas just launched a new high-speed 4th Axis that uses this approach. They hold that cam pretty tightly on both sides. It would be interesting to try to machine a Globoidal Cam with enough precision to work in such an application. Enough about the rotary motion, we also want to be able to stop our 4th Axis. In addition, we want significant holding force when stopped.
Traditionally, this can be done either by chucking up the part in the mill spindle and putting the lathe tooling on the table, or by sticking a lathe headstock on the mill table and mounting the turning tools on the spindle. Both methods work, but with a 4th Axis that is capable of spinning fast enough to act as a lathe headstock as well as capable of indexing as a 4th Axis, there are a world of possibilities. For the most part, the principals of 4th Axis use with a CNC Router on wood are much the same as the more metal-focused articles that have come before.
The goals of 4th Axis woodworking are often a little different. You seldom see 4th axis as a way to access more sides of the part without more setups or as a way to machine more parts in one setup through indexing. In fact their limited Z clearance would make it hard to use one for the purpose anyway. Most 4th Axis woodworking is about continuous indexing in order to do round work such as engraved cylinders of columns of various kinds for architectural work:.
The video shows a lot of the typical pineapple and other shapes common to ornamental turning. Slinging the workpiece alongside the table allows for quite large work to be done and gets away from the Z-travel limitation that many router tables have.
One of the most exacting and beautiful uses for CNC 4th Axis Woodworking is inlay work, particularly for custom guitars, pool cues, and similar work. A quick way to access a lot of small parts with a Fourth Axis. The cylinders can be swapped out quickly for almost palette-changer like setup times.
Another cylindrical fixture for small parts. Note the washer cutout. Lots of small parts in a fourth axis fixture with pneumatic clamping….
Another setup for making lots of small parts. It overhangs the 4th and the tailstock so the tombstone can use the full travels of the machine for maximum production…. Depending on your application, it makes sense to think about how to make setup faster. Dialing in the fourth axis and tailstock can be a pain, but if you have a fixture plate, you can set up for drop in repeatability.
Next question is how to repeat installing you fixtures on the fourth axis? This shop-made fourth axis tailstock that goes with the same Jergens locked tombstone above has some cool ideas. On the other side of the tailstock is a little movable v-block that holds the tombstone until the sliding ballnosed pin can be engaged to hold it securely.
Very well thought out! For this part, access on the two sides was important, and the fourth axis makes that easy. Note the lever to release the pneumatic lock on the left. Very slick tombstone trunnion from Stevens Engineering has quick locks for fixture plates. Another neat fixture from Stevens Engineering. Check out the uniforce clamps on this fixture for holding small parts.
Parts are supported via V-block cradle and individually hydraulically clamped. What kinds of neat fourth axis fixturing have you used on your jobs? Share some examples in the comments below!
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