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Examples of Use

Direct Rotary Table and Dividing Head control

DivisionMaster is well suited for use as a controller for a CNC dividing head or rotary table. The following photo shows two Vertex rotary tables, the HV6 (6" diameter) on the left, and the HV4 (4" diameter) on the right, adapted for use with the DivisionMaster controller. The coupling and mounting hardware used to mount the Size 23 stepper motors can be seen just in front of the controller box. Both the HV4 and HV6 tables are best driven with motors rated around 200 oz-in holding torque; the HV4 table in the photo is fitted with a smaller motor, around 140 oz-in, but the larger motor is preferable. The converted HV4 and HV6 tables sold by us (see Prices page) are all fitted with 227 oz-in motors.

The next photo shows the HV6 table being used to mill a curved slot in a brass disc, with the DivisionMaster controller set to the appropriate angle of rotation, and the milling operation being performed as the table is rotated under (stepper motor) power.

The following photo shows a Vertex BSO dividing head adapted for use with the DivisionMaster controller. The same mounting hardware used for the Vertex rotary tables is used, along with a motor of around 200 oz-in of torque.

The photo below shows the Sherline 4" diameter "CNC-ready" rotary table, fitted with a small stepper motor (about 60 oz-in holding torque); as the Sherline table is exceptionally free-running, a small motor like this will drive the table, although around 100 oz-in would be preferable. For a larger table (or a small table that presents a greater frictional load to the stepper), a higher power motor would be appropriate.

Taig also sell a CNC rotary table (based on the Sherline device but with their own motor and coupling arrangment) to use as a 4th axis with their CNC mill.

It is possible to adapt a wide variety of devices for use with the DivisionMaster controller. The next picture shows a 5C collet spin indexer that has been adapted by attaching a standard gearbox (normally used for reduction drive with electric motors) to the back end of the spin indexer shaft.

Many model engineers have built dividing attachments based on the George Thomas design that drive the bull wheel of their Myford lathes to give direct indexing capability in the lathe. The ML7 version of this dividing attachment is somewhat problematical from the division plate point of view, owing to the fact that the bull wheel on the ML7 has 65 teeth (as opposed to 60 on the Super 7, a more useful number for dividing use). However, replacing the manual indexing arm and dividing plates on one of these devices with a stepper motor controlled by DivisionMaster fixes the problem very nicely. The following photos show such an attachment attached to an ML7; in the second photo, the controller is set up for 43 divisions, not easy to produce on a dividing head with a 65:1 drive ratio. The third photo shows the attachment removed from the lathe; fixing/removal of the attachment takes a few seconds. A writeup of this dividing attachment can be seen by following this link.

The following photo shows a small stepper-controlled dividing head, designed around a modified Taig lathe headstock with a 72:1 worm drive attached (Follow this link to see the complete design of this dividing head and its accessories).

The dividing head was originally built to use as a 4th axis for a Taig mill; however, it can aslo be used under the control of DivisionMaster, and as it is designed around a Taig headstock, the dividing attachment (stepper motor and mount, plus worm drive) can be directly attached to a Taig lathe, as shown in the next photo.

Using DivisionMaster can increase the versatility of a 4th axis device - it is no longer dedicated to use with the CNC mill, but can be used in other applications as well.

The same dividing head was later pressed into service as part of a clock wheel cutting engine, made out of Taig (Peatol) lathe components and accessories, that is used to demonstrate DivisionMaster's capabilities at the various Model Engineering exhibitions that we attend. The next two pictures show a plan view of the the wheel cutting engine and detail of the dividing head holding a completed wheel. Full details of the wheel cutting engine appear in issue 96 of Model Engineers' Workshop.

Although DivisionMaster's internal power stage is limited to driving motors of up to 2A/phase, it can be used with much more powerful motors, driving much larger rotary devices, with the addition of a suitable external power stage, as illustrated in the next photo. John Stevenson, who runs an engineering business in Nottingham, UK, has been using DivisionMaster to drive this Hoffmann dividing head, which he has fitted with a MEMA 42 size 9A/phase stepper:

Here, the step-and-direction signals generated by DivisionMaster are being used to drive a Gecko G210 motor drive stage, which can supply up to 7A/phase - less than the motor's capacity, but plenty for this application. The Gecko was set to operate in half-step mode. This Hoffmann dividing head has a 40:1 gear ratio between the motor and the output spindle. The 12" ruler gives an idea of the size of this beast - it took 2 of us to lift it onto the table for this test.

John uses the Hoffmann dividing head in conjunction with his horizontal milling machine, as shown in the next set of pictures.

The top left shows the dividing head in position on the mill bed, with a multi-tooth gear cutter fitted to the mill spindle. Top right shows gear cutting in progress, cutting the seventh tooth - he was cutting four 27-tooth gears simultaneously. Bottom right shows the display of DivisionMaster at this point - the actual position is 93.330 degrees. The theoretical position should be 93.333 degrees; John said that the positional error on any one of the 27 moves was never more than 0.008 degrees.

The final photo shows the finished gear. To quote John: "No problems occurred doing this job. It went very smooth and saved a large amount of time as opposed to manually indexing. Biggest saving was peace of mind, as I was running two other machines at the time. The display told me exactly where I was. Time taken from start to finish, less setup time, was 47 minutes."

The "Alan Timmins" dividing head

Some while ago, Alan Timmins designed a dividing head aimed primarily at Myford ML-7 users, for which Blackgates Engineering supply a set of castings. He has recently adapted one of his dividing heads for use with the DivisionMaster controller, using a modified verion of our Vertex motor coupling and a 140 oz-in size 23 stepper motor. The following photographs illustrate the conversion and the dividing head in use.

The first photo shows the dividing head being used to mill the winding square on a clock winding arbor:

The second photo shows the same setup from the rear of the dividing head:

The third photo shows a 0.6 module 144-tooth Great Wheel being milled:

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Copyright 2006 Tony Jeffree.