Help with rotary table

[Eric CoxParticipant @ericcox50497]

When cutting spokes on a fly wheel by removing segments on a rotary table how do I ensure that the spokes are square to the hub and not leaning forward or backwards.

[Eric CoxParticipant @ericcox50497]

[Les Jones 1Participant @lesjones1]

Start by setting the X and Y zeros of your DRO to the centre of the flywheel. Calculate how many degrees each segment is at the outer diameter allowing for the radius of the cutter. work out how many degrees between the sides of each spoke again taking into account the radius of the cutter. Start with the rotary table set to zero degrees. Rotate the table to half the angle of the spokes. Now take the cut swinging backwartds and forwards between that point and that point plus the angle of the segment to be removed. when you have gone all the way through add the width of a spoke angle to the end of that segment position and repeat the process until you have made the outer cut of all the segments. Set the table back to zero degrees. (I will asume the sides of the spokes will be cut in the Y direction.) MOve the table in the X direction untill the cutter lines up with the start of the first slot. You will have to adjust the Y position very slightly. Cut the side of the spoke by moving the table in the Y direction. Repeat for that side of all the spokes. Back to the first spoke move the X axis to the other side of the spoke and repeat the process cutting the other side of each spoke. When you have done all the spokes set the X axis back to zero. Position the cutter at the inner end of one of the spokes by adjusting the Y axis and rotary table angle. Cut the inner radius to the next spoke rotating the table and judging by eye when yo meet the next spoke. You can calculate these angle but remember that with parallel spokes the angle og the inner cutt will be different to the outer cut.

Les.

[EmgeeParticipant @emgee]

Hi Eric

For parallel spokes if using the rotary table on a vertical mill centre the flywheel to the spindle centre.
If you are going to use the X axis to make the cuts move the Y axis in by the sum of halve the spoke width plus halve the cutter diameter.

So for a 8mm wide spoke using a 6mm diam cutter Y axis will be 7mm off spindle centre.
After the 1st cut raise the tool clear and move the Y axis to the other side of centre by the same amount, 7mm in the example above.

If the spokes are tapered with the small dimension at the circumference you will need to offset the rotary table a few degrees each side of the indexed position for every cut, the amount can be calculated easily.

When all spokes are cut you can use the rotary function to cut at the hub and inside rim diameter to remove the pieces.

Emgee

Call this method 2, Les beat me to it.

 

 

Edited By Emgee on 17/08/2018 11:20:28

[Clive FosterParticipant @clivefoster55965]

If you have a suitable CAD program its well worth drawing the job out first to ensure your visualisation of what you intend to do is right.

A good time to use layers. Put the drawing on the bottom layer then make a transparent layer above it. Put the cut lines corresponding to the centre line of the tool on in a different colour. Add cutter diameter circles at the ends of the cut lines so you can see where the cut finishes.

Play around with cut line lengths and angles until you are sure you understand what can go wrong. Then print it out on sticky back paper and do a test cut on suitable scrap material.

Best to make the start point whole number of 10's. Zero if you can make that work. Write the numbers down clearly & neatly where you can see them whilst driving the machine. I have a decent size whiteboard on the wall for that which not only provides plenty of room for cut position lists but also lets me make decent size sketches to show exactly what I'm trying to do.

Angle offsets can be total bear. Best if you can arrange each cut to be on zero, or at least an easily set whole number, on the fine setting dial. My bigger rotabs have a sliding vernier rather than dial which sometimes makes visualising what's going on much easier.

Errors will stand out like an elephant on a snooker table. The Mark 1 human eyeball is superb at detecting such asymmetries. You must use travel stops.

One of those jobs that is really hard work first time though needing total concentration. Door locked, "Danger P-Off Model Engineer at Work" sign up, phone unplugged and mobile in the house. But after the fourth time you will wonder what all the fuss was about. As always with such things the trick is to get your thinking done first.

Clive.

Edited By Clive Foster on 17/08/2018 13:31:54

Edited By Clive Foster on 17/08/2018 13:32:33

[Tim StevensParticipant @timstevens64731]

The force acting on a spoke of this sort diminishes as you go outwards, so some spokes were made tapered. Not too much or it can look silly. This might be good news if you are struggling …

Cheers, Tim

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