Saturday, December 5, 2009

Planning the Steps Involved in Machining A Job

A CNC program is a series of operations performed for specific selections of the tool, for a specific orientation/fixation of the job and at a selected combination of settings of the machine.

The series of operations is decided by the design of the job. So lets start with a simple part such as that shown in the picture below.

Here is a picture of the stock available to you.

Based on the stock and the final object desired, we determine that we need to machine both sides of the stock. We also determine the specific procedures and tools needed for each side and make a list pertinent to each side. 

Based on the two lists, we can already know some of the tools we need to load into the machine. In addition, we also need to determine if some of the steps need to be repeated with a finer tool for better finish. This is usually determined by the machinist after test running a piece to see the quality of the output and checking that against the requirements of the customer. 

For the first side, we need the following procedures performed. Let us assume that we do not need to machine the two off center holes on the job drawing:

a) The top of the cylinder has to be faced in order to me make sure that the the surface is truly perpendicular to the height of the cylinder and to give it a smooth finish.
b) The central hole has to be drilled.
c) The chamfer on the outside rim has to be machined
d) The champfer on the inside rim has to be machined

This is what the job looked like after the first side was done.

For the second side, we determine that the following procedures need to be done.
a) The bottom of the cylinder has to be faced in order to me make sure that the the surface is truly perpendicular to the height of the cylinder and to give it a smooth finish.
b) The outer rim of the cylinder has to be machined for a smooth finish.
c) A large partial hole concentric with the central hole has to be machined.

This is what the job looked like after the second side was done.

Bob and I ran (alright, I admit I didn't write the program or pick the tools) the test run and determined that for the first side, step (c) needed a finishing step after the main step and the same repetition for step (d) for the first side and step (c) for the second side. Thus all in all, we actually ended up with 5 steps on the first side and 4 steps for the second side.

I find that CNC machines are very fascinating! Here is a shot of the machine in action.

Some useful tips to remember:
1. When you start a CNC machine at the beginning of the day, for the first job, you need to back off about a thousandth on your cutting tool calculations because everything is cold. This manifests as the cutting tool cutting a little less. 

2. Conversely, I also observed the opposite - after several runs (this was a 200 piece order), the tool bits do expand from heating and you might have to move in another half-a-thou. Otherwise the holes you drill may be the slightest bit loose.

3. Unloading and Loading tools into a CNC:  In order to change tools on a CNC, you can generally (although this is specific for Mazak) find a TOOL menu item which can be expanded to show several options. Choose the MDI (Manual Data Input) option. Then you will be prompted to enter the tool number you want to change (typically up to 10 tools) and hit INPUT. The machine will then move the tool block so as to present the request tool head to the user. Twist and pull out the tool. 

Putting in the tool must always be done in the same way, with a large dot on the tool always positioned either to the front or the back (depending on the machine involved), so be aware that there is danger for misalignment if this is not observed.

Above you can see some of the finished pieces stacked together.

Tuesday, December 1, 2009

The Kidd Effect and Faraday's Law of Induction

Consider the flywheels of the RelMachine. They are mounted in frames, on ball bearings to facilitate their smooth rotation. The frames themselves are affixed to the (rotatable) central machine axis. When we rotate the flywheel assembly about the central axis of the machine, what are the conditions that obtain? The flywheels have mass. They are being spun about the central machine axis. Under such conditions, the flywheels are being acted upon by the machine axis - the machine axis is exerting a centripetal force.


A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the "real" or "reactive" centrifugal force: it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[5][6][7]
The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[8] Newton's reactive centrifugal force still appears in some sources, and often is referred to as the centrifugal force rather than as the reactive centrifugal force.

Now, so far the flywheels haven't themselves been spun up. Therefore, in accordance with Newton's laws, the flywheel then exerts an equal and opposite centrifugal force upon the central machine axis.

What happens if we first set the flywheels spinning to a large, fixed rotational speed ω z rpm and only then started spinning the entire flywheel assembly about the central machine axis? The answer to that question depends on whether or not there is a significant rate of change of angular acceleration in the motion of the flywheel assembly about the main machine axis.


If there IS a significant rate of change of angular acceleration, the answer proceeds as follows:

In order to extrapolate the expected behavior of the flywheel in this case, we reason that since the flywheel is inductively suspended, we must look to the behavior of an inductor. An inductor RESISTS a rate of change of current through it.

Thus when an inductor begins to feel the surge of rate of change of current, it will correspondingly generate enough potential difference to overcome and cancel that current so as to maintain its previous state. However, if there is even so much as a tiny bit of capacitance coupled to the inductor, them the together form an LC circuit and will therefore have a unique threshold frequency peculiar to them. - This is an element of a low pass circuit, which means that any and all frequencies below the threshold frequency will receive a 'pass' from this circuit.

The exerted surge can have a periodic character or can be more of a simple speeding up character. Lets analyze the two.

If the surge is cyclical for example like this, the analysis is perfectly analogous to the LC low pass filter circuit. Thus all such inputs will meet the 'pass' condition of the low pass filter circuit.

Under such conditions, the circuit will resonate with the energy and some of it will leak into the ambient surroundings. The equivalent of this in the mechanical case would be the SHEDDING OF CENTRIFUGAL FORCE.

If the surge is more just a transient thing on the way to acheiving a steady torque used to accelerate the assembly to a large angular velocity about the central axis, this is what the time vs angular velocity, acceleration and rate of change of acceleration will look like.

We can see that the inductive phenomenon will only be effective for the following time periods: the beginning when the wheels starts speeding up about the central machine axis, and at the end, when the flywheels were brought to a stop. Thus the effect would be transient and barely noticed excepted at the beginning and the end of the operation.


If there isn't a significant rate of change of angular acceleration: This is similar to situations where the flywheel is spinning and the assembly itself is
i) being moved in approximately straight lines,
ii) or being moved at constant accelerations
iii) or being moved at constant velocities.

Under such circumstances, relativistic effects are hidden from our view. The phenomenon proceeds as a Newtonian interaction.


We can see from the graph at the very beginning of the Kidd Effect video, that there is large rate of change of acceleration being deliberately induced by vertical motor at the top of the Relmachine, in a cyclical fashion. Thus the flywheels respond as in CASE A.

Now, some energy from this capacitance-inductance circuit will 'leak' into the surroundings i.e. the flywheels will shed centrifugal force. It means the flywheels will lose part or all of their ability to produce a centrifugal force in response to the exerted centripetal force. This shedding of centrifugal force has consequences. The most direct consequence is that if there is a way the flywheels can move, either inwards or upwards they will move. The conditions governing the movement are as follows:

1. The flywheels are spinning fast enough (condition 1) and the applied rate of change of torque is large enough (condition 2) to over the gravitational force acting downwards, and the force rquired to forcibly move the flwheel vertically is less than the force required to move the flywheel horizontally (condition 3): Flight will result.

2. If condition 3 is not met, then if the conditions 1 and 2 are met, then we see what happens in the end of the video, when the flywheels forced themselves inwards.

3. If condition 3 is met but 1 or 2 are not met, then the RelMachine will show no net movement, but will show a net leakage of energy because the energy channel is open. Just not full. As conditions 1 and 2 are fulflled, the channel will fill up and the relMachine will fly. Until then, the leakage of energy to the gravitational field will steadily increase as we increase our ability to meet conditions 1 and 2 (ie we increase the flywheel speed or the rate of change of acceleration).


In Sandy's patent, he exerted forces on the flywheels in a slightly different, but nonetheless very creative manner.

"means for periodically forcing said masses towards one another from a predetermined position and allowing said masses to return to said predetermined position so as to generate a pulsatile force in said mounting means."

US Patent # 5,024,112

Thus the wheels were physically pushed towards the central machine axis. This is equivalent to the RelMachine's operation. In the RelMachine, that 'pushing' force is being exerted by the centripetal force, which in Sandy's machine, it was being done by a cam, in a very physical way.

Thus, in the case of his machine too, a cyclical consistent amount of lift will be delivered. Depending on the match between the resonance frequency of his machine and the applied cyclical torque, the output could have been suboptimal.


I have determined that at this point, I must amplify the output. I will endeavor to do so in the coming weeks. I expect to run new, amplified experiments within the next 3 weeks.