Board Sensor, really stupid question

[John]

I think LHR should do away it. All it does is confirm what it should all ready know. If an operator can figure out how to "build" a project with the software, surely they are capable of using a tape measure to tell the machine the correct starting size of the project. If the machine can find the top, left hand corner of the board it should be good to go. This could be easily accomplished by manually jogging the end of the board to a reference point, and then telling the machine "you're good to go." What am I missing here??

[newcarver]

I have went through several board sensors and would have to agree, or else at least design a better one. It could be made like to the probe and simply jog to the specific points on the board.

[Jeff_Birt]

The board sensor does way more than just measure the board. It also tells the machine where each edge is w.r.t. the axis encoders. BTW, they have recently been shipping SEALED board sensors. I think that is a step in the right direction.

[John]

The top edge is always at the same place. Shouldn't be too hard to find where that is without a board sensor. Just a reference point for the Y axis would work.

Calibration, you ask? Could easily be done with a test pattern like a printer does, ie. which lines, line up, A, B, or C?

[Jeff_Birt]

The top edge is always at the same place. Shouldn't be too hard to find where that is without a board sensor. Just a reference point for the Y axis would work.

?????Just watch the machine work...It finds each edge of the board. This not only tell the length both WHERE it board is W.R.T. the axis encoders. Otherwise it has no idea how big the board is or where the board is.

[John]

?????Just watch the machine work...It finds each edge of the board. This not only tell the length both WHERE it board is W.R.T. the axis encoders. Otherwise it has no idea how big the board is or where the board is.

How can I make this any easier to understand?? For argument sake, lets say a board has 4 edges. A top, a bottom, a right and a left. The top will start (and hopefully remain) against the rail on the keyboard side of the machine. The left will start at a TBD (to be determined) reference point, which will be verified by the operator. Now, for the sake of argument, this board is 10" top to bottom, and 20" right to left. Is it too much to ask for the software and hardware to figure out where 10" from the rail on the keyboard side is? Same scenario, for the right and left. The TBD reference point will be X distance from the board position sensor so with a little addition and subtraction both right and left edges should be easy to locate.

Now, I certainly don't want to insult my own intelligence, I just want to have some fun with this and try to understand why a board sensor is necessary. I can't come up with a reason / situation where one is necessary.

[Jeff_Birt]

John I see where you are going but I think you are still missing a few key points on what the board sensor does. I'm also not trying to be contentious, rather I'm trying to bring to light some of the benefits of having the board sensor. I've design automated machinery as part of my job and can say with confidence that machinery is quite stupid. Things that you and I might take for granted as being quite evident are not so from a machines point of view.

I use a small bench top mill at work that operates very much like you are saying. You home the mill clamp down your workpiece and then you have to move the mill to one corner of your workpiece and zero the mill. Then you can start cutting. Getting all three axis zeroed properly is not trivial.

When you start up the machine it has no idea where any axis is at. It will go through the homing routine which lets it know where the Y and Z axis are in relation to a fixed point on each axis. The X axis of course is the traction belts and has no reference to compare against.

Now when you put a board in the machine it will no where the Y and Z axis are in relation to a fixed point on each axis; but the machine will not know where those fixed points are in relation to the board. That might sound funny but due to manufacturing tolerances you can never know unless there is some method to calibrate the offsets and then that calibration needs to be regularly checked. Also you have no idea where is the X axis the board is or what size the board really is.

So, the CW machine starts to measure the board. It finds the top edge then the bottom edge; now it knows where they are w.r.t. the Y axis encoder reading. Then it measures the length of the board and knows where the board edges are in relation to the X axis encoder. When you put each bit in it checks each on to find its position relative to the Z-axis and relative to the top of the board. If you used fixed reference points as you describe then you open up lots of problems with operator error and continuously trying to calibrate the offset for the Y axis.

The side effects of having the machine measurement are that it can verify that you are using the correct size of stock, if you are using a different size stock then it can automatically scale a project for you.

I hope that all makes sense...

[John]

Jeff, you have convinced me I could not be more correct. One sentence confirmed my thinking.

"I've design automated machinery as part of my job and can say with confidence that machinery is quite stupid."

I could not agree more. I bought a high priced hammer (yes, a quite simple automatic machine that is very stupid). I swing the hammer at the nail, the hammer hits the nail, and the nail automatically goes deeper into the wood. However, one of the first times I used that hammer it automatically just about smashed the end of my finger to smithereens. Now granted, I was a lot younger, and at the time didn't realize how stupid the machine was that I had just bought. Since that experience I have been much more careful how I use that simple machine.

So, how does this relate to the CW? (I'm glad you asked!) The CW is very stupid. It is a combination of belts, bearings, screws, leds, lcds, transistors, diodes, etc. etc. etc. Together they make a nice boat anchor. HOWEVER, the smart software developers at LHR can make it sing (so to speak). Just as the maker of the hammer I bought, had confidence I could program myself to hit the nail, they will have confidence that I can tell the CW the board size and load it with the top against the rail and one edge at a TBD reference point. Too simple. Not at all. I can think of even simpler methods, but will not bore you all with them. Thanks for listening, John

Begin Edit:

The above is to be regarded as a compliment to the LHR software development team. I have nothing but respect for them. Do I think they are looking for input from users to improve the software? I hope so. At least two readers have misunderstood this whole discussion. I hope this clears up my position on this matter.

[Jeff_Birt]

The reference point is the problem John...

[optionman]

the reference point should always be (0,0,0) bottom,right corner, or bottom left corner. from (0,0,0) if i tell the machine that my board is 10x14x1, i assume the bit can find any point on the surface from there on. Sorry for my 2 cents but that's my first impression.