resetting X cal by hand

[myshop1044]

I know we discuss this at the conference, but I don't remember the steps.
I have 14" designer board and 12 1/16" foam board. I am getting a scale to length notice 13.747/1400.
I did a x measure of the board and it had 20.753". I went to reset x cal by manual, did a #2 for new and that is where I got lost, (the default is .890.43) which way do I go up or down on the input to reach the proper distance. I tried .900.43 and nothing happened, not sure if I reset the cal or not. Can some one direct to the steps to reset the x cal by hand. I looked in the softwhere manual and saw not title to this effect.

[DaveN]

Its not in the softwhere manual, you'll find CALIBRATING THE MACHINE OFFSETS on page 50 in the Owner's Manual

[myshop1044]

Yes thanks you I found what I was looking for and you were right. Something is still strange.
I measured a 36" board and reset the x cal so it measured 34.988, so I thinks is very good.
I put in the 21" foam board and it still measures 20.789, seems like whatever I do it want measure right on the foam board.
I'll keep trying or just add an extra inch to the foam board and keep going.
thanks again.

[myshop1044]

I had a typo the board measured 35.988.

[bergerud]

Am I dyslexic or are the x calibration instructions backwards from the behavior of the machine?

To calculate the value to enter, first take a look at the difference in the measured
lengths. If the hand measured length is longer than the machine measured
length you will need to add units to the displayed current value, and conversely, if
the hand measured length is shorter than the machine measured length you will
need to subtract units from the current value setting
To find the magnitude of the change to the current value subtract the two
numbers (Length difference - _________inches). Although not an exact
correlation, you should change the current value setting by 1 unit for every 0.03”
(or for every 1/32nd of an inch).
So now you have a direction (add or subtract) to change and a magnitude
(number of units). As an example: say you have a board that measures exactly
36” long by your tape measure and the machine measures board at 35.875”,
adjust the X axis cal number by +4. If the current value was set to 890.000,
change it to 894.000. Or if the machine measures 36.125”, adjust the X axis cal
number -4.

A board which was 21.20" long was measured by the machine to be 21.345". According to the instructions I should decrease the 890 number by (21.345-21.2)*(0.03)=0.004 to be 886. In fact I had to increase the number to 894 to get the machine to measure the board right.

The more I think about this, the less sense this makes to me! If the 890 number represents the conversion of a relative unit of measure, then the error should depend on the length of the board. A board which is twice the length would give an error twice as large.

Here is my guess: The number 890 represents the conversion factor from machine units (lets call them c’s for carvewrights) to inches (x’s). If the default calibration is correct, then the real length of the board is x = 890*c. If, however, the machine is measuring the board to be longer that it really is then x+error = 890*c and the number 890 is not the right conversion factor. If we let m be the right conversion factor (ie x=m*c) then x+erreor = 890*x/m. Solving for m we get m = 890/(1+error/x) or approximately m = 890*(1 – error/x). (If the board length x happens to be 1/0.03 = 33 1/3 inches, this agrees with the procedure in the instructions.) According to this result, if the machine measures the board too long then we make m less than 890.

Ok, I agree with the instructions. When it comes to changing how the machine measures, however, it is backwards. You have to increase the 890 if the machine is measuring boards too long. Either my analysis above and the instructions are wrong or someone has got the sign wrong in the machine software.

This is no big deal but I wonder how long it has been this way.

[fwharris]

I got the same thing!!! bassackwords!!

[bergerud]

Thank God, I am not dyslexic. Now I want to know where the error is.

[fwharris]

I think it is in the add to or subtract from directions.. bassackwords...

[bergerud]

I think it is the software but it is hard to know unless we know what the 890 number really represents. Hopefully LHR will tell us!

[Digitalwoodshop]

With my Analog computer background we used numbers like that as Scale Factor numbers. You see the black lines on the Encoder and know that each line is a pulse in motor rotation... somewhere you need to convert the pulses into a inch of board length.... Considering all the gearing from the encoder to the sand paper belts.... 890 pulses could = 1 inch.... or something like that.....

You could run a test..... IF the X encoder could be monitored.... push the belts 1 inch and look at the numbers BUT I believe the X Data is actually looking at the Brass Roller Encoder...... What the heck... Try that..... place a board on the machine by hand and call up the X data and push the board AND both belts with your hands..... I do it all the time trimming the sand paper belts.... but the power is OFF.... Try it.... 890 may be 890 brass roller pulses.... weather it is 1 inch or 1 foot... don't know.... or 10 CM or MM...... since the machine thinks in METRIC......



AL