Accuracy of the board sensor

[Arkat3]

Quick question for the more experienced users.

What is the accuracy of the board sensor?

I am using a sled for a small project and every time it measures the width I get a slightly different measurement. I did not write down all the results but roughly +/- .003 inches.

It has not caused any problems but I am curious if this is within tolerance for the sensor?


Thanks


Dana

[ChrisAlb]

I've always found it to be very accurate. I'm not sure but I "think" the claim is the machine is accurate to within .006". So your +/- .003" would fit within that.

Just curious, are you measuring the same board several times and without removing and reinstalling it?

All I know is, 6 thousandths of an inch is a tad more accurate than any of my tape measures over 35 years...LOL

[Digitalwoodshop]

Dana,

Masking tape on the bottom of your sled to let the brass roller have something to grip will help. Measuring in Length is ALL About the Brass Roller....

And remember it is WOOD not metal and Humidity will change the wood minute by minute. .003

AL

[ChrisAlb]

Dana,

Masking tape on the bottom of your sled to let the brass roller have something to grip will help. Measuring in Length is ALL About the Brass Roller....

And remember it is WOOD not metal and Humidity will change the wood minute by minute. .003

AL

Hey you!! LOL...Dana was talking width...LOL

Just busting ya buddy...:razz:

[Arkat3]

Thanks for the quick response. The jig is two pieces of 1/2 MDF laminated together. And yes I am removing between scans as I am putting in new pieces to be carved.

Sounds like it is within tolerances so I won't sweat it.

I started watching the width closely as I had one scan measure 2" less on the width and carved up my jig and half the work piece. So now I make sure it scans the correct width before I continue.


Dana

[ChrisAlb]

Since you're measuring different boards, I'm not surprised at all by the small variance. I have an incredibly accurate table saw but it will never cut any two pieces "exactly" the same. At least, not to within .00X" anyway.

[bergerud]

Masking tape on the bottom of your sled to let the brass roller have something to grip will help. Measuring in Length is ALL About the Brass Roller....


How can this be since the board leaves the brass roller when each end is measured. Seems to me that the brass roller is used only when the board is under both rollers. Measuring the belt movement must be how x is measured. I notice on my machine that the y measurement is more reproducible and accurate than the x.

A clear explanation of how measurements are made along with an explanation of the calibration procedure would be most welcome. (Maybe the brass roller is used to calibrate the belt servo during each measurement.)

[Digitalwoodshop]

Hey you!! LOL...Dana was talking width...LOL

Just busting ya buddy...
__________________
Christopher Neil Albrecht
Occasional Carvings
Just A Flowing With The Grain
Ver. 1.132




How can this be since the board leaves the brass roller when each end is measured. Seems to me that the brass roller is used only when the board is under both rollers. Measuring the belt movement must be how x is measured. I notice on my machine that the y measurement is more reproducible and accurate than the x.

A clear explanation of how measurements are made along with an explanation of the calibration procedure would be most welcome. (Maybe the brass roller is used to calibrate the belt servo during each measurement.)

Looks like I was 90 Degrees out..... And yes BUSTED..... Wrong Again.... I should really read the question first..... Sorry.... I hang my Keyboard in shame.....

AL

[ChrisAlb]

How can this be since the board leaves the brass roller when each end is measured. Seems to me that the brass roller is used only when the board is under both rollers. Measuring the belt movement must be how x is measured. I notice on my machine that the y measurement is more reproducible and accurate than the x.

A clear explanation of how measurements are made along with an explanation of the calibration procedure would be most welcome. (Maybe the brass roller is used to calibrate the belt servo during each measurement.)

As I understand it, The brass wheel works in tandem with the front (right) roller and IR board sensor. When measuring the length, the board comes out from under that roller at which point the CW knows there is approx. 3-1/2" left. The IR board sensor finds the end and the board reverses. As soon as it hits the brass wheel again it's calibrated and the brass wheel (X-tracking sensor) keeps track of the boards position from there.

[bergerud]

I think the state of the brass wheel is ignored unless both rollers are up. (I have seen the brass wheel randomly rotating from machine vibration when it is not in contact with the board.) As far as measuring is concerned, when the board leaves the upper rollers or when it touches the brass roller cannot give an accurate position of the board end simply because these rollers are round. It seems to me that the part of the measurement which is not under the rollers must depend totally on the position of the belts (the x drive motor). I have noticed that the x drive pauses as the board leaves either of the upper rollers. Does this indicate that the machine is switching between different measuring methods?
If I put the board on a sled, can the machine measure the board length using only the brass roller? This would be a single measurement instead of a sum of three.
(Why did Carvewright not use two brass rollers: a brass roller under each upper roller?)

Sled does not work: the program expects the board to come out from under the rollers while measuring length.

[AskBud]

Quote: "Sled does not work: the program expects the board to come out from under the rollers while measuring length."

The sled/project must leave each roller in order for the machine to measure the length. The sensor, in the truck, looks for the "End of the Board" after the roller releases. I presume that is why the last 3 1/2" of the sled ends must have a solid surface (it's looking for that board edge). I found that you may have gaps between your project board and that 3 1/2" end, but you need the end pieces. If you watch, you can see the project wiggle as it deals with measuring the length(s).
AskBud