Triangular calibration for 12' beam, 30" height question (webcontrol)

My beam is exactly 12’, distance from top of sheet to motor 30".
When I did the chain extension calibration I use 2032mm per the instructions I found in webcontrol.

After running the calibration cuts and I entered the measurements and then re-ran the calibration test, Distance 1-2 and 3-4 were perfect at 1930 (default number). The Y measurement, top of sheet to top of the horizontal cut (#5) was 114.3mm after initial cut but corrected to 238.125 (default is 300mm). I have run it 4 more times and this measurement gets about 2mm less each time but the other dimensions remain at 1930mm dead on. So am I to conclude the measurement #5 should be 300mm?

When it stops, it is at 0,0 as measured with a tape measure.

Is this a function of the chain extension calibration? Should I be using longer chain setting?

if your beam is exactly 12’ long, the distance between your motors is a little
less than 12’ (and this distance measurement if very important)

if you are using webcontrol, try the holey calibration, it produces better
results than the older calibration method.

David Lang

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No, I built it with the motor shafts at EXACTLY 144". The odd thing is that I kept getting 238mm instead of 300mm yet, I have since discovered that I can send it to the 4 corners and it looks to be dead on. I was thinking it was going to cut high on the sheet but it knows exactly where the sheet is.

I was going to but it appeared to be dithered on my controls. I guess I didn’t try to push the button because of that. I’ll definately check it out but it looks like I am calibrated even though it didn’t appear to work. I’ll just push the “I believe” button on this one. Time to dance a little jig!


Someone please correct me if I am wrong, but I believe that default (300mm) is really a starting point. Once you start running the calibration, and then inputting your measurements from that, the machine will adjust itself (change that default) to what it actually is. As we are taking measurements (and every method has its own inherent errors in that), there is sort of a starting point, and then adjustments from there to get as accurate as you feel comfortable with.

After I have run my calibration routine (I use Holey through WC), I send it to center and verify it is dead on there. Then I make 3 marks: 1 at top of sled, 1 on the side, and 1 on a diagonal. I then command the sled to move a specified distance (usually between 12 and 24 inches) make a mark, and then command the sled to return to center. I then check to make sure the sled returned to the same center point (based off the 3 marks), hang the sled and measure to make sure the distance I commanded the sled to move is the correct distance. I do this 1 at a time in each direction. If any of that is off, or when returning to center it is off, I run the calibration process again. If it is still off, I start over and reverify I haven’t measured wrong, or more likely, fat-fingered or missed a measurement input. So far I have had very good results. I don’t know what my calculated accuracy is, but my usual results on the projects I do are close enough that it doesn’t bother me.