Assistance needed with tricky real-world geometry problem
Assistance needed with tricky real-world geometry problem
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singlecoil

Original Poster:

35,831 posts

275 months

Friday 6th November 2020
quotequote all
I have a CNC router and the gantry (the X axis) is very slightly out of square. I need to square it up, the technique used is to swing one end of the gantry by the required amount having. Naturally the hypotenuse should be 1000 but in my case it's 1001.74.

The problem is to work out how far I need to move the gantry at the adjustment point to correct it. I could do this by trial and error but I'd like to reduce the number of attempts needed if possible. Having struggled with it for a while I thought I would present it to the geometricians here for their suggestions.

TIA

shtu

4,520 posts

175 months

Friday 6th November 2020
quotequote all
Surely the way to do that is ignore geometry, get yourself a dial gauge and align it that way?

Abom79 on youtube shows that process in many of his videos. Mills, shapers, etc, but the process should be much the same.

singlecoil

Original Poster:

35,831 posts

275 months

Friday 6th November 2020
quotequote all
Thank you for the suggestion, but that would not be an appropriate solution in my case.

Ledaig

1,806 posts

291 months

Friday 6th November 2020
quotequote all
20.35mm

singlecoil

Original Poster:

35,831 posts

275 months

Friday 6th November 2020
quotequote all
Ledaig said:
20.35mm
That's a lot more than I thought it would be, way more than the range of adjustment built in to the machine would allow anyway.

Ledaig

1,806 posts

291 months

Friday 6th November 2020
quotequote all
How accurate is the 90 degrees at x=0, y=0?

Tango13

10,071 posts

205 months

Friday 6th November 2020
quotequote all
singlecoil said:
I have a CNC router and the gantry (the X axis) is very slightly out of square. I need to square it up, the technique used is to swing one end of the gantry by the required amount having. Naturally the hypotenuse should be 1000 but in my case it's 1001.74.

The problem is to work out how far I need to move the gantry at the adjustment point to correct it. I could do this by trial and error but I'd like to reduce the number of attempts needed if possible. Having struggled with it for a while I thought I would present it to the geometricians here for their suggestions.

TIA
If the 800mm and 1001.74mm measurements are correct then the 600mm will be 602.90mm

My trig says move it 3.01mm and you should be close enough

Glade

4,512 posts

252 months

Friday 6th November 2020
quotequote all
How accurate is the measurement of all the lengths?

Ledaig

1,806 posts

291 months

Friday 6th November 2020
quotequote all
Tango13 said:
If the 800mm and 1001.74mm measurements are correct then the 600mm will be 602.90mm

My trig says move it 3.01mm and you should be close enough
Agree at the 2.9mm (2.8955), take that at 220mm from the pivot point gives and angle of 0.754 degrees. Take that angle over the full bed length of 1546mm would give 20.346mm.

Where did you get 3.01 from? I'm missing something...

Tango13

10,071 posts

205 months

Friday 6th November 2020
quotequote all
Ledaig said:
Agree at the 2.9mm (2.8955), take that at 220mm from the pivot point gives and angle of 0.754 degrees. Take that angle over the full bed length of 1546mm would give 20.346mm.

Where did you get 3.01 from? I'm missing something...
Pythagoras tells us that A squared + B squared equals C squared.

Type 600mm, 800mm & 1000mm into a triangle caclulator app and you get angles of 36.87, 53.13 and 90

Type 800mm and 1001.74mm into the same app ignoring the 600mm and you get 602.90mm, 800mm & 101.74mm with angles of 37, 53 and 90

An angle of 0.13 over 1326mm is 3.01mm so an adjustment of somewhere between 3mm and 3.5mm should be somewhere in the ballpark

Ledaig

1,806 posts

291 months

Friday 6th November 2020
quotequote all
Tango13 said:
Pythagoras tells us that A squared + B squared equals C squared.

Type 600mm, 800mm & 1000mm into a triangle caclulator app and you get angles of 36.87, 53.13 and 90

Type 800mm and 1001.74mm into the same app ignoring the 600mm and you get 602.90mm, 800mm & 101.74mm with angles of 37, 53 and 90

An angle of 0.13 over 1326mm is 3.01mm so an adjustment of somewhere between 3mm and 3.5mm should be somewhere in the ballpark


Edited by Ledaig on Friday 6th November 23:30

Tango13

10,071 posts

205 months

Friday 6th November 2020
quotequote all
Ledaig said:
Tango13 said:
Pythagoras tells us that A squared + B squared equals C squared.

Type 600mm, 800mm & 1000mm into a triangle caclulator app and you get angles of 36.87, 53.13 and 90

Type 800mm and 1001.74mm into the same app ignoring the 600mm and you get 602.90mm, 800mm & 101.74mm with angles of 37, 53 and 90

An angle of 0.13 over 1326mm is 3.01mm so an adjustment of somewhere between 3mm and 3.5mm should be somewhere in the ballpark


Edited by Ledaig on Friday 6th November 23:30
Once more, with feeling...

If the triangle is correct at 600mm, 800mm & 1000mm the the three angles will be 36.87, 53.13 and 90 degrees

The triangle is not correct, the hypotenuse is 1001.74mm or 1.74mm too long. Calculate a triangle with sides of 800mm & 1001.74mm and the thrd side will be 602.90mm which gives angles of 37, 53 & 90 degrees, a difference of .13 of a degree from the correct triangle

The whole gantry is out of square by 0.13 degrees

0.13 of a degree over 1326mm is 3.01mm or 3.51mm over the full 1546mm

0.13 of a degree over 220mm is 0.5 of a millimetre not the 2.9mm you have shown on the sketch.


Ledaig

1,806 posts

291 months

Saturday 7th November 2020
quotequote all
Tango13 said:
Once more, with feeling...

If the triangle is correct at 600mm, 800mm & 1000mm the the three angles will be 36.87, 53.13 and 90 degrees

The triangle is not correct, the hypotenuse is 1001.74mm or 1.74mm too long. Calculate a triangle with sides of 800mm & 1001.74mm and the thrd side will be 602.90mm which gives angles of 37, 53 & 90 degrees, a difference of .13 of a degree from the correct triangle

The whole gantry is out of square by 0.13 degrees

0.13 of a degree over 1326mm is 3.01mm or 3.51mm over the full 1546mm

0.13 of a degree over 220mm is 0.5 of a millimetre not the 2.9mm you have shown on the sketch.
Thank you Sir.

singlecoil

Original Poster:

35,831 posts

275 months

Saturday 7th November 2020
quotequote all
Thanks for the assistance chaps. I'll have a go at it this morning and post the results smile

anonymous-user

83 months

Saturday 7th November 2020
quotequote all
Only on pistonheads could there be an argument about trigonometry hehe

take-good-care-of-the-forest-dewey

7,870 posts

84 months

Saturday 7th November 2020
quotequote all
slopes said:
Only on pistonheads could there be an argument about trigonometry hehe
Happens on mums net a lot.

Loads of threads about how obtuse men are... sorry

anonymous-user

83 months

Saturday 7th November 2020
quotequote all
take-good-care-of-the-forest-dewey said:
slopes said:
Only on pistonheads could there be an argument about trigonometry hehe
Happens on mums net a lot.

Loads of threads about how obtuse men are... sorry
rofl

T5R+

1,226 posts

238 months

Saturday 7th November 2020
quotequote all
take-good-care-of-the-forest-dewey said:
Happens on mums net a lot.

Loads of threads about how obtuse men are... sorry
An acute observation.



T1547

1,240 posts

163 months

Saturday 7th November 2020
quotequote all
T5R+ said:
take-good-care-of-the-forest-dewey said:
Happens on mums net a lot.

Loads of threads about how obtuse men are... sorry
An acute observation.
This is going off on a tangent

ellroy

7,834 posts

254 months

Saturday 7th November 2020
quotequote all
I thought this may be interesting, but it’s not.

So I’m going to sine off.