You can actually make good measurements with a larger spot. This assumes you are using software and not just eyeball estimates. Typically you can do about 1/10th pixels position estimates. With micro-meter scale pixels this become way-overkill for machine work. I would not bother to do more then roughly align the laser.
Yes you need a sensor. A $10 webcam with the lens replaced by a welding glass filter would work but you'd need to experiment with different filter and laser power. I would not adjust anything r "zero". between measurements. leave the target and laser bolted down solid. Just record the numbers and when you are done cal the smallest number "zero" To get the center point, just use the "centroid" the same math if looking for the balance point of the laser spot. You should be able to make a measurement at least once per lead screw revolution, maybe many times more per revolution. On Mon, Sep 10, 2018 at 12:09 PM Gregg Eshelman via Emc-users < emc-users@lists.sourceforge.net> wrote: > I have a LASER that is made to mount in a chuck or collet. It has > alignment screws and adjustable focus. Aim it at a wall far away and adjust > the focus for as small a dot as possible. > Make a target to mount on the carriage, chuck and center the body of the > LASER then use the alignment screws and adjusting the target and rotating > the spindle until the spot no longer describes a circle when the spindle is > rotated. > > Move the carriage to the right end as far as possible. Move the cross > slide intil the dot is on the target. There's your zero. Advance the > carriage toward the bed until the dot moves off the target. Adjust the > carriage until the dot is back on target, at least in the X axis. A really > good way to map the bed would be to have a sensor as the target so the > carriage could be moved by the control and read a continuous stream of how > far off X it gets. Barring that, stop every X distance then adjust to > re-zero and interpolate slopes between adjustment points. > If you put the target on a vertical slide to re-zero Y at each stop, the > error map (with appropriate math) could compensate for that too. Perfectly > straight cutting even with a very worn bed, as long as the vertical error > doesn't drop the cutting tools too low. > > On Monday, September 10, 2018, 1:55:36 AM MDT, Chris Albertson < > albertson.ch...@gmail.com> wrote: > The lasers are easy to find on Amazon but be warned the laser is not > perfectly aligned with the housing. But as I said, this does not matter > if you spin the spindle. > > I think a laser is the only option. If you are measuring the bed your > reference needs to be at least 10X straighter then the bed. Precsion rods > are not good enough but a $20 laser is literally perfect (as long as you > rotate the spindle.) > > With effort you can use the same laser to measure the error with the lead > screw pitch. Use it as a laser range finder or laser inferometer > > But all this measurement may be moot if the lathe is not reputable. The > error might be random. Maybe the carriage moves like a tuck on a dirt > road? > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
