Reading it, it implies to me that to check the square of the machine, I push the gantry all the way to the back and check for contact on both y axes with the back of the machine. I found that in my case, y2 was contacting before y1 and so I shimmed using aluminum foil for a result of almost perfect contact simultaneously.
Somewhere I read or saw a video that measured the gap with the machine in the home position. After shimming as discussed above, I put the machine in the home position and measured about 2mm difference between the y1 and y2 gaps.
This leads to my questions:
Which position should I measure squareness from? Back of the machine? or homed?
Why would it matter? Shouldnāt the gap be consistent no matter which position the machine is in?
Your y-carriage v-wheels could be making the machine be not square in home position, they have precision washers, but can still be off a little as a wholeā¦
Hi Jeff. No offense taken. I probably took too many shortcuts in my description of what I saw and did. I did shim the front of Y2 and the back of Y1 to get the x axis to contact the back at the same instant. After that, I read or saw where someone checked for squareness by measuring the gap from the homed position. If āhomedā only refers to the position of the z-motor then I did misspeak. I meant to describe the position of where the router bit is when the shapeoko is connected to carbide motion and the homing sequence is performed.
Hopefully that describes the situation both in how I first checked for out of square (at then back end) and then when āhomedā the measured difference in gaps between y1 and y2 to the back stop was 2mm.
I canāt wrap my head around why a fraction of an inch of travel (from āhomedā to back stop) would create a two mm difference and it made me wonder if there was a correct location where I should be measuring for square. That said, I had intended to follow the link I posted above and after squaring at the back end, slide the gantry forward and check squareness at the front end.
Anyway, Iām all ears looking for wisdom on how to do this. And again, the link seemed to indicate the place to check was at the complete rear of the machine and when I saw the video (which I cannot find now) I got to wondering and figured here was the place to get more info.
thanks.
al
ok. I have re-shimmed my XL and I have almost perfect contact of Y1 and Y2 on the back stop. I then moved the x axis forward all the way to the front. Y2 contacts first and there is about a 1.4 mm gap between front of Y1 and the front end stop.
At this point, all belts are removed and the v-wheels are loosened on both sides of the x axis. (I had to loosen the v-wheels in order to be able to add shims.)
a change of 1.4 mm over about 23 1/2 inches of travel doesnāt seem great to me. But maybe Iām wrong?
(Iāve also checked the machine to be square within 1/16th of an inch and it is level)
Which is more square to the rails? Front or back? I like for the squarest endplate to be at the front, then one can pull the gantry up against the front endplate and hold it there as one powers up the machine ā the rear endplate just needs to be square enough to allow the homing switch to work.
I know it is a chore but maybe this warrants removing both Y beams and laying them side by side to check for matching length. You could try measuring them while still mounted on the machine, but for better accuracy, remove them.
This may sound dumb, but you did also loosen the wasteboard screws (the ones attaching the wasteboard to the frame) as you were making these shim adjustments, correct?
Aha, then you may have less of an issue as maintaining the alignment is more of a job for the drive system than the V Wheels.
The Y endplates are quite flexible (I believe this is deliberate as the V Wheel strength is limited and this allows for some alignment errors in assembly). It is normal to be able to alter the angle of the X beam relative to the Y beams by applying small forces fore and aft on the Y plates. These forces are substantially lower than the working forces from the belt drive system.
Assuming the base is already properly squared and the Y beams are coplanar (level with a flat base).
Whatās important is that in the homing (rear) position the machine sits with the X beam normal to the Y beams and parallel to the plane of the base. This allows the drive system to start up with the X beam āsquareā and is the reason for the advice often given to gently roll your X beam into the rear stops before powering up if you need it really square.
Once the machine has started up the Y steppers are operated in step with each other and will apply corrective forces to keep the X beam at whatever angle it started up at.
If the X beam will adjust to being square to the Y beams along itās travel with small forces (a couple of Newtons) then I would expect the belts to deal with the remaining alignment for you.
I would expect so, in that video I found my machine was 0.7mm off front to back due to imbalance in the belt tension
Itās still worth checking your Y rails are parallel and of exactly equal length, I would do that before trying to make the X beam align at the front as you want it square and if the front and back steel plates arenāt parallel youāre just pulling the X beam out of square with the belts.
How much force does it take to pull the X beam into line with the front plate?
it takes very little force to get the y1 side to contact the front after y2 contacts the front.
I checked the y rails were parallel (and they were)
I noticed that the front stop on the y2 side was slightly tilted towards the back of the machine. That made me think that the reason for contact on Y2 side first was that the front end plate was leaning towards the rear of the machine. I shimmed the heck out of it and could never get any change. Basically, no matter what I did, Y2 contacted first and the same approximate gap existed on the Y1 side.
Just out of curiosity, what would one do if the Y rail lengths were not exactly the same length?
I appreciate that but itās not necessary in my case. the y rails look perfect in length and at least with a tape measure, they also look square.
Once I connected all the belts and set the v-wheels, front and back travel is perfect. I also set the z axis which was out significantly in the front/back direction but spot on in the left and right direction.
Next is the spoilerboard surfacing but that may be a different day.
(I also learned the value of a good and reliable level today.)
I gave up on mine and learned to live with the little difference in Square and just position the work piece to the x Axis. do wish i could get it to level a spoil board more consistent though.
