Weird problem with squared machine

[HalbesHaehnchen]

Hello again,

looking for a hint what could be wrong here. I set up a new machine and had problems with unclosed shapes (circle lines dont hit each other). Since its the 3rd machine I built, I already knew its the v-slot wheels that sit to tight. I installed new ones and got rid of that problem.
However, more complicated shapes are still broken. I thought its the same issue but its not. Machine frame is square, belt is fine, nothing is screwed together to tight or lose. When I move the Y gantry by hand it hits the frame at the same time on both sides.

Now when I set an offset for the auto square feature it suddenly gets better. Now the gantry has a little gap when I send it on the very end of the workspace but the engraving is much more accurate.

What could cause this? Its probably a physical problem, but where? Since I checked (and disassembled) almost everything multiple times I am a bit lost now.
Maybe someone has an Idea I didnt think of yet.

[phil-barrett]

Have you read my blog on autosquare? It has a process for determining where your limit switches should be set to have a square gantry. If your limit switch targets are not adjustable, you could adapt the procedure to find the correct Y dual axis offset ($171). The basic idea is to cut 4 holes (or any feature) in a rectangular pattern (or burn a rectangle with a laser) and measure the diagonals. When they are equal, your gantry is square. Knowing how far out of square it is, you could probably come up with a fairly good number to change $171 by.

Hmmm, I feel a new blog coming on...

Edit: I realize I did not directly answer your question but I suspect your frame is not truly square. It appears that with $171=0, there is a serious misalignment. Try burning a rectangle and measuring the corners. It is also possible that you have some backlash in your machine.

[phil-barrett]

No problem, glad to have your questions here.

[HalbesHaehnchen]

maybe other little question, after turning the controller off, I can't home it with my software. I have to use ioSender to unlock the machine. $x wont do it, I always get error:79.
Is it set by $484 ? If so, it wont let me change to 0. It switches back to 1 everytime.

[phil-barrett]

Not sure I understand, is "turning the controller off" a typo? In ioSender you do a reset and an unlock.

[HalbesHaehnchen]

nah probably just my broken English knowledge. I mean when I disconnect the controller from (USB) power and it boots again after connecting it, it does not accept any commands. It probably boots into some Alarm status. I have to do the reset/unlock thing with ioSender. Is there a way to disable it and let the board just boot up unlocked ?

[phil-barrett]

I think the ioSender console will show you what it does. You will need to check the verbose box and uncheck the other two boxes.