Diagonal measurement difference before concrete

I am at the step right before pouring concrete on my MR-1 but would like to check in on a concern I have or get a recommendation.

On my y-axis rails, I have met all the dimensions, except for the diagonal dimensions. I am seeing a 3/16" difference in the diagonals. 49 6/16" for one diagonal and 49 9/16" for the other. I’ve used tie wire based on a forum post and I can bring the diagonals to within 1/16".

BUT, even if I retighten the screws to “lock in” the y-axis rail positions, and then cut the tie wire, the whole thing flexes back to my 3/16" difference.

I don’t feel like I can keep the tie wire on during the concrete pour because I need to add on the y-axis rail stiffeners and the baseplate and I think the tie wire would interfere.

Would it be ok to pour my 7 bags of concrete, add in the y-axis rail stiffeners and the base plate, add the last bag, and then try to use tie wire to bring in the diagonal dimensions while the concrete is still setting?

sounds dangerous to me. Have you found the cause of the problem? I don’t have a MR1 so I have no idea

I used epoxy to stick the frame square in the pan before pouring the concrete.

I had a pretty good difference on my angle during assembly. Ended up using tie wire across the long angle and twisting it to pull the rails square. After the concrete is set it’s not going anywhere.

I had the same issue. I used a ratchet strap to get it square and then used some sheet metal screws through the bottom of the pan to keep it in location. I removed the the strap and checked, poured concrete and it held. Make sure you locate one corner first so you can keep the frame centered in the pan. Good luck!

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