Quote Originally Posted by richardsenior View Post

So I had an idea.
There's a gap of about 5mm between the back of the z axis and the two extruded aluminium struts (on which the control board mounts).
What if I just shim that gap with some PTFE?
That way, we're still using the guide rails for accuracy, but you can't bend the guide rails because the PTFE will touch on the extruded bars.



Hello :)
I bought myself a much smaller version, the 1610, in January to learn about CNC. I too am impressed with the accuracy and repeatability, I set up a DTI and checked all 3 axes one by one and found less than 0.02mm backlash, the sprung brass leadscrew nuts obviously do a good job.

I don't see as much movement in the Z-axis as you do, maybe the increased Y-axis allows more flex in the linear guides and/or the horizontal 2020 sections you are talking about using as auxiliary bearings. Also, on my machine I changed the verticals to gain increased height so I could mount MDF waste-boards on the table and still get the full travel of the Z-axis. In the process I added corner blocks to every junction I could.

The only problem I forsee is that the increase in friction might cause skipping in the stepper.

There are two other paths you could consider:

1) with extra 2020 material, double up the verticals and the horizontals on the Y axis, as the increased rigidity might prevent so much twisting force being transmitted to the Y-axis linear rods from actually bending the frame. In the process, add extra corner blocks wherever you can.

2) replace the Y-axis linear guide rods with fully-supported linear rails. The extra material forming the support with also help with beefing up the horizontal 2020 sections mentioned in 1)



Despite the advice to go no further with this and buy a better machine, I think it worth persevering, 2020 section is cheap, fully-supported rails likewise, and the main thing is, if everytime you discover some shortcomings in a machine you go out and buy a "better" one you are going to amass a collection of machines.