[IN-WondeR]

They look like square type linear rails, so they are probably not to blame...
I do however think the stiffness of the gantry is a bigger issue, atleast in one direction...
It looks to be a 40x120mm which is not all that stiff.

The Z axis looks to extend well below the gantry, which means there's a lot of deflection in the backplate when it's under pressure. This is a design flaw seen on many builds sadly. Unless the Z axis moving plate is 25mm thick then there will be a chance of deflection in the plate it self.

[kostas1]

They look like square type linear rails, so they are probably not to blame...
I do however think the stiffness of the gantry is a bigger issue, atleast in one direction...
It looks to be a 40x120mm which is not all that stiff.

The Z axis looks to extend well below the gantry, which means there's a lot of deflection in the backplate when it's under pressure. This is a design flaw seen on many builds sadly. Unless the Z axis moving plate is 25mm thick then there will be a chance of deflection in the plate it self.

It is 40x160mm.

The Z axis plate is 20mm thick and the tool's diameter is 3mm. So small tool can cause such a gantry deflection? Please remember that I get these lines and the inaccuracy even if the cut pass is 2mm deep.

Thanks.

[kostas1]

Ok guys, here are my test results from the weekend just past.
Firstly, I measured the deflection in Y axis by getting the gauge probe touch the Z axis along the Y axis and pressing with my fingers the Z axis and then the spindle. Below are the results when Z axis was up and when it was down:

Z Axis Up
Gauge probe touches Z axis side. Force is applies from the other side of the Z axis towards to the gauge probe:

1 finger 0.07mm
2 0.10mm
3 0.14mm
4 0.19mm
hand 0.25mm

Z Axis Up
Gauge probe touches spindle tool bit mount:

1 finger 0.12mm
2 0.18mm
3 0.24mm
4 0.28mm
hand 0.35mm


Z Axis Down
Gauge probe touches Z axis side. Force is applies from the other side of the Z axis towards to the gauge probe:

1 finger 0.10mm
2 0.14mm
3 0.19mm
4 0.22mm
hand 0.38mm

Z Axis Down
Gauge probe touches spindle tool bit mount:

1 finger 0.16mm
2 0.19mm
3 0.22mm
4 0.26mm
hand 0.40mm

After that, I tried some cutting tests with 24mm stickout and 6 passes of 3mm depth each pass in 18mm thick material (wood linden -> soft wood):

The climb cut just resulted in a bigger piece which was far from this in the design (aspire).
Then, I tried a rough cut and then I left 0.5mm (a little more than my max deflection 0.4mm in above test) for the finishing path and the result was almost perfect with the size I want and no 'side step lines'. This led me think that my gantry's vertical aluminium profiles are thin and they are not mounted properly in the horizontal aluminium profiles that run along the X axis. Please see the attached image for better understanding.

My thoughts for reinforcing the gantry are:
1) Replace the vertical and horizontal 40x80mm profiles with 80x80mm alu profiles,
2) Make the vertical profile a bit longer so as it reaches at the very end bottom of the gantry side
3) Replace the little plate with a larger and thicker one.

My questions:
1) What are your thoughts on this please?
2) Is it apparent that my cnc produces these faulty parts because of this deflection?
3) Should I look into something else to find the reason?
4) Is there any setting in aspire that lets you rough cut and then finish cut without requiring from you to draw duplicate designs (one small and the other a bit bigger)?

Thanks again.