Ok, i give up With my eShapeoko i run in some issues, the first and IMHO the biggest was the inaccurate milling. In example, if i mill a pocket with 15x15mm, i got only 14.7mm. Or better, mill a tray for SMD Tape then it was in every case to small. I change everything, the timing belts + pulleys. The CNC Controller to tinyg (thanks john!) and the power supply. Nothing, in every case i lost ~0.2 mm.
The second problem, i run with my VFD Chine Spindle in an USB EM Problem, in every case i switch my spindle on and the PC lost the USB Connection. But i can handle this.
Yesterday, i checked again the inaccuate bug with a dial indicator and i found a very interesting issue, if i move in relative the X-Axis only 0.1mm then i lost the first move, the second move are 0.06mm and the next move are correct. This is happend on every axis! Ok, i can compensate this in my CAM program over the tool diameter (i.e.: Dia 3.0mm => 2.9mm) but …
I DON’T WANT
I decide (together with my lovely Wife) to get a CNC 3040T, they are realy cheap here in germany. But i spend some bucks more and will buy a machine with 2 years warranty:
I got my 3040 on eBay and after some test cuts I found there is a deviation ~0.25mm per 100mm cause by lack of perpendicularity between X and Y axis. I had to mechanically calibrate it, which took some hours last weekend and now it looks OK.
After I got it perpendicular I mounted a low power laser with a cross beam on the spindle and tested on a calibration sheet 200mmx200mm with printed rows and columns every 10mm and some diamonds and circles inside. Playing with steps/mm ($100 and $101 in grbl) few times did the trick.
My limit switches are disabled, except for homing due to noise I got. I use software limits to make sure I am not above machine limits.
In addition to ball screw vs trapezoidal, I suggest to look for machine with more powerful spindle, I think with 230W spindle you have to reduce cut depth.
I have experience with following two spindles and I’m thinking to go for the third one soon:
300W DC Spindle (Torque 400mN.m): rotation speed slows down when I increase cut depth more than 1mm.
500W DC Spindle (Torque 500mN.m): Excellent at the beginning, but after three months it started generating noise and causes machine to skip in all axes.
Ok, now i buy this one: http://www.ebay.de/itm/271920866786 a CNC 3040 DQ for 685 Bucks. I’ll change my electronic enclousure to John’s TinyG enclousure. So now, the only one big thing … build a holder for 1.5kw VFD and try to find a solution for my electrical noise and lost connection bug. But i hope the enclousure (metal) can help me
if you’re running a VFD you should consider adding a matching EMI filter to the input, zero phase reactors on the motor lines, and a line reactor to the power input, if the vfd to motor doesnt have a line reactor, add one there too. vfd’s do all sorts of nasty things to the electrical supply, and nearby electronics. it’ll also improve the life of the drive, and keep it cooler.
The further x axis is to right or left of middle or y lead screw the more leverage y axis has to slightly twist the Gantry and flex. With pcb probably not an issue so much. When spindle cuts into material there’s also force applied to spindle mount…Ive seen flex there too.
With my eShapeoko i run in some issues, the first and IMHO the biggest was the inaccurate milling. In example, if i mill a pocket with 15x15mm, i got only 14.7mm. Or better, mill a tray for SMD Tape then it was in every case to small. I change everything, the timing belts + pulleys. The CNC Controller to tinyg (thanks john!) and the power supply. Nothing, in every case i lost ~0.2 mm.