my 6040 experience (yeah, and problems) so far

[JAZZCNC]

I'll probably go back to 16 microsteps giving a max feed around 2300 as I don't think I'll be needing 4700 mm/min.

Be aware that this will put more stress on the parallel port as your needing twice the pulses to travel same distance no matter what the speed so your open to missed steps if the PP struggles at higher feeds.!
Don't think of MS in terms of increasing resolution because in reality at this level it doesn't really it has bigger affect on smoothing the motors. But it does come at a price by putting the system under more stress. With machines running external motion control cards this isn't an issue but it can be trouble some for PP driven machines. Esp if using cheap drives and Bob's etc.!

[jimbo_cnc]

I'll leave it at 8 then, and enjoy high speed rapids over my 60x60mm workpiece :)

2 new drivers arrived today. Everything now appears to be working. I took one of the dodgy ones apart and the heatsinking was poor - blob of paste covering about 25% of the surface area. A nicely ground bit of aluminium plate between chip and heatink, but it had been chopped leaving a burr which lifts the end!

Before I do any sustained work, I think I will take my good ones apart and ensure a good heatsink connection.

Also spotted one very poor solder connection, so there is a posiibility of fixing the bad ones.


I did take the goods ones apart, and made sure the heatsinking was good. The 2 replacements, and the one original that worked had smaller (but flatter) heat sink pads than the faulty ones. Indicating that the design is at least evolving! The pad edges still needed a clean up though, and the paste was still only 20% coverage.

[EddyCurrent]

So what was causing the faults / resets when jogging from the keyboard ? did you change the breakout board ?

[jimbo_cnc]

2x faulty Tongka M542 drivers. It would appear that the original BOB is OK.

[jimbo_cnc]

YAY! first cnc cuts done.

Another Mach3 mistake though. I set Z high and ran the gcode in free air, double checking the x and y extents weren't going to hit the vice. But the way I stopped mach3, set Z zero and then started again meant that it re-started mid code. Instead if doc 1.5mm with my 3.2mm cutter, it plunged to 9mm and started pocketing. The noise wasn't too bad, I only stopped it because the pocket was filling up with 15mm long strands of swarf all standing up and filling the pocket.

So I went back to line 0 this time and started again, much quieter.

At least I know that cutter is good for more than 1.5mm doc !

feed was 800mm/min, RPM 11500 (need to adjust my vfd as that's the max I can get)

[jimbo_cnc]

Somewhat risky for a newb like me to have metal screws in the work area, but I took a chance. All went well until I hit the z-axis limit switches (piss poor planning) in the middle of my job. In the confusion I did the same as before, started the job mid program but I'd done a goto zero. I should have noticed it was heading off inthe wrong direction but I wasn't ready ready to pounce onthe stop button.

The tool scored a direct hit on a holding down screw.

Hopefull no damage to my spindle.


All seemed to be going well but I've got one concern. The third pocket, is undersized slightly eg 13.85mm instead of 14.0mm in the long axis direction. Does that indicate missed steps?

I ran it again at 70% feed and another sliver got taken off one face, so now 0.10mm undersize rather than 0.15mm.

[jimbo_cnc]

I think I understand the undersize problem on long axis, I think it comes from slack on the long axis bearings. I can feel slack when I rock the gantry back and forward (on top of the flexibilty).

The setup is SBR20 round supported rails with matching bearings. I don't suppose they are adjustable? or maybe I can buy adjustable repalcements?

[Christian Knuell]

Hi,

Somewhat risky for a newb like me to have metal screws in the work area.

whenever I'm not sure if everything will be OK I put some styrofoam on the machine (with doublesided tape) and add a mechanical stop to the z-axis just before the tool touches the machine bed. This way you don't need to worry about breaking anything even if things go completely wrong.

Christian