Mirrored cuts

[justin2604]

Hi I just put together my M3 and I'm playing around with Fusion 360 and UGCS. I haven't made any cuts yet since I haven't set up my spindle but I've been playing with 2D drawings using the M3 and a sharpie. I'm successfully able to convert a JPG to a SVG file and convert that into Gcode using Fusion 360. However, when the CNC machine is working I'm having a problem with all of my drawings being mirrored. I was just wondering if maybe I set up my CNC shield wrong, if I'm modeling my drawings wrong in Fusion, or anything else I may have missed. Any help would be very appreciated and thank you in advance! 

Justin 

[Derek the Admin]

Hey Justin.

This is an easy fix. Is it mirrored in Y or X or both?

Here is the check:
Use jogging controls on UGS. Give an X- movement. Did the machine move to the left (as you look at it m the front). It should move left when you go X- and right when you go X+. If it doesn't, power everything down including disconnecting the USB cable. Turn the plug for the X motor the other way around.

Now test the Y. Go Y-. The table should move away from you when you go Y-. If not, power all off and reverse that plug.

Congrats on the build. Let us know if you have any questions.

[justin2604]

Thank you! Problem fixed! It was my Y plug

Thanks again

[justin2604]

Hi sorry but I have another question regarding my build. I still haven't made a cut yet with my M3 but I was wondering if it's normal for the Z and X bearing plates to rock back and forth if you were to apply a out of plane force to the top of the X bearing plate. Obviously the machine isn't going to experience that force during cutting but I just wanted to make sure that this is normal before I start. Thanks again for all the help!

[Derek the Admin]

Yes, it's completely normal. The plate is just bending under the force. You can also observe some deflection of you grab the bottom of the end mill and push and pull in the Y direction. It's pretty typical for this class of machine, but it doesn't stop some really nice and precise work being done as long as you keep the cutting forces appropriate.

That said, it will bend with a steady force. If it clunks back and forth then you should check the eccentrics to make sure they are adequately tightening the v wheels to the rail.

[justin2604]

Okay thanks! I'm having the problem with it clunking back and forth and with one of my v wheels not grabbing onto the track. By tightening the eccentrics are you talking about the two eccentric spacers located under the two top v wheels?

[Derek the Admin]

I see. The clunking is no good and is a result of those v wheels loosing contact with the rail. I need to look back at the instructions and make sure we directly address this.

The eccentrics tighten with a 10mm wrench. They are the spacers that are spacing out the top two v wheels from the X axis bearing plate. Tighten them so they are snug to the rail, but if you overtighten the material will deform under the pressure and cause the wheel to be out of round until you loosen it and let it "rest" for a few hours.

[aforww]

Real quick, the amount of force should be somewhat legitimate. I found that there was probably 4-5mm deflection front to back on my Z plate. I tightened the V wheels down a bit and now it's rock solid. Also, Derek I think I know why those bits kept digging on the aluminum. I put a 1.5 inch planer bit in just to check on squareness. With the bit orientated along Y axis the back was about 2mm higher than the front! That much out of square over 1.5 inches was nuts. The bits were only cutting with that leading edge. I spent the next hour getting that thing dead balls on square. I also noticed some how my bed ended up lower at the front right. It was all catywompus. Lol.

[Derek the Admin]

Dang man that thing was way out. I think I need to add "improve instructions for tuning the build" to my list. If those eccentrics are loose it'll clunk back and forth pretty significantly, as you noticed. I've gotten a good feel for the very edge of how tight the eccentrics can go before deforming the wheel.... and you've seen the work I do in aluminum. That was probably as much of your problem as it being can't rd because without them tight it just wants to chatter against the material. Of course, even when it's all just perfect you've got to to still take it easy in things like aluminum or brass, but your odds are definitely better now.

[justin2604]

Thanks guys! What I ended up doing was getting a marker and marking each wheel so I could see if it was grabbing on to the slotted track (the wheels are clear so its hard to see if it's moving without marking them). What I found was that if you tightened an eccentric spacer just a bit too much one of the wheel would have too much friction and not spin while the other one would be a little lose. I had to alternate and evenly tighten each eccentrics just a little at a time until my Z and X plate were rock solid and that each wheel still moved when moving the bearing plates along the slotted track.

[justin2604]

So I almost have everything ready to go to make my first cuts (just waiting for my router bits to get delivered) and I just set up my 400W spindle but I was just wondering how do you know how fast the spindle is spinning? Do I just assume that when I turn the knob all the way to the right its at it's max RPM of 12,000? Or is the only way to get an accurate RPM is to set up the controller board though PWM?

[Derek the Admin]

That is correct Justin. It's a linear potentiometer meaning that halfway should be 6k and all the way should be 12k.

You could set it up for PWM. It involved reflashing to the spindle PWM version of the firmware where that PWM signal will come from Z limit and the Z homing switch will go to spindle enable. That sounds backwards but it's correct. I reassigned pins to use the hardware PWM in that Grbl version. Let me know if that makes sense.