F-arc, f-arc!

**arose62** · 15th December 2011, 05:09 PM

Should sound like Graham Kennedy's "crow call".

This post is my "walking away before I hit something", trying to work out why what is promised on the screen isn't what's delivered by my freshly CNCed Sieg X3 mill.

I installed a Promica kit, and it went 90% smoothly - a bit of filing here and there, and a couple of questions quickly answered by Marc of Promica.

I was in the middle of drilling and filing holes in the back cover for the cables to pass out through, when I had an epiphany, and though I should use the machine to cut out lovely smooth, neat professional and identical holes, using its brand new CNC capabilities.

Now, I've always found that real learning happens when someone else says "I need *this*", and you have to work out how to deliver a real-world result, so enough of jogging the table around manually - let's make a *real* cut!

From cover plate to model in Sketchup was easy. Imported into CamBam, but couldn't work out how to use the model, so used an image from sketchup, and traced that. The model looks OK in CamBam, so I generated the toolpath and Gcode, and took it to the mill.

I cut air a few times (with much gleeful chortling

, then popped a pencil into the chuck and put an exercise book on the table.
I gingerly ran the job closer and closer, worked out homing stuff, and was mega-chuffed to see the mill draw the holes I wanted. Almost

The shapes are a rectangle with a half circle bulge at the top. In Sketchup, CamBam and EMC preview, the shape looks correct, but the mill produces one shoulder higher than the other, the bottom left corner is square rather than rounded, and the half circle looks dragged to the right.

Grrrrrr

I've played with arc centre incremental and absolute, added the G90.1 and G91.1 commands to the EMC post processor in CamBam, and am about to try with TurboCNC driving the mill.

Any suggestions most welcome!

If I do come back here for more help. I'll attach pictures and files

Cheers,
Andrew

**munruben** · 15th December 2011, 06:07 PM

Sounds interesting but you lost me I'm afraid.

**WillyInBris** · 15th December 2011, 06:48 PM

So this is a vent thread or you need help, that kit has a hefty price tag.
Are you losing steps pics will help?

Mind you for the amount you have paid promica for the kit they should be able to give you some after sales service no doubt.

**rodm** · 15th December 2011, 08:04 PM

Try changing the IJ mode in config in mach3 - just guessing and more info needed to be of any real help.
If you can attach your gcode I should be able to track it down for you.

**arose62** · 15th December 2011, 10:10 PM

This was more of a vent than a request for help, though the IJ arc setting was a useful pointer - indeed, I'd pretty much convinced myself that the problem was in that area, and had generated Gcode with all the combinations of settings.

However, it turned out to be much more basic than that, and the walking away did the trick - I noticed that the weirdness was when the Y axis changed direction, then noticed that jogging the Y axis had a dead spot when reversing direction. Tugging on the table showed a few mm of backlash, so a bit of disassembly, one added washer, and the mill finally produced exactly what the computer screens had been promising!

So, thanks for listening to my rant, and I take back all the horrid things I was thinking about CamBam, EMC2, and Gcode in general!

Happy, happy, happy!
Cheers,
Andrew

**marty989** · 16th December 2011, 02:32 AM

Hi Andrew, I'll also be undertaking a promica conversion shortly so for my benefit do you mind providing a little bit more detail of your solution?

**arose62** · 16th December 2011, 09:50 AM

Hi Marty,

when I assembled the Y-axis, I tightened the grub screw on the pulley BEFORE I put the capscrew into the end of the leadscrew.

This meant the pulley wasn't pulled against the bearings, so there was lots of backlash. Just follow the instructions.

In my defence, I'd assembled and disassembled a few times, and was racing to get it demonstratable for my dad...

The only real gotcha I found was that the ICA3 controller has changed from what the documentation says, and only triggers pin 10 when ANY limit switch is tripped. The document lists settings for each limit switch to trigger its own pin.
I lost a few hours trying to work out whether it was PC, cable, settings, faulty controller etc. etc. Writing down step by step my testing, trying different cables, different software etc.
However, a post on the Promica forum was answered very quickly.

I also found a couple of round holes had very slight ridges inside them, so a bit of judicious filing here and there seems par for the course.

All in all, I'm happy with the way it went together - about 3 days in total, with life interfering, as it does.

While I had the mill apart, I also brought the motor speed control, and an Estop, onto a pseudo-pendant, because I didn't relish the thought of reaching across a motorised table to adjust the spindle speed.

Cheers,
Andrew

**marty989** · 16th December 2011, 03:26 PM

Thanks very much for the detailed response Andrew, my X3 should be arriving this Arvo

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