X-axis jump: ruined two pieces so far.

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sdrevik
Posts: 35
Joined: Sat Jan 31, 2015 11:05 pm

X-axis jump: ruined two pieces so far.

Post by sdrevik » Sat Aug 01, 2020 4:12 pm

I have had two runs where the X-axis suddenly jumps (the last one being +69mm, or you can think of the zero as changing -9mm) for no reason I can discern:
1. I verified workpiece did not move, not even 0.1mm
2. Seems to happen around where the +Z change occurs
3. Wouldn't seem to be 'slip', as (a) the spindle moving in +x direction roughly at the time and (b) I tested manually moving and pushing against the spindle, with arm force I could not get motor/belt to slip. I also slowed the feed rate down, and I am manually vacuuming any waste out to make sure the bit has a clear path.

After the last error, I manually jogged back to my marked zero point, and indeed it had it as the wrong value for X.

Could this be something happening in the controller? The fan blowing on the back of the board quit, and it's about 80 degF in the shop, so is the heat causing the controller to screw up the X? But I figured if the board had a heat problem, it would just up and disconnect.

Help! the blanks I am using are a bit of work to make, and I don't want to waste anymore.
Image

sdrevik
Posts: 35
Joined: Sat Jan 31, 2015 11:05 pm

Re: X-axis jump: ruined two pieces so far.

Post by sdrevik » Sat Aug 01, 2020 5:44 pm

I should add- the outer contour, I am cutting a very deep channel (1.5"), and the flutes only cover about an inch. It did happen at about the 25mm depth, so I'm wondering if the unfluted section of the bit pressing against the top of the channel could be an issue.

So, I'm going to make a new round of Gcode for the outer profile:
1. Tell code generator that bit is 7/16 to cut an outer profile to 3/4" depth
2. 1/4" bit (real profile) to 3/4" depth
3. 3/8"" bit profile to 1.5" depth
4. Finally at 1/4" bit to 1.5" depth.

Thus the top of the shank should be clear, at least on the outside. Can't do anything about the inside (although arguably if I accepted a "step" in the bottom of my piece... but I think this should do it.)

Thoughts?

WillAdams
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Re: X-axis jump: ruined two pieces so far.

Post by WillAdams » Sat Aug 01, 2020 8:24 pm

Slotting is difficult --- avoid it where possible --- add geometry and cut as a pocket down to at least tab depth, see:

https://community.carbide3d.com/t/addin ... -pass/9993
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

sdrevik
Posts: 35
Joined: Sat Jan 31, 2015 11:05 pm

Re: X-axis jump: ruined two pieces so far.

Post by sdrevik » Sat Aug 01, 2020 9:48 pm

Thanks, so it sounds like my idea of running an outer perimeter will help quite a bit. Do you think that's what caused the jump?

WillAdams
Posts: 8597
Joined: Mon Apr 09, 2012 6:11 pm
Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: X-axis jump: ruined two pieces so far.

Post by WillAdams » Sun Aug 02, 2020 3:15 am

The 100% tool engagement of slotting can cause missed steps, so yes.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

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