Z-axis cut starts above stock surface

CNC Machines Shapeoko
1

I’ve used my standard Shapeoko 3XL intermittently for the past 18 months, with few hiccups. The problem described below is happening now for the first time.

The first operation in my current project is a registration pass, boring 3//8in holes on the center line, passing through the stock and into the waste board. In later cuts I will flip the stock and insert pins into the registration holes to position the workpiece for milling the opposite side.

Here are the settings that I think are relevant:

CARBIDE CREATE
Job Setup
Stock Thickness: (Z) 0.517in (actual measured thickness)
Top
Retract Height: 0.250in
Units: Inches

Toolpath
Contour
Start Depth: 0.00 in
Max Depth: 0.90 in
Pocket

AT THE SHAPEOKO 3XL
Standard Z-carriage. Belt is tight, set screws are tight. Springs attached and healthy.

I first used the BitZero probe at the corner of the stock to set X, Y & Z. When I ran the g-code, X & Y positioned properly, but Z started cutting well above the stock.

So I zeroed the Z manually with paper and tried again. This time Z began cutting about half the distance closer to the stock.

It appears that the first cut starts roughly an inch above the stock using the BitZero probe, and less than 1/2 inch above when zeroing with paper. I’m tempted to say these offsets are the same as the Max Depth of cut when zeroing with the probe, and Max Depth - Stock Thickness when zeroing with paper, but I don’t have actual measurements.

Help?

This is the beginning of the g-code:

(Design File: /Users/larrymartin/Desktop/Projects/Guitar/Working Drawings/
telecaster V7 dxfs/telecaster_v7_20200502.c2d)
(stockMin:0.00mm, 0.00mm, -13.13mm)
(stockMax:530.23mm, 355.60mm, 0.00mm)
(STOCK/BLOCK,530.23, 355.60, 13.13,0.00, 0.00, 13.13)
G90
G21
(Move to safe Z to avoid workholding)
G53G0Z-5.000
(registration)
M05
(TOOL/MILL,6.35, 0.00, 0.00, 0.00)
M6T201
M03S18000
(PREPOSITION FOR RAPID PLUNGE)
G0X31.98Y176.97
Z6.35
G1Z-1.59F381.0
X31.83Y177.14F2540.0
X31.75Y177.27
X31.67Y177.40
X31.62Y177.54
X31.57Y177.69
X31.54Y177.84
X31.52Y178.00
Y178.18

2

I would look into just that zeroing issue first. You don’t have a BitSetter, do you?
Probe XYZ, then jog manually (and carefully) back to 0,0,0: are you at the expected zero point then?
If you then jog up manually by 1 inch, does it move by 1 inch?

1 Like
3

I have exactly the same issue. I have only used the xxl one time im the last year since i purchased it. It worked fine. Now after about 10 months i was going to cut out a few basic shapes and it will not lower to cut after using the touch probe, stays about an inch up. Tried everything i can think of to fix it too no avail. So now it sits in the back of the shop until some time down the road when i can figure it out. I will just continue using my shaper origin. I really wish it would work, sad time.

4

If you have such difficulties, post the .c2d file, generated G-Code, step-by-step notes on how you are securing your stock and setting zero relative to it, and a photo of a failed attempt at cutting here or to support@carbide3d.com and we’ll do our best to work through it with you.

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5

Check your setup. I had this issue the other day and did a search. Found that I had set used material bottom, switch to material top and problem solved.

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6

Thanks, Julien. No BitSetter. I haven’t followed your direction exactly because I got distracted. Here’s why. I repeated the XYZ probe with BitZero properly positioned at the corner, then raised the Z axis and rapid positioned to the center. Then I rapid positioned to Z+6mm and the end mill stopped at about1 inch above the stock. Frustrated, I reset zero with paper then, and rapid positioned all three axes. That time the end mill wound up properly positioned at 000+6mm. Hmm. So I ran the file and it worked. I know that’s not a proper diagnostic, so I’ll try your suggestion again tomorrow.

7

Thanks Will. I’ll do that if I don’t get it sorted tomorrow.

8

Thanks Michael. I’ve made that mistake, too, but this time it seems to be something else.

9

Another thing to check. Did you set home zero when you initialized the machine? Home, set zero, clear offsets.
Found that I forgot to do that and had some odd issues. I found if I do this for each tool path everything lines right up.

1 Like
10

@WillAdams When is this necessary? I’ve not read this before.

11

It should only be necessary if you need to set a new zero — I’ll often set zero, use the machine, power down, re-connect, then let the machine remeasure the tool and continue where I left off.

12

Hi Will,

I had this happen the other day. My tool paths were saved for 3 operations. 1 make a group of squares 2mm deep. 2. Clean up edge with 1/16 bit and make squares nice and crisp 2mm inner cut. 3. Through cut of pattern in squares.

Initial tests I was dialing in my workflow and every time I started the file over it would move in a little not lining up. Traced my steps and looked at the xy coordinates and noticed they were off 2mm When back zeroed and tried again, found each time if I zeroed it was exactly where it needed to be.

Panel was never moved after an operation.

13

I don’t understand. Are you saying I should initialize and zero X,Y & Z in the home position? Then clear offsets and…run?

14

Initialize the machine. Home, zero all, clear offset. Then jog to your start position and probe x, y, z. And run.

15

If you can come up with a repeatable set of steps which cause that, please document them and let us know and we’ll try to have a developer look into them.

16

I’ll give it a try .

17

What caught my attension is the clear offsets. What does that really do after a homing procedure?

18

What that does is gives your true home. The machine goes home, then moves out and over. so when you zero, you set zero, and the clear offset gives the true position of say -3, -3, -3 for argument sake. Here is a link to carbides doc on this https://docs.carbide3d.com/shapeoko-faq/shapeoko-enable-homing/

19

There’s only one mention of the word “offset” at that link. There may be somewhere a link to what “clear offsets” does, but there is no connection described in those docs.

Given that those “docs” are not anywhere complete or up-to-date.

So, I still don’t understand why that is necessary, wanted or needed.

20

Are you using the latest versions of create and motion?

Have you tried another file? Just to eliminate that you may have a corrupt file.

Probe sitting in the cutout not on top of material?

1 Like