Sudden inlay woes

How To Machining
1

Hey everyone, I’ve been making these pieces for years, and am suddenly running into challenges with my inlay vcarves that I just can’t seem to figure out. It’s a classic problem people have run into before, and I’m wondering if we have a standard troubleshooting protocol to help get it solved.

The issue is, I make these diamond inlays, and as you can likely see, the corners of the inlays are getting ever so slightly blown out during the carve.

IMG_4503
IMG_45033024×4032 1.97 MB

IMG_4502
IMG_45023024×4032 2.47 MB

Here is a couple image of the “naked” carves I made during a test, so we can see what’s happening.

IMG_4504
IMG_45043024×4032 2.4 MB

The issue seems to be with the final pass, when the spindle “lifts” in order to sharpen the corners. It seems as though the bit is going ever so slightly too far in each corner, going slightly past the sides of the diamonds that it just carved.

Here is how I am doing the carve, using vector aspire:

  • Surfacing path (let’s say .015)

  • Tool path 1: 1/8” bit, clearance pass, start depth of .015, flat depth of .2”

  • Tool path 2: 60 degree vbit, start depth of .005, flat depth of .2”

  • Tool path 3: 60 degree vbit, start depth of .015, flat depth of .2”

As you can see, I am backing off of the start depth by .01 in my second step, in order to minimize possible deflection in the final pass.

And yet, I am getting the results in the images above.

Here is what I’ve done to troubleshoot and experiment so far:

  • checked tramming. I am very slightly heavy on the left side, but not enough to cause this issue I think.

  • replaced old vbit with brand new 1550 bit, to make sure i didn’t lose the sharpness of the tip

  • updated post-processor in Aspire

And here are some experiments I tried:

  • Test 1: standard carve, with a vbit pass depth of .1

  • Test 2: same, but with final pass depth of .2 for toolpath 3 (so it does it the final pass as a single pass, rather than two)

  • Test 3: same as test 2, but set vbit angle to 61 degrees

  • Test 4: same as test 2, but set vbit angle to 59 degrees.

Anyone have any suggestions as to what else I should try? I really want to get these inlays as precise and consistent as possible!

Also I am using the 1550 vbits bits from Carbide (are they called 302 now? Same bits?) I’ve never had issue with these bits, so I am confident that they are sharp and the 60 degree angle is accurate.

Any help would be appreciated!

2

Are you using the inlay mode in Aspire or doing it the manual way before that was available? Just curious, I doubt that it has anything to do with your issue.

Belt tension maybe?

Variance in the wood?

That’s an impressive looking piece, At least what we can see of it. Show us a full picture.

3

Hey thanks for the kind words. I’m going to double check my belt tension and see if that could be the culprit, it’s been awhile since I’ve checked!

Here is a shot of the full piece, which is a representation of a philosophical concept known as the “four quadrants”.

IMG_4507
IMG_45073024×4032 2.8 MB

1 Like
4

Did you check to make sure there’s no damage to your V-bit? I the tip is chipped, it may be blunted and cutting wider than expected.

1 Like
5

Hey @wmoy, yeah I even tested a brand new v-bit and had the same issue.

I am going to try tightening my belts to see if that might be the problem. But my sense is it won’t help, especially since I’m seeing the same deflection in both axes. Though I suppose it’s possible all my belts have a bit too much slack in them!

I was also thinking maybe there is some deflection in the z axis. If the material were to very slightly rise between the carving of the sides and the “up and out” carving of the corners, that could produce a similar effect, with slightly blown out corners and the tool marks I highlight in the image below. However I am a bit skeptical about that too, because that final pass is so light, just .01", and I can’t imagine it’s generating enough force to compress the material or the machine bed itself.

deflectionlines
deflectionlines1920×2560 561 KB

6

I noticed something similiar, slowing the speed/acceleration helped but didn’t cure it for me.

Hope your testing finds you a solution.

I didn’t notice anything on the plug side, did yours only affect the pocket to?

7

How about runout? If you spin a V-bit in the spindle, does the tip appear to wander at all?

1 Like
8

@wmoy Doesn’t seem to! And if it was, my thinking is that this would effect the entire carve, both the sides of the diamonds as well as the corners, since it’s all being done with the same tool and the same tool path. Or maybe I’m wrong?

9

Yeah my male inlays seem to be coming out just fine, it’s only the “up and out” carving of the female pocket that is being effected.

That might be because in this inlay technique, the male pieces are being made with a .02 flat depth, so there is far less of that “up and out” movement (the starting depth is whatever surfacing depth I used + .18, with a flat depth of .02, which makes the male pieces .2 in total). The female pockets, meanwhile, have a .2 flat depth, so there is far more z movement there, which seems to be where things are going wrong.