How can I fix this disaster

I am trying to cut a practise logo as attached. Initially I tried a practice cut on cheap ply but found tearout to be a real issue - as expected. The logo itself seemed to be reasonably clear cut though(comparatively).

I then moved to Kwila as I thought the harder timber would be better. Although it cut better the letters them selves are pretty awful.

Both times I used a 301 v bit (Vcarve)with no finishing pass as I wanted to see what the one pass would deliver. I have added an Advanced V Carve toolpath using a 30degree v Bit and simulation looks great and more like I was aiming for. Before I actually run it I’d appreciate advice whether that is the correct process or if I am totally going in the wrong direction

There are plenty of flaws but the main ones I would like guidance on if Advanced V carve is not the way to go.) are:

*The scallop on the border above the Z & S
*The downstroke on the Z
*The overall quality of the letters
Sorry for the quality of the photo. The wood colour is pretty consistent and I don’t know why the photo shows the silver fleck in the cuts…its not on the original stock.

I now have 30, 45 & 60 degree vbits I can use but don’t know if the bit angle is the problem or something more basic.

I have a reasonably thick skin so feel free to let fly
MenzShed Coaster.c2d (1.5 MB)

Hey Alan!

Your .c2d file has path for normal VCarve, and a separate one for Advanced VCarve, for the MENZSHED bit.
You should probably remove the normal VCarve and add a very small (1mm?) pocketing tool to the Advance VCarve.

The definition of the letters can be improved by using a “pointier” VBit, like a 15 degree one.

3 Likes

So, the logo you want to carve is relatively small, I see it’s about 75mm x 40mm

That number of letters within that small-ish area means that to get a reasonably precise carve you’ll need to go with more acute vbit angles, like @Gerry said.

In theory, you can use a given depth limit (specifically in Advanced v-carve) and you could use a 90° bit, but in practice, the wider the vbit angle, the more small depth error show in the result (i.e. a 0.1mm depth error will translate to a much “wider” slot when using a 90° vbit, that when using a 30° vbit)

Then, whatever vbit you end up using, this photo tells me a few things. First, you probably need to have go a tighten thing up a bit, those top angled lines should be perfectly straight and they are not:

which is probably an indication that some v-wheel needs tightening, and/or belt need tensioning, and/or feeds and speeds needs adjusting.

Second, that lower left corner is a bit “too” rounded,

image

which can happen if your Z zero is not quite perfectly set OR is your stock is not perfectly flat to being with.

  • for setting Z zero for vcarve, there are two pitfalls: if zeroing manually using the paper method, the first pitfall is jogging a bit too low, and since the vbit is so pointy, one can easily dent the surface without noticing, and then the Z zero ends up being set a little too low. The second pitfall is that a vbits are not infinitely pointed, and some even have deliberate flat on their tip, so again you need to artificially raise the Z zero by a hair, to compensate for that (which means, zero normally, then jog up by a small amount which is the height of the “missing” tip, and reset Z zero only
  • running a surfacing pass over the stock surface BEFORE setting zeroes and running the vcarve toolpath goes a long way to remove uneven depth issues. The smaller and more precise the vcarve needs to be, the more mandatory this becomes. In wood, it’s easy anyway so I really recommend doing that, it will help immensely to get a perfectly even vcarve.

long story short(er):

  • run a surfacing pass
  • zero as precisely as you can off that freshly surfaced area
  • use a 30° vbit (or at least 60° if you have a #302 and don’t have a 30° vbit?)
  • you may or may not need to leverage advanced v-carve. I say try with a regular vcarve first, it seems to me that the “v grooves” look is what you are after anyway in this project.
  • run the vcarve toolpath a second time without changing anything, that usually clears up any fuzzies
  • and finally, set your depth per pass to about 1mm rather than 2mm (on your file you have 1.27mm for the adv vcarve, and 2mm for the regular vcarve, and ~1mm will be more conservative in hard wood and help minimize defects)
3 Likes

Also, interestingly this just popped up in my YouTube feed, a video from @ChrisPowell that covers exactly those points (and a few more), so if you prefer video over text, that’s an interesting watch

3 Likes

Hi Gerry
Thanks for your response. I knew I had both the V Carve and V carve in separate toolpaths. I added the Advanced toolpath after running the cut without it and in anticipation of trying it as a cut tomorrow. I wanted to leave the original V Carve in the file while I got things clarified.I also disabled the various cuts to see what their individual impact was on the simulation

I assume I could put the V Carve as the first part of the Advanced V Carve and I will do as you say and drop the cut down to 1mm.and maybe try using the various smaller v bits to see what the final result is.

I have added the 30, 45 and 60 degree tools but don’t have anything pointier. When adding them I just edited the regular v bit with diameter, angle etc but left speeds and feeds untouched in the tool database as I understand those parameters are not now used in the calculations of basic feeds and speeds.

I did run the Advanced V Carve toolpath after adding it to see what the simulation gave and it looks way better. Fingers crossed the actual cut looks as good.

Thanks for your advice

1 Like

Hi Julien,

As always very helpful in your response.

Yes logo is small…to maybe fit a coaster eventually. I have been using it more as a means to gain experience in importing SVGs and resizing and positioning them. Finally had to see what the finished product might look like.

Re the top line being crooked. Would the larger bit contribute to the "scalloping as well? I have tightened the belts and v wheels are clean but I will have another look at their tightness. I have not retrammed my machine since relocating it from my shed back in to the garage so I think I might go back to basics and get it setup again.

Once I have done that I’ll do some more runs and include changes to feeds/speeds…time for another read of the “Bible” :grinning_face_with_smiling_eyes:
Good pickup on the rounded lower left corner. It is indeed the z set too low. I actually set it and then before running the cut lowered the Z a “tad”(technical term to add to “Bible”) to see what impact that would have on the cartoon character and forgot what that would do to the Vcarve…Doh!!

I did set the zero using paper but I actually have an (uninstalled) BitZero. I really must get it installed but have been putting it off until after I relocated my machine. No excuse now so I’ll do it this weekend.

You have convinced me to add a Surface pass to the the toolpaths. I ran the stock through a thicknesser and, even knowing you said elsewhere that you still recommend surfacing, laziness took over…and probably came back to bite. I’ll let you know how the surfacing went. On reflection it is probable that there was Snipe on the board from the thicknesser and I was cutting right where snipe would have formed. Surfacing will eliminate that

Thanks also for the tips re depth per pass.

I am not sure I fully understand Advanced V carve yet and there are no tutorials that I have located.

I have been following Chris Powell amongst others but had not yet viewed the one you linked to.

1 Like

This topic was automatically closed after 30 days. New replies are no longer allowed.