Hey guys, I’m scratching my head on an issue I’m having. I am working on making a sign with V-Carve text and ran a sample on 3/4" Baltic birch plywood. The sample looked great except for a minor correction with the text location. Depth of cut and everything was crisp. I then milled up my almost 1" oak and put it on the table. I corrected the material thickness/text location and ran new G-codes and started it up again. I am using the factory spec feed/speeds and the 301 v-carve bit. I started at a depth of cut at 0.2 which had a few letters not even fully showing. I then dropped it to 0.3, and it was only marginally better. I used a few gauges to check the flatness of my board (what was jointed and sanded on a drum sander prior to). The board had a ever so noticeable low spot when using the gauges to check it, but nothing that would even come close to explaining the depth inconsistencies. Any ideas?
The only conclusion I can make is the board has a few harder spots (no knots area near the text area). I know the factory speeds/feeds are supposed to be very conservative so that doesn’t seem likely, but I don’t know what else to try. The bit is brand new and I’m using a Shapeoko Pro XXL.
Kinda looks like some of the lines in the font are just too narrow for any decent depth of cut. Perhaps bold the text to see if adds some bulk, or select another font.
I’m using the Bitsetter V2, taking off the V bit and throwing on the plain rod to get the measurements. Throwing the V carve back on and doing a bit change so it hits the bit zero then starts the project.
You still need to set the Z-Zero at some point.
1 - Init the machine against the Bitsetting with the plain rod (you can just leave the V Bit in).
2 - Set the Z-Zero using the BitZero or the manual method.
From then on you can do tool changes without using the Bitzezo, but you must set z-zero at least once.
I tried all that and same results. I threw on the 60 degree bit and re-programed it. Clean and crisp everything. It’s just odd that the 90 degree was so off on hardwood compared to plywood and then the 60 degree had no issues. I’ll stick with the 60 for now since that’s working.
I’ll add that any subtle variation in stock thickness will be exacerbated, and more so with a more acute endmill like Will mentioned. I highly recommend running a surfacing pass on the stock before zeroing Z on the freshly cut surface and running the vcarve job, it makes the result much more predictable and repeatable.
The thing to keep in mind with VCarve is that it wants to “carve” between two lines as opposed to a profile cut. It’s more in tune with a pocket. The difference is that the depth of cut is determined by both the angle of the bit as well as the distance between the 2 lines.
In this example the distance between the 2 lines is 1", the only difference is the bit on the left is 60D and 90D on the right. When using a 90D bit the margin of error is tiny in comparison to the 60D. You need to be spot on with the Z-Zero, when using higher angled bits, as Julian mentioned above.
I appreciate the timely feedback. I’ll have to run a surfacing pass and see what happens. It’s just odd that the material threw the text off by a huge percentage. The cut quality in the oak compared to the plywood was a night and day difference when it came to depth/clarity etc. I’ve been doing woodworking for awhile now and know the surface to be perfectly flat since I have machines that can do it much faster than running a surfacing pass. However, I do understand that a slight variation from the bed to the material can cause that issue, which would likely indicate an “area” on the board, not random letters throughout. I even was using a micrometer on the wood to enter the thickness. I mic’d the corners and had a negligible difference. The plywood I used for the test cut had zero v-carve variations throughout the entire text. I might have to try a different brand of 90-V bit and see if that makes a difference in the much harder oak. It’s a basically new Nomad bit that came with my kit. I definitely love the learning process here and all the help!
If my observations are correct, your cut in oak with your font and a 90 degree 301 is the correct theoretical result. This is in line with what most everyone has already mentioned. I ran your gcode and your largest letters look to be about 1 inch high, the smallest 0.5 inch high. Your font also has very narrow sections on some letters ( eg. the left side of the "A"s.) I dont know the narrow section’s widths, but a 90 degree v bit will only need to go one half that width in depth to carve that section. With the 90 degree bit those narrow sections will surely be much shallower than the max depth of 0.2 or 0.3 you were trying. This explains why 0.2 and 0.3 depths looked the same. If sections of your letters were all less than 0.4 inch in width, I would expect them all to look the same regardless of 0.2 inch or 0.3 inch max depth settings. Shallow cuts become very susceptible to imprecision in zeroing, stock thickness, and V bit point diameters. As sections to be carved become narrower, carving with a 60 will be preferable due to its increased depth. Likewise, extremely narrow carving may require even sharper V bits.
I purposely avoided that part of the puzzle, but the gcode you posted shows the depth of cut within the “S” in “ACTS” at 0.052 inch. (Less than 1/16 inch). I dont see more than one pass through there, so if it mics deeper than that, something was off affecting Z when the pine was cut. I would be surprised if the cut in pine could be reproduced with the posted gcode using a 90 V bit.
