Signmakers! advice needed on cutting

[myxpykalix]

I'm tring to make a small version of a big sign i'd like to make and i'm having trouble with the cut and wanted some advice. This is approx. 8"h X 10"w. It was cut with a 1/8" endmill for clearing, a 60 degree V bit for carving the logo and the "contruction co & pleasant hill.
I have a low res pic below, but a high res pic that shows better detail is located at:
http://centralvawoodturners.org/temp/100_0066.jpg
(its a big file, 2 megs)
I bought a 60 degree v bit from sears (I know), but i needed it in a hurry.
The detail is not good on the sign and wanted to get advice as to why? I did a second pass of the files and that cleaned up about 80% but the smaller letters still didn't turn out good. It was cut at 16000 rpm at 2 ips. Thanks

7129

[paco]

The bit appear to be tipped off; with a small flat at the tip. Look for a more "pointy" tool.

[billp]

Jack,
I may be wrong here, but I don't think that file was ever written for a V-bit. The reason I say this is that it looks amazingly similar to a file I wrote for another Shopbotter over three years ago (see attached). If I remember correctly the letters and image were ALL done with flat bottomed bits. It needed multiple clearing passes because even at it's larger size the initial bit was too large to get inside some of the smaller areas.
It appears to me that this version of the file was attempted in another program (possibly VCP?)using the V bit concept. If so I don't think you'll have room to get all of the crane boom detail properly cut, and there won't be room between your large letters either....
I think I sent all of the final files to that Shopbotter so you'd have to check with him regarding the bits used.
7130

[myxpykalix]

I'm sure its the same file/shopbotter. The problem i was concerned about was the quality of the cut. That was why i put the big file on our website so you could see the details. If you look at it what you see is "fuzzies" around the lettering and other parts that looks kind of like end grain tearout. Has anyone cut walnut like this with no problems? If so could you post a pic to compare it to, or even send me to view? The wood was 6 yr old air dried walnut and a new 60 degree vbit. When i reran the file it cleaned it up alot but i don't want to have to run a file twice to get one sign. I suspect it might be the bit. There was a 1/8" end mill used for clearing and the 60 vbit for the crane details and lettering. The "scarring" to the left of the G is a result of a warped board and a low safe Z height. As i look at the picture more and more as i write this the problem areas are what was carved with the V bit. Any recommendations on a mfg who has SHARP bits? Any other recommendations? Thanks

[jhicks]

Jack, I recommend the insert bits from Her-Saf. The arbor and bit holder may cost a bit more on the front end but replacement knives are cheap and insure easy replacement to new sharp edges on V's round overs and other shapes.
Beyond that, there are several other factors at play here for clean cuts.
Unless everything is dialed in, variations will show up so are all settings dialed in like:
Flat table and hold down.
Square x/y/& Z?
Speed and feed may be a contributor as well.
Is the 90 V really 90 degrees? You may find its 89.5 and not cutting exactly whare you think it is.
Bit deflection, dull bits
Cut direction, depth of cut, and final depth pass.

All these and more have been discussed specifically and in general but its suprised me many times that an axis is out of square, a piece loose on the table, or even a loose Z gantry bolt or V roller bearings.

Unless you know everything is right and tight, its open to suspicion.
In spite of numerous calibration stages, we still find that when there is a concern with a cut, there is a reason thats usually mechanical or operator dependant.
Verifying once a quarter or once a month just isn't enough to be sure since things vibrate loose or get bumped out of position and may become progressively worse over time.
Just to be sure double check all positions and develop a calibration routine you can implement quickly and regularly so you know you're on before you cut critical pieces.
We've seen as much as 1/8" variaton on Y Car axis out of square on our PRT120 between bottom and top X rails by simply turning off the motors one day and starting up the next as motors reengage and you hear that "KLUNK" sound but now have a 2 minute verification and recalibrate method that lets check any time we need to in a matter of seconds to be sure.
Good Luck

[myxpykalix]

Thanks jerry, You bring up several good points most of which I don't think come into play here for these reasons. The "semitry"(?) of the cuts look to be ok. The G and O and R and V and other letters cut ok but it is what is left behind (the fuzzies) on those letters that cause the problem. When i rerun the same file over it again it cleans up about 80% of it. THe machine is brand new. I've only cut a handful of things on the table so far and the issues don't seem to be alignment based problems but rather cutting issues. Thats what makes me believe its in the bits. However they are from 2 or 3 different mfg's and all brand new.

If anyone has cut a small plaque in walnut with good results, if you could possibly send me the file (I don't care what it is) and a picture of your results, I would like to try to duplicate it to see if there is something about this file that is the problem. If you could just tell me the type of bit you used would be helpful too. Thanks

[burchbot]

Hi Jack
Brand new does not mean sharp. I have some brand new bargain V bits that don’t cut worth a damn. I have heard that CMT laser point bits are great ( that bit is on my got to get list )
If I was to try that sign I would have put on 2- 3 coats of shellac before machining. This seems to help when doing fine detail. Feed would be 60 ipm. First I would run the v bit, end mill second.
Finally there is only so much detail you will be able to route into wood with good results because of the mature of wood.
Dan
P.S. I no expert, just my 2 cents worth

[thecustomsignshop]

What type of hold down system are you using? Vacum?

What software package are you using to create your toolpaths?

I have cut letters let than .25 inches high w/o issue in Oak and Wallnut using a dremmel v-groove bit.

[myxpykalix]

hold down with vacumn, clamps and screws. The 1/8" endmill cuts look ok but the vbit cuts suck. It was made in V carve pro. The more i talk about it the more convinced i am its the bits.