Need to run a V-carve twice

[JerryBurks]

I did my first V-carve experiment today and used a 0.25" 60-degree bit with the pyramid shaped tip (no real flutes).
This worked in principle quite well, but at a speed where the bit does not burn the wood (I used 60 ipm) the forces on the bit were enough to see the colt router flexing in the holder (or maybe the whole machine was flexing). Accordingly the bit tip was not really where it was supposed to be and the cut surface was very wavy and rough. When finished I just ran the whole job again and this time the bit took only away the remaining waviness, edges and burrs.

The final result looks very good but I was wondering if running the job twice is really necessary or if there are other ways to skin the cat. I attached the Vcarve file and maybe somebody can give me advice how to do this better. I carved this in baltic birch with the Colt speed between 1 and 2.

Door2.crv

(4.43 MiB) Downloaded 426 times

[jeb2cav]

Hi Jerry - if you're seeing flex, then you need to either slow down the IPM, or reduce the pass depth - or a combination of your choice.

You could rerun your test - this would not change the pass depth you've selected - and set the FRO slider to 30 or higher (don't go lower than 30 there's a reported bug at less than 30). Assuming no flex at 30, you could "slide up" until you started seeing the flex. Then you'd know "good" IPM for that pass depth and that bit in that material for that cutter.

If you still see flex at FRO 30 with your current project, go back in and edit the tool parameters to a smaller pass depth, recalculate the toolpath, and repeat. As you can imagine, even though two cutters may have the same geometry, they may have different tool library settings if they are constructed differently. The handful of v-bits I've purchased for use with this CNC machine are definately different than the v-bits I've purchased to use with my router over the years.

[Consultingwoodworker]

Jerry,

Your chip load is too great, the side pressures are causing the flex. I am guessing you are using one of the engraving bits where the cutting edge is acually just a flat milled into the bit. These are engraving bits, designed to cut very shallow passes to create signage. Switching to a 60 degree router bit would likely solve most of your issues.

Even full sized industrial routers flex a bit under load. The more rigid the machine the less flex. This system is not terribly rigid, but certainly rigid enough when programmed appropriately.

I have a program that requires a fairly large undercut, and the finished results must be very accurate. I mill the pocket away with a straight bit, then mill the undercut. THEN the program mills it a second time using the same lines and perameters. This "finish pass" insures that the undercut is exactly what I asked for.

A more simple solution for your issue may be to simply change the allowable cutting depth of the bit. In the tool file, you can specify what the maximum depth of a single pass can be. If your program needs a deeper cut, the software will automatically create multiple passes.

Ralph

[JerryBurks]

Thanks for the advice. Yes I did use the solid engraving bits and went pretty deep so their cutting capacity is apparently just not that great. I will try another one sometimes with a router v-bit and maybe just let off with the pass depth.

[Haltex]

Guys I want you to know that I fowned a bit that runs off one pass and there is no chipping out when the bit gets close to the outter bowns of the other passes that you have have made there is no cleaning of your work. I have been using it for about 8 months now its really dose the job . You will find out also that the bit last for a very long time and dose not get hot. You can finish the job and reach up grab the bit,its as cool as when you started the job. The bit is changeable with a allen wrench. Its called In Grove you can get it at Tooltoday, Its made by Amana Tools, After you buy the shaft that the bit fits on that is the biggest cost because the flat bit cost about $20.00 for one bit. The way it is made that it only has one surface contacting the wood that sets the bit to be cleaned out completely. I hope you will try it it made a believer out of me. Hal

[Buc]

I agree with Hal. I was impressed with the crisp, clean cut. Here is a link to go to. It worked for me.

Here is a link
http://www.toolstoday.com/c-454-in-groo ... nives.aspx

Buc

[Haltex]

Hi Buc so you are useing the In Grove bit also, I have yet to see any!!!!!!!!!!!!!!!! router bit to compare with don't you think. I we could just get them to try it theyl buy it.

[JerryBurks]

Jeez....you guys should not do that. This new CNC hobby is going to cost me a divorce.

[jeb2cav]

Wait until you tell the boss about the larger table, Aspire upgrade, poly finishes, that...

[Haltex]

You have to make sure that the other half has got the first pic of your work and you won't have that problem , I make sure that is not a problem( yes dear, no dear, wright now dear, ok dear, their is a pattern here you know that) you will get use to it , it takes time. Hal


If you need a coures in this let me know.