Multiple pass carvings

[FelixPQ]

Hi,

say for example one as pretty large pattern to carve (say 14.5" W x 60" L x 0.7" D). What I'd like to do is something like this:

first pass: remove as much material as possible using a 1/2" ball noose bit as fast as possible. (assume I can create the intermediate patterns if necessary)

second pass: remove as much material as possible using a 3/16" ball noose bit as fast as possible and start where the previous pass left us. (assume I can create the intermediate patterns if necessary)

Final pass: use the 1/16 ball noose bit at low speed and low depth of cut to create as nice a finish as possible and start where the previous pass left us of course.

Is something like this possible and if so would you have any suggestion on how?

Thanks,
Felix

[jaroot]

I would guess that it is possible but the end result will be a much longer carve. The last carve will take just as long as it would if you didn't make the first 2 carves. And the last pass on "optimal" will give you as good of a finish as the machine can produce. I don't think that you would gain anything by the multiple passes.

Just my 2 cents worth.

[FelixPQ]

jaroot,

I would believe you're right for the time issue but the additional pass would in my mind be a mean to improve the overall quality of the result base on the fact the 1/16" bit would be less loaded if it had less material to remove. Less load equate basically to less movement (however tiny) and more accuracy and problably better finish as well.

You can add to all this much less risk to break bit.

Regards,
Felix

[LittleRedWoodshop]

What you are proposing is not necessary with a CarveWright. But if you have to try something like it ... run the carve as we always have .... then move the crank handle down a quarter turn and run it again. The second pass will just remove a few thousandths of material.

[Alan Malmstrom]

The beauty of the carvewright is the carving bit moving rapidly back and forth to obtain detailed carvings. When it makes small passes back and forth it shaves of a little at a time kind of like shaving a wall of wood. And getting the detail with just the tip of the bit at the bottom. It would be useless to use a big bit to shave off the top layer and then go back with the tip of the carving bit to get the detail of the surface when you can just do it all at once in my opinion.

Alan

[mtylerfl]

Hi,

say for example one as pretty large pattern to carve (say 14.5" W x 60" L x 0.7" D). What I'd like to do is something like this:

first pass: remove as much material as possible using a 1/2" ball noose bit as fast as possible. (assume I can create the intermediate patterns if necessary)

second pass: remove as much material as possible using a 3/16" ball noose bit as fast as possible and start where the previous pass left us. (assume I can create the intermediate patterns if necessary)

Final pass: use the 1/16 ball noose bit at low speed and low depth of cut to create as nice a finish as possible and start where the previous pass left us of course.

Is something like this possible and if so would you have any suggestion on how?

Thanks,
Felix

Hi Felix,

For what it's worth...

What you are describing is what we do with "brand-x" CNC machines, that are not quite as automated as our CarveWright machines. It is common to run a roughing pass with a larger bit to remove the bulk of material, then follow that with a finish pass using a smaller diameter bit that can reach into the remaining nooks and crannies that the large bit could not fit into, as well as removing excess material left intentionally over the entire surface of the project during the roughing stage. (A few thousands of an inch are purposely left on the surface in case the rough pass chips a little...the finish pass cleans that up after the roughing.)

Now, the main reason this is usually done is not to save time necessarily, but rather to protect the smaller diameter bit from breaking. Most of the smaller diameter bits available for other CNC machines are more fragile and don't have the same cutting depth capability as the CarveWright 1/16" tapered bit. The CW bit is designed to be more robust and less fragile than your commonly used smaller-tip bits for the rest of the CNC world. Having said that, you certainly COULD use the CW bits in any other CNC machine, if desired!

Achieving a time-savings by performing a roughing, then a finish pass can be "iffy". It's true you can set the speed and feed rates reasonably fast for the larger bit and remove a lot of material rather quickly on other CNC's. However, the final finishing pass will normally take just about as long as the CW does using just the 1/16" tapered carving bit in one pass. Yes, I can increase my feed/speed rates for the finish pass on my ShopBot CNC machine, BUT it seldom saves much time. Why?...because the Z-axis motion slows everything down anyway. For example, if I set a feed rate of 3 inches per second for the finish pass along with a small stepover of say, 6% or 8% (to get a fine quality finish on a relief carving), the machine really will NOT actually reach a speed of 3 ips because of the combination of the small stepover and Z-axis moves (it might achieve as little as 1/2" to 1" ips actual speed/feed).

I often experiment with speed/feed settings on projects that I run roughing/finishing passes on. The software I use for generating the toolpaths with (Vectric Aspire) has an accurate time estimator, just as the CW software does. The times are LONGER when running both a roughing and finishing pass for a project. The overall time will vary depending upon the detail contained in the carvings for the project. If I need to use a 1/16" Ballnose to get all the detail to carve nicely, the carve time is usually going to be about the same as the identical carving performed with the CarveWright machine. If I can get away with using a 1/8" or larger ballnose bit (for less detailed carvings), obviously the carve time will be faster (which is true for the CarveWright machine as well). The main time-saving gain is at the cutout stage of a project...I can run the cutout profile vectors and pocket cuts a lot faster on the ShopBot than on the CW (which has preset speed/feed rates)...mainly because I normally use a 1/4" spiral bit to perform the cuts on the Bot. You can push a 1/4" bit pretty fast through the material.

For the present, the CW and Designer software simplify a lot of procedures and shield us from certain "complications". We don't have to concern ourselves too much with speed and feed rate settings, RPM settings, toolpathing and all that. Clean and simple operation is the goal of the CW machine, so practically anyone can run it (if they can follow directions, that is!). That's not to say later down the road that a future CW software package wouldn't add more advanced features for those who may "need" it, and hopefully understand, the various manual settings they may have to deal with.

[cestout]

For the 5/4 top option on my "Treasure Chest" project (in the Pattern Store) I recomend that and have the files included to do that. YOu put the piece thru twice for a two sided carve.
Clint

[FelixPQ]

mtylerfl,

basically, I agree with you, I understand the CW was designed more specifically for carving with a small bit in mind and Designer was probably optimise for just that and I can add to that ease of use.

My concern is more about other task then carving per say, I saw many post where folk said they broke their 1/8" strait bit. I have to say I just bougth my CW and I have only one 1/8" bit and not to mention, it cost me as much to get it here then the bit is worth so I'll be very careful not to break it. The first real project I want to do is shown below and basically there is no carving, just cuts and a lot of holes. I have no idea of what will happen with this kind of work and can't find much if any info on all other type of cuts then carving. Ah! Yes, I forgot to mention, designer is basically useless to setup drilling hundreds of holes, I was lucky to find a utility that does it via ai2mpc but then again it seems that either ai2mpc or designer itself offset the hole pattern by a small amount in both x and y. I bougth both the dxf and stl importer and I would have thought especially with the dxf importer that I would be able to select all my holes and setup a drilling operation for them (as you probably can with Aspire for example) or things like pockets on this kind of geometry but designer seems to have no clue of what to do with closed geometry.

It's probably true that I don't have to be concern with multiple pass, multi bits when carving stuff is involved but for all other types of operation the machine can do, it seems to be another story. Though I'll do some test before the real parts trying to find out how cutting through a 3/4" board is done by starting with small depth of cut but it would have been nice of LHR to mention somewhere how things are done for other types of operation then carving and also what happens with different bit size especially since we have no control on speed, stepover, plunge rate, etc?


Thanks for your time,
Felix

[jaroot]

Now that is an entirely different question. Yes a lot of us have broken the 1/8" straight bit. And yes multiple passes help, help solve that problem. Those passes can be programmed in the "cut through" dialog. Another way to help with the 1/8" carving bit is to only use it if the detail of the piece requires it. I recently bought the 3/16" cutting bit and it is much more robust than the smaller one. Of Course you can't make the same tight cuts with it. I don't think anybody has broken the carving bit.At least not while using it to "carve" with.

My concern is more about other task then carving per say, I saw many post where folk said they broke their 1/8" strait bit.
Felix

[dbfletcher]

I think one of the most common reasons we see here for broken 1/8 bits is users not following to +7 rule. The board comes out from under one of the rollers, tips up..... snap... $$$ down the drain.