Question
I have been using a 3/8" mortise compression spiral. I am getting packing of chips in the kerf and therefore low bit life. I want to try a spiral bit with much more of an up-cut. Onsrud has one with .6" up-cut but it is a 1/2" bit. I know I can run faster with 1/2" but will I see more bit life for the extra dollars. All things being equal, does a 1/2" bit get better life than a 3/8"? I am cutting on a Rover 30 with a 10 hp dust collector. The Rover has such a big dust shroud I don't think it helps much in evacuating the chips.
Forum Responses
(CNC Forum)
From contributor M:
Take a look at the Vortex 3130XP. I am routinely getting 75 plus densely packed sheets of melamine with it. It would likely be a lot more if I did not have to switch to other materials occasionally in between runs of melamine. I switched a few years ago from Onsrud for exactly what you are describing. The extra upcut with this 3/8 tool is key for chip evacuation. The website does not list the upcut specifically, but it is much more than the Onsrud.
I went to a 15 hp collector. Getting ready to buy a RCN collet from BVC. Also, are you sure your port is shutting off for the drilling block? This might help, and I really don't think a 10 hp has the oomph to get over the monstrous shoe that is on the 30.
On some of the bigger machines I ran a similar 3/8 tool at 900 ipm, even faster when it was sharp (Onsrud MW series 60-126 I think it was?). But had to watch for throwing parts more. Operator had to stay at the machine and still not the tool life I have now by any stretch.
I am cutting a nest of fairly regular sized cabinet and drawer system parts, not just a few large closet ends.
Like contributor J, I am not concerned with cycle time overall. I onion skin all perimeter cuts not so much for holding power (although small parts need this), but for improved chip evacuation. Climb cut the first pass, conventional the second, parts come out perfectly sized and the kerf is pretty clean.
You could also choose a 3 flute at 1000 IPM and 16KRPM, but unless you have a really quick machine out of the corners the 2 flute is a better choice overall.
When you say chip evacuation, do you mean cleaning the kerf after the 2nd pass? I am now cutting most parts in one pass. Chip evacuation might be one of my issues. I am using a RCN fan collet. Where the tool path is shared with another part we have a totally clean kerf. Only on the outside parts at end of a sheet are there any chips in the kerf. But those chips are packed really tight on the bottom.
I am running pretty much the same chip loads both of you are. I have tried cutting back at the speeds. I wonder if the climb cut, then conventional is somehow easier on the bit?
We are doing wholesale closet parts, so really would like to cut at the highest speed possible. Things are really starting to pick up here.
Would you consider a Biesse Rover 30 fast enough out of the corners to use a 3 flute bit? I might be able to accept a production rate at 1000 IPM in 2 passes? I might be able run at 1200 IPM on the 2nd pass. It would take me a bit to rewrite the post processor to this on non-square parts but might be worth it in the long run.
The passing first in climb is best for me since it biases all of the accumulated deflections away from the part while under load in climb. Then the light pass conventional trims the part very true. If I do both passes in the same direction I sometimes find a very slight lip on the parts after the second pass is complete. It took a while to figure this out and it may be machine dependent. What works for me may not work for you. All other things being equal, if I could achieve good results with 2 conventional passes, I would do that.
As far as the Biesse Rover getting out of the corners, I suspect not, and you may be best sticking with a 2 flute bit. To be certain you would need the acceleration curve for that machine. (Good luck getting that information from the manufacturer - I found it impossible.)
The reason I suspect the Biesse would be slow out of the corners is that it, like my Holz-Her, is a high quality overarm machine, sturdily built and durable. It carries a drill bank, tool carousel and lots of mass, especially on its x axis. Best I can tell it takes about 20 inches to reach 1600 IPM in the x direction, all the while spinning at constant 18KRPM. In the corners the 3 flute just gets too hot and wears prematurely. I wish it were possible to control the rotation speed in relation to the travel speed, but few controllers allow for this not to mention effects on the spindle.
In the end I have heard great things on the RCN and if I had one I would very likely do as you already do, single pass the large parts and only onion skin the small ones. For now, cycle times are not a great concern for me and I will sit pat with what I am doing.
I question the need to worry about chip extraction so much while cutting. I have my machine run a very short sweeping routine as soon as it pushes the cut sheet off the table. Then the next sheet is slid on and hit go while my operator moves parts to the next process (usually edgebanding) without the need for an intermediate storage step. I have a little dust at the edge of my machine, simply sweep over to the floor sweep every so often, but no airborne dust.
Basically you need to check how hot your tool gets while cutting. If the tool is too hot (can't touch for more than a second), you need to either speed up the tool or slow down your rotation. I am currently running 25 metres per minute with 16000 rpm on my Biesse skill.
