Hello all I was running some tests today and I wanted to show you my findings as I hope it could help at least 1 person out
So what will we be routing today?
Pine, Lumber, Dimensional Lumber, Trash wood, Douglas Fir, white wood
there are many names for it but basically its the wood that you find at the home center in the form of 2x4, 2x6, 2x12, etc
Why do we want to CNC route this?
we because its cheap easily accessible and works for many things and if your really picky you can create knot free panels and projects
What tools are we going to use?
Support Tools
Jointer, Table saw, planer
We use these tools to square and prepare our stock in order to get it ready for milling.
CNC Tools
HSS (or carbide) Single Flute Downcut
Carbide 3-flute Low Helix Downcut Finisher
So lets start by thinking about what we are cutting
We are cutting soft wood and this means that things like tear-out and fuzzies will happen often and we are going to try and minimize that effect
Here is the material test we are going to run
this is a 6.5 wide x 8.75 long x 1" thick piece of pine. When testing materials its best to not skimp as you might make mistakes so give yourself room to explore many different CAM strategies
okay so basically we are going to make a pocket .75" deep with a couple circles and 1 circle with a pocket inside of it and run a test to test edge finishes please note that floor finishes are something we can tackle latter
this test really is only to test surface finish of 2d carving straight off the machine so there are no need for things like slots or complex shapes but we do want to be able to test the tools with the grain and across the grain
Here are the 2 tools that we are going to work with
1. 1/4" HSS (or carbide) Single Flute Downcut
I choose this tool because we are working in softwood and its paramount to maintain proper chipload and shearing action of the tool against the wood. Single Flute tools allow us to take a large chip per revolution out the the material while maintaining slower feedrates for smaller more flexible machines. Also single flute tools generally have a lower helix angle which is what we want when working in softwoods especially
Now I said HSS or Carbide personally I prefer HSS in this case even though I am a firm believer in everything Carbide. The theory is that HSS can hold a sharper edge than carbide because carbide is brittle and if you get it to thin then it will just chip and well I by that. So I went with a 1/4" HSS Downcut tool
I choose a down cut because I am just making a pocket here and I want a good top side finish and downcut tools will force the material towards the spoilboard providing better holding power
This tool will preform all out our roughing operations leaving .04" of stock to clean up later. This is VERY VERY you must leave stock to get a good finish even though you will get a decent finish with the single flute tool we can do better
Here are the settings I used for my test (your setting may vary but maintain the same chipload)
RPM: 22000
Feedrate: 132 ipm
Plunge Rate: 60 ipm
Lead-in/Lead-out Rate: 60 ipm
Chip Load: .006"
DOC: .25"
Stepover: .0825" 33% of tool diameter
Cutting Direction: Conventional
Remember your chipload formulas and always check your tooling manufactures chip load recommendations when programming to insure warranty and tool life if you cannot run at these setting then adjust accordingly to maintain chipload
2. 1/4" Carbide 3-Flute Down cut Low Helix Finisher please note the pic shows a upcut but we use a downcut here
I choose this tool because we want low helix flute geometry and we want to take small tall shavings off. Think of your 3-blade planer or jointer and how they make wood feel like glass when the blades are sharp.
Also a downcut spiral will provide better top finish, work-holding, and provide less chance of tear-out compared to straight bits
This tool will perform all the finishing operations and take that .04" of material off that we left in the roughing operation at FULL DEPTH
We want to run the tool at full depth to maximize the surface quality. Even though we are only running a small 1/4" tool we can go full depth in 1 pass because we are only taking off .04" radially. However it is just as important to use what they can Lead-in and Lead-out when finishing. This brings the tool down to depth away from the material and then pushes in and around the material at full depth. If you lower the spinning down straight down on the material you can leave behind a line caused by tool deflection. Ramping into the material can leave the same line
On your finishing pass you want to program into your toolpath at least .001" stock to leave as not to mess up the floor finish you might need to experiment with this depending on how accurate your machine is
Here are the settings I used for my test (your setting may vary but maintain the same chipload)
RPM: 18000
Feedrate: 150 ipm
Plunge Rate: 40 ipm
Lead-in/Lead-out Rate: 150 ipm
Chip Load: .0028"
DOC: .75"
Stepover: N/A
Cutting Direction: Conventional and Climb
Remember your chipload formulas and always check your tooling manufactures chip load recommendations when programming to insure warranty and tool life if you cannot run at these setting then adjust accordingly to maintain chipload
So as far as cutting direction goes conventional or climb it really does not seem to matter a whole lot you can get tearout on both and you can get clean finish on both. It just seems to be whatever mood the wood happens to be on that. I need to do further research on why that is. In my experience however you want to Conventional cut outside profiles and Climb cut internal profiles when finishing. When roughing I would just run conventional all the time
So following these different suggestions lets see what we get right off the machine shall we?
Here is what the piece looks like overall after all machining was done there was not sanding or post processing done
Showing here is the inside pocket that we made I used climb milling here and got a glass smooth finish on the edge even through the knot
Here I am showing with the grain cutting I used climb cutting here as well and the surface finish is glass smooth and no tear-out
So on this circle I used climb milling on the outside profile and you can see that we have fuzzies but these can be taken off with a quick 220 grit paper
This was the best out of them all no tear-out and no fuzzies I used conventional and ran finishing at full depth
So on this circle I used climb milling and also a ramping toolpath which you can see a faint line off where the tool ramped down
Here I am showing the cross grain finish and I think it turned out pretty well and there is minimal tear-out
Here I am showing the floor finish the floor finish is a little rough and you can see some tear-out but the point of this test was edge finish no floor finish and this is to be expected with a single flute tool to clean up the floor you can use a 3 or 4 flute flat bottom endmill and clean it up ASAP
I hope this helps with your pine routing adventures
Also note that Pine/Douglas fir lumber like any wood will change with humidity and temps so once you are done routing be sure to seal the wood as even within a matter of hours your fuzzies and roughness can come back
