For today's project, I'll be using yet another beautiful model purchased from Etsy, (3DmodelsMD). 3d STL Model for CNC Router Engraver Carving Machine Relief Artcam Aspire _ Armed Forces There are plenty of other models to choose from in different price ranges. You can use the steps covered in this project to create any of them.
- Machine Type:
- CNC Router
- Vecric Cut3D, bCNC
- Machine Time:
- 6.0 -7.5 hours
- Bit or Laser Size:
- .250 DownCut & .125 Ball end mill
- Feeds & Speeds:
- Roughing pass: 80 IPM/ 60 plunge rate. 0.1" pass depth. Finish pass: 60 IPM/ 40 plunge rate.
- 1" thick Oak stair tread, stain and polyurethane finish. Sand paper, sanding mop, Dremel tool, various Dremel bits......
I will once again be using a 1" thick piece of Oak stair tread purchased from Lowes or Home Depot. You can use whatever type of wood you have on hand though. Even XPS works well on these projects, which is also available at either place too. You can find it being sold as craft foam, and it comes in pink or green sheets.
The stair treads are 11.5" wide so unless you glue two of them together, you are limited to that width for your carving! They also have a bull nosed edge on one side which takes a little bit away from the usable 11.5" width. Knowing that, I will set up my model size as X= 11" x whatever the length(Y) comes out as. Mine comes out as 13.652" ( You will want to keep the LINK XYZ box checked when setting width and length of the model to maintain the proper aspect ratio of it). You want to uncheck the box afterwards, to set the model thickness!
Next step is to enter the material size you will be using. I chose 11x15x1 for this carving.
I like to have extra length or width so I can screw my material down, or use clamps and not be in the way of the tool path with them. The most important thing about setting the material size is the thickness. The thickness you enter will determine how deep your cutout tool path is. There is an option to change the depth of the cutout tool path in step five. Under tool path parameters, material to leave. You can enter a positive or negative value in the box there. For me, I like to set my cutout path a few hundredths deeper than the thickness of the material, so I enter -0.05 which adds an that little extra cut depth to the tool path. You could set it as 0.05, or even 0.1 to leave the model attached to the material. You could then finish cutting it out by hand afterwards. Up to you!
Step3: Choose bit and parameters for the roughing pass.
The standard rule for this is typically to set your cut passes to half the diameter of the cutting tool. I am using a .250" diameter 2 flute downcut end mill bit. I set my feed rate at 80 IPM and plunge rate to 60. That "rule" has many variables that depend a lot on the material you are cutting. There are plenty of charts and calculators floating around the web that can help you with calculating your speeds and feeds, but you will find they don't always work as written. The more you use your machine and experiment with different bits, materials and speeds, the better your understanding will become.
That rule is just a figure to get you in the ballpark. You can pretty much listen to the machine and know if it's cutting right, or if something is set wrong. Too much, too fast or slow etc.... Experience is the true teacher.
I set my pass depth to 0.1 for the rough pass on this carving. I find that Oak has a tendency to chip out if you try taking too much at one time. The machine is capable of taking larger passes, but it's best to take the extra time, and have a great finished piece when it's done.
Step 4: The finish pass. The time consuming pass!
I almost always use a standard .1250" ball nose end mill bit, using 9 or 10% stepover for carvings of this size. I enter 60 IPM with a plunge rate of 40. The depth of cut is determined by the model, and whatever material is left to carve away from the roughing pass. You can adjust your speed up or down a little, but the max speed it will cut, depends on the capabilities of the machine you are using. With all the intricate details in some of these models, the speed will be limited by all the axis working in unison. I usually end up with a pretty good looking carving that requires minimal sanding running 60 IPM. Just make sure you use a good quality, sharp bit.
Once the finish pass has completed, you can run a cutout pass to free your project from the remaining stock.
Here is where you can adjust the amount of material left remaining if you choose. As long as the material depth was entered true during set up, there is really no need to make any adjustments here. If you entered 1" thick , and it is actually 1.1" thick, then the cutout path will not cut all the way through the material. You would need to enter a negative value here as -0.10 in order for it to reach all the way through to your spoil board.
I entered a negative value of -0.05 here because the wood is actually 1.03" thick. I could have entered that value in the beginning, but just didn't, lol. It makes no difference as long as you adjust for it in the cutout tool path.
The one thing about using Cut3D that I hate is that the previous toolpaths will already clear most of the depth away around the profile, and there is no way to change the starting cutout toolpath depth. You end up making 10 passes around the profile cutting air before ever reaching the remaining material .
Okay, next checkout the preview screen and make sure it looks like it should and proceed to the next step.
Last step. Saving your toolpaths!
Saving your tool paths and creating the g-code that tells your machine what to do each step of the way. The post processor you choose makes it customized for your machine. I am using the Openbuilds Lead 1010 that uses a GRBL controller, so I choose the GRBL gcode post processor. Using the wrong one will probably generate code that is not recognized by your controller and you will typically end up with error messages when you try to run it.
I bought a sanding mop off the internet. I don't remember where from now, but I recommend getting one. I just run it in my cordless drill to clean up most of the little leftover fibers and rough spots left behind. It does a pretty good job without destroying any details of the model. I follow up with some 220 grit in other spots. A Dremel tool or equivalent, comes in handy as well for detailing some of those harder to reach spots.
Good luck, and have fun.