Chip loads for a .060 bit

[brian]

Does the chipload calculations apply to such a small bit.
I'm doing a lithophane and this is the first time I've used such a small bit(I bought 4 just incase)and I don't want to over do it.I don't imagine it would take to much effort to snap this bit.
Is 1 ips at 15000 to much for this bit??

I'm going to do a rough pass with a .125 bit to speed things up.The standard value for material left on a rough pass is .02.Can I decrease that to .01.Does this leave enough material for a successful finish pass


Brian

[Brady Watson]

Brian,
Chiploads are not really factored in when cutting 3D. How much material is getting hogged out, does and often a roughing pass makes a big difference and allows you to cut faster. Since you are not removing a lot of material from the lithophane, this is not as critical. If you were doing, let's say a 0.5" relief, then you will want to do a roughing pass. Many people don't get the concept that running a roughing pass 1st, leaving .02" on the material and then following it up with a 3D finishing pass is faster and cleaner than doing it in one go...

In terms of your lithophane, make 2 toolpaths, one with an 1/8" ball and one with the 1/16" ball. Run the 1/8" toolpath for 10 passes and stop. Switch to the 1/16" ball and go .5 IPS on the 1st and 2nd passes. Then you can speed it up. If you are going to break a tool when doing 3D, it's going to be on the 1st pass (when rastering). The tighter (smaller) your stepover distance, the less likely you will break a tool in the middle of the file as rastering just shaves off the stepover distance. I would do a .007" stepover.

Just watch the 1st pass...that's where breakage will occur. If you slow things down, you should be fine.

-B

[brian]

Brady
When doing multipull finish passes,how does one determine the depth of the finish pass.Assuming the first pass starts at the set stepdown distance would the last pass be -.246.The final material thickness is set at .004(thinest portions of the lithophane)
Dumb question but after a 8hr toolpath I'd hate to screw up on the last pass
Brian

[Brady Watson]

Brian,
You can just run both at finish depth. What detail the 1/8" will miss, the .0625" bit will get. If you wanted to do it leaving a skin on the 3D with the 1/8" bit, enter a value of .02" in the allowance field (if your CAM program does this). The .0625" ball gets calculated with zero allowance.

-B

[brian]

how does one figure out a more accurate toolpath time.I've found the artcam toolpath calculator to be unaccurate.
I get the part when it says based on feedrate of 1 ips but what does the time scaling factor of 4 mean
Brian

[Brady Watson]

You have to play with the scaling factor for your machine...I no longer use it.

If you want a relatively accurate time estimate, you need to run the file in SB3 previewer on the same computer that runs the tool. Alternatively, you can run it in the office IF the VR and JS values are identical. Grab one of the .log files from a known file and check that against the log file you get in preview (if not the same computer).

-B

[brian]

thanks Brady

Brian