Feed/plunge rate chart?

How To
#1

This is probably one of those noob questions that experts will scoff at, but here goes:

Since we all have the same machine and pretty much the same materials in the Mega kit, would it make sense to collect in one place feed and plunge rates that we’ve found to work well? Or has someone already done this? Or is this not possible to do because it varies by what shape you’re cutting? The fact that our software is mostly in inches is doing my head in a bit. :slight_smile: (European here) (EDIT again: Found Change to mm button)

EDIT: A more elaborate version of this could be a mobile-optimized web app where people could put in their settings, add a photo of the design and the end result, and add a rating of how it went. Then others could do a search with certain parameters and see others’ experiences, what tools they used and at what settings, and so on.

#2

It’s complex.

We’ve got a simplistic beginning to this on the ShapeOko site: http://www.shapeoko.com/wiki/index.php/Materials — it would be great if the two projects could collaborate on this.

See instead:

There’re also some reference materials / links as well as links to online calculators. One really cool tool is the GWizard from the CNC Cookbook folks which has a really nice licensing model.

I use this technique on a chunk of scrap: http://www.precisebits.com/tutorials/calibrating_feeds_n_speeds.htm

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#3

@spongefile

Good Idea, It would be great if we got some postings in this thread where people showed a screen shot of the Toolpath settings they have used for different materials. Even if settings vary between types of cuts and machines it would provide a good starting place for someone wanting to cut a new type of material.

The Carbide3D guys have done some great cuts in the videos they made available, would it be possible to post screen shots of the tollbooth parameters used for cutting the knife handles, the brass bracelet, Apollo’s heart necklace, the race car, etc…

I started out using the auto generated Toolpath parameters from the Tools—Carbide Auto Toolpath and found the results to generally be too fast. I had better results when I slowed them down. I had good success on different wood and acrylic cuts using the Toolpath parameters shown below. I am still tweaking them and welcome any suggestions.

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#4

I guess one thing could simply be a general range–anything beyond this or that for a particular material definitely spelling disaster, but Your Mileage May Vary in between.

#5

Isn’t there some sort of integration between GWizard and MeshCAM?

Here: http://www.grzsoftware.com/blog/releases/g-wizard-integration/

Probably a good choice for people who are willing to use closed-source / proprietary software.

and another link w/ a familar-looking screengrab:

http://blog.cnccookbook.com/2011/03/01/meshcam-great-ease-of-use-in-a-3d-cam-package/

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#6

I’ve commented elsewhere about this too, it’s actually rather complicated to get the right feeds/speeds/plunge-rates/step-overs/waterline-pass depth etc… because they’re in an interconnected relationship. That said, there are a few constants you can work from:

  1. Recommended chip-loading for your given cutter in a given material. You can find chip-loading charts online in a number of places. Onsrud in particular has a few decent ones for their tools, and here’s one from [PDS spindles][1] that’s also pretty good.

  2. Maximum spindle speed and axis feed-rate your machine can offer. In our case with the Nomad it’s ~12krpm, but I would recommend keeping it under 10krpm, and 100ipm maximum travel speed on an axis. As I’ve posted elsewhere, it’s an inverse relationship between torque and speed, so the faster you go, the less force you can exert. If your spindle is being asked to spin too fast, it may not be able to exert enough force to work at the recommended chip-load for the cutter & material. If you have too high of a feed-rate you’re “crashing” the spindle into the material instead of letting it cut, so the steppers miss steps. This is most pronounced in dealing with turning corners and lateral entries into the material, and is the worst when you’re doing a full-diameter plough-cut with the tool. Taking a slightly less aggressive step-over can help a lot to reduce the lateral force on the spindle.

  3. Recommended depth-of-pass/maximum step-down for cutters is recommended to be 1x the diameter of the cutter if working at the recommended chip-loading, or you can decrease feed by 25% for 2x depth, or 50% for 3x depth. Because of the machine limitations, you’ll probably need to reduce feed/speed rates to make things work out at the right depths, but you’ll probably end up with less cutting-time overall and less wear on your tools as a result.

Until we can collectively get some values put together, those guidelines should help, plus the formulas which I’d put up for [3dSteve here][2].

Happy machining!
[1]: http://www.pdsspindles.com/engineering-speeds
[2]: First 3D Cut and Lessons Learned

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