Help for fast-along-the-length 3D Machining

[sushantdEFMT]

Hello everyone, I am looking for a solution to quickly 3D machine the top of the sample shown above. I need it to make a pass along the length of the object (along x-axis), with multiple shallow passes but as fast as possible. What is my best course of action?

[a.laasW8M6T]

Hi, welcome to the Forum

"As fast as possible" could mean many things and without more information its hard to provide a concise answer.

What machine will you be using?

What RPM spindle do you have?

What is the Material you are cutting?

Has the Part been roughed out first?

What tool will you be using to finish?

By multiple shallow passes do you mean small stepovers in the Y direction, or do you mean step-downs in the Z direction?

If you want the tool to traverse the part in the X axis only whilst following the profile then the Parallel toolpath is what you want.

If you want to machine along X and follow the curves in YZ too then the Blend toolpath would be a good option.

It is always helpful if you can provide your Fusion file to the forum as it makes it much easier to demonstrate possible solutions.

Goto File>Export>Save as .f3d/.f3z and attach to a reply here

[matt.fame]

You'll have to cut past the bottom of the part, so the material needs to be stood off the table / fixture

If I were doing this, I'd rough it all 3D adaptive with an end mill using all the flute 10% tool diameter for the step over, then set the fine steps according to the geometry. Leave a little axial and radial stock for this rough.

Then I'd use a ball starting from the bottom of the part (minus the cutter radius) and run a 3D contour with a big step down appropriate to the geometry and cutter. Inside 3D contour there's a shallow step over which you can set to machine across the top 3D as well. You have to play with these numbers. You might even make this two operations because if you want to save time, you should really be able to cut high speed across the top 3D.

To use this method you'll have to hide the holes with a patch. I would NOT use "avoid geometry"

But I have no idea how rigid your machine, tools and fixture so.....

[sushantdEFMT]

Thank you for your reply. I've attached my file below and will answer your questions.

The machine is a Probotix CNC. The spindle speed is fixed at 5000 rpm. The material I'm using is a hardwood (Oak). The rectangular stock has been milled to the require size. The tool I am using is a 2-inch diameter face end milling tool. Please note that I am cutting the material out of the rectangular stock using the 2D contour option and want to go through the top surface (as shown in the figure) using a big diameter tool as quickly as possible.

By multiple shallow passes, I mean step-downs in the z-directions. Since the tool diameter is pretty large, the step over shouldn't be an issue is my understanding. I want the tool to go along the x-axis but it's a 3D cut.

Thank you for your time.

[matt.fame]

If you want beautiful finish on the top I'd use a BULL nose instead of a ball. It gives you a wider cut path on top and maximizes your stepover. Maybe something with a 25% radius to the diameter..... like R.125 on a 0.500" end mill. A ball on top you have to have a tiny 0.01" or so stepover to eliminate roughness which increases the machining time considerably..

[sushantdEFMT]

Hello, thank you for your response. I have attached my CNC file in the previous reply, so please take a look at that.

The material only needs to be cut in the top surface. Only the top surface needs to be machined. I used the 2D contour function to cut the material out of the stock. I just need to make sure that the top surface is machined according to the drawings. Since speed is a key requirement for my process, I want to use something that goes along the x-axis removing a little bit of stock every time, but pretty fast. Since the diameter of my tool is 2 inches, I want to remove a small amount of material, but as fast as possible.

[matt.fame]

Oh it's WOOD! Dang dude, yea I'd run high feed, lower rpm. Maybe about 300SFM? The worst thing you want to do is spin the cutter too fast or feed too slow. If it's HSS I'm thinking 550rpm and .005 - .007 c.l. You might get by with a lower feed as long as you keep your revs low. You want chips, never ever dust or particles. Dust chips will burn the wood and kill your cutter.

I plane soft wood at 1000rpm and 200ipm which is beautiful. A bunch yahoo's reviewed the cutter I used, said it was junk. They were all spinning 18k at 50 and 100ipm.

[matt.fame]

All respect to you bro, I'm not going to write your program. You need to get in there and make your own mistakes and break stuff. Honestly, it's the only way. I have thousands of hours in this stuff.

Don't be afraid to push the machine. Prototrak isn't bad. I've used one. I bet you are using a knee mill CNC thing. They're ok. Lots of backlash. Install the cutter deep as you can and do not run the quill out. Keep it all tucked in and pull the table up instead.

If you are using a fly cutter with a edge radius it should work great You might consider the "Flow" operation. I don't like it ,but for what your combination it might be the best option.