Millenium Mill CNC Series: Episode 1

Hi Guys today is the start of something a little different for me and this blog. Traditionally my focus has been on 3D printing or Additive based manufacturing. This series however will focus on the exact opposite, subtractive machining with a CNC mill. CNC Machining is one of the most used methods for production of metal parts worldwide and now possible on a 3D printed (Come on you don’t think I would of forgotten about it all together did you?) CNC machine!

This series will be released as both blog and videos so watch along and then check back here for the details!

This series will be focussed on using the Millenium Mill, a design based on the OpenBuilds MiniMill. Jake, the lead designer has been kind enough to lend me his original machine to show you all what it is capable of.

The Millenium Mill v1.5 no longer uses any of the original components from the OpenBuilds design and is therefore a build from scratch design of a similar style but much higher performance. Designed from the ground up to be 3d printable but have the ability to cut aluminium and other softer materials. The project is accessible to anyone with access to a 3d printer as there are no custom metal parts required to get up and running. There are no full kits available currently and self sourcing cost is around £1000.

The version I am using has got some of the 3d printed parts upgraded to aluminium plates courtesy of Fabreeko! Do check out his page as without his support many open source projects would struggle to get custom parts made and the cost of uptake much higher for those interested in them!

To test this mill I will be using the Titans of CNC fundamentals course parts. They use these parts to teach professional machinists on professional grade machines but I wanted to see what was possible on a 3d printed hobby grade machine.

Today we are going to kick the series off with the Titan 1M. A relatively simple part made from 1×2 inch bar stock. As part of the tutorials you model the part and then program the toolpaths. I will let you watch those in your own time but I will describe the settings used as they vary a lot from those used on an industrial mill.

Tooling

Fixturing for this part is pretty simple and I used the same low profile vice for both the main machining ops and removing the stock from the bottom. This is the first full part I’ve done with these DLC coated end mills from Dreanique and I really am impressed. For dry cutting aluminium they are great and I’ve not had any gumming up of the end mills.

Machining

I will try to use similar machining steps/methods in these videos as are used on the titans of CNC tutorials however there will be changes to accommodate the end mills I have and the machines capability.

OP1001 – Face top of stock

  • 6mm DLC single flute end mill
  • Spindle speed: 24k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.04 mm
  • Depth of cut: 0.5mm
  • Stepover: 4.2mm
  • Machining time: 1 min 49 secs

OP1002 – Adaptive clearing

  • 6mm DLC single flute end mill
  • Spindle speed: 24k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.04 mm
  • Depth of cut: 25mm (limit)
  • Optimal load: 0.6mm
  • Machining time: 7 mins 50 secs

OP1003 – External contour

  • 6mm DLC single flute end mill
  • Spindle speed: 24k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.04 mm
  • Depth of cut: 25mm (limit)
  • Maximum stepover: 0.5mm
  • Machining time: 0 mins 23 secs

OP1004 – Adaptive finishing pass

  • 6mm DLC single flute end mill
  • Spindle speed: 24k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.04 mm
  • Depth of cut: 25mm (limit)
  • Optimal load: 0.6mm
  • Machining time: 1 mins 25 secs

OP1005 – Edge chamfer

  • 6mm 90 degree chamfer mill
  • Spindle speed: 12k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.08 mm
  • Chamfer width: 0.5mm
  • Machining time: 36 secs

OP1006 – Hole boring

  • 3mm DLC single flute end mill
  • Spindle speed: 12k RM
  • Feed speed: 500 mm/min
  • feed per tooth: 0.01 mm
  • Ramp angle 2 deg
  • Machining time: 3 mins 39 secs

OP2001 – Bottom face

  • 6mm DLC single flute end mill
  • Spindle speed: 24k RM
  • Feed speed: 1000 mm/min
  • feed per tooth: 0.04 mm
  • Depth of cut: 1mm (0.5mm finish)
  • Stepover: 3mm
  • Machining time: 7 mins 42 secs

Finished part

Overall I am very impressed with the outcome of this part. The major issues in it are down to operator error (I.E. I was stupid and didn’t double check the length of the stock!) and due to a bolt coming loose in the back of the Z axis at the end of the facing op for the top. Dimensionally the part is within 0.1mm in most locations although there is a bit of perpendicularity issue on the outside walls – This is due to flex in the Z and I really needed to run the outer contour pass a bit lighter.

Stay tuned for episode 2 where I will be machining another of the Titans of CNC parts using what I’ve learnt form this video.

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