The good spindle is what makes my machine really expansive. I need high speeds since I want to use milling tools smaller than 1 mm. This basically means than spindle should be ideally capable of 60 000 RPM.
Spindle
I bought used Jäger Z33-M060.10 K2S15. It is the smallest spindle from Z series with just 180 Watts. That should be for my purposes more than enough. It has nice 60 000 RPM and inner taper run out under 1 micrometer.
The connector is Amphenol (male no. C016 10H006 000 10) and since I plan to have the frequency drive in the box with other drivers I bought the female receptacle with crimp termination (no. C016 10G006 000 12) which can be mounted on the box. The crimps are for the wire gauge 0,14 - 0,5 mm² (10 A N02 016 0003 1).
Collet ER8
Mine Jäger uses collet ER8 with a clamping range up to 4.5 mm. The guerrilla guide says it is preferable to use the collet whose upper clamping value match the tool. I.e. a 3.00-2.00 mm collet is better than a 4.00-3.00 one when holding a 3 mm tool. After some search I found that most of the micro tools use 3 mm and 4 mm shafts so I'm ordering good quality Rego-Fix Ultra-Precision ER8 collet (type 1108.03001) with the range 2.5 mm - 3mm (T.I.R. < 0.005 mm at the distance 10 mm) and 1108.04001 with the range 3.5 mm - 4 mm.
Kress 800
Frequency inventor
This is makes expansive part.
Cutters (read Guerrila Guide)
- Material
- cobalt steel alloys (HSS) - better than carbide for low RPM spindels
- tungsten carbide in a cobalt lattice (carbide) -
- requires high RPM
- are 3x stiffer than HSS - suitable for small tooling
- HSS + PM (powdered metal)
- Coating
- titanium aluminum nitride (TiAlN), AlTiN or TiCN increases tool life and are not much more expansive
- amorphous diamond
Aluminum
Three Key Points
- Use an end mill specifically designed for aluminum machining.
- Use a machine with high speed and feed capabilities.
- Be sure to evacuate chips from the cutting zone.
Make sure:
- is soft and sticky --> sharp edge and high rake angles are needed to separate a chip from the parent material
- high helix angle (>35 degrees, but generally around 45 degrees) is desirable -->
- less stress in horizontal direction --> less tool deflection
- high helix helps move chips up and out of the cutting zone --> speeds chip removal
- more cutting-edge in the cut
- the axial rake is more positive so better shearing
- Hi-Helix end mills like allot of feed or they will chatter
- BUT - with more cutting-edge in the cut the tool is much more aggressive and may have a tendency to pull into the material. In soft materials this may pull the tool out of the holder
- two- or three-flute end mill works best because this allows for larger flute areas.
- peripheral rough milling - three flute
- full width slotting - two flute
- a core diameter of slightly less than 50 percent of cutter diameter is optimum as this also allows for larger flute areas
- an open flute design is essential for easy chip movement away from the cutting zone
- Surface finish on the flute is also critical. Long-chipping, low silicon aluminum alloys have a tendency to stick to cutting tools. As a heated chip flows over the flute it will try to adhere to the tool surface. The flute surface must be very smooth to counteract this tendency.
- slick tool coatings are desirable (low friction coefficient) - for example TiCN coating is not as good
- coolant is important for chip evacuation and keeping the tool cool
- whenever possible try to avoid using a dead sharp corner. Sharp corners tend to break down quickly. Using a corner radius or chamfer type end mill will increase tool life.
What is an upcut router bit?
Upcut spiral tools are the most popular type of spiral fluted tool. Use these for grooving or slotting, for upward chip evacuation and best finish on the bottom side of the part. These bits allow for rapid cuts since the tool clears the chips away from the material. While ideal for cutting thicker materials, this type of tool is not recommended for thinner or softer materials. When working with these types of material, the upward force can pull the material causing a ragged finish on the top surface, or even worse, eject the part from the table. This type of geometry is used whenever the best finish is needed on the bottom side of a part.
What is a downcut router bit?
Downcut spiral tools are best used for thinner materials which will be pushed down into the machine bed rather than being lifted with an upcut spiral. This can be particularly useful when using vacuum hold down where maintaining the seal between the material and sacrificial bed is crucial. These tools are predominantly used when a high quality cut finish is required on the top surface of cut parts.
Downward spiral tools often require reduced cutting speeds because the chips are pushed back into the material. The chip extraction is generally less effective with this type of tool than it is with an upcut spiral tool.
Cutters
From WIDIA series 7N02 Vision Plus Micro
MJ1 - Coating AlTiN - Aluminum Titanium Nitride, black in color, is a harder, smoother variation of TiAlN. Created for abrasive and high temperature applications (> 800ºC). AlTiN creates an aluminum oxide layer during the cutting process. It is increasing in popularity for drilling, counterboring and milling. Applications: Excellent in dry milling of chip classes 20, 40, and 60. Because of the high hardness of the coating however, very hard steels may cause chipping of the cutting edge (first consider TiAlN). Can be used for wet milling of titanium alloys, high temperature alloys, and other abrasive and difficult to machine materials when chipping is not a problem
RJ1 - Coating TiAlN - Titanium Aluminum Nitride, violet bronze in color, actually forms a hard aluminum oxide layer in hot (> 800ºC), dry machining applications. This further reflects the heat back into the chip and away from the tool and workpiece. Greater ductility makes it a good choice for interrupted cuts. Increased production levels at higher feeds and speeds and longer tool life in high heat applications are the primary benefits. Applications: Excellent in milling and drilling of high strength steels, hard die steels, and high temperature alloys, including nickel base & titanium (chip classes 120 & 140) where high heat is generated and chipping is a problem.