Multipurpose CNC Machine

CNC Base

@Oct 25, 2014 – 23:24

Added the project page

@Nov 16, 2014 – 23:33

Before procuring actual parts I would like to try out with existing parts. So, I dig into my old parts and pulled out the stepper motors. Around 15 years(may be more than that) back I was using these stepper motors for my custom built audio amplifier as motorized volume control with complete discrete logic circuits; no microcontroller. Still they are working very much fine. So, started playing with them with microcontroller to figure out the required torque and other possibilities with couplings etc etc. Hmm! This is just beginning, lot of stuff to do.

@May 18, 2015

BOM

  • Smooth rods: Qty 6Nos [Bought]
    • Size: 8mm
    • Length: 40 mm
    • Linear Shaft Rail Support Unit. I am planning to construct using wooden frame so mostly SHF8 will be used.
      • SHF8 – ???
      • SK8 – ???
  • Bearing for smooth rods: Qty: 9/12Nos.
    • Linear bearing [Bought]
    • Copper bushings
    • ABS bushes
  • Threaded rods/ACME-Lead Screw: Qty: 3Nos.
    • Size: 12 mm [Bought]
      • Better to have same as stepper motor shaft size for easy coupling?
    • Backlash nuts ???
    • Standard hex-nut: ???
    • Ball bearing for holding: [Bought]
  • Stepper motors: Qty 3Nos.
    • Step Angle 1.8°/step
    • NEMA: 17/23/???
      • NEMA 23 – Model: 57SH51-4A.SM [Datasheet-1] [Datasheet-2] [Bought]
        • Shaft diameter: 6.35 mm
        • Motor weight: 0.650 Kg.
        • Holding Torque : 10.1 Kgcm. 1.01 Nm
        • Maximum Detent Torque: ??? N.M
        • Total inertia (kg.m.m): ??? Kg.m.m
        • Total friction (kg.m/s): ??? Kg.m/s
        • Rated Voltage : 2.3 V
        • Rated Current/Phase : 2.8 A
        • Price: ₹1000/-
      • NEMA 17 -???
        • Shaft diameter: ??? mm
        • Motor weight: 0.350 Kg.
        • Holding Torque : 4.2 kg*cm
        • Maximum Detent Torque: ??? N.M
        • Total inertia (kg.m.m): ??? Kg.m.m
        • Total friction (kg.m/s): ??? Kg.m/s
        • Rated Voltage : 3.2 V
        • Rated Current : 1 A
        • Price: ₹960/-
      • NEMA 23 – 7.2 Kg-cm (0.707 N-m or 99.98 oz-in)/…
        • Shaft diameter: ??? mm
        • Motor weight: 0.650 Kg.
        • Holding Torque : 10.2 kg*cm
        • Maximum Detent Torque: ??? N.M
        • Total inertia (kg.m.m): ??? Kg.m.m
        • Total friction (kg.m/s): ??? Kg.m/s
        • Rated Voltage : 3.3 V
        • Rated Current : 2 A
        • Price: ₹1500/-
    • Shaft Diameter : 5mm/6mm/8mm/??? mm
  • Stepper motor to threaded rod couplings [Got them]

    • 6.35 mm to 12mm
  • Stepper motor controller

    • Microcontroller: [Bought] – Atmega 2560
    • Extension board: [Bought] Rams 1.4
    • Motor controller: A4988/A4983/DRV [Bought] – DRV8825
  • Drilling/routing motor [Bought] Spindle Motor

    • BLDC motor ???
    • Brushed DC motor ???
  • Spindle [Bought] – 300W Spindle motor with ER11 Collet and Chuck.

    • JT0 chuck/collet
    • Brass chuck/collet
    • Ball bearing spindle
      • Shank
      • Collet
      • Chuck
  • Drilling bits [Bought]

    • Shank size: 3.175mm
  • Engraving bits [Bought]

    • Shank size: 3.175mm
    • Angle: 30°
    • Size: 0.1mm
    • Type: V Shape Engraving Cutting Bit
  • Frame
    • Material type: ???(Aluminium/Wooden/…)
    • Width/Length/Height/…: ??? mm
  • Power supply
    • Computer SMPS ???

@May 25, 2015

Smooth Rods

After roaming a lot and visiting so many shops at last I could get 8MM smooth rods and linear bearings for the same size. I got these rods from a printer repair shop. They charged little more than what I expected but definitely less costlier than online. The only limitation is I have to live what ever the size they gave(~40cm). Online I can order as much length as I want, but as this is just to do some PCB milling/drilling 40cm is not a problem at all. May be later if required I can upgrade with larger working area.

Stepper motor couplings

Hmm! I think I am facing problems with all the items, this is expected as I am getting them from different sources instead of buying all as a single kit. I hope this will reduce the cost of total items even though I have to spend more time and do more research. But any way I am learning a lot as I am picking up each and every item by my self.

Most of the coupling that I see online were for 5mm motor shaft. But the stepper motors that I got had 6.3mm. So, may be, couplings also I have to do myself.

Luckily I found a workshop with lathe and I ordered there. After getting them they turned out that not a good fit. There is a little bit of free-play when they fixed to motor shaft. May be I need to tweak them by putting some glue or some rubber housing to make them tight fit.

Threaded Rods

Bought 12mm diameter. As fitting bolt through hole is easy, I drilled hole on thread rod so that coupling can be fitted easily. But because through-hole there is a little bit free-play between coupling and rod. I need to apply some glue or need add some rubber housing to remove free-play.

Milling Spindle
This week end I tried a lot getting it in shops, but could not find any where. Again thought of buying it online as do not want to spend time on making it and also its difficult to make myself as I do not have any lathe machine. Checked some Chinese models. But when I saw their internal structure, they do not have ball bearing constructing the way I wanted and as their run out will be more. So, again gone back and looking for alternatives(Still, I do not want to spend 10s of thousand rupees on spindle as this is my hobby project) and leaning towards making myself. But the difficult part again is getting proper motor with required shaft size, shank, collet, etc. Let me see in the end what I will end up.
Searched a lot to get 8mm BLDC motor as I can directly replace with C8 ER11 shank. But could not find a proper source. The problem with sourcing from online is waiting time(3 to 4 weeks).

At last I received the Spindle. Here is a quick view.

Spindle

 

@June 29, 2015

POC – As I procured core parts I would like to design the frame. Even though I can use some CAD programs on computer, I thought I will try with some simple card board to feel how they appear physically. So, the results are…

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