Fraisou - A home made XYZ CNC milling machine

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Introduction

Fraisou is an home made CNC router. It's a gantry mill type made from aluminium extrution profiles.

General specifications
Control Computer Numerical Control
Spindle axis orientation Vertical
Number of axes 3-axis
Cutting area L * W = 1300 * 840 mm = ( 51.1 * 33 in )
Bed size L * W = 1590 * 1040 mm = ( 62.6 * 40.9 in )
Foot print L * W * H = 1650 * 1120 * 600 mm = ( 65 * 44 * 23.6 in )

Period of construction: 04/12 - 6/13.

Electronics

I detail in this section the electronics used for this machine. The last sub section list the parts and some prices.

Power supply

Specifications
36V[1] 8A[2] For X and Y stepper motors. To rate your power supply read this french article.
30V 8A For Z stepper motor.
  1. The motors have a rated voltage of 2.4V.
    From this very instructive article, we can apply from 10 to 24 times the motor's voltage.
  2. How much current to provide: {\text{nbr of phase}\times\text{ intensity by phase}\times\text{ nbr of motors}\over 2}={2 \times 3 \times 3 \over 2}=9A

I recycle multiple power supplies so I compose with their characteristics. Reference is LUT14V133, specifications are:

  • input: 170-250VAC OR 230-330VDC 135WATTS
  • output 1: 5V 8A (+/-5% adjustable)
  • output 2: 12V 4A
  • output 3: -12V 0.5A

Wiring Diagram :

.----= CASE RIGHT =------------------------------------------------------------------------------------.
|                                                                                                      |
|                                     .-------------------.                                            |
|                          0V°        |                   |         36V°                               |
|  .-------------------------------------------.        .-------------------------------------------.  |
"  | 240VAC    -12V 0.5A    12V 4A    5V 8A    |        | 5V 8A       12V 4A    -12V 0.5A    240VAC |  |
C  |             -   +       -   +    -   +    |        | +   -        +   -      +   -             |  |
A  '-------------------------------------------'        '-------------------------------------------'  |
S                               /        /                   /            /                            |
E                             /        /                   /            /                              |
                             |        |                   |            |                               |
B  .-------------------------------------------.        .-------------------------------------------.  |
A  | 240VAC    -12V 0.5A    12V 4A    5V 8A    |        | 5V 8A       12V 4A    -12V 0.5A    240VAC |  |
C  |             -   +       -   +    -   +    |        | +   -        +   -      +   -             |  |
K  '-------------------------------------------'        '-------------------------------------------'  |
"                               /        /                   /            /                            |
|                             /        /                   /            /                              |
|                            |        |                   |            |                               |
|  .-------------------------------------------.        .-------------------------------------------.  |
|  | 240VAC    -12V 0.5A    12V 4A    5V 8A    |        | 5V 8A       12V 4A    -12V 0.5A    240VAC |  |
|  |             -   +       -   +    -   +    |        | +   -        +   -      +   -             |  |
|  '-------------------------------------------'        '-------------------------------------------'  |
|                                °36V     °30V                °0V          °0V                         |
|                                                                                                      |
'----= CASE LEFT =-------------------------------------------------------------------------------------'


Stepping Motors

Specifications
Model 23HS2430
Step Angle 1.8^\circ
Motor Length 112\ mm
Motor Size 57\ mm(NEMA 23)
Rated Current 3\ A
Voltage 2.4\ V
Phase Resistance 1.6\ \Omega
Phase Inductance 6.8\ mh
Holding Torque 280 \text{ N.cm Min}
Detent Torque 12 \text{ N.cm Max}
Rotor Inertia 800 g.cm^3
Lead Wire 4
Motor Weight 1400\ g
23HS2430 Stepping Motor.

Micro Stepping Drivers

Specifications
Model Microstep Driver CW-5045
Input 20\text{VDC}\sim50\text{VDC}
Output current 1.5A\ -\ 4.5A
Microstepping Imperial: 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256,

Metric: 1/5, 1/10, 1/25, 1/50, 1/125, 1/250.

Maximum Pulse Rate 100kHz
Automatic Half Current yes
Protections Over temperature, motor wiring error
Environment \text{Temperature }-15\sim40^\circ\ \ \ \text{Humidity }<90%

Spindle

Specifications
Model Kress 1050 FME-1
Power Input 220V_\cdots240V\sim\ \ \ 4.8A\ \ 50/60\ Hz
Power 1050\ W
RPM 5,000_\cdots25,000 min^{-1}
Speeds 1 = 5000 rpm
2 = 7700 rpm
3 = 12500 rpm
4 = 16500 rpm
5 = 21000 rpm
6 = 25000 rpm
Dimension 289 x 73 mm
Collet 8 mm
Collar 43 mm
Weight 1.7 Kg
Noise 74 - 88 dB(A)

Parts list

Designation Unit
Price € HT
Quantity Total
Price € HT
Stepping Motors 23HS2430 24 3 72
Micro Stepping Drivers CW-5045 31 3 93
Breakout board 15 1 15
Spindle Kress 1050 FME-1 168 1 168
3 piece Kress Collet sets 3mm, 6mm and 8mm 60 1 60
Spindle mount 33 1 33

Motors, drivers and the breakout board came from Changzhou Rattm Motor Co., Ltd., the shipping cost was 95€. He send me the whole order in only two days.

The Kress spindle came from IronWood Distribution, the shipping cost was 15€. Full shipment within 3 days.

I reuse a computer case and the power supplies.

Mechanical

Plan

Math

XY

Parameters:

  • The transmission chains have a pitch of 8 mm (ISO 05B-1: 5/16 inch).
  • The transmission chains for Y and X axis are drive by 8 teeth sprockets.
  • The stepper motor make a full revolution in 200 steps.

The resolution with a 200 steps stepper motor (without micro-stepping) will be:

\text{Resolution}=\frac{\text{nbr. of teeth} \times \text{Pitch}}{\text{nbr. of steps for a full resolution}}=\frac{8 \times 8}{200}=0.32 \,mm

With 1/10 micro-stepping, I will get:

\text{Resolution}=\frac{\text{nbr. of teeth} \times \text{Pitch}}{(\,\text{nbr. of steps for a full resolution} \times 10\,)}=\frac{8 \times 8}{2000}=0.032 \,mm

This is a theoretical resolution. In practice, you can increase the real resolution to a half step precision. Here it's about 0.05 mm.

Mach3 need the number of steps per unit. The unit is in millimetre so the value for Mach3 in Motor tuning will be with 1/10 micro-stepping:

\text{Steps per mm}=\frac{\text{nbr. of steps for a full resolution} \times \text{micro-stepping}}{\text{nbr. of teeth} \times \text{Pitch}}=\frac{200 \times 10}{8 \times 8}=31.25

Z

Parameters:

  • The trapezoidal screw has a pitch of 2mm and a diameter of 10mm (TR10x2 compliant with the DIN 103 standard).
  • The stepper motor make a full revolution in 200 steps.

In full step mode, the resolution is:

\text{Z axis resolution}=\frac{\text{move of the table for a full resolution in mm}}{\text{nbr. of steps for a full resolution}}=\frac{2}{200}=0,01mm

For Mach3 with 1/10 micro-stepping: \text{Steps per mm}=\frac{\text{nbr. of steps for a full resolution} \times \text{micro-stepping}}{\text{move of the table for a full resolution in mm}}=\frac{200 \times 10}{2}=1000

Y

X

Z

The slide table has been assembled by Igus, it has some axial backlash due to the pillow blocks. I've added two server ball bearing slide rails...

The specification can be found in the pdf file from igus: DryLin SLW-1040.

Parts list

Slide system by Igus:

Designation Unit
Price € HT
Quantity Total
Price € HT
WS-16 Rail DryLin® W 29.68 5 148.4
SLW-1040-DryLin® SLW, slide table 126.09 1 126.09
WJ200UM-01-16 pillow block DryLin® W 5.25 8 42
AWMP-08 aluminium shaft 8.65 2 17.30

Igus charge me 50€ for the delivery. Shipment details: ordered on 2 may, ship on 10 may, delivered the 15 may.

Ball bearings, sprockets, chains by TRI Distribution:

Designation Unit
Price € HT
Quantity Total
Price € HT
Simple sprocket pitch: 8 mm, # teeth: 8 0.84 3 2.52
Simple sprocket pitch: 8 mm, # teeth: 16 2.13 6 12.78
5 Meters of chain pitch: 8 mm 32.15 2 64.3
Ball bearing 8mm 608-ZZ 0.873 12 10.476
Clamp of 8 mm (for the shaft coupling) 3.8 5 19
Clamp of 10 mm (for the Z table coupling) 4.34 1 4.34

The shipping cost was around 12€. One delivery was very long (4 weeks) but they warm me about this delay (importing time).

I reuse old aluminium profiles, this probably save me 150€.

Bits

Article about spiral upcut, downcut and straight: www.woodcraft.com.

Stock Cutting d Shank d Cutting l Overall l Desc Price Ref
2 1 3.175 4 40 Engraving 1F center cutting Carbide 5.09 htkminitools A1L3.1004
2 1.5 3.175 6 40 Engraving 1F center cutting Carbide 5.09 htkminitools A1L3.1506
2 2 3.175 12 40 Engraving 1F center cutting Carbide 5.09 htkminitools A1L3.2012
1 2 3.175 4 40 Ball 2F Carbide 3.69 htkminitools 2Q3.2004
1 3.175 3.175 6 40 Ball 2F Carbide 3.49 htkminitools2Q3.06
1 0.5 3.175 33 60° V 0.5 flat Carbide 2.99 htkminitools JD3.6005
1 0.1 6 40 30° V 0.1 flat Carbide 6.49 htkminitools JD6.3001
1 0.1 6 40 60° V 0.1 flat Carbide 6.49 htkminitools JD6.6001
1 3.175 3.175 38 60° V 1F spiral for small text engraving. 0.15 per pass 9.70 ironwood
1 6 6 16 50 30° 3F 13.45 ironwood
1 8 8 20 70 R4 Ball HSS 11 ironwood na
1 0.5 3.175 3 38 30° 1F 8.30 ironwood
0 1.5 3.175 12 38 30° 1F 11 ironwood
0 3 3 8 40 30° 2F carbure right spiral 6.10 otelo 22101207
1 5 - 6 6 10 60 30° 3F HSS right spiral 3.10 otelo 16201050
1 1 - 1.5 3 2 40 30° 2F HSS right spiral 2.70 otelo 16201010
5 3 3 10 60 Downcut solid carbure 1F wood/plastic 15 0107D31060
3 3 3 10 60 Downcut solid carbure 1F aluminium 21 0107D31060A
1 20 6 40 V shape (laser) 2F 90deg 92 17845

Software

Tips

Fix Circular Interpolation (G02/G03)

I get this error while trying to load G-code on MACH3 generated by the NX 8.5 Post Builder:

Radius to end of arc differs from radius to start on line

After a little search on Google, Mach3 is looking for absolute values (G90) but NX generate relative values. To solve this issue open the Post Builder utility:

Open your the pui of your machine.

Go in Program -> Tool Path -> Circular Move:

Click on circular move to display the parameters.

Change the IJK definition from "Vector - Arc start to center" to "Vector - Absolute Arc Center":

Change the IJK definition.

Alternatively, you can decide to don't generate circular moves but only linear positions (XY):

Select linear move instead of circular.

You will no more find any circular move in the code.

With circular moves:

N0090 X100.095 Y68.736
N0100 X102.479 Y76.44
N0110 G03 X105.396 Y84.466 I-128.569 J164.951

With only linear moves:

N0090 X100.095 Y68.736
N0100 X102.479 Y76.44
N0110 X103.972 Y80.441
N0120 X105.396 Y84.466
N0130 X105.515 Y84.93
N0140 X105.566 Y85.231
N0150 X105.475 Y86.418