Mini CNC Router, Complete Plans and Instructions

The Mini CNC project is a complete set of plans and instructions on how to build a 3 axis CNC machine that is functional and also precise. The Mini CNC is very simple and easy to build and if you have all the materials and parts prepared you should have it ready to work in less than 5 days.

I wanted and also needed to build this Mini CNC machine so I can make faster and more precise the parts that I need for my other home projects.

Mini CNC Specifications

The working area of the machine is X=450mm (approx. 17.5 inch) and Y=250mm (approx. 10 inch) and can mill parts as high as Z=110mm (approx 5 inch).

The maximum milling speed on X an Y axis is 2400mm/min. and on Z axis is 1800mm/min.

The resolution of each axis is 1/50 or two hundredths of an mm and one axis revolution means 4 mm of movement.

The router used for this CNC is a Kress 1050.

The number of parts used for building this Mini CNC machine is 42 excepting screws and nuts.

Required Tools and Skills

For this project you will need to have a set of screwdrivers and a set of hex keys or Allen keys, a drill for some extra holes, metal cutting saw to cut some custom parts, soldering station or soldering gun join the wires so they`ll have a good conductivity , and a multimeter.

You should have knowledge of basic electronics, how to solder and how to use a multimeter

Ordering Components

All the parts used to build were bought from local dealers, so i suggest you do the same if it`s cheaper (parts + transport). If not you ca find all the part on eBay.

The trapezoidal cylindrical nut was made in a local workshop.

Mechanical Components - Aluminum Profiles

The frame is made of aluminum profiles and the part are:

- X base parts 2 pieces of 400x120x30mm

- Y frame parts 2 pieces of 400x120x30mm

1 piece of 380x60x30mm cost: 13.16$

- Y carriage 1 piece of 120x120x30mm

- Z carriage 1 piece of 120x120x30mm

- Z frame parts 2pieces of 120x60x30mm

- machining the aluminum profiles

The product code for ITEM 120x30 aluminum profiles is 0.0.419.04 and for the ITEM 60x30 aluminum profiles is 0.0.419.04

Mechanical Components - Shafts, Bearings and Leadscrews

1) Precision steel shafts:

- Ø20mm precision steel shafts for X axis (cut from 1 piece of 60 inch=1524mm shaft)

· 2 pieces of 600mm long

- Ø16mm precision steel shafts for Y axis (cut from 2 pieces of 30 inch=762mm shaft)

· 2 pieces of 390mm long

- Ø16mm precision steel shafts for Z axis (cut from 2 pieces of 372mm shaft left from the Y axis shafts)

· 2 pieces of 300mm long

- machining the precision steel shafts

· 6 pieces

2) Ball bearings/bushings

- Ø20mm (Ø32 outer diameter) ball bearings/bushings

· 4 pieces

- Ø16mm (Ø26 outer diameter) ball bearings/bushings

· 8 pieces

3) Trapezoidal lead screws cut from a 1500mm long trapezoidal lead screw:

- Ø16mm trapezoidal lead screw with 4mm pitch for X axis

· 1 piece of 657mm long

- Ø16mm trapezoidal lead screw with 4mm pitch for X axis

· 1 piece of 447mm long

- Ø16mm trapezoidal lead screw with 4mm pitch for X axis

· 1 piece of 357mm long

- end machining for the trapezoidal lead screws in a local workshop

· 3 pieces

4) Trapezoidal cylindrical Nuts that I made on a lathe in a local workshop:

- Ø16mm with 4mm pitch nut

· 1 piece with Ø32mm outer diameter and 32mm long

- Ø16mm with 4mm pitch nut

· 2 pieces with Ø24mm outer diameter and 24mm long

Electronic Components - Motors

The motors chosen for this project are 3Nm 8 wire stepper motors that can be wired as unipolar or bipolar, depending on everyone’s choice or what driver you have (unipolar or bipolar).

- 3 pieces of 3Nm stepper motors

A unipolar stepper motor has two windings per phase, one for each direction of magnetic field. The motor has only five leads.
Bipolar motors have a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole. There are two leads per phase, none are common.

The difference is: “Unipolar and Bipolar Half Coil, because we're using less turns, doesn't give us great low speed torque, but because of the low inductance, holds the torque out to high speeds.
Bipolar Series uses the full coil so it gives very good low speed torque. But because of the high inductance, the torque drops off rapidly.
Bipolar Parallel also uses the full coil so it gives good low speed performance. And its low inductance allows the torque to be held out to high speeds. But remember, we must increase current by 40% to get those advantages.”

Electronic Components - Motor Controler

The stepper motor driver used is a unipolar 4 axis driver for 5A/phase motors, the input power is 20-40V DC (local shop).

Electrical properties
Input Power 20-40V DC
Stepper motor drive current 1.5A - 5A/phase
Compatible Stepper motors 2 or 4 phase, 6 or 8 lead stepper motors, 5A max.
Dimensions 18 x 12 x 6 cm (L x W x H)

This board allows you to control 4 stepper motors, as well as receive input from two limit switches/ motor and from an emergency stop button and has a relay spindle interface for spindle motors.

Power Supply Components

The power source contains one 600W toroidal transformer, one 50Amps rectifying bridge and one 20000µF capacitor.

Motor Controller Case

For the motor controller case I used an old Keithley236 source measure unit. I have got out all the guts of the old thing to make way for the new motor controller and power supply.

Electrical Wiring - Power Supply

The input of the transformer is for 230V AC current and has two 21V AC current outputs. The outputs are connected in parallel and then they go in to the rectifying bridge. The rectifying bridge transforms the AC current from the input into DC current on the output. The positive and negative output of the rectifier is connected to the positive and negative of the 20000µF capacitor that smooth-ens the current. From the capacitor you can now connect to your drivers DC input.

Electrical Wiring - Motor Controller

An 8-lead stepper is like a unipolar stepper, but the leads are not joined to common internally to the motor. This kind of motor can be wired in several configurations:

- Unipolar.
- Bipolar with series windings. This gives higher inductance but lower current per winding.
- Bipolar with parallel windings. This requires higher current but can perform better as the winding inductance is reduced.
- Bipolar with a single winding per phase. This method will run the motor on only half the available windings, which will reduce the available low speed torque but require less current.

The motors are unipolar motors so you will need to run 5 wires from a motor controller to each motor. The two so called common wires from the motor controller are connected to the four (red, green, yellow and black) wires motor, making a thick common wire.

Testing the Stepper Motors

In this test i tried to connect the motor with a serial cable but it was to thin for the current that was passing it so it was heating very fast. But the connections were good so I just replaced the cables back with thicker ones, as you seen d in the previous steps.

Machining Mechanical Components - Aluminum Profiles

Before mounting all the parts well need to make some machining to the aluminum parts.

The drawings that show you how to modify this parts are in dxf and pdf format so feel free to use them.

The modifications that you`ll have to make must be done on a milling machine and not by hand. You will have to make some holes thru which screws and trapezoidal lead screws cross (X Base, Y side parts, Z parts), some 5 mm deep holes in which the precision steel shafts are centered, some 5 mm deep holes in which the trapezoidal lead screws end bearings stand (X Base, Y side parts, Z parts). You will also need to make 3 holes in the Y cross section, two of them for the linear ball bearings and one in center for the trapezoidal nut. In the two pieces of X Y carriage profiles you will have to make 5 pockets in witch will sit tight the 16mm linear ball bearings and a trapezoidal nut.

The machining of these parts was made in a local workshop on an old Conventional 3-axis vertical milling machine.

Machining Mechanical Components - Linear Shafts

For the precision steel shafts you will have to make some end screw holes so you can fix them on the aluminum profiles frames. It will be indicated that you make that hole on a lathe., because it will be centered and coaxial with the shaft.

Machining Mechanical Components - Trapezoidal Lead Screws and Nuts

The next step will be to machine the ends of the trapezoidal lead screws so you can mount the bearings. This will also need a lathe to make the ends more accurately so that the bearings wont be moving in all directions.

The trapezoidal nuts were made from scratch, out of POM or Polyoxymethylene that is "an engineering thermoplastic used in precision parts that require high stiffness, low friction and excellent dimensional stability "
There are two types of 16mm trapezoidal nuts, first one has 32 mm outer diameter and 32mm in length (one piece) and the second one has 24mm outer diameter and 24 in length.

Machining Mechanical Components - Ball Bushing Supports

Finally the last component that you will have to make is the X ball bearing support.
You will need two pieces , one for each part of the X axis.
You should do it on a 3 axis milling machine.

All the machining operations were made in a local workshop.

Mechanical Assembly - Z Axis

For this axis you will need:

- 1 piece of 120x120x30 aluminum profile

- 2 pieces of 120x60x30 aluminum profiles

- 2 pieces of Ø16 by 300mm long precision steel shafts

- 4 pieces of Ø16mm (Ø26 outer diameter) ball bearings/bushings

- 1piece of Ø16 by 357mm long trapezoidal lead screw

- 2 pieces of 6000zz ball bearings

- 1 piece of Ø16 by Ø24mm outer diameter and 24mm long trapezoidal nut

- 4 pieces of M5x40mm screw

Now will mount the ball bushings in all 4xØ26mm holes of the aluminum profile them will mount the trapezoidal nut in to the Ø24mm hole. Next mount the trapezoidal lead screw in to the trapezoidal nut and then mount the 2 pieces of 6000zz ball bearings in to the Ø26mm hole of the 120x60x30 aluminum profile. Insert the 2 shafts into the ball bushings and then mount the 2 pieces of aluminum profiles at each end of the shafts and trapezoidal screw.

The last operation is to mount the screws in to the shafts hole to fix the whole assembly.

Mechanical Assembly - X Axis

For this axis you will need:

- 2 pieces of 400x120x30 aluminum profiles

- 1 piece of 380x60x30 aluminum profile

- 2 pieces of Ø20 by 600mm long precision steel shafts

- 4 pieces of Ø20mm (Ø32 outer diameter) ball bearings/bushings

- 1piece of Ø16 by 657mm long trapezoidal lead screw

- 2 pieces of 6000zz ball bearings

- 1 piece of Ø16 by Ø32mm outer diameter and 32mm long trapezoidal nut

- 2 pieces of ball bushing supports (see drawing)

- 4 pieces of M5x40mm screws

- 2 pieces of M5x60mm screws (for the ball bushing supports)

For start mount the ball bushings in the 2xØ32 holes of the 380x60x30 aluminum profile and then the trapezoidal nut in the Ø32 hole from the middle of the aluminum profile.

Mount the 2 pieces of 6000zz ball bearings in the 2xØ26 holes of each 400x120x30 aluminum profiles and 2 pieces of Ø20mm ball bushings in to each ball bushing supports.

Now insert the shafts in the mounted ball bushings and the trapezoidal screw in the trapezoidal nut and then mount the 2 pieces of 400x120x30 aluminum profiles at each end of shafts and trapezoidal screw.

Fix the shafts on to the 400x120x30 aluminum profiles with the 4 pieces of M5x40mm screws.

Mechanical Assembly - Y Axis

For this axis you will need:

- 2 pieces of 400x120x30 aluminum profiles

- 1 piece of 120x120x30 aluminum profile

- 2 pieces of Ø16 by 390mm long precision steel shafts

- 4 pieces of Ø16mm (Ø26 outer diameter) ball bearings/bushings

- 1piece of Ø16 by 447mm long trapezoidal lead screw

- 2 pieces of 6000zz ball bearings

- 1 piece of Ø16 by Ø24mm outer diameter and 24mm long trapezoidal nut

- 4 pieces of M5x40mm screws

The first thing you`ll have to do is to mount all the Ø16mm ball bushings and the Ø16mm by Ø24mm trapezoidal nut in the 120x120x30 aluminum profile like in step 6 and then insert the shafts in the mounted ball bushings and the trapezoidal lead screw in the trapezoidal nut.

Mount the 2 pieces of the 6000zz ball bearings in the Ø26 hole of each 400x120x30 aluminum profiles.

Next mount the 400x120x30 aluminum profiles at each end of the shafts and fix them together with the 4 pieces of M5x40mm screws.

Mounting All the Axis Together

Now will have to mount all the axis together to complete the mechanical assembly.

First mount the Y axis on to the X axis by fixing together the 2 pieces of 400x120x30 aluminum profiles with the 380x60x30 aluminum profile and the 2 pieces of ball bushing supports.

Next fix together the Y axis with the Z axis by mounting the 120x120x30 aluminum profile of the Z axis over the 120x120x30 aluminum profile of the Y axis but at a angle of 90º.

Mounting the Motors

Now will have to mount the stepper motors on to the CNC machine, but first we need to make some motor supports.

I used a threaded rod and I cut it in smaller pieces to make the support for the motor. Over the pieces of threaded rod I have put some smaller tubes of aluminum that will act as spacers between the motor and the CNC frame.

Now mount at one end of the rod, a nut, and place the rod with the nut in to the 4 mounting holes of the motor.

Between the motor and the lead screw I have put a rubber hose and over it two hose clamps that will act as a coupler.

Now over the rod put the aluminum spacers and mount the motor on the frame with the rods in to the 4 holes in the frame.

Repeat this for all the 3 motors.

Mounting the Cable Suports

I have made the cable supports from U shaped aluminum profile and two steel corner braces.
For the X axis I cut the profile to the required length and mounted the two steel corner braces at each end of the profile.
After I mounted the steel corner brace onto the profile I mounted the cable support on the CNC machine with 4 screws ant 4 t-nuts.

Same goes for the Y axis only there I did not used steel corner braces, I just mounted the profile on the CNC with two screws and two T-nuts.

Motor Wire Conections

As I was saying at step 11, we will use a unipolar wire configuration, this means that will have 5 wires.
Now the 8 wires that the motor has are:
First coil - A is yellow/white and it is the start of coil, neg A is yellow and is the end of coil;
Second coil - neg C is red and is the start of coil, C is red/white and is the end of coil;
Third coil - B is green/white and is the start of coil, neg B is green and is the end of coil;
Fourth coil - neg D is black and is the start of coil, D is black/white and is the end of coil.

Now to make 5 wires from 8 wires will have to connect all the neg wires between them and make a single wire.

Now we have 5 wires that we can connect to the controller driver board.

The cable wires between the motors and the controller are 1.5mm thick so that they wont heat up.
When you connect two cables, solder them together because the connection is stronger and insulate them with shrinkable plastic tube.

Limit Switches

Home switch is for mechanically setting the machine's reference position when you power it up.

Also the limit switches are used to prevent you running the table either off the end of the ball screw or into the ball screw bearing housings.

As you can see i have mounted the Z axis limit switches right on to the aluminum part using two drilled holes and threading them.
The Z axis hast two limit switches, one for going up and one for going down. The two limit switches are connected in series and then connected to the controller thru a serial cable.

The Y limit switches needed some extra support so I had to make 2 supports from a piece of aluminum.
The X limit switches are mounted on the X axis cable suport.

CNC Software Configuration

Now in ordertoputintooperation and start cutting and drilling with this CNC machine we have to configure the CNC software (in my case Mach3)

First of all I will set the native units to mm, because I am using the metric coordinates.

Next will have to configure the motor outputs from the ports and pins menu. As you can see I have entered the corresponding pin number for every motor step and dir. This information comes with the controller driver board.

Now that we have the pins configured we have to configure the limit switches inputs and the input of the E-stop. This information also comes with the controller driver board.

After configuring all the pins we have to setup the motors. Access the Motor tuning menu under Config menu and fill the steps /mm box with how many steps must your motor to turn so that your gantry moves 1mm (mine dose 50 spets/mm because my lead screw has a pitch of 4mm and my stepper motors have 200 steps/ rev, so when the gantry moves 4mm the motor makes 200steps and for 1mm it makes 50steps).

Now will adjust the velocity of the gantry (I set it to 1000mm/min for now) and the acceleration to 50mm/sec/sec.

The last images shows how to configure your hot keys and how to configure your soft limits for each axis.

Testing the Mini CNC Machine

And finally the last step, testing the CNC machine.

In this test I used some V shape bits and a cylindrical bit. I am still waiting for some good bits to do some real cutting.

Enjoy.

Here i used a 5mm cylindrical bit.

And here a v shape bit

What`s Missing?

What do you think that is missing or what is not very clear at this project?
I wood like to make it better.
If you have some ideas or suggestions please free to tell.