3 axis cnc milling machine

by:Gewinn     2020-06-06
For many projects, CNC milling machines are required to achieve good and fast results.
After doing some research on the currently available machines, I came to the conclusion that in the price range before 2000, all the machines were not able to meet my needs for working space and precision. I want:-
Working Space: 900x400x120mm
Relatively silent spindle with high power at low rotation rate-
As much stiffness as possible (
For milling aluminum parts)-
As accurate as possible-USB interface-
To meet this requirement, I spent less than 2000 euros and started the 3D build as an iterative process, checking many of the parts available.
Main focus: parts must be assembled together.
Finally, I decided at 30-
Type B nut 8 aluminum frame with 16mm ball-circulation-
Spindle, 15mm ball-
Circular guide bearings and 3Amp.
The NEMA23 stepping motor is easy to install into the installation system ready to purchase.
Special manufactured parts are not required, this part is perfectly combined.
A good plan is everything. .
Order parts arrive a week later.
After a few minutes, Xaxis was ready. -
Easier than I thought!
15mm HRC linear bearings are of very good quality and you already feel they will do very well after installation.
The first question after 2 hours is: the spindle does not want to enter the rolling bearing.
My fridge is as small as 1060mm ingots, which is why I decided to buy dry ice, which means to suspend the item for a week.
Friends with dry ice packaging came, and after a few minutes of freezing, the spindle was perfectly mounted on the roller bearing.
There are also some screws that look a bit like a CNC machine already. The mechanical parts are now finished and I came to the electrical parts.
Since I am very familiar with Arduino and would like full control via USB, I initially selected an Arduino Uno with GRBL shield and TB8825 step drive.
This setting is very simple to run, after viewing the settings, the machine is controllable on the PC. Great!
But when TB8825 runs on max 1,9 Amp and 36 v (
Very hot)
, It\'s enough to run the machine, but I realize that too low power can cause loss of step.
When I think about the long milling process at this temperature, it doesn\'t feel very good either. .
I bought a cheap TB6560 from China (
$5 per piece, 3 weeks delivery)
And connect them to the GRBL shield.
The voltage rating is not very accurate for this board, you can go from 12-
This board is 32 V.
Since I already have a 36 v power supply, I just try to use it.
Results: Two Step drivers are working fine, one cannot withstand a higher voltage and one can only turn in one direction (
Cannot change direction)
So look for a good driver again. .
TB6600 is my final solution.
It is completely covered by the aluminum cooling unit and is easy to install.
Now run my stepping motor on the x and y axis with 2.
2 amps and Z axis with 2. 7 amps.
I can reach 3 amps, but since I have a closed box to protect the circuit from aluminum dust, I decided to run on 2 amps.
What is enough for my needs and hardly generates heat.
Also, when I give them too much power, I don\'t want the Pacers to destroy the machine in any wrong case.
I have been thinking about a solution for a long time to protect the power supply of the stepping motor and inverter from small aluminum parts.
In many solutions, the converter is installed very high or has enough distance from the milling machine.
The main problem is that this device generates a lot of heat and requires active cooling.
My final solution is my girlfriend\'s tights.
It is very simple to cut them into 30 cm pieces and use them as protective hoses and provide good airflow.
Choosing the right spindle requires a lot of research.
At first I wanted to go with a standard Kress1050 spindle, but since it has only 1050 W at 21000 rpm, I can\'t expect too much power at a lower rate.
For my requirement for dry grinding aluminum and some steel parts I need 6000-12000rpm.
That\'s why I finally chose 3kw VFD from China.
335 euro converter.
The quality of the spindle is very good.
It is very powerful and easy to install.
I underestimated the weight of 9 kg but luckily my frame was very strong and there was no problem with the heavy spindle. (
High weight is the reason to drive the Z axis on 2. 7 amps)It is done.
The machine works very well and I have no problem with the step drive but overall I am very happy with the results.
It cost me about 1500 euros and there is a machine that fully meets my needs.
In POM, the first milling item is negative. -
The machine is doing very well!
I have seen the torque on Y-in POM
The bearing is a bit high and the machine is bent under a high force around the y axis.
So I decided to buy a second y-
Track and upgrade the gantry accordingly.
After that, there is little movement now due to the force on the spindle.
Great upgrade worth 120 euro of course.
Now I\'m ready for aluminum.
Using AlMg4, 5Mn, I have achieved very good results without any cooling.
Building your own CNC machine tool is really not a rocket-science.
I have poor working conditions and equipment, but with good planing, I only need very few bits, screwdrivers, fixtures and ordinary rigs.
1 month CAD construction and procurement plan, 4 months to complete the construction of the machine.
It would be much faster to build the second one now, but without any pre-
Knowledge in this field, I have to learn a lot about machinery and electronics during that time.
Here you can find all the main parts.
I recommend that AlMg4, 5Mn alloys be used for all aluminum plates.
I bought all the electrical parts on ebay. Arduino+GRBL-
Shield: step drive: € 12/pc.
Power supply: 40 euro stepping motor :~ 20 euro/pcMilling spindle inverter: 35 euro mechanical: Linear bearing: guide rail: Bracket: coupling: China coupling for 2,5 euro/pc
Frame: bottom profile: For Rails: for X-
Shaft step/spindle mounted on line X
Bearing: 100mm/mounting plate: 5mm aluminum plate 600x200. Y-
Profile: 2x plate: 5mm 250x160 aluminum plate-
Slide plate for spindle installation: use CAD, CAM and G-last 5mm 200x160 aluminum platform
The sender of the code was very disappointed.
After a long search, I found a good software solution
Friendly, powerful software and very affordable (50€).
It completely covers the Arduino and controls the stepping motor on its own.
There are many good documentation features.
The trial version provides a complete software feature with only some waiting time.
For example, find the edge.
Simply connect the wire to the Arduino A5 pin and connect the wire to the workpiece (
If not metal, then temporarily Cover with aluminum foil).
With machine control, you can now drive the ground milling tool to the workpiece.
Once the circuit is off, the machine stops and sets the axis to zero. -Very useful! (
There is usually no need to isolate the ground because the spindle should be grounded)
So far, both the y-axis and the z-axis have temporary plastic brackets to transfer the force of the spindle nut and move the milling spindle accordingly.
The plastic holder is made of solid plastic but I don\'t believe it. .
Imagine that the Z axis bracket will brake and the milling spindle will drop (
Apparently during the milling process).
That\'s why I am milling this bracket with aluminum alloy now (AlMgSi).
The result is attached with a picture.
This is now much stronger than the plastic version I made before without a milling machine.
Now practice a little bit, the machine has produced very good results (
For hobby purposes)
This photo shows the nozzle of AlMg4, 5Mn.
I had to grind it from both sides.
There is no further polishing or sandpaper on the last piece.
I used a VHM tool for 6mm.
I found 4-
The 6mm tool has achieved very good results on this machine.
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