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Alexandre
18-08-2016, 05:17 PM
Hello id like to show my new project. A bigger and stronger CNC machine for my workspace.
Main objective of this project is that this machine can cut aluminum in a regular basis.

Cut area will be X800- Y400- Z100

For this i will use:

Linear guides THK GSR20 for x and y
20mm diameter Chinese ball screw with supports
Z axis will be recycled from a dismantled machine ( perfect for this machine)
Chassis 40X40 aluminum profile
Aluminum 5083 for parts that need to be machined (16\20mm thickness)
Nema 23 3NM 4.2A for all axis ( to convert to closed loop servos later)
drivers Leadshine 2M542
48V power supply
Mach3 software
Spindle motor Perske 0.7 Kw and 400V 1kw Omron VDF


Here it is how it looks so far.

19046
19047
19048
19049

Any reviews or suggestions will be much appreciated.
Thanks
Alex

Clive S
18-08-2016, 06:54 PM
Alex
You are going to need a much stronger base than 40x40 also it needs triangulation if you want to cut ali also the Z would benefit from linear rails as well. Most of the parts would be better out of 20mm ali and if possible try and go up to a 68V non linear power supply (just check that the drives can handle that)

Alexandre
18-08-2016, 07:09 PM
Hello Clive

Yes i need a reinforced base but i only had 40X40 bars( recycled from other machinery). For this reason i use "6 legs" to support the weight of machine. But it is possible that i will place some triangles to reinforce all structure.
Z also have linear rails from THK and ballscrew from NSK, it is a complete "head" dismantled from another machine.
Sure most of the parts are 20mm but there are a few like motor supports and spacers that was not necessary.
What is the difference of non linear power supply and others?

Thanks

routercnc
18-08-2016, 09:59 PM
Here is a technical explanation of linear power supply vs switch mode:
https://www.circuitspecialists.com/blog/power-supplies-switch-mode-vs-linear/

A linear power supply is often preferred for CNC machines. My understanding is that SMPS can generate more electrical noise (as it is switching currents on and off rapidly), and you don't want stray signals interfering with the drive signals.

Also, as I found out, the linear power supply is relatively straightforward to build, although you need to work out a few things first such as the size of the transformer. But there was lots of help on this site for the specification of the components (have a search for linear power supply build) - obviously you need to be sure of yourself when working with dangerous mains voltages.

Clive S
18-08-2016, 11:40 PM
Alex I see its been answered but one of the advantages is the non linear P.S. is that they handle back EMF much better and you can generally use a small amperage one as the caps store the energy. You only need the transformer, rectifier and caps to build one as long as you are happy with handling the mains voltage of about 230V.

Boyan Silyavski
19-08-2016, 01:14 AM
Hi Alex,

here are my thoughts:

-For metal milling i would reinforce the whole gantry with a backing plate. for example aluminum 20 or 25mm thick. I suggest to copy aluminum gantry design from the build logs here in forum. Many people here have nice aluminum gantry machines. Just read the logs.

-Square rails 20 size is perfect. 20 size ball screw is too much. 1610 for all axis and 1605 for Z is what most people on this forum use. Fast enough for wood, good resolution enough for aluminum.

-Convert to closed loop later? Not a good idea. Use 500-600w 70VDC power supply, drives Leadshine Am822 with the 3nm motors you have chosen or straight go to 400W servo / 200 would work 1:1.5 or bigger but as there is no price difference../ . its difficult to find a belt size that will fit both motors, pulleys will be different bore, same as motor holes, which would change belt size... / By the way- ball screws driven via short belts /~250-350mm/ is best. 15mm HTD 5 belt, 20t puleys for 1:1

-0.8kw spindle could cut aluminum with 6mm cutter ok at 3mm depth, even at 6mm sometimes. But 2.2kw spindle will be better here. I use for this purpose 3kw, but 2.2 pricewise is best. Anyways 6mm is the most used cutter as not to waste material. For small stuff 3mm. Toshiba VFD drives are better and best priced in ebay from Italy.

-Z100? Not good. At least 150mm i would say. Fixtures, boards, they would eat from the height. Design the machine so that you have 200mm clearance from gantry and Z to table for that 150mm travel. I would sell the Z if 10mm travel and make one from scratch, which will suit 100% what i am doing. As Z is important. Best design is rails and plate to move, not bearing blocks.

-15mm plates from aluminum could bend if long enough. I would use at least 20mm or 25mm. or reinforced with steel. Steel is ~ 3 times stronger, 3 times cheaper and 3 times heavier than aluminum.

-Unsupported aluminum table bed is NOT strong. +Its very expensive. best value is to make a steel table from UPN 100 profile in your particular case. Best is to weld them. Cross table, one next the other... Then drill holes and tap them. It would make your machine very rigid. which is desirable.


In short read some build logs, all the info is there.

Boyan Silyavski
19-08-2016, 01:35 AM
By the way have you seen that? Unfinished Project - Fixed Gantry M/C - 500x400x100mm Approx - Cost over 3K in parts (http://www.mycncuk.com/threads/10089-Unfinished-Project-Fixed-Gantry-M-C-500x400x100mm-Approx-Cost-over-%C2%A33K-in-parts)

I live in Spain and there are constantly transports going from here and back to UK. Must be same with Portugal. Cause more or less that's the machine for doing aluminum. I would change the Z rails to square supported, but that's not expensive as they are very short. And having in mind that the machine is working already, you could do that as first job.

A_Camera
19-08-2016, 09:32 AM
In my opinion it is far too large and weak for cutting aluminum on regular basis.

My machine is build of 45x90 but even that is not enough if I'd want some efficiency. Yes, slowly it can do it, but not with speed. I would not even think about building it with 40x40, not even half that size. Also, my machine is fixed gantry type, so the table moves in Y direction and the Z moves on the X beam, which is making it more rigid than a moving gantry type, like the one you plan for. The cutting area I have is 450x250, so even that is much smaller than yours. On the other hand, 100mm Z clearance is maybe a minimum, so that in my opinion should be increased. My version one had only 70mm, like most small machines, but I realized it was not enough so when I started with my upgrade I decided to approximately double that. I now have 130mm Z clearance, which I think is the minimum for any kind of serious metal works. Remember that you will need a very good wise as well, and those steal quite a bit from your Z clearance.

Even the spindle motor is too weak. The least you could do is to double that, but if I had some serious plans on working with metal I'd chose a low speed high torque spindle, not the cheap Chinese ones which run at 24k RPM. But OK, I don't know that motor, so perhaps that is exactly the right type for the work, though I think 0.7kW is not going to work.

I think you should revise your plans. Sorry.

A_Camera
19-08-2016, 09:39 AM
By the way have you seen that? Unfinished Project - Fixed Gantry M/C - 500x400x100mm Approx - Cost over 3K in parts (http://www.mycncuk.com/threads/10089-Unfinished-Project-Fixed-Gantry-M-C-500x400x100mm-Approx-Cost-over-%C2%A33K-in-parts)



I live in Spain and there are constantly transports going from here and back to UK. Must be same with Portugal. Cause more or less that's the machine for doing aluminum. I would change the Z rails to square supported, but that's not expensive as they are very short. And having in mind that the machine is working already, you could do that as first job. Yes, that is definitely a nice machine, even if it is difficult to transport. Anyway, I think he needs something very similar to that, but it does not have the work area he had in mind. It is very similar to what I have designed and built for myself, and the fixed gantry really increases the rigidity as well as it decreases the complexity and to square it is also much easier than a moving gantry type with slaved motors on one axis.