First CNC build plan.

[3rdHalf]

Hi everyone!
I am new here.


Here is my story: I am tinkering hobbyist with a small garage shop.
Recently, I have had a few future project ideas, that would require a CNC(for woodworking and aluminum). For past few months, I have spent like a hundred hours researching youtube and forums about CNCs and machining in general. Currently I am at a point, where I need some direct expert viewpoint about making my first CNC.


My budget is ~1000€. At first, I considered buying some cheap-o CNC kit, that I would be able to upgrade in future, but I decided against it, because I want this CNC project to be a learning experience.


So, let's start with the plan. Although I am rather experienced with 3DS Max - vector based CAD programs like Fusion360 are new to me. So, I am starting this project by learning Fusion360, and making this CNC plan.
Here Is my Fusion360 of this 'work in progress' plan, that I will reference throughout this thread: http://a360.co/2jcqaBI

Like I mentioned before - I have a small garage shop. I don't have a lot of tools in my disposal. So, my priority is to make and workflow the design to be as simple as possible. Also, I am planing that this project will take me a year, to salvage necessary parts, tools and skills, to finish it, so this thread isn't very urgent.

Here is my current plan of action:
#1 The base of CNC will be made from rectangular steel tubes(Recently, I applied to welding courses, to finally learn welding)
Why steel, not aluminum extrusions? Because here, where I live, aluminum extrusions are hard to get and relay expensive(Cheapest 4080 extrusions and assembly hardware for this project would cost me like 400€), but steel would cost me less 75€.
#1.1 I will start by making Y gantry from 100X150X4mm square tubing, in which I will cut necessary holes.
After making those holes - I will send it out to local metal shop, to machine it flat, because I am sure, that the tube will warp quite a bit, after cutting holes in it. After that - I will weld the legs of gantry to it.
#1.2 The base of the machine I will veld from 50X50X4mm and 100X50X4mm steel tubing.
To make X axis as flat as possible(in my powers) - I plan to use granite counter-top as a guide(granite surface plate is not an option in my country, with my budget).
#1.3 The gantry won't be welded to base, but attached with 4 bolts, so it is possible to square and tram the Y axis in future.

#2 Aluminum hardware.
For most of structural parts I plan to use 10mm thick aluminum. Because I don't have necessary tools to precisely make most of these parts - I plan to order 2D CNC cutting of these parts. I think I will be able to fit everything on 550X750mm sheet.
#2.1 To assemble everything - I will need to drill and tap a few holes in sides of previously mentioned 2D machined parts and that I will be able to do by myself on a drill-press.

#3 Rails.
For guide rails - I will risk getting cheapo AliExpress HGR15 linear rails. 600mm X-axis, 600mm Y-axis and 300mm Z-axis. This would make my CNC's working are approximately 400X470X170mm. Although, this is not cut in stone, because my plans may change, if I get a good deal on other lengths. Actually, I am considering using SBR16 rails for X-axis, because X-axis should have the least amount of load and for the price of 600mm HGR rails I could get 1000mm SBR rails.

#4 Linear motion hardware. For moving X and Y axis I plan to use 1204 ball-screws. For Z-axis I haven't decided between ball-screw and lead screw. I think lead screw is better choice for Z-axis, because it is possible to get them with smaller pitch(like 1mm), making it less likely for Z-axis creep under the weight of spindle.
#4.1 As for ball-screw bearings - I still haven't decided between ready made ball-screw support blocks and custom made ones, that I could machine with previously mentioned(#2) CNC machining operation. In the end - it all will come down to price and convenience.
#4.2 Another field about what I am not totally sure is connection between ball-screws and steppers.
#4.2.1 I would like to attach X-axis ball-screw straight to stepper(with flexible coupling, of course).
#4.2.2 For Y-axis I haven't decided between attaching ball-screw straight to stepper and using timing belt, because I am not sure yet, what could be most convenient way to mount motor to the gantry.
#4.2.3 Z-axis I will most definitely mount with timing belt. The reason why is, because I think that mounting motor straight on top of ball screw would place the motor very high, that would make it top heavy, therefore making it prone to unwanted vibrations. So, by mounting stepper using timing belt - it would somewhat equally balance weight between spindle and stepper motor.

#5 For motors I plan to buy one of 'those' cheapo 3 axis Nema23(57BYGH115-003B) kits. Although, as I understand, controller boards of these things aren't the most reliable things, so I will need to upgrade it as soon as I can.

#6 For spindle I will probably go with 2.2kw water cooled one, if it will fit within my budget. If not - 800w air cooled one will do(for some time).

#7 After assembling everything - I will square and tram everything by moving and shimming the gantry(that is mounted to the base with 4 bolts). For attitudinal corrections - I think I will be able to shim spindle mount to z-axis.

Soooo... - his is my plan, so far. I would like to hear criticism/suggestions/corrections about this plan. Is there anything I am missing?
Like I mentioned multiple times before *rolls eyes* - I am rather inexperienced in machining and similar stuff, so some additional educational resources won't come to the detriment.

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[awerby]

Hi everyone!
I am new here. [COLOR=#000000][FONT=arial]

.

Here is my current plan of action:
#1 The base of CNC will be made from rectangular steel tubes(Recently, I applied to welding courses, to finally learn welding)
Why steel, not aluminum extrusions? Because here, where I live, aluminum extrusions are hard to get and relay expensive(Cheapest 4080 extrusions and assembly hardware for this project would cost me like 400€), but steel would cost me less 75€.
#1.1 I will start by making Y gantry from 100X150X4mm square tubing, in which I will cut necessary holes.
After making those holes - I will send it out to local metal shop, to machine it flat, because I am sure, that the tube will warp quite a bit, after cutting holes in it. After that - I will weld the legs of gantry to it.

[The tube shouldn't warp too much if you drill the holes. If you cut them with a torch, it will warp a lot. Machining won't help, because the tubes are too thin; if you machine off too much of them, they will lose their strength. Try clamping things down to your granite while you're welding them flat, and skip around, avoiding getting too much heat in any one place at a time.]

#1.2 The base of the machine I will veld from 50X50X4mm and 100X50X4mm steel tubing.
To make X axis as flat as possible(in my powers) - I plan to use granite counter-top as a guide(granite surface plate is not an option in my country, with my budget).
#1.3 The gantry won't be welded to base, but attached with 4 bolts, so it is possible to square and tram the Y axis in future.


[If you can't make things perfectly flat, make them adjustable, so you can use shims to achieve square and tram.]

#2 Aluminum hardware.
For most of structural parts I plan to use 10mm thick aluminum. Because I don't have necessary tools to precisely make most of these parts - I plan to order 2D CNC cutting of these parts. I think I will be able to fit everything on 550X750mm sheet.
#2.1 To assemble everything - I will need to drill and tap a few holes in sides of previously mentioned 2D machined parts and that I will be able to do by myself on a drill-press.

[It's not clear which parts you're talking about here, but you only need to use aluminum for moving parts where weight is an issue. Otherwise steel will be stronger and cheaper. The only parts on the design pictured above that move are the table and the piece that holds the Z axis. If you've got a machine shop to work with, use them to put T-slots in the table base that fit whatever inexpensive clamping kits are available in your country. You can also use the aluminum to make mounting plates for your motors.]

#3 Rails.
For guide rails - I will risk getting cheapo AliExpress HGR15 linear rails. 600mm X-axis, 600mm Y-axis and 300mm Z-axis. This would make my CNC's working are approximately 400X470X170mm. Although, this is not cut in stone, because my plans may change, if I get a good deal on other lengths. Actually, I am considering using SBR16 rails for X-axis, because X-axis should have the least amount of load and for the price of 600mm HGR rails I could get 1000mm SBR rails.

[The HGR rails will work a lot better. If you want to cut aluminum reliably, use them throughout, not the round rails.]

#4 Linear motion hardware. For moving X and Y axis I plan to use 1204 ball-screws. For Z-axis I haven't decided between ball-screw and lead screw. I think lead screw is better choice for Z-axis, because it is possible to get them with smaller pitch(like 1mm), making it less likely for Z-axis creep under the weight of spindle.

[Get the C7 grade ball screws, which are more accurate than the lower grades of rolled ball screws. The Z axis has the most weight to lift, so the use of a finer-pitched screw will give you better mechanical advantage as well as back-driving less.]

#4.1 As for ball-screw bearings - I still haven't decided between ready made ball-screw support blocks and custom made ones, that I could machine with previously mentioned(#2) CNC machining operation. In the end - it all will come down to price and convenience.

[Most people advise getting dual angular-contact bearings to fix one end of the screw firmly in place, but letting the other end be lightly constrained, so it can expand and contract without warping.]

#4.2 Another field about what I am not totally sure is connection between ball-screws and steppers.
#4.2.1 I would like to attach X-axis ball-screw straight to stepper(with flexible coupling, of course).

[That should work okay; I'd say use an oldham-style coupler with a zero-backlash spider. The inexpensive aluminum helical couplers fail quickly in CNC applications.]

#4.2.2 For Y-axis I haven't decided between attaching ball-screw straight to stepper and using timing belt, because I am not sure yet, what could be most convenient way to mount motor to the gantry.
#4.2.3 Z-axis I will most definitely mount with timing belt. The reason why is, because I think that mounting motor straight on top of ball screw would place the motor very high, that would make it top heavy, therefore making it prone to unwanted vibrations. So, by mounting stepper using timing belt - it would somewhat equally balance weight between spindle and stepper motor.

[I'm not sure that's such a big issue; the added weight of the pulleys and the mechanism that holds them would tend to cancel out whatever benefit lowering the motor would confer.]

#5 For motors I plan to buy one of 'those' cheapo 3 axis Nema23(57BYGH115-003B) kits. Although, as I understand, controller boards of these things aren't the most reliable things, so I will need to upgrade it as soon as I can.

[Avoid buying the drivers and motors until you've built the rest of this thing. Those cheapo kits usually feature underpowered drives and motors with a lot of inductance that require a lot more power than the drives can handle. People who buy them often end up buying something else when their machines don't work right. In the meantime, you can read about motors and drives to make a more informed decision.]

#6 For spindle I will probably go with 2.2kw water cooled one, if it will fit within my budget. If not - 800w air cooled one will do(for some time).

[More power is better. Air-cooled spindles are generally preferred. Watch out for improper grounding on those Chinese spindles, though.]


#7 After assembling everything - I will square and tram everything by moving and shimming the gantry(that is mounted to the base with 4 bolts). For attitudinal corrections - I think I will be able to shim spindle mount to z-axis.

Soooo... - his is my plan, so far. I would like to hear criticism/suggestions/corrections about this plan. Is there anything I am missing?
Like I mentioned multiple times before *rolls eyes* - I am rather inexperienced in machining and similar stuff, so some additional educational resources won't come to the detriment.

[It sounds like a pretty good plan as far as the basic structure goes, but perhaps over-optimistic on the budget. Keep reading build threads on this site; many of the issues you raise have been debated extensively here.]

[1Jumper10]

Only one thing I see that you may want to think about that Awerby didnt cover -

1 - Why cut the holes in your gantry? It only weakens it and harms rigidity. Is it necessary?
Wait, I see. Your driving your Z axis with a ballscrew and you need the nut to run inside the gantry beam. OK then, just nevermind what I posted

Good luck with your build. Keep us updated.

[3rdHalf]

#1.1 I will start by making Y gantry from 100X150X4mm square tubing, in which I will cut necessary holes.
After making those holes - I will send it out to local metal shop, to machine it flat, because I am sure, that the tube will warp quite a bit, after cutting holes in it. After that - I will weld the legs of gantry to it.

[The tube shouldn't warp too much if you drill the holes. If you cut them with a torch, it will warp a lot. Machining won't help, because the tubes are too thin; if you machine off too much of them, they will lose their strength. Try clamping things down to your granite while you're welding them flat, and skip around, avoiding getting too much heat in any one place at a time.]

I plan to make the holes by drilling and some love of angle grinder, or circular saw, if I get a carbide blade for it.
And I wonder - would it make any difference if instead using 100X150X4mm tubing - I would use 100X150X6mm

#2 Aluminum hardware.
For most of structural parts I plan to use 10mm thick aluminum. Because I don't have necessary tools to precisely make most of these parts - I plan to order 2D CNC cutting of these parts. I think I will be able to fit everything on 550X750mm sheet.
#2.1 To assemble everything - I will need to drill and tap a few holes in sides of previously mentioned 2D machined parts and that I will be able to do by myself on a drill-press.

[It's not clear which parts you're talking about here, but you only need to use aluminum for moving parts where weight is an issue. Otherwise steel will be stronger and cheaper. The only parts on the design pictured above that move are the table and the piece that holds the Z axis. If you've got a machine shop to work with, use them to put T-slots in the table base that fit whatever inexpensive clamping kits are available in your country. You can also use the aluminum to make mounting plates for your motors.]

Here are all parts I was planing to CNC cut from 10mm aluminum: http://www.cnczone.com/forums/attach...8&d=1485767344
Although, I could make some of them from steel, by myself.
Basically, I know that I will need to CNC cut the table(X-axis), the and most of Y-axis and Z-axis parts, because I want the holes for mounting bearing blocks to be as straight and square as possible(I doubt that I would be able to do it myself)

As for making T-slots - My idea was to order CNC cutting of the table(420X520mm) from previously mentioned 10mm aluminum too, to make sure, that holes for mounting HGR blocks, are drilled precisely. After assembling the whole machine - I planed to drill and tap holes into the table, for mounting hardware, with CNC itself.

#4.2.3 Z-axis I will most definitely mount with timing belt. The reason why is, because I think that mounting motor straight on top of ball screw would place the motor very high, that would make it top heavy, therefore making it prone to unwanted vibrations. So, by mounting stepper using timing belt - it would somewhat equally balance weight between spindle and stepper motor.

[I'm not sure that's such a big issue; the added weight of the pulleys and the mechanism that holds them would tend to cancel out whatever benefit lowering the motor would confer.]

Here is approximate illustration of why I didn't want to mount Z-axis stepper directly to ball-screw: http://www.cnczone.com/forums/attach...0&d=1485767344
My hypothesis was, that mounting 1.5gk motor so high would make the structure of Y-axis too tall and slim. I thought, that such tall and top heavy structure would have a huge possibility of resonating with vibrations of milling. Also, by mounting motor on top - the whole weight Y and Z axis would be on the front(right side in the drawing) of the Y-axis rail.
But I may be overreacting.

#5 For motors I plan to buy one of 'those' cheapo 3 axis Nema23(57BYGH115-003B) kits. Although, as I understand, controller boards of these things aren't the most reliable things, so I will need to upgrade it as soon as I can.


[Avoid buying the drivers and motors until you've built the rest of this thing. Those cheapo kits usually feature underpowered drives and motors with a lot of inductance that require a lot more power than the drives can handle. People who buy them often end up buying something else when their machines don't work right. In the meantime, you can read about motors and drives to make a more informed decision.]

I will certainly do more research about motors, bur currently I look at this kit: https://www.aliexpress.com/item/EU-f...662299205.html
Mostly because I wouldn't have to deal with import taxes, by importing from Germany

[pippin88]

Don't put the ball screw within the tube. It reduces rigidity and adds work for no real benefit.

[3rdHalf]

Don't put the ball screw within the tube. It reduces rigidity and adds work for no real benefit.

Could you elaborate?
I thought, that making ball screw inside gantry would increase the rigidity. If I would place the ball-screw in front of gantry - I would have to move the whole Y-axis head at least 2cm(best case scenario) to the front, that would make the structure more front heavy(i.e. less stable).

[ger21]

Cutting a slot in the beam for the ballscrew will weaken it more than moving the Z axis 2cm away.

[3rdHalf]

Cutting a slot in the beam for the ballscrew will weaken it more than moving the Z axis 2cm away.

Thanks for input. I will rethink the design.

[3rdHalf]

Question about VFD's:
So, I was thinking about buying one of Chinezium 2.2kw spindle/vfd kits, but after thinking about voltages involved - I really cautious about it. So, I was thinking - maybe go a bit safe and buy something with some kind of reputation.
After searching a bit - I found Hitachi WJ200-022HF, could be an option, but it costs three times as much as stuff from AliExpress and E-bay.
So, I have a question - Is it worth it, looking, that I want to make my machine on budget? Maybe there are other brands, that are worth considering...

[nlancaster]

I bought one of the Chinese 2.2KW spindles sets of ebay. About $300, still going strong 2 years later.