CNC router build to machine wood and aluminium (1mX1mX0.4m)

Hi folks,

I am a newbie in CNC stuff. I have started desginign a CNC router out of my need. I am a hobbyist and I own a small lathe, A drill press, Spot welder, sheet rolling machine, dremel etc. Its a small hobby workshop that I have built out of passion. I use to mill small stuff occasionally on my lathe using a milling attachment. But this is painful and also very limited to what I can mill on it. So finally decided to go CNC router route.

Commercially available router are very costly for my requirement. for the last 1 week I read about CNC router on this forum and have come up with a design. I appreciate everyones input here to direct me and help me avoid any pitfall.

Objective: Mostly light aluminium work and some wood carving for RC aeroplane work.

I first studied some CNC routers and came up with my design. This is like 3rd iteration and I expect it to change here and there. As I will be milling aluminium, I tried making it rigid by having dual linear shaft rod on both side of X axis with four mounting support to avoid any twist/moment.
Most of the parts are aluminium/aluminum either flat rectangle or extrusion. I have depicted the proposed dimensions on the rough sketch (Little old school).

Estimated rough weight of the load on each axis: (I calculated it based on metal and part weights)

Gantry: 32Kg (All vertical load like. Y+Z+vertical support plate)
X axis: 18Kg (bed+lead screw)
Y axis: 16Kg (load of Z axis component and its own weight)
Z axis: 6Kg (including router)

Below is my spec. I have tried to get what I can get in my country and within my budget. My req. is hobby purpose so it won't be running 5 hours a day.

3 Nema 23 = (26kg-cm)(368 oz-in) holding torque
3 DM542 driver
1 Power supply 40V, 7.4Amp
Mach 3 breakout board
Router makita 700W (1HP, I know this is low for aluminium but I could not find any other powerful router here, spindle with VFD are very costly like 4 times)
Ball screw= Two option available 20X5 or 16X16(this is relatively cheap) I was looking for 16by5 but its not available here.
Guide linear shaft =16mm on X and Y and 12 mm for Z axis

Router dimension:
X end-to-end =1meter
Y end-to-end =1meter
Z end-to-end = 0.4meter

I will work on CAD after I finalize the drawing to get all the parts right and fit well. I have no access to big mill and due to Covid shops are shut mostly. So I will do it all by hand with whatever I have. Could you please help me if I am going right.

I have not purchased anything yet. I am sizing all parts and cost for it. This whole setup translate to 1200 USD so far. It could have been cheaper but china is not shipping to India. So I am buying locally which is little costlier but quality is certain.

Open to hear from you guys.

Quote:

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Originally Posted by Tony_Stark

Hi folks,

I am a newbie in CNC stuff. I have started desginign a CNC router out of my need. I am a hobbyist and I own a small lathe, A drill press, Spot welder, sheet rolling machine, dremel etc. Its a small hobby workshop that I have built out of passion. I use to mill small stuff occasionally on my lathe using a milling attachment. But this is painful and also very limited to what I can mill on it. So finally decided to go CNC router route.

Commercially available router are very costly for my requirement. for the last 1 week I read about CNC router on this forum and have come up with a design. I appreciate everyones input here to direct me and help me avoid any pitfall.

Objective: Mostly light aluminium work and some wood carving for RC aeroplane work.

I first studied some CNC routers and came up with my design. This is like 3rd iteration and I expect it to change here and there. As I will be milling aluminium, I tried making it rigid by having dual linear shaft rod on both side of X axis with four mounting support to avoid any twist/moment.
Most of the parts are aluminium/aluminum either flat rectangle or extrusion. I have depicted the proposed dimensions on the rough sketch (Little old school).

Estimated rough weight of the load on each axis: (I calculated it based on metal and part weights)

Gantry: 32Kg (All vertical load like. Y+Z+vertical support plate)
X axis: 18Kg (bed+lead screw)
Y axis: 16Kg (load of Z axis component and its own weight)
Z axis: 6Kg (including router)

Below is my spec. I have tried to get what I can get in my country and within my budget. My req. is hobby purpose so it won't be running 5 hours a day.

3 Nema 23 = (26kg-cm)(368 oz-in) holding torque
3 DM542 driver
1 Power supply 40V, 7.4Amp
Mach 3 breakout board
Router makita 700W (1HP, I know this is low for aluminium but I could not find any other powerful router here, spindle with VFD are very costly like 4 times)
Ball screw= Two option available 20X5 or 16X16(this is relatively cheap) I was looking for 16by5 but its not available here.
Guide linear shaft =16mm on X and Y and 12 mm for Z axis

Router dimension:
X end-to-end =1meter
Y end-to-end =1meter
Z end-to-end = 0.4meter

I will work on CAD after I finalize the drawing to get all the parts right and fit well. I have no access to big mill and due to Covid shops are shut mostly. So I will do it all by hand with whatever I have. Could you please help me if I am going right.

I have not purchased anything yet. I am sizing all parts and cost for it. This whole setup translate to 1200 USD so far. It could have been cheaper but china is not shipping to India. So I am buying locally which is little costlier but quality is certain.

Open to hear from you guys.

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You are past the magic number, you will need ( 2 ) Ballscrews for the Y or X axis what ever you are calling it ( 1 ) each side or you will get racking and jamming of that axis 20 x 10 Ballscrew is best for the X and Y axis 16x5 for the Z is ok

Hi Mactec54,

Two ball-screw will make things costlier. As this means one extra ball screw & one more motor as slave.

I need to redesign this I guess. I am thinking, what if I replace the 2 linear guide shaft rod on each side of X axis with single 20mm linear guide rail slide arrangement each side. Will that help having single ball-screw arrangement as shown above? Or this issue might still persist as the Y axis is long?

Quote:

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Originally Posted by Tony_Stark

Hi Mactec54,

Two ball-screw will make things costlier. As this means one extra ball screw & one more motor as slave.

I need to redesign this I guess. I am thinking, what if I replace the 2 linear guide shaft rod on each side of X axis with single 20mm linear guide rail slide arrangement each side. Will that help having single ball-screw arrangement as shown above? Or this issue might still persist as the Y axis is long?

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1 meter is to long for a single central Ballscrew, around 1/2 a meter is all you can get away with in both directions X and Y, it would not matter if you changed the linear rails the same problem happens , the Gantry has to be extremely well designed / built as well so that no flex can happen

Fixed Gantry with a moving table you can use ( 1 ) central Ballscrew but this design is not for everyone

I strongly suggest that before going too far with a 0.4 metre Z axis that you should draw an accurate diagram of the spindle and collet.Then draw a line from the tip of the tool to the corner of the spindle body,it will allow you to see how you may be limited in terms of places you can get the machine into.If it doesn't look too bad you can progress to adding the spindle backplate and repeating the exercise with the tool tip and the corners of the backplate.You may find that the desire for a big Z axis movement will create a machine that only has limited possibilities for using all the travel.

I totally agree. Having such a long Z axis is not desirable. I will not be able to use all the travel. I have reduced it to 0.2meter.

I switched to 2 ball screw design as you suggested.

Hi,

I have started the designing process. I am using single rail on each side of X axis with 20mm ball screw. What could be the best arrangement here. Does this look ok?

Quote:

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Originally Posted by Tony_Stark

Hi,

I have started the designing process. I am using single rail on each side of X axis with 20mm ball screw. What could be the best arrangement here. Does this look ok?

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Looks fine some more details to do for the Ballscrew mounting but the general idea is fine the Ballscrew can be below the rail also, so what ever works best for the rest of your design

I have now made my mind on 2 stepper motor for X axis as suggested. Also while I am designing the router in CAD, I have started hunting for the parts. electronics first as rails/guides/ball screws length might change here and there in CAD.

I have got a good deal on Nema 23 motors with 426 oz-in holding torque. It was little costlier than 368 oz-in one but i liked the built and feel of it when I saw it. So bought 4 of them now. The driver are DM542, four of them. I was looking for a power supply for it as I have 4 motors now to run and 4 drivers.

Here is how I have calculated the power supply required, please let me know if I am thinking it right.

Stepper Motor: It has 2.8mH inductance and current rated at 4 Amp.

Vmax= 32* Sqrt (2.8)= 53.5 volts

Current= 4 (amps)* 4 (motors) * (2/3) = 10.6Amps

Drivers: Drivers are rated at 20V-50V DC.

Now I have two option, Either I go with 48Volt, 10Amp unregulated supply or 36volts 10 Amp.

48Volts will give out the max speed to motor but its close to driver max range. Shall I settle for 36Volts 10Amp power supply thereby safe guarding the drivers?

Hi, Tony. I didn't see that you decided on a controller yet - you might consider 32-bit GRBL. While the old 8-bit GRBL has a lot of limitations, the "HALified" 32-bit version has removed them - most notably, step rates of over 200 kHz are supported, you can have up to 6 Axes and Ethernet interface. It runs on a wide range of microcontrollers - 13 at latest count. You can find out more about it here: https://github.com/terjeio/grblHAL. No SW license fee required - it is opensource. The test branch has autosquaring for ganged axes (like you recently moved to) and a really nice configuration section. It should be moving over to the master branch in a week or so. I'm running it on my small router. Several people are running it on ganged axis machines like yours. I have a breakout board on Tindie for the Teensy 4.1 (600 MHz ARM Cortex-M6 processor) - https://github.com/phil-barrett/grbl...ster/README.md. I call it an unkit - all SMD components are there, you just add easy to solder through holes components like connectors and the Teensy. All in cost including connectors and the Teensy is about $65 USD. Though, schematics, gerbers and an OSHPark upload are available if you want to build your own. Worth checking out.

Attachment 448288

Hi Philba,

Thank you for your input. The mentioned controller is way costlier here in my country..around 300 USD.

I have Mach3 parallel port one but I didn't knew it won't through USB.

$300? For the one I showed? Hmmm, it's around 65 USD. $26 for the breakout board from Tindie. $26 for the teensy and 12 or so for the misc parts. Shipping and customs depend on location but $200+?

Quote:

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Originally Posted by Tony_Stark

Hi Philba,

Thank you for your input. The mentioned controller is way costlier here in my country..around 300 USD.

I have Mach3 parallel port one but I didn't knew it won't through USB.

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You can use Mach3 with a USB or Ethernet you just need something like a Smooth Stepper which came in both USB or Ethernet, Ethernet being the best choice, or a cheaper option a UC-100 this is very good

CNCdrive - motion controls

Quote:

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Originally Posted by mactec54

You can use Mach3 with a USB or Ethernet you just need something like a Smooth Stepper which came in both USB or Ethernet, Ethernet being the best choice, or a cheaper option a UC-100 this is very good

CNCdrive - motion controls

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Unfortunately the UC100 is also about 100 USD here. I have decided to ditch the parallel port one buy the USB Mach3 one (runs on external power and data transfer through USB). Lets hope that works.

Quote:

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Originally Posted by philba

$300? For the one I showed? Hmmm, it's around 65 USD. $26 for the breakout board from Tindie. $26 for the teensy and 12 or so for the misc parts. Shipping and customs depend on location but $200+?

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I can get it shipped from other countries but the shipping is not reliable at the moment due to COVID and also charging high then normal. This is unfortunate but this is what it is. I inquired local CNC shops. They are industrial shops and use very sophisticated looking drives and breakout board. way above then what I need.

So I put in a lot of time is refining and calculating/designing the specifications of the router. Now it is in much better shape. Here are some pics.

I still need to work on the height as I have around 160mm of travel through the lead screw but the current gantry height is giving me just 80mm. I made some calculation mistake it seems. Need to correct the gantry height so that I get close to full travel.

I have been mixing X and Y axis in my earlier conversation. The long axis travel is around 900mm and the cross is about 600. Z axis should be 160mm (need to alter height of Gantry as mentioned)


how does this look? I welcome any suggestion.

Hi TS - You will need two bearings on your long axis. It will rack and wear quite fast with one (from experience on my first router). Plus I recommend getting high preload bearings. Normal zero clearance bearings will develop clearance in about a years of use. Peter

I see you only have one car on each rail, sorry you will need 2 bearings per rail. They need to be at least one bearing length apart prefer more. Cars are cheap its the rail thats $$$. If cost sensitive then fall back to round rails, they are about half the cost of square ones but they are not as stiff.

Quote:

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Originally Posted by peteeng

Hi TS - You will need two bearings on your long axis. It will rack and wear quite fast with one (from experience on my first router). Plus I recommend getting high preload bearings. Normal zero clearance bearings will develop clearance in about a years of use. Peter

I see you only have one car on each rail, sorry you will need 2 bearings per rail. They need to be at least one bearing length apart prefer more. Cars are cheap its the rail thats $$$. If cost sensitive then fall back to round rails, they are about half the cost of square ones but they are not as stiff.

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Hi Peter,

Many thanks for the advice. I am little unclear on 2 bearing on long axis comment. By 2 bearing you mean 2 ball screw nut on ball screw? or 2 BK support?

About car, i understood. I initially had 2 cars on each rails for X & Y. I will revert to that design. Do I need two cars on each rails of Z-axis too?

The stiffness of round rails has prevented me to have it. Will try accommodating on guide rails only. Cost is offcourse a factor but let me see how far I can push it.

Hi TS - Comment does not refer to drive system. 2 bearings on long axis means 2 cars (bearings) per rail. ie 4 cars per axis. Ideal spacing for a axis car "set" is square. So if your transverse axis gantry rails were 150mm apart then the bearing set would be 150x150 centre to centres. Same as Z axis the cars would form a square. The long axis can do that but the column bases would be huge!! This is why the long axis racks, it is geometrically unstable. It would be like a car that has its wheelbase shorter then its track.

So cars on the long axis make as far apart as possible but this makes the footprint of the machine bigger. My usual start point is to make the cars one bearing (bolt spacing apart) prefer two spacings especially as you want to cut aluminium. Because you want to cut aluminium I'd seriously consider a moving table fixed gantry design. In this way the bearing set for the table is square so much more rigid then a moving gantry machine. Plus you only need one drive system for the bed. Footprint doubles however. For a mill this is the usual configuration at that size machine. If you want to do 1m long objects for planes they are unlikely to be 1m wide so to reduce footprint and make machine stiffer, make a long 1mx500mm machine with moving table. We be much more accurate then a moving gantry machine. Peter