Garage CNC - A gantry style machine design

Hello everyone,

After working with CNC machining centres and grinders for most of my adult life I've decided to include my mid life crisis with work and build a home CNC.
Purchased the following from Ebay :-

Nema 34 1090oz motors, PSU's and drives
RM1605 1350mm X and Z, 300mm Z.
16mm linear bar rails and blocks
2.2kW water cooled spindle and VFD with ER20 toolholding.

Going to use 40mm box section for frame - going to get help from fitters in work who are excellent welders, so hoping to keep distortion to a minimum. Going for centre take off Y axis - single leadscrew, mounted underneath the table.

Kicking off tomorrow so will keep all posted on progress. :eagerness:

Good luck, post lots of pics. Only thoughts are: you may regret those motors unless they are the more expensive 3.5mH ones, and single X screw might be an issue for heavy cuts off-centre due to racking.

definitely go for two screws on the x fella if you can,you wont regret it ,my first router started out with a single 1200mm 1605 screw down the centre(x) and I bought in a second sharpish,

Thanks for the replies - will see how much the extra ballscrew will cost. Already have an extra motor as I bought for a potential headstock upgrade in the future.

I'll re-design the gantry if I adopt the second X axis screw. Will keep you posted.

If your machine really is 1350mm square (X & Y) then a single ballscrew is not up to it unless you are cutting foam/polystyrene or similar. I cut mainly wood on a ~700mm wide machine and upgraded to twin X.
600mm width is a rough transition point from single to twin X ballscrews.

40mm steel box section is also on the small side unless by 'frame' you mean just the bed, in which case it might be OK if you are using lots of them for crossmembers. If they are for the gantry etc then this is too small for anything other than foam or similar.
If that is all you have to hand then you could weld them back-to-back to create bigger pieces, but if you have a choice you need to go larger. Frame 60-80mm, gantry 80-160mm are better sizes, and at 1350mm machine size I would aim for the upper end of these numbers.

For a machine this size I assume you are cutting wood, acrylic, etc and not aluminium.

On the plus side the profile bearings and 2kW spindle are both good choices.

Please don't hijack other people's threads, start your own. Suggest you do so and delete this then I'll answer your question.

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Originally Posted by daniebjoubert

Hi there all CNC'rs,
Coming from a technical background due to my father, I was always interested in automatic/computer control for machines.
My interest is actually the electronic part of the projects.
I have semi-finished a table top cnc, to be used as an engraver in my friend's jewellery shop.
The driver boards were home made using a 4070 Ex-Or ic, 4027 Flip-Flop and L298 H-bridge driver
I have tested movements with 4 wire stepper motors running at 12 volt/0.3A, recovered from old plotters.
The results look ok but now I have to move on!
In South Africa I can get hold of Nema17-3.7V/1.68Amp stepper motors.
I am planning to use a beefed-up 5 volt supply but with current limit, set at approx 1.2 amp.
My question, if some-one can perhaps help is the following;
Will the L298 H-bridge be able to except a supply voltage of 5 volt/1.2Amp and drive the 3.7 volt stepper.

I don't want to buy the low voltage steppers and discover that it does not work.

Thank you forum group in advance

Danie

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Hi all,

Had price for extra RM1605 leadscrew and ballnut, BK/BF12 blocks and end machining for 145USD - think it's worth the extra after listening to your advice.

Hoping to machine various materials, but engraving in slate would be my primary initial use as several people have asked if I can.

Honestly it's my mid-life crisis toy - better than a sport's car in my opinion:cool:
Thanks for the help.

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Originally Posted by fandango

Hi all,
Hoping to machine various materials, but engraving in slate would be my primary initial use as several people have asked if I can.

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I don't know much about stone working but I'm sure it involves a lot of water, so you need to design the machine to handle water from the outset.

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Originally Posted by fandango

Hi all,

Had price for extra RM1605 leadscrew and ballnut, BK/BF12 blocks and end machining for 145USD - think it's worth the extra after listening to your advice.

Hoping to machine various materials, but engraving in slate would be my primary initial use as several people have asked if I can.

Honestly it's my mid-life crisis toy - better than a sport's car in my opinion:cool:
Thanks for the help.

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Can i just say the way your going about it and buying stuff without research or asking then it's going to cost as much has any sport car.!!

So far your component choices are severly going to restrict your goals.!! . . Motors are most likely too large and I'd wager your PSU will be Too low a voltage, on top of this the 5mm ballscrew pitch is too slow to be ok for cutting awide range of materials. The combination of the motors and the screws will make it very hard to cut softer materials that need higher feedrates, softWood's, plastics etc will all need feed rates higher than you'll probably achive with this combo.
Slate and harder materials won't be a problem has they will require low feedrates but then you'll need to mind the spindle and machine strength and cutting conditions. Like someone as said 40mm box just won't cut the mustard so you'll want to beef the frame. Like Eddy say's Stone, slate etc needs water or cooling so you'll want to think about that otherwise tool wear will be high and costly. The spinlde is also a bit too fast for stone cutting correctly but will just about be ok for engraving slate with correct tooling and conditions.

Now please don't take this wrong way and think I'm pissing on your parade or just giving you a hard time for the sake of it, i'm really not. What I'm saying is you need to take a step back do a little research and ask some questions, Start a build thread and post up your thinking or ideas.

If you don't slow down then you risk a very big chance of being dissapointed with the outcome and high risk of wasting money. I wouldn't buy another thing untill you have come up with the machine design because so far you have made some typical newbie mistakes which are going to limit what you'll be able to achive with machine.

Best advise is start a build thread and post the design or ideas and thoughts for the design and we will guide you in the right direction.

PS: Sorry to be so blunt but it needed to be said for your wallets sake.1:dejection:

I'm OK with blunt so don't worry.:cheerful:

Individual PSUs running @60V @6A to the motors so I think they'll be OK.

Not sure about the high feed rates in softer material statement though - I haven't worked with wood previously but have cut plastics before and feeds / speeds can be adjusted accordingly.

40mm box was for the frame only - was going to use 125 x 20mm BMS for the gantry sides, with 50 x 20mm flat bar as anchor points and mounting. Can beef up the frame to 60 box no probs, but was going to anchor to the floor after leveling so thought it didn't matter about 40 box.

Chose 1605 deliberately as I though accuracy was was a better trade off. In no rush to make things as this is going to be a hobby not a career.

Will re-start the design on the weekend and will post it bit by bit. Use Inventor to draw 3D so will have to draw all up from fresh - so won't be quick :whistle:

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Originally Posted by fandango

I'm OK with blunt so don't worry.:cheerful:

Individual PSUs running @60V @6A to the motors so I think they'll be OK.

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No not really.!!. . 60V is low for a nema34 motor and 75V would be a minimum to get anything like decent speed and torque from them. You'll be lucky to reach 800rpm with 60Vdc and get anything like usable torque. So with your 5mm pitch you'll have maximum speed of around 4000-4500mm/min and that will be rapid speed with torque at it's lowest so realistic maximum cutting speed will be around 3500-4000mm/min. Which for wood's and some plastics just isn't fast enough to get anything like correct chip load.
It's wrong to think about feedrates in terms of Business or Hobby because it's more to do with tool life and quality of finish than whether or not your in a rush.!

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Originally Posted by fandango

40mm box was for the frame only - was going to use 125 x 20mm BMS for the gantry sides, with 50 x 20mm flat bar as anchor points and mounting. Can beef up the frame to 60 box no probs, but was going to anchor to the floor after leveling so thought it didn't matter about 40 box.

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I've built plenty of steel framed machines now and 50x50 is the minimum I'd use for a machine this size on any major frame parts. 40x40 will be ok for diagonal braces etc but not structural frame work. 60x60x5 is my prefered choice.

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Originally Posted by irving2008

Please don't hijack other people's threads, start your own. Suggest you do so and delete this then I'll answer your question.

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Probably better still to start at the very beginning and not have an advanced build thread like this in the "New Member Introductions" section?

But really, this is nothing more than VERY New Members finding their way around........ Please give peace a chance .......

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Originally Posted by AndyGuid

Probably better still to start at the very beginning and not have an advanced build thread like this in the "New Member Introductions" section?

But really, this is nothing more than VERY New Members finding their way around........ Please give peace a chance .......

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On the money there Andy, not sure why Irving replied in such an abrasive way, must of been having a bad day or something?

Will do the moderating on this thread shortly and make any adjustments, will start you a fresh one Dan.

.Me

Didn't think I was abrasive :(, I said please... But answering Dan's questions would have hijacked the thread further.

Might have been frustration over inability to do the moderating myself :) given the number of spam-like posts that have annoyed me recently :(

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Originally Posted by irving2008

Didn't think I was abrasive :(, I said please... But answering Dan's questions would have hijacked the thread further.

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No neither did I Irving you where polite and to the point.!! . . . . . Some people are just too sensitive.:sorrow: . . . . (Makes a change from me getting slated for being abrasive thou.:hysterical:)