I NeeD HeLp PLease AM882 a good choise

[jpsicilia]

Jazz, first of all I would like to thank you for your help, I really appreciate it because I have not received any help from these forums and I do not know how to get started. I have decided some things but before buying any products I would like to be certain so as not to regret it later.
I need a CNC to produce aluminum moulds and be able to produce products with less hard material such as poliacetal or mdf. I am an Industrial Designer and I work with software such as Solid Works and Rhino which help me to verify movements and assembly. I know a little about dimensioning structures but I do not know anything about electronics. I am trying to use the tools I have and reading a lot to be able to build the CNC.
You asked me about the measures of the CNC, and I believe that with the axis X 1m, axis Y 1m, axis Z 0.3m I will be able to manufacture the pieces I need.
I did a 3D model to verify the dimensions of the metallic frame, I will attach some pictures so that you can give me your opinion, because I have problems starting with the linear movements and the electronic, but regarding your observations I will be able to change them.

Axis X :
HIWIN Brand linear guide rail 2PCS HGR20-L1000mm+4PCS HGH20CA HGR Series Narrow Carriages ZH075 - 337 uSs
RM2005 Ballscrews L1150mm with ballnut with end machining+1set BK15/BF15+coupler - uss 164

Axis Y:
2pcs SBR20 -L 1000 mm Linear shaft Support + 4pcs SBR20UUBearing Blocks - uss 179
1antibacklash ballscrew RM1605-1020mm+BK/BF12+coupler - uss 149

Axis Z:
2pcs SBR20-L300mm Linear Bearing Rails + 4pcs SBR20UU SY1860 -uss 69
1pcs antibacklash ball screw 1605 -L300mm-C7+BK/BF12 + 2pcs 6.35*10mm couplers - uss 83

Electronic:
As regard Electronics, I have read that the nema 34 has a good torque that I why I thought of using them, but I am not sure if they are appropriate for what I have in mind. There are several kits advertised on ebay for example this one:
Electronic kit on ebay:
3 PCS Nema 34 Stepper Motor with 1090oz-in (7.7N.m) holding torque,5.6A current,99mm motor body length,
3 PCS Stepper Motor Driver DQ860MA,24-80VDC,7.8A Peak Current, 256Micostep replacing MD882,
3 PCS 350W, 60VDC,5.9A Power Supply.
1 PC Breakout Board & 1 Parallel Cable
Uss 480.

Jazz thanks again for everything and I hope to be able to assemble the Cnc and learn something about electronics with your help!

[JAZZCNC]

Pleased to help you Juan,

Let me say from the beginning that your requirements to cut multiple materials causes conflicts with design and component selections.
To cut aluminium correctly with accuracy and still give quality of finish required for moulds requires a very different design and components compared to a machine designed for wood and softer materials. Now It is possible to build such a machine to cut all materials but you have to realise it will only ever be average at all of them.!! . . . . It will also require certain design features to successfully achieve this. IE Adjustable Bed.

The problem comes from the fact Aluminium requires a very very stiff machine with shortest possible tool and Z axis extension to reduce chatter and give best finish quality. The resolution required, esp for detailed work like moulds is high. Also feed rates are relatively slow along with spindle speeds. On top of this to give best tool life and finish quality coolant is required.

Now softer materials like wood don't require high resolution but they do require high feed rates. This causes component conflict number one.! Ballscrew pitch Selection.?
High resolution requires fine pitch so 5mm or less ballscrews but this fine pitch makes achieving high feed rates required for correctly cutting wood difficult. To achieve feed rates needed for woods/plastics etc requires ballscrews with larger pitch 10mm or more but this reduces resolution required for Aluminium.!!
Now this is also where stepper selection plays a big part and why new CNC builders often fall victim to "Bigger is better" .? Larger Nema 34 size steppers spin much slower than smaller nema 23/24 and this lowers feed rates even further.

Now you have selected the Worst combination for Cutting softer materials.? Having 5mm pitch and larger Nema34 motors will mean you won't be able to achieve feed rates for cutting woods and plastics correctly. This will mean poor finish and poor tool life.

To cut aluminium doesn't require massive torque and the smaller Nema 23 motors easily handle it. They spin much faster and cost less, they don't require expensive high voltage drives.

Now thru experience I know the best combination for cutting both types of materials at the size of machine you require is 16mm Dia 10mm pitch ballscrews connected with timing belts and pulleys to 3.1Nm Nema23 motors running between 65-70Vdc using 80V drives.

To get round the higher pitch screws lower resolution causing problems when higher resolution is required is simple.? just change the ratio of the pulleys. Changing to 2:1 form 1:1 doubles the resolution and doubles the torque but half's the speed, Remember we don't need speed for Aluminium so this is no problem and gives best of both worlds.
In reality you will find you rarely need to change ratios has 10mm pitch will be fine for most aluminium jobs except when really high detail is required.
But with this combination you have the option.! You also have the option to go other way with 1:2 ratio and cut even faster if required or any in between ratio that may suit your requirements.
Also on top of this using timing belts has the added benefit of eliminating the negative affect resonance from machine has on the motors.

Regards the Frame design to allow best possible compromise for hard and soft materials then you need high sided with gantry sat direct on rails design along with adjustable bed. Look around the Forum and you will see both Jonathan and Me posting designs using this design.

I'd also look towards using profiled linear rails on all Axis has they are much much better than SBR rails and will handle cutting Aluminium much better and last far longer.
Hope this helps and forget the Nema 34 motors they are wrong for your needs.