need help! choosing right kit

[JAZZCNC]

Well you really have got a problem with this selection because the motors and PSU voltage don't match together well.

R&P needs the JK86HS78-5504 (NM 4.6 - 651 oZ 5.6A 3.4mh) or the JK86HS115-4208 (NM 8.7- 1232 oZ 6A) and with only 60Vdc you don't have enough voltage to get good performance from these.

The JK57HS112-3004 (NM 3 - 425 oZ 3A 6.8mh) are not suitable for R&P and are better suited to 1610 ballscrews but again with only 60V and high inductance the performance will be lower. They really need 70+Vdc to get good performance.

My advise would be don't buy any of them has they are not matched nice but if I must choose then I'd say go with 3Nm and 1610 and build to this size.

If you can push the Voltage upto 70-74Vdc and use toroidal transformer PSU then you could get away with JK86HS78-5504 (NM 4.6 - 651 oZ 5.6A 3.4mh) and 28T R&P with 5:1 ratio.
This would give pitch equal to 22mm (Mod1.25 28T DP = 35 x pi / 5=22 ) which would give decent resolution for wood and good speed so you could tune motors down so they run slower where torque is higher and still maintain good feed rates.

Really the only motors you can use are the JK57HS112-3004 (NM 3 - 425 oZ 3A 6.8mh) and JK86HS78-5504 (NM 4.6 - 651 oZ 5.6A 3.4mh) and both these need more voltage, esp the 4Nm 34's.
The JK57HS112-3004 (NM 3 - 425 oZ 3A 6.8mh) with 70Vdc would perform best.

[HipoPapi]

Hi there,

In My opinion the best way to estimate weight is the following:

First 1. Use Sketchup to build your model.
Step 2. Any components in your build must be converted into groups or components otherwise you are f****d in sketchup.

So for instance if you make a 100x100x3x 1500 solid in sketchup turn it into a group or component as soon as is made.

Step 3. if you right click a group or component and go into entity info depending on your unit setup (which should be mm for this type of work) you will see the exact cubic mm of the component.

Step 4. Go here: http://www.aqua-calc.com/calculate/volume-to-weight

If you dont see the cubic mm option click show more units and will be there.

Search for steel or aluminum or whatever and calculate.

Have a good night.

Vass

[msacnc]

thank you very much JAZZCNC for your help

i think i will go to ballscrew as you suggest
one 2510 for X (2m long) but what about wrapping..
one 1610 for Y (1.2 m)
one 1605 for Z (0.5 m)

according to eq. from cncrouterpart suitable V = sqrt(mh)*32 which mean that Nema34 with 3.4mh required 59v for best performance which is close to 60v PS is this correct

i know that Nema23 425oz is better specially for speed but as you mentioned it requires at least 72V which is not available

can i use central 2525 ball screw with Nema34 for X and Y axis

[Boyan Silyavski]

can i use central 2525 ball screw with Nema34 for X and Y axis

Dont do that. Especially at that size gantry and that Z travel.

At 300mm z travel you have to make sure when you design it, that the long ball screws are more or less on the height where the cut happens. One design consideration most people overlook.
That is good for you because you will have maximum actual travel 2000mm long - ball nut legth

[msacnc]

To reduce the risk i will reduce the overall machine size frame to 2000*1150*400 mm

X one ballscrew 2510 length 1750

Y one ballscrew 2510 length 950mm

z one ballscrew 1605 length 300 mm

[msacnc]

i also plan to use design made from steel like this



X gantry using 50*70*3mm box

all bed made using steel

one central ballscrew 2510 for X gantry

[msacnc]

also i plan to pay this steppers

http://www.aliexpress.com/item/3-PCS...789406140.html

i am confused vender say suitable PS 24-48V but acoording to sqrt(3.8 mh) * 32 = 62V ???

[msacnc]

i need advice JAZZCNC for ordering one Power supply 70V~90V 12A in this link

http://www.aliexpress.com/item/800W-...126181657.html


i already have 4 driver 80V 7.8A


and i hope this PS match The JK57HS112-3004 (NM 3 - 425 oZ 3A 6.8mh) with 2510 and 1610

is one enough for 4 nema 23 steppers

thanks

[msacnc]

thanks irving2008 for reply i appropriate your effort with me thanks again

Single ballscrew on that width isn't going to work,

2 ballscrew mean double cost what is the max width of gantry that work well with one

what is your opinion about the design of steel machine above

Inertia of 25mm screw is too high for a 2.8Nm motor

i pay this PS 70~90V with previous Nema23 3NM is this work also double 1610 with 1750 mm length work good or not?

[JAZZCNC]

Ok well it,s been said but will say again to backup. Forget Single screw down centre gantry will twist at this width. Forget 25mm screws unless running nema34 with high voltage AC drives.

Now the sqrt(3.8 mh) * 32 is just a guide and in practice you can go higher without any issues or shortening motor life too considerably. (One thing to note because your in a Hot country I would consider putting cooling fans on the motors, PC CPU fans work well)

The PSU you linked too would work ok but first I would look into making your own.?
It's very easy all you need is toroidal transformer, 1 x brdige rectifier and capacitor/s. Obviously these need to be sized to give the output your require which we can help with.
You must have electrical component suppliers like RS components in your country so I would enquire about costs because Unregulated toroidal PSU is much better for CNC when your running near the drives Max voltage.

So Definately go with 2 x 3nm/1610 running 70V. Will warn thou that at 1750mm length with 16mm screws your at the point when whip at higher feeds can cause problems so you may still need to limit motor tuning to lower rapid speeds.?
Also the mounting and alignment will need to be perfect, which it should be anyway, but if your off just a little then this is amplified at this length which can introduce whip and resonance.!

So hopefully now you see why WE all have been asking you to slow down and think about it becasue so many things affect other parts of the machine and for good machine you need balance and components working in harmoney not fighting each other.!! . . . . In CNC we Make LOVE(chips) not WAR. .Lol