Taark's CNC Router

[Taark]

Hi all,

Just thought I would start a build thread for my machine. To show you guys what im doing and get advice on the way...

This is going to be a pretty heavy duty machine for mainly cutting aluminum.

Details so far are:

Z axis

20mm x 5mm ball screw
20mm THK Lineal Rails & Bearings
Nema 34 Stepper Motor 878oz

Y axis

25mm x 5mm ball screw
20mm THK Lineal Rails & Bearings
Nema 34 Stepper Motor 1600oz

X axis
2x 25mm x 5mm Ball Screws
20mm THK Lineal Rails & Bearings
2x Nema 34 Stepper Motors 1600oz

Micro Step Controllers
2x 350w power supplies
Spindle will be 2.2kw with VFD unit

The cutting area will be little over 1/3 sheet (1300x850mm)

Fully designed in solid works to make sure it will all come together.

Fully welded frame for rigidity.

Attached a 3D drawing for you. Not finished but getting there.

Things I want for the router or am not sure about:
Tool Length Sensor
Setting up the 2 x axis motors to work together?


Taark

[Taark]

Ordered my control gear today...

Got it from a company called Longsmotor

Ordered:

3x Nema 34 Stepper Motor 1600oz (Single Shaft)
1x Nema 34 Stepper Motor 878oz (Single Shaft)
4x Stepper Driver DM860A Up to7.8A, 24-80VDC, DM860A
2x Power Supply 350W-48VDC
1x Breakout Board

$769.00 USD

[Pplug]

What are you going to use for a spindle?

Duhhhh... I just re-read the post! Sorry

The build looks good though!

[Taark]

Sorry, just updated it...

Will try the 2.2kw water cooled Chinese model and see how it goes. Might chuck some ceramic bearings in it if it doesn't last long.

Taark

[ger21]

Unfortunately, I think you're going to find that your motors and ballscrew combinations are going to give you very poor performance.

Typically, larger motors will have less torque at higher rpm's than smaller ones. And the screws you've chosen (5mm lead) require high rpms's to get high speeds.

600 oz motors and 10mm pitch ballscrews would probably give you 2-3 times more speed, and still have more than enough power.

The Chinese have a habit of selling poorly matched components to unsuspecting buyers, who think that bigger is better.

[acondit]

Unfortunately, I think you're going to find that your motors and ballscrew combinations are going to give you very poor performance.

Well that depends on what type of performance you want. What Ger said is true if speed is the most important consideration. However, if accuracy is more important then 5mm lead will give you more accuracy (resolution) than 12mm lead or 25mm lead all other things being equal.

Typically, larger motors will have less torque at higher rpm's than smaller ones. And the screws you've chosen (5mm lead) require high rpms's to get high speeds.

600 oz motors and 10mm pitch ballscrews would probably give you 2-3 times more speed, and still have more than enough power.

Here I am in total agreement with Ger. What you will probably get with 1600 oz. motors is a lot of cogging and not smooth motion.

The Chinese have a habit of selling poorly matched components to unsuspecting buyers, who think that bigger is better.

[Taark]

Thanks for the replys guys...

This machine will be used for cutting thick aluminium at slow speeds with a high acuarcy.

As my steppers are not going to be connected directly to the ball screws (will be using timing belts and pulleys) I will be able to adjust the gear ratios as nessisary.

Worst case senario I will just swap over to servo motors and encoders.

This is how a worked it all out.

The steppers I have chosen max out at 3000rpm. So even if I use up to 1000rpm using a 1-2 step down ratio to get 500rpm at the lead screw this will give me around 42mm/s. And adjusting the ratio I can go up from here.

What do you guys think?

Taark

[acondit]

I think you will find it very difficult to achieve enough rigidity in the machine to justify the difference between 600 oz/in and 1600 oz/in.

On my last router I had 3/4"x5tpi screws with 200 oz/in nema34 steppers. I had a 3/8" bit in my router one day and I started the machine moving without turning on the router. It snapped the bit off like it was nothing and never even slowed down. Another time I was cutting a part and I had a steel screw head sticking up about 0.010" above the bed. When the router bit (1/4" carbide) hit it, it just changed pitch for a split second as it machined off the head. A nice clean cut and no lost steps and I was cutting at 75ipm(31.75mm/sec). I was running direct drive no gear down. I just can't imagine the need for more than 600 oz./in. running direct drive, let alone geared down.

Alan

[Taark]

Hmmm,

Is there any down side to using the larger size motors?

Might not be too late to swap over to 4x 878oz motors...

Taark

[acondit]

I have three Nema42 1500oz/in that I thought I was going to use originally. First problem was that they required 170v drives, expensive. Then Mariss of Gecko said that the higher powered motors would in essence snap from one step to the next rather than moving smoothly liked its lower powered brother (unless of course you could in fact load it appropriately). It is called cogging.

Alan

[Taark]

Hi Alan,

Thanks for the info... I have just contacted longsmotor to see if I can swap to the 878oz nema 34 motors.

Hopefully its not too late.

Taark

[Taark]

Well... It was too late. The motors have already been sent.

But no drama, if they dont work I will just swap over to servo motors.

Also ordered the ballscrews, nuts and bearing blocks.

Hopefully have them all soon so I can finish designing the table and get it made! Woo hoo

I guess im lucky in a way as I run these machines for a job so I can cut all my parts out for free...

Just out of interest we have:

1x 2x3m ATC Tekcel router
1x 1.5x2.7 ACT Tekcel router
1x 1.5x2.7 Tekcel Router
1x 1.5x2.7 Tekcel Router converted to a plastic cutting laser
1x 1.5x3m Amada 3000w steel cutting laser
1x 1.2*0.8 Gaia 200w Engraving laser