[pancakeshake]

Hey Everyone,

I know this has likely been posted 100x before but looking for some specific guidance on my build. I have build a G0704 with a stepper setup, but I’m now looking to convert a larger mill with Clear Path servos. From my understanding, you DON’T need separate servo drives for these as the drive is “built in” to the Teknic motor. Is that correct?

Current build plan:
Double Ball screws. TBD on pitch
Keeping the gibs/ways, not upgrading to linear rails.
Weight balanced vertical column
X and Y: 698/209 oz.in Nema 34’s. Belt driven: TBD Ratio
Z: 922/276 oz.in Nem 34. Belt Driven: TBD Ratio
Target rapid speeds: 100 IPM
Target machining speeds 30 IPM


Do I need servo drives for the Teknic's? Or is that build in and I just go straight to the BOB?
What is a good pitch on the ball screws to achieve the rapids I’m looking for?
What is a good pulley ratio to achieve the rapids an power I’m looking for?
Are my motors undersized?

Where I am stumped is the BOB/SS. I see too many options on Automation Technologies website to make sense of it…

My goal:
Spindle control (VFD driving 3 phase motor)
3 Axis movement
Limit switches on 3 axes (soft limits on the other end or travel range)
E-Stop
Tool setter
USB / Ethernet connectivity

What is my best option to achieve what I am looking to do?

[awerby]

If you're talking about the "all in one" Teknic motors, it does seem that the drivers are built onto the motors. For your other questions, the first people to ask are the support staff at Teknic - they say they provide support, but if that's not true, please let us know: https://teknic.com/products/clearpat...-servo-motors/

[joeavaerage]

Hi,
1) You do not need separate servo drives for Clearpath servos, they are built in. You will need a high current DC power supply to power them up though.
I use Delta 750W B2 servos. They have a separate drive that is powered direct off-line by 230VAC. The servo, servo drive and cables cost me $438USD plus shipping.
Clearpath servos are (usually) more than that and only 400W. Clearpath are good, but 'bang for your buck' there are better choices.

2) I personally use 5mm pitch ballscrews. My servos are rated for 3000rpm, and thus when direct coupled result in rapids of 15m/min (590IPM), and when I tune for their max 5000rpm I have rapids
of 25m/min (985IPM). I find 15m/,min any amount enough, in fact I seldom use all of it, 7.5m/min to 10m/min is entirely fast enough. Bigger question is ballscrew diameter. The potential acceleration of your axis
(higher the better is desired) is determined often by the rotational inertia of the ballscrew. This is counter intuitive as most think that its the mass of the axis, but in fact the opposite is often true.
As an example the axes of my machine (pictured) the momentum is 80% ballscrew, 12.5% servo armature, 7.5% axis....and each axis is 150kg!

The rotational inertia of a ballscrew is proportional to the fourth power of diameter. Thus if you increase from 20mm ballscrew to 25mm ballscrew int increase in inertia is 2.44 times. Very dramatic.
Before you spend any money on servos or ballscrews you should do the calculation to ensure you end up with a good result.

3) With 5mm screws then you don't need a belt reduction, you'd be better of direct coupling to the ballscrews.

4) With 5mm pitch screws just 1Nm of servo torque is required to hold aloft a 125kg Z axis. Depending on your servo you may not need a counterweight at all. My machine does not have a counterweight, the Z axis
servo (2.4Nm rated, metric equivalent to a 34 size) holds the 30kg aloft without a care in the world. Note that I used a Delta servo with a built in electromagnetic brake to stop the Z axis sagging when depowered.
I don't think Clearpeth have an electromagnetic brake version.

Craig

[pancakeshake]

Hi,
1) The servo, servo drive and cables cost me $438USD plus shipping.

Where did you source those?

Thus if you increase from 20mm ballscrew to 25mm ballscrew int increase in inertia is 2.44 times. Very dramatic.

This has always been another burning question I have had...why would I go with 20mm over 12mm? Its there any reason for the larger size screw?

With 5mm screws then you don't need a belt reduction, you'd be better of direct coupling to the ballscrews.

I was hoping for increased resolution and reduced duty cycle on the motors. Am I crazy tho? Does this just add unnecessary complexity

Note that I used a Delta servo with a built in electromagnetic brake to stop the Z axis sagging when depowered.

How does that work? Is the brake active anytime the motor in enabled and not actively being told to "move"? Or is there an external command that activates the brake?

Thanks for the responses!

[joeavaerage]

Hi,

https://www.fasttobuy.com/flange-80m...er_p28084.html

I've bought five for myself over three years and another five for others, all at the same price. Costs $156USD to ship to New Zealand. Record is two days 20 hours, and the longest is four days and 8 hours. So shipping
is not cheap, but you get what you pay for. The braked servo cost an extra $100USD. I also bought a programming cable for $68USD, of course that I can use and reuse over all my Delta servos.

If you spin a small diameter ballscrews too fast it will 'whip' and be very short lived. Most of the manufacturers have a recommendation, and you need to abide it. I use 32mm ballscrews and they are 700mm long, and
I can spin them at 5000rpm without them whipping, in fact I could use 25mm and probably even 20mm ballcrews without whipping of the same length. I want and need rigid ballscresws, and I got my screws
near new second hand. They are 32mm C5 (ground) double nut (BNFN) by THK with FK25 ball mounts each end. I got three complete sets including shipping to New Zealand for $1000USD. If I had bought new
these ground ballscrews and ball mounts would have cost over $7500USD...so I got a bargain.

The short answer is get the biggest and best you can afford without going too far and requiring ultra high torque servos to spin them.

Servos, even Clearpaths that have low(ish) resolution still have more than enough WITHOUT needing a belt reduction. My Delta's have a 160000 count/rev encoder......so extremely fine resolution,not the you can use it all!!
I have set the electronic gearing such the the 'effective' encoder count is 5000 count per rev (direct coupled to 5mm pitch screws) giving me a linear resolution of 1um....and that is way fine enough for me!
Don't worry about resolution, even the cheapest of servos will have more than enough without a belt reduction.

The electromagnetic brake requires that you power it to release the brake. Thus is the power fails the brake comes on within a few milliseconds. I have set my machine up that as soon as the servo is enabled
(and therefore able to support the weight of the Z axis) the brake is OFF. Whenever the servo is disabled the brake is ON. Very easy.

I understand Clearpath have a separate brake unit that couples to one of their servos, but if I recall correctly they are $375USD.

Craig

PS: correction, a 34 size brake unit from Clearpath is $296USD

https://teknic.com/products/spring-a...er-off-brakes/

[pancakeshake]

Hi,

The short answer is get the biggest and best you can afford without going too far and requiring ultra high torque servos to spin them.

Don't worry about resolution, even the cheapest of servos will have more than enough without a belt reduction.

The electromagnetic brake requires that you power it to release the brake. Thus is the power fails the brake comes on within a few milliseconds. I have set my machine up that as soon as the servo is enabled
(and therefore able to support the weight of the Z axis) the brake is OFF. Whenever the servo is disabled the brake is ON. Very easy.


https://teknic.com/products/spring-a...er-off-brakes/

All great advice. Thanks!

No onto the BOB question....

I see tons of options here.

A) Do I need to run a smooth stepper if i'm running servos? Is that what gives my the Ethernet / USB connectivity capability for better data rates?
B) These three (below) all seem very similar and appear they will all accomplish what i'm looking for. What are the benefits of one over the other?

https://www.automationtechnologiesin...nals-for-mach3
https://www.automationtechnologiesin...pindle-control
https://www.automationtechnologiesin...ers/6-axis-ess

[joeavaerage]

Hi,
I think you are asking the wrong question, and confusing a breakout board with a motion controller.

The usual setup is that CNC software runs on a PC, either Windows (eg Mach3, Mach4, UCCNC, Cenroid ACorn etc) or Linux (eg LinuxCNC) and that connects to a motion controller, usually Ethernet or USB.
Most motion controllers require an additional breakout board. the breakout board does not really provide any functionality, it is just a buffer amplifier and a secure place to connect to the real-world hardware.

The question you should ask is 'what CNC software do I want to run.....and THEN ask so what sort of motion control board is required for that software......and THEN does that motion control
require a breakout board?'.

The most commonly discussed hobby CNC software on this forum are Mach, either 3 or 4 (by New Fangled Solutions), UCCNC (by CNCDrive), Centroid Acorn or LinuxCNC (open source). There are others, like Planet CNC,
Masso, WinCNC...and any number of GRBL (Gcode senders) variants. You need to decide what software you want to run and that will determine other choices you need to make.

Craig

[joeavaerage]

Hi,
for instance you have linked to various breakout boards, but they all have an Ethernet SmoothStepper, and an Ethernet SmoothStepper is driven by Mach (3 or4) only. Is that what you intend?
You cannot use an Ethernet SmoothStepper with LinuxCNC for example.

If you want to use UCCNC THEN YOU MUST use one of CNCDrives motion control board, either a UC100,UC400,UC300, either with or without a breakout board.

Craig

[pancakeshake]

Ahhh yes. My bad. Thank for the clarification...hence my confusion haha.

Mach 3 is what I run now.

So Mach 3 (or 4 if its better)

[joeavaerage]

Hi,
OK, I run Mach4 and have done for ten years (from Mach3 previously) and its light years ahead of Mach3 in my opinion. Having said that Mach3 still works.

If you are committed to Mach (3 or 4) then an Ethernet SmoothStepper is a good choice. There are other choices, some maybe a little cheaper, some more expensive, but really an ESS is
at least as good as any of them. The ESS has the (potential) of 51 inputs and outputs. The breakout boards you linked to only exploit a fraction of that total. For the long term flexibility
and maximizing the potential of your machine then I would recommend a breakout board that uses ALL 51 IO's. An MB3 by CNCRoom is a popular choice....not cheap, but well developed with a good
balance of inputs and outputs, differential outputs for the servos, good quality with a good PWM to analogue conversion circuit for controlling a VFD. Despite the cost, good value for money.

https://cncroom.com/en/product/mb3/

Craig

PS: Just as a matter of interest I use an ESS but made my own breakout board. Differential outputs for the servos, 24V sourcing inputs, balance of 24V sinking and sourcing
outputs, with a nicely linear PWM-to-analogue output for the VFD, a switching 24VDC circuit for the electromagnetic brake.