Hybrid stepper or servo system for uc300

[Davemorl]

Hi all,

I currently am running a uc300 usb with mach3 and I have open loop steppers. This was fine for a homemade small router I had built as a prototype but I am now building a new heavy duty frame to migrate all my hardware onto. As I'm upgrading the lightweight frame I am also going to upgrade the positional motors as the weight of the table being moved is now steel and considerably heavier. Prob around 120kg so it is going to be pretty rigid

What my choices are is a closed loop stepper system or a servo system. But I am thinking of using UCCNC instead of mach3 as I've seen it gives better results. I've been looking at these drives and motors;

3HSS2208h-100 with 20Nm nema 42 motor
https://rover.ebay.com/rover/0/0/0?mpre ... 2187432593

Also this servo configuration
https://rover.ebay.com/rover/0/0/0?mpre ... 2411229621

My question is basically this, has anyone got any experience with these options and how do they perform. Also how would I go about if it's possible to have a fully closed loop system to uccnc. Is it possible with the uc300 usb?

Or if anyone else has any options of better motors and drives to get? My budget is max around £1000.

Thanks,
Dave.

[cncdrive]

My opinion is that you should be careful where and how much weight you put in a machine, because however more mass mostly increases the stiffness of the machine (if the mass is placed in the proper places),
but the same time too much weight can make your machine slow and lazy.
Also placing mass into the head of a portal router makes the machine "head-heavy" which will make the portal trying to nod when there is a rapid acceleration or decceleration.

Oversizing the motors can help to overcome the problem of moving heavy weight, but please note that the larger your motors are the larger the rotor intertia is and so the motor is more "lazy".
Especially when moving Nema frame size up the inertia increases greatly, because the mass on the rotor is on higher diameter.
So, go with Nema 42 size only if you really have to put in that much mass and if you really need that high torque.

Servos are a different from steppers, because while with steppers it is easy to oversize the motor with servos the oversizing can easily become costy and it is not as easy to oversize the system as it is with steppers, because you have to match the inertia of the motor to the inertia of the plant (moved axis with the gearing), if you not calculating that properly then you can easily end up with a very unoptimal driving system which could mean slow possible accelerations and therefor slow overal machining times, but this is the better case, the worse is if the inertia of the servomotor is really small compared to the inertia of the plant then you can end up with an untunable axis. Especially if there will be even a small backlash the inertia unmatching can make the system untunable.

So, be careful where and how much mass you put in your machine and what size and type of motors you selecting.
Dealing with stepper systems even if it is a closed loop one is much easier than it is with servos.
However if you properly sizing thing then a servo can give you benefits in machining times.

Any stepper or servo drive which has step and direction interface will work with the UCCNC.
And any stepper or servo drive which works with Mach3 will also work with the UCCNC.

Fully closed loop system is not possible with the UCCNC. And also not possible with Mach3.

[Davemorl]

Hi,

Thanks for your in-depth reply. I have considered the rotor inertia but I'm not sure what will be acceptable and what wouldn't. If my entire mass of the table with work, vice etc won't exceed 120kg how would I find a suitable motor?

Also if I was to get step dir servos linked in the previous post at nema 34 4Nm 1Kw would these be suitable with a 5mm/rev ball screw? Or would it need to be a geared system with possible pulleys?

Also would they work with a UC300?

I've added some pictures as a picture paints a thousand words.

Dave.

[Robertspark]

I don't work for cncDrive {but have an interest in landrovers too, new bulkhead?) + in the UK

The UC300 will work fine, I would recommend the Ethernet version over the USB version (better noise immunity).
I would also I'd recommend you consider UCCNC over Mach3 (much better motion, mach3 stopped development years ago).
I'd recommend you consider something like the cncRoom UB1 breakout board too as it's 24V and really easy to interface

{or at least consider these things}

I don't think you'll get the answers you require on which drives and motors to choose from here.... there are a lot of things that go into that selection, and not many people will stick their neck out to say anything (especially a company), they'll expect you to make that decision.

Suggestions:
What do you want to cut / machine {material}
What do you want to cut it with {bit diameter, material, coating, number of flutes}
What rapid speed are you looking for, what acceleration are you looking for? {you may need to calculate the above values first before arriving at these numbers}
What is the mass of each moving assembly {suggest you finish building the elements first, allowing space for ballscrews if that is the way you want to go, or estimate the mass of the assembled components}

[Robertspark]

A few links for you to ponder that may help:

http://www.mycncuk.com/threads/1524-Wha ... -do-I-need

http://www.cnczone.com/forums/mechanica ... lling.html

https://www.kennametal.com/en/resources ... 0574519793

https://www.mmsonline.com/articles/a-ne ... d-formulas

http://www.orientalmotor.com/motor-sizing/index.html

http://www.d.umn.edu/~rlindek1/ie1225/M ... _1_doc.doc
http://www.fordtool.net/pdf/209.pdf

[Davemorl]

Hi Rob,

Thanks for taking time to reply.

I had a feeling that would be the case. I suppose it's a bit of a gamble especially with Chinese drives etc...

Yeah I'm currently rebuilding a 110 van. I have replaced the chassis for a galv one and am in the process of repairing the bulkhead. It's pretty much a full renovation. I thought I may as well while it's in so many bits you know how it goes. The more you look the more you find!

I currently only have a 2.2kw Chinese spindle but have been looking at feeds and speeds on FSwizard and with a 6mm 4 flute end mill with tialn coating it's well within the range. Obviously this all depends on rigidity if it is feasible. But as long as it cuts aluminium I'll be happy.

Rapids is be happy with around 3000-4000mm/min

Dave.

[Robertspark]

I've not had a problem with my Chinese drives (but you pay for what you get) - Leadshine AM882H, sold in high volumes via aliexpress + fleebay, mainly refurbished. Now found new as an upgraded drive EM806 (but they may be a bit small for your application).

Landrovers {I've been rebuilding mine for years (90, tartcart ragtop), started out as a chassis + bulkhead replacement, swmbo ain't happy ... suppose to be moving house sometime.... been a long nut & bolt rebuild ... very long + slow} its why I got into cnc... plasma

fswisard works well, used it before myself.

Note that your material below is steel, feeds and speeds in aluminium will be much higher (especially with 4 flute cutters)

I tend to use Onsrud cutters (expensive, think 62 series from memory, single flute O spiral)
http://www.onsrud.com/xdoc/Metal-Cutting-Tools-And-Bits

This guy tends to be the best for uk import:
https://www.ebay.co.uk/sch/m.html?LH_Pr ... os=L39+4SE