[Tornfeldt]

Hi
Im about to buy a 3axis 6040 from ebay. (the newer one with black control box and ready installed limit switches)
My aim with this machine is mainly to do hobby stuff in aluminium (clamps, brackets,fittings e.t.c), but occasionally some woodwork also.

I have spent some time investigating the pros and cons with this machine, and im aware that i probably need to do some upgrades to the electrical system. That is ok by me and my budget :-)

But. the only question i still haven´t found a good answer to, is the spindle strength.

Will a 1.5kw spindle be enough for aluminium, or should i go for the 2.2kw spindle ?

thanks in advance

[ger21]

Those machines are so lightweight that either of those spindles has more power than you can use.Having said that, you'll typically get longer life from a larger spindle, which will usually have larger bearings that can handle higher loads.

[dharmic]

2.2 I think has the er20 collets which mean larger tools.

And yeah, your frame and steppers will fail before either of these spindle powers

[Tornfeldt]

Thanks for the quick replies.. :-)

I think i will go for the 2.2kw spindle.

Since both spindles are probably overkill for my applications, the 2.2kw seems more "futureproof".

I´m not sure about the er20 collet, (it says er11 in the description, but they are usually copy/pasted between the different models, so i can´t really trust that info). If i´m lucky it will be an er20 and that will give me more options for end mills. If not.. Well it is the same collet size as a 1.5kw anyways, so there is atleast no drawbacks.

If i can hope for a longer life out of the bearings, that is a bonus that makes up for the extra cost.

well.. i suppose i will take the chance with this machine :-)

I will post a quick review when i have got the machine. I suppose there are many newbies like me that might be interested :-)

[jfong]

Mine is the 2.2kw with ER20. At the time, the price difference was negligible so I went with the bigger spindle. I'm glad I did, since my Onsrud surfacing bit I bought is 1/2" shank.

[A_Camera]

Thanks for the quick replies.. :-)

I think i will go for the 2.2kw spindle.

Since both spindles are probably overkill for my applications, the 2.2kw seems more "futureproof".

I´m not sure about the er20 collet, (it says er11 in the description, but they are usually copy/pasted between the different models, so i can´t really trust that info). If i´m lucky it will be an er20 and that will give me more options for end mills. If not.. Well it is the same collet size as a 1.5kw anyways, so there is atleast no drawbacks.

If i can hope for a longer life out of the bearings, that is a bonus that makes up for the extra cost.

well.. i suppose i will take the chance with this machine :-)

I will post a quick review when i have got the machine. I suppose there are many newbies like me that might be interested :-)

Beware of another thing or two...

The 2.2kW VFD draw pretty much current, so before you pay for such huge machine, make sure you have enough current in your home. My circuits are 16A maximum, so I wouldn't even dream about getting a 2.2kW motor and VFD. The 1.5kW I have requires about 14A, my vacuum cleaner takes 8A so I can't have them both on the same circuit. My CNC takes about 1A, so that is OK to share, but that's about all.

The second thing you should check and think about before ordering is that the 2.2kW motors weigh quite a bit more than the 1.5kW motors. I went for a 1.5kW, 65mm diameter motor and that weights 2.6kg plus an additional 0.5kg for the holder, so that is pretty heavy already. As far as I know, a 2.2kW weights about 5kg alone, and the holder is also about 1kg for an 80mm. So, check your steppers, there is a lot of dead weight they must carry around and lift all the time. I would not bother with a 2.2kW motor for such small and light CNC.

ER11 is good if you only aim at small tools. The limit is 7mm, but in reality I think 6mm shank diameter is the maximum. If you ever plan to use large tools, typically used for wood, then aim at ER20. I like the ER11 because it is very small, and because I doubt I'd ever need to use large tools. I believe collet precision is higher in the small ER11 nuts, so that is what I need, but consider this also before buying.

[dharmic]

Ah yeah. My 2.2kW is the 220/240V version so is only 10A. I believe the options on the OmioCNC had a 110V 2.2kW spindle which was ER-16 and the 220/240V version at ER-20.

[jfong]

I put in a separate 20amp 220v just for the spindle.

[Tornfeldt]

Thanks for the great responses i get for this topic..

Very interesting that you bring up the current issue. I had thought about it, but then ignored it as "no problem".

But now when i hear your experiences, especially A_Camera. (It seems like he is using the Swedish electrical system building codes, and i live in Finland, so we are practically neighbours).
I live in a quite old house with the electrical system quite messy (it has been re-routed many times), so I have no idea what ampere my fuses in the garage are. (probably 16A) The only thing i know for certain is that i am able to run my 2kw heater and a small MIG-welder at the same time.

I called a friend of mine that is very skilled in electrical stuff (swedish : starkströmselektriker), and he told me that normal 230v/16A fuses are supposed to hold about 3kw. So i will be quite close to the limit.
But he is also quite certain, that the fuses will hold. (luckily he also offered to make a separate outlet just for the router if it is necessary. (i like having friends))

The weight issue of the spindle is also something that i have to live with. I am planning to upgrade the electrical system (if necessary), and that includes the motors.
A longer life and the possibility to be able to use 8 or 10mm shafted endmills, makes it all worth taking the risk of the 2.2kw spindle.

But if i look it the other way around.. The absolute worst case scenario is that i need to buy a 1.5kw spindle. (about 150€ extra)

[dharmic]

Something to consider - although your 2.2kW spindle may draw a million amps at full load, chances are you're never going to bog it down to a tenth of that. They ship here with a standard power socket where, in Australia, anything over 10A per appliance needs a special 15A plug with a larger earth and, I believe, a dedicated circuit.

You could put an 8A breaker onto the unit between it and the power cord so that it tripped before it took anything else out, and just rely on the fact you're unlikely to go anywhere near full power draw.

[Stigoe]

I live in Norway and i have a 16A circuit for my whole workshop. So far i haven't really loaded the spindle much, but I run the CNC with 2.2 kW spindle, vacuum cleaner, PC with monitor for the CNC, main PC with dual monitors and lighting without any problems.

[A_Camera]

Ah yeah. My 2.2kW is the 220/240V version so is only 10A. I believe the options on the OmioCNC had a 110V 2.2kW spindle which was ER-16 and the 220/240V version at ER-20.

That must be on the output (motor) side, not the input requirements of the VFD. 2.2kW 220V = 10A... but that's not what is needed to feed it. Unfortunately, that data is never given by the cheap Chinese VFD manufacturers. I bought a Bosch Rexroth and the manual of that it is pretty clear about this.

Attachment 318832

So in Australia, if you run it on one phase 230V then the input current requirements for a 2.2kW should be around 17A, not 10A. If you run it on three phases than the input current need is around 6A. Of course, this is not the same that it always draws this much, probably it is highly dependent on how you are using your mill, what you mill and how hard, but that is the specification.

[A_Camera]

I live in Norway and i have a 16A circuit for my whole workshop. So far i haven't really loaded the spindle much, but I run the CNC with 2.2 kW spindle, vacuum cleaner, PC with monitor for the CNC, main PC with dual monitors and lighting without any problems.

That's cool. It probably means that I won't have any problems with my 1.5kW. Anyway, just my vacuum cleaner alone takes half of what is available in my wall plug, since I also have 16A in every circuit, so if I can run the CNC and everything else from the same plug then I'll be happy. Never the less, the specifications say differently, and if you really run all that from the same 16A then you are not following the specs.

[jfong]

On my Chinese VFD, there is a setting that can be changed to display current on the LED front display. Maybe that can help figure out actual mains current usage.

[A_Camera]

Thanks for the great responses i get for this topic..

Very interesting that you bring up the current issue. I had thought about it, but then ignored it as "no problem".

But now when i hear your experiences, especially A_Camera. (It seems like he is using the Swedish electrical system building codes, and i live in Finland, so we are practically neighbours).
I live in a quite old house with the electrical system quite messy (it has been re-routed many times), so I have no idea what ampere my fuses in the garage are. (probably 16A) The only thing i know for certain is that i am able to run my 2kw heater and a small MIG-welder at the same time.

I called a friend of mine that is very skilled in electrical stuff (swedish : starkströmselektriker), and he told me that normal 230v/16A fuses are supposed to hold about 3kw. So i will be quite close to the limit.
But he is also quite certain, that the fuses will hold. (luckily he also offered to make a separate outlet just for the router if it is necessary. (i like having friends))

The weight issue of the spindle is also something that i have to live with. I am planning to upgrade the electrical system (if necessary), and that includes the motors.
A longer life and the possibility to be able to use 8 or 10mm shafted endmills, makes it all worth taking the risk of the 2.2kw spindle.

But if i look it the other way around.. The absolute worst case scenario is that i need to buy a 1.5kw spindle. (about 150€ extra)

Please note that so far I have ZERO experience with any VFD, just read the specs of what I bought, but still waiting for it to be delivered. The reason why I bought the Bosch Rexroth was partially the very fact that Bosch is expected to follow EVERY requirement in EU and Sweden, and after I checked out their manual, compared with the cheap Chinese VFDs I came to the conclusion that there is no way I'll buy those eBay VFDs. The manual is like night and day... Another reason was that since almost everyone seems to buy the Chinese eBay inverters, I actually thought that buying a brand, a professional quality would ruin my economy, but after checking out on eBay and the Internet, I realized that this is not the case at all, even if the Bosch is a bit more expensive, it is very far from unreachable in price, so I was about to hit the "Buy now" button when I accidentally found a UK company selling it for a very low price, so I bought it from them. I have already paid, but not yet received, so I hope the company is not a fake, but I am sure it is a serious company, so I am not really worried. Anyway, as I said, I still have no experience with a VFD...

Regarding your friends comment about the power capacities of 16A, that is easy to calculate, since V * I = P so 230V 16A = 3680W in other words, he is right, but...

That equation is not valid for an inverter, it is the maximum power of your wall plug. The inverter converts that single phase into a three phase 2.2kW, you can't just take 2.2kW and say that that is less than 3.6kW so that is fine. Remember that your motor is three phase and EACH phase is 2.2kW...

Anyway, you may not need to buy a new, weaker motor if you'll have trouble running the 2.2kW... depending on your inverter, you may have the possibility to limit the output current, in which case you can still use your motor but it will be "crippled" so it will not have the maximum possible power. My inverter has a setting for that, check your manual if you are not sure.

BTW, I bought this cable:

http://www.conrad.se/Sl%e4pkedjekabe..._90694_6140110

...just in case you can't easily find something better. Though, according to my manual, a 2.2kW motor should use a 4mm2 not a 2.5mm2.

[A_Camera]

On my Chinese VFD, there is a setting that can be changed to display current on the LED front display. Maybe that can help figure out actual mains current usage.

I think that display is only for the motor current, not the input current. Never the less, to measure the input current is very easy, there are cheap energy meters which can be plugged in into the wall, between a machine and the wall plug, showing mains voltage, used current, used power and kWh, run time, costs and some other things.

Anyway, what would be interesting to know if there is a setting to limit the current.

[jfong]

I think that display is only for the motor current, not the input current. Never the less, to measure the input current is very easy, there are cheap energy meters which can be plugged in into the wall, between a machine and the wall plug, showing mains voltage, used current, used power and kWh, run time, costs and some other things.

Anyway, what would be interesting to know if there is a setting to limit the current.

I wasn't sure, lost the VFD manual some time ago. I have to borrow the kill a watt meter from my brother but I'm not sure if his is 220V compatible. He also has my fluke AC clamp on amp meter which I need to get back. When I get a chance, I'll run some tests.

[tjbaudio]

******Please note that so far I have ZERO experience with any VFD,******

That equation is not valid for an inverter, it is the maximum power of your wall plug. The inverter converts that single phase into a three phase 2.2kW, you can't just take 2.2kW and say that that is less than 3.6kW so that is fine. Remember that your motor is three phase and EACH phase is 2.2kW...

I do have education and experience in this. The specifications for power (watts) is total system power. If it is single phase then that power is delivered over 2 wires or 3 wires if split phase. If it is 3 phase then the power is delivered over 3 wires (delta connection, most common for motors) or 4 wires (Y connection, less common for motors.) A 2.2kW motor is going to be 2.2kW regardless. If it really was 2.2 kW per phase then it would be marketed as 6.6 kW!

The math is more complex for 3 phase since the 3 legs are 120 deg out of phase with each other. This leads to using trigonometry to figure out current draw. Also keep in mind efficiency and power factor can increase the current needed.

[A_Camera]

I do have education and experience in this. The specifications for power (watts) is total system power. If it is single phase then that power is delivered over 2 wires or 3 wires if split phase. If it is 3 phase then the power is delivered over 3 wires (delta connection, most common for motors) or 4 wires (Y connection, less common for motors.) A 2.2kW motor is going to be 2.2kW regardless. If it really was 2.2 kW per phase then it would be marketed as 6.6 kW!

The math is more complex for 3 phase since the 3 legs are 120 deg out of phase with each other. This leads to using trigonometry to figure out current draw. Also keep in mind efficiency and power factor can increase the current needed.

The math is more complex for 3 phase, that's for sure you are right about. Read your VFD specification once again, that is if you have one... Anyway, it is pretty obvious that the 1.5kW Rexroth VFD (1K50 model) I am waiting for is specified to be able to provide an output current of 6.1A at 240V and if you run that VFD on single phase 240V it will require 13.5A. Now, since the efficiency of the VFD (this specific VFD) 95% the 6.1A simply must be per phase, it can NOT be total output because where is the rest of the current gone in that case? 95% 13.5A is 12.825A, so about 0.6A is heat and loss, but what about the other missing 6.725A between input and output?

Attachment 318900

It is pretty obvious that either Bosch is totally wrong and not know enough about their own VFD or you are missing something, because Bosch clearly claims that the input current for my VFD is 13.5A at 240V. Of course, before you correct me, I know, my mains is 230V, so that input current need will be increased to about 14.1A

You might have an education and experience in this, but if that is true than you should educate us and explain why am I wrong and why Bosch is wrong in their specification, not just emphasize what I don't keep a secret, that I am still waiting for my VFD to arrive, which is why my discussion is still purely theoretical. That comment, which you emphasized with all those stars, are meant to be read as "I am still waiting for my VFD, so I can't measure anything, and since I have never had a VFD before, I don't have any experience with one." That's all. It does not mean I don't have an education in this, even if my electrical education took place more than 40 years ago, I hardly think Ohms law have changed...

I don't understand why you mention Y connection at all. The VFDs we are discussing, and the motors we use as CNC spindle motors are all delta connected. The fourth wire is protective earth, NOT neutral. So please, don't increase the confusion here, because if you really have education in this than you should know this.

Also keep in mind that efficiency of a motor is not interesting because REGARDLESS of that, the MAXIMUM current of the VFD is already specified by the manufacturer of the VFD. We are not trying to find a VFD for a given motor with a given, fixed power here, in which case you must look at that motor efficiency, but we discuss a VFD with an already specified parameter.

I'd appreciate if you'd use your education and explained why am I wrong, not just claim that you are right. Ripping apart my answer and empasize/twist words is pretty rude in my opinion. I have no problems in being proven wrong, but claiming that "I do have education and experience in this." is a pretty lame proof. Sorry.

In short, if I am wrong please tell me why. Not that you know better, because that's not very educative.

[A_Camera]

Something to consider - although your 2.2kW spindle may draw a million amps at full load, chances are you're never going to bog it down to a tenth of that. They ship here with a standard power socket where, in Australia, anything over 10A per appliance needs a special 15A plug with a larger earth and, I believe, a dedicated circuit.

You could put an 8A breaker onto the unit between it and the power cord so that it tripped before it took anything else out, and just rely on the fact you're unlikely to go anywhere near full power draw.

It may be so that a spindle is never really loaded enough to take maximum current, that is true, but it is also true that if you run a 2.2kW spindle on single phase 10A than you don't meet the current requirements, at least not according to the Rexroth manual unless you can have about 19A available in that plug. Of course, that doesn't matter if you know you never reach that.

BTW, I measured my vacuum cleaner, that is 2.2kW single phase, and it uses 8.5A so that is 1.955kW measured, so 89% efficiency. It means that it is probably not possible to use the 1.5kW spindle on the same circuit because it may trip the circuit breaker if the spindle runs into a difficult moment... so I will definitely measure before I'll run on the same circuit.