[davida1234]

There are people here on the Zone that have been using Gas strut's for years without any problems.

Hi Mactec54 - Going off this comment of yours, I went to McMaster's site and all of their struts have a limit of 6 cycles per minute. Would you know if those people are using gas struts on slower moving mills or faster routing types with tens of up and downs a minute?

[mactec54]

Hi Mactec54 - Going off this comment of yours, I went to McMaster's site and all of their struts have a limit of 6 cycles per minute. Would you know if those people are using gas struts on slower moving mills or faster routing types with tens of up and downs a minute?

First you have to get the right type of Gas spring, so that it works basically, just like an air cylinder. which you can use also.

Many different CNC machines use Gas springs, you have to look at the companies that manufacture the different types, commodity Gas struts are not what you would be using.

https://www.cnccookbook.com/improve-...install%20them.

[Zorbit]

The springs found on kids home trampoline would be a lot easier to use. Probably longer lasting too.

[peteeng]

Hi - I used an automotive gas spring on my first machine and it worked fine for 3 years then I sold the machine, but I had to take a scale to the store and measure their loads as the spec'ed load was incorrect. My current machine has an electric motor brake on it and its so much better, no bracketry, reliable . Peter

[mactec54]

Hi - I used an automotive gas spring on my first machine and it worked fine for 3 years then I sold the machine, but I had to take a scale to the store and measure their loads as the spec'ed load was incorrect. My current machine has an electric motor brake on it and its so much better, no bracketry, reliable . Peter

A Gas Spring is normally there to assist with the weight of the Z axis, and so the motor has a balanced load in both directions, this makes for a smoother Z axis action, a Brake only stops the head from moving when power is off, the Gas Spring does both.

[peteeng]

Yes Mactec - But when the Z axis system is strong enough to lift the Z axis many fold why bother balancing the system? It will not necessarily be smoother unless you are trying to have an extremely fast Z motion and then inertial loads come into play. But that's extreme, way past hobbyists ands makers accelerations. Smoothness has lots to do with mechanical precision (stick slip and backlash) & electronic jerk control vs just being in balance...Peter

[mactec54]

Yes Mactec - But when the Z axis system is strong enough to lift the Z axis many fold why bother balancing the system? It will not necessarily be smoother unless you are trying to have an extremely fast Z motion and then inertial loads come into play. But that's extreme, way past hobbyists ands makers accelerations. Smoothness has lots to do with mechanical precision (stick slip and backlash) & electronic jerk control vs just being in balance...Peter

Your lack of experience in machine building is at play again. Even Hobbyists that use Gas Springs, are because there Z axis is to heavy for the motors, that they can use, Axis Smoothness comes from the drive motor seeing the same load in both directions, most hobby builder want to be able to do 3D machining with ease at a good speed, ( 100 / 200 IPM Plus ) this is another reason Gas Springs are good if they are needed.

[JayneV]

Hi everyone,

After going back and forth between belt drive and direct drive ballscrews. There is a valid argument for using either method and I have finally settled on direct drive. I just placed an order for the linear rails and ballscrews, so there will be no more changing my mind .

[peteeng]

Ah Mactec your disrespect is noted again... and your comment that "hobbyists" get the motor sizing incorrect is correct. If the motor/drive system is correctly sized then balancing is not needed on small/medium machines. Smoothness does not come from "seeing" the same load in two directions and in reality the load is not the same going up or down anyway, smoothness is a system attribute not a load attribute...

Well done Jayne - onward to new stuff. Peter

[JayneV]

Hi....

New question........ What type of spindle is recommended for a machine like mine?
I have seen that many people opt for one of those 2.2kW water cooled spindles through the Asian online vendors. The 2.2kW spindles have an ER20 collet which might be more useful than the ER11 collet on the smaller spindles. I have seen some specs for these spindles saying they can operate from 0-24000rpm and others saying about 8000-24000rpm. How important is the speed range? Is there a better option in a similar price category that is a better option for wood router that can also (hopefully) cut aluminium?

I want to figure out how to adjust the tramming and it would be helpful to know what the spindle mount will look like. Currently thinking about using eccentric bushings (similar to what is used on my 3D printer), or a pivot pin through the spindle bracket and Z plate with some grub screws to rotate the bracket left and right.

[mactec54]

Ah Mactec your disrespect is noted again... and your comment that "hobbyists" get the motor sizing incorrect is correct. If the motor/drive system is correctly sized then balancing is not needed on small/medium machines. Smoothness does not come from "seeing" the same load in two directions and in reality the load is not the same going up or down anyway, smoothness is a system attribute not a load attribute... Peter

No disrespect what so ever just the facts you can fool some people with all your theory, but have no experience to back it up.

[mactec54]

Hi....

New question........ What type of spindle is recommended for a machine like mine?
I have seen that many people opt for one of those 2.2kW water cooled spindles through the Asian online vendors. The 2.2kW spindles have an ER20 collet which might be more useful than the ER11 collet on the smaller spindles. I have seen some specs for these spindles saying they can operate from 0-24000rpm and others saying about 8000-24000rpm. How important is the speed range? Is there a better option in a similar price category that is a better option for wood router that can also (hopefully) cut aluminium?

I want to figure out how to adjust the tramming and it would be helpful to know what the spindle mount will look like. Currently thinking about using eccentric bushings (similar to what is used on my 3D printer), or a pivot pin through the spindle bracket and Z plate with some grub screws to rotate the bracket left and right.

For your spindle 0-24,000 does not exist, in these types of High speed 400Hz / 800Hz spindles,( this is just a sales thing and bad advertising ) all water cooled spindles have a minimum speed of 6,000 RPM air cooled have a higher minimum speed, unless they have an electric fan, the one exception is the G-Penny spindles, they have a minimum of 3,000 RPM only because of there motor design. I doubt that they can cut much at that low RPM though.

Spindle size will depend on your power supply you have a whole machine, and with a 2.2Kw spindle and single Phase Power supply you need a minimum of 25A supply just for the spindle so the average machine normally needs a 30A minimum supply, with a spindle this size.

More spindle Hp is always going to be better, if you have the Ac power supply Amps to drive it. ?

Things to look in spindle choice, the Amp rating of the spindle, it has to be in the range of 8.5A up to 10A for that size spindle, if advertised as lower Amp rating, then this is not a true 2.2Kw spindle, G-Penny is one of the better spindles to look at.

Spindle option, Ceramic Bearings if you can afford that option, will out last the steel Bearing by 2 to 1 so an easy choice, they also take more abuse than the steel Bearings.

?Traming is a subject by it's self, which can be simple or complicated. once you decide on a spindle and spindle mount then you can design the traming into the mount.

[JayneV]

Hi Mactec,

I actually discovered the G-Penny spindles last night, they look pretty decent.

Your power supply figures are correct for countries with 110V power. I am in Australia, we have 240V power so for the same kW spindle, the current required here is approximately half of what is needed at 110V. I have a dedicated 15A circuit in my garage which will be used for the CNC.

[mactec54]

Hi Mactec,

I actually discovered the G-Penny spindles last night, they look pretty decent.

Your power supply figures are correct for countries with 110V power. I am in Australia, we have 240V power so for the same kW spindle, the current required here is approximately half of what is needed at 110V. I have a dedicated 15A circuit in my garage which will be used for the CNC.

There is no 110v supply in NA it is 120v / 240v single phase which is in all homes and small businesses

In the US. 240v single phase is the same as what you have, except yours is 50Hz, USA is 60Hz, the numbers are correct, A 240v / 15A single phase circuit will not drive a 2.2Kw 400Hz spindle.

The snip is from one of many VFD Drive companies, this shows you the input Amps and the output Amps for the motor being used

For single Phase to 3 Phase which is what your Spindle Motor is, you have a simple calculation of 1.73 x10=17.3 Amps plus the safety factor required by code =25.95Amps for the circuit, which you could squeeze by with 25A circuit, so you will need a 30A circuit for your whole machine double of what you have. this is normal for all home shop build's like this.

So any VFD Drive and spindle motor you choose it will roughly require 2 x the input Amps as the output plus the safety factor required by Code, that can be anywhere from 125% up depending on the type of load, so check your electrical code requirements for a 30A circuit, for cable size Etc.

[JayneV]

I’m not sure I’m understanding this right. If the spindle is rated at 2.2kW and the input supply requirement is 220V / 23A (for the above example), that means 220x23=5060W or just over 5kW is the input power the VFD needs to produce an output of 2.2kW to the spindle. That is less than 50% efficiency. I have zero experience with these VFD’s, have I made a mistake? Does the VFD get extremely hot to dissipate the remaining 2.8kW that doesn’t make it to the spindle?

[mactec54]

I’m not sure I’m understanding this right. If the spindle is rated at 2.2kW and the input supply requirement is 220V / 23A (for the above example), that means 220x23=5060W or just over 5kW is the input power the VFD needs to produce an output of 2.2kW to the spindle. That is less than 50% efficiency. I have zero experience with these VFD’s, have I made a mistake? Does the VFD get extremely hot to dissipate the remaining 2.8kW that doesn’t make it to the spindle?

It's not the VFD Drive, and has nothing to do with efficiency, VFD Drives are vey efficient, the Output is 3 Phase @ 10A the Input is Single Phase, so to make it simple, the Input supply has to make up for the missing Phase, which means more juice Amps are needed to make up for that missing Phase

!.73 to be exact, times the output Amps, that the motor being driven requires, this is what the VFD Drive needs at the Input to make up for the missing Phase.

Normally a VFD is quite cool running, they have a fan that is on when it is running, they are very efficient in operation, it will not draw that much power ( Current ) unless under full motor load, and when starting

So the whole deal is you have a Single Phase supply, if you had 3 Phase supply then this would not be an issue.

[JayneV]

I understand the conversion from 1ph to 3ph, what I'm not clear on is the way the specs are written. Is the 10A ouput per phase or total? If it is 10A per phase, wouldn't the power rating of the spindle be 220V x 10A x 1.732 = 3810W (assuming a power factor of 1 to keep things simple)? So working backwards for a 2.2kW spindle....2200W / 220V / 1.732 = 5.77A per phase.
This is a link to a machinery supplier here in Oz that sells 1ph-3ph converters https://www.machineryhouse.com.au/E150. In the description and the specs further down the page, they talk about the 2.2kW version being able to plug into a standard 10A outlet and the 3kW version into a 15A outlet. 10A outlets are the standard size in all households. I'm just confused with the power rating and the current draw figures advertised with these spindles.

Worst case, I will ask an electrician friend to run a second 3ph circuit to my garage. My house already has one 3ph power coming in from the street to run our air conditioning system.

[mactec54]

I understand the conversion from 1ph to 3ph, what I'm not clear on is the way the specs are written. Is the 10A ouput per phase or total? If it is 10A per phase, wouldn't the power rating of the spindle be 220V x 10A x 1.732 = 3810W (assuming a power factor of 1 to keep things simple)? So working backwards for a 2.2kW spindle....2200W / 220V / 1.732 = 5.77A per phase.
This is a link to a machinery supplier here in Oz that sells 1ph-3ph converters https://www.machineryhouse.com.au/E150. In the description and the specs further down the page, they talk about the 2.2kW version being able to plug into a standard 10A outlet and the 3kW version into a 15A outlet. 10A outlets are the standard size in all households. I'm just confused with the power rating and the current draw figures advertised with these spindles.

Worst case, I will ask an electrician friend to run a second 3ph circuit to my garage. My house already has one 3ph power coming in from the street to run our air conditioning system.

If you already have 3Phase then they can most likely can tap off another line with it's own Breaker, as you will have a 3 Phase Power meter, that Phase converter is 240v to 415v and a lot of money and won't do what you want, there is no magic, you can't get anything for free when it comes to power requirement's.

As you already know 240v to 415v the output of the converter would have half the amps at 415v to the 240v single phase supply

I have a Phase Perfect Converter it is 98% efficient, it still need 200A Single Phase supply to make 96Amps 3 Phase, which is the same in reality as your VFD Drive requirement's. when using a Single Phase supply. and needing 3 Phase.

[Zorbit]

Worst case, I will ask an electrician friend to run a second 3ph circuit to my garage. My house already has one 3ph power coming in from the street to run our air conditioning system.

Most people run these from an ordinary household supply with no problems, there isn't really 2.5kw of power evaporating in the VFD.

Re the er11 / er20 - I'd go for the er20 for better tooling choice. Most router bits will be quite small, 1/2" / 12mm are the biggest I regularly use, but occasionally you might want to use a tapered tool to cut draft angles and useful sizes are often on 16mm shanks, so er25 would be good.

[JayneV]

Yes, I have a 3ph meter in the meter box at home and adding a new 3ph circuit on its own breaker to the garage is possible. I’d have to get a quote from my electrician friend to see how much that will cost. I don’t expect it to be very cheap, because the meter is at the opposite end of the house to the garage so will means a long cable run. The cable alone will probably cost more than I’d like to spend, but I’ll ask for a quote anyway.

The phase converter I linked previously was meant only as an example. I forgot to factor in the higher output voltage, my apologies. Such a converter would be pointless for me anyway, since my house already has 415V 3Ph power available at the meter box.

I’m still not clear with how current and power are defined when asking about 3ph. So, using the 2.2kW spindle as an example, it is rated at 10A and 2.2kW, so do those numbers refer to each phase? In other words, does each of the three windings require 10A, or is the net current draw 10A with each winding drawing 10/1.732=5.77A? I’m a bit rusty with my 3ph theory.