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Thread: Thoughts on buy a used Colombo spindle of unknown history?

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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    That goes against everything I have read on this topic. I.e. They all said that, unless you specifically buy a constant torque spindle (which are more expensive) then your torque and cutting power reduces with the spindle speed. If all spindles were capable of full torque even at low speeds then the existence of constant torque spindles would make no sense.

    They also said that spindle torque is largely dependent on the size of the motor and that the stated power ratings tell you little to nothing about torque (and cutting power). That's why a 1hp milling head has superior metal removal to a 4hp router spindle at the same speed. Looking at the GMT spindles (as an example), the ones designed to produce high torque at lower speeds are twice the price of their high speed spindles with the same power rating.

    Is it possible that your ATC spindles happen to be constant torque? They are usually a lot more expensive than MTC spindles so it would it would make sense that they were.

    Take a look at the price difference on the Ugracnc site between their 6000rpm .8kw spindle and their 8,000 - 24,000rpm .8kw spindles.

    https://ugracnc.com/index.php/online...ooled-spindles

    It's another data point to suggest decent lower speed torque is not a standard feature and that higher power does not always equal more torque unless all else is equal.

    It's easy to see how a guy like me could get confused by all this. I think that most of us want it to be easy and intuitive when you choose. We expect a 3kw spindle to be able to cut faster and deeper than a 1kw spindle. The only thing I am positive about now is that it is not that simple. I am 80% sure that the best way to choose for me is to look for a spindle that is designed to have maximum torque in the rpm range I will most commonly use for milling aluminum and to prioritize this above the power rating.

    I haven't yet been able to find any info on how each Colombo model deals with torque at lower speeds. If I find what looks to be a good deal on one, I plan to contact Colombo directly to find out if it's really suitable for my needs in terms of 2000 rpm to 16,000 rpm torque.

    If I can't find a good deal on suitable used premium brand spindle then I am tempted to go with this one:

    https://ugracnc.com/index.php/online...-high-torque-s

    or maybe this one:

    https://ugracnc.com/index.php/online...80v-12000rpm-s



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    You're not going to find a spindle capable of 2000-16000 rpm. You're trying to get the best of both worlds, which doesn't exist. You can either get a low speed spindle (<10K RPM), or a high speed spindle (18K-24K RPM), but not both.

    You can find plenty of threads where people have built solid machines for cutting aluminum, and all of them are using high speed router spindles.

    Gerry

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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    skrubol was right with this: Be careful about reading too much into that.

    In this discussion we should focus primarily on there phase induction motors.

    Quote Originally Posted by Goemon View Post
    That goes against everything I have read on this topic. I.e. They all said that, unless you specifically buy a constant torque spindle (which are more expensive) then your torque and cutting power reduces with the spindle speed. If all spindles were capable of full torque even at low speeds then the existence of constant torque spindles would make no sense.
    When it comes to motors operating under a VFD I'd defer to the manufactures torque graphs which will be rather flat over part of the operating region. As pointed out above sometimes the real limitation is heating which is where water cooling may be of value. For air cooling you have to understand how various fan assemblies work and the effect of RPM on air movement and required power. A little engineering background can be had here: https://www.engineeringtoolbox.com/f...aws-d_196.html. In a nut shel power varies dramatically with RPM thus fans are often undersized when the spindle is running at a low RPM. A common alternative beyond water cooling is to have a separate fan motor running at a constant speed.

    They also said that spindle torque is largely dependent on the size of the motor and that the stated power ratings tell you little to nothing about torque (and cutting power). That's why a 1hp milling head has superior metal removal to a 4hp router spindle at the same speed. Looking at the GMT spindles (as an example), the ones designed to produce high torque at lower speeds are twice the price of their high speed spindles with the same power rating.
    Beyond the fact that you wouldn't run the router at the same speed in aluminum I believe this is misleading as you would need to know the power output of the router at the speed you want to run the spindle. That means consulting the torque charts at a given RPM. You are still talking about power here. A router rated for 4 HP at 30000 RPM will have a different torque value than say one rated to top out at 15000 RPM. In other words you don't have an argument nor even a solution until you run the numbers.
    Is it possible that your ATC spindles happen to be constant torque? They are usually a lot more expensive than MTC spindles so it would it would make sense that they were.
    As stated above the torque will be constant over part of the operating range of the motor and VFD combo. But here is the thing torque isn't important by itself, you really need to know power output.
    Take a look at the price difference on the Ugracnc site between their 6000rpm .8kw spindle and their 8,000 - 24,000rpm .8kw spindles.

    https://ugracnc.com/index.php/online...ooled-spindles
    Now ask yourself how does one get 1 horsepower out of a 6000 RPM spindle? You have to develop more torque thus a larger motor. A larger motor means beefier drive components.

    Take for example some machinery I worked on some time ago. These machines used air bearing spindles to turn small optical components on. The integrated rotor was very tiny as all the motor had to do was achieve a very high RPM. In the case there was little power involved but the point is you don't need massive components to achieve high RPM's and high RPM's means a lot of power is produced at low torque capability. That torque might not be usable in a lot of situations but it doesn't mean that the power calculations are wrong
    It's another data point to suggest decent lower speed torque is not a standard feature and that higher power does not always equal more torque unless all else is equal.
    I think you are a bit confused here. Maybe what might help is running the math yourself, find a motor manufactures engineering data and see what the power output is for a series of RPM's. Also realize that manufactures data has to be read carefully. For example motors can have advertised torque flatnesses over various ranges such as 10:1, 20:1 or 5000:1. Some of those flatter curves are specified with Vector style VFD's only. It really comes back to understanding the specific motor in question. If you can't get valid graphs for a specific spindle you either have to learn by experience or rely upon the data of others.
    It's easy to see how a guy like me could get confused by all this. I think that most of us want it to be easy and intuitive when you choose. We expect a 3kw spindle to be able to cut faster and deeper than a 1kw spindle. The only thing I am positive about now is that it is not that simple. I am 80% sure that the best way to choose for me is to look for a spindle that is designed to have maximum torque in the rpm range I will most commonly use for milling aluminum and to prioritize this above the power rating.
    To an extent it can be confusing but understanding that there are a number of factors to consider here helps. In a nut shell the spindle has to be suitable for the tooling you expect to run in the aluminum molds. In most cases one thinks about smaller diameter tool usage as being common in mold making, especially if a lot of detail is involved, but a mold for a boat or car panel would blow that out of the water. You have to understand the tooling you expect to be using. I'm going a big out on a limb here but I suspect you could benefit from a higher spindle RPM due to the described usage.

    By the way I do hope that you have a solution for coolant/lubricant for his machine because you likely will need it. That will lead to an enclosed machine.

    I haven't yet been able to find any info on how each Colombo model deals with torque at lower speeds. If I find what looks to be a good deal on one, I plan to contact Colombo directly to find out if it's really suitable for my needs in terms of 2000 rpm to 16,000 rpm torque.

    If I can't find a good deal on suitable used premium brand spindle then I am tempted to go with this one:

    https://ugracnc.com/index.php/online...-high-torque-s

    or maybe this one:

    https://ugracnc.com/index.php/online...80v-12000rpm-s
    Well again it is your machine and process but I suspect you will be far better off with a high speed spindle. With aluminum you can do up to 2000SFM that can imply a very high spindle RPM for very small cutters. I'm not suggesting that you will want to do 2000 SFM but manufactures consider it an upper limit in aluminum. So at that end of the spectrum even a 30000 RPM spindle might be considered slow.

    You mentioned a Bridgeport head at some point in this thread. From time to time I have to do a bit of aluminum in the Bridgeport at work. To put is simply that machine can't run the spindle at speeds considered possible for machining aluminum. Not even close really, yet it can get work done. Even so I would never suggest a Bridgeport, with a standard spindle head, for somebody wanting to buy a machine to process aluminum regularly, it wouldn't be cost effective.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by Goemon View Post
    That goes against everything I have read on this topic. I.e. They all said that, unless you specifically buy a constant torque spindle (which are more expensive) then your torque and cutting power reduces with the spindle speed. If all spindles were capable of full torque even at low speeds then the existence of constant torque spindles would make no sense.
    Spindles are generally constant torque, even the cheap water cooled ones. It's VFD's that can be run as constant torque or variable torque. Most of the VFD driven spindles that have torque falloff at more than 1/10th their max RPM either have their VFD set up incorrectly or the VFD has issues that prevent it from running correctly at lower RPM's. Vector drive VFD's can run motors down to 0 RPM with full torque.
    Also, it is 100% true that your cutting power is reduced as you reduce spindle speed below the rated RPM. Torque stays the same.

    They also said that spindle torque is largely dependent on the size of the motor and that the stated power ratings tell you little to nothing about torque (and cutting power). That's why a 1hp milling head has superior metal removal to a 4hp router spindle at the same speed. Looking at the GMT spindles (as an example), the ones designed to produce high torque at lower speeds are twice the price of their high speed spindles with the same power rating.
    Milling heads also generally have some gearing or pulley ratio to reduce RPM and increase torque. If the milling head has it's 1 HP at 2400 RPM it will have 2.5x the torque as a router spindle that has 4HP at 24000 RPM.
    Is it possible that your ATC spindles happen to be constant torque? They are usually a lot more expensive than MTC spindles so it would it would make sense that they were.

    Take a look at the price difference on the Ugracnc site between their 6000rpm .8kw spindle and their 8,000 - 24,000rpm .8kw spindles.
    Assuming they are both constant torque spindles, the 6000 RPM spindle will have 4x the torque of the 24000 RPM spindle with the same power. That's just how power and torque work.
    It's another data point to suggest decent lower speed torque is not a standard feature and that higher power does not always equal more torque unless all else is equal.

    It's easy to see how a guy like me could get confused by all this. I think that most of us want it to be easy and intuitive when you choose. We expect a 3kw spindle to be able to cut faster and deeper than a 1kw spindle. The only thing I am positive about now is that it is not that simple. I am 80% sure that the best way to choose for me is to look for a spindle that is designed to have maximum torque in the rpm range I will most commonly use for milling aluminum and to prioritize this above the power rating.

    I haven't yet been able to find any info on how each Colombo model deals with torque at lower speeds. If I find what looks to be a good deal on one, I plan to contact Colombo directly to find out if it's really suitable for my needs in terms of 2000 rpm to 16,000 rpm torque.

    If I can't find a good deal on suitable used premium brand spindle then I am tempted to go with this one:

    https://ugracnc.com/index.php/online...-high-torque-s

    or maybe this one:

    https://ugracnc.com/index.php/online...80v-12000rpm-s
    You really don't want a constant torque spindle. You want one with a constant power band. This is what the higher end spindles and milling spindles have (milling spindles in VMC's tend to have a much broader range.) This gives you more torque at lower speeds. A spindle that has constant power from 12000 RPM to 24000 RPM has twice as much torque at 12000 than 24000.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Vector drive VFD's can run motors down to 0 RPM with full torque.
    Keep in mind that if the spindle isn't designed for this, it won't last long. You can probably burn up a chinese spindle in a few seconds if you try running it too slow.

    Gerry

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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by ger21 View Post
    Keep in mind that if the spindle isn't designed for this, it won't last long. You can probably burn up a chinese spindle in a few seconds if you try running it too slow.
    Why? If it's not cooled by a shaft mounted fan, and you aren't violating the current rating of the spindle it shouldn't be generating any more heat than while spinning with the same current draw.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Am I looking at this backward by trying to choose a spindle for the material to be cut instead of for the tool size?

    I don't know what is considered "fine detail" in CNC terms but a rifle stock mold like this one is fairly typical of what I'll be making in 6061:

    https://www.stockysstocks.com/wp/wp-...03/M40CF-1.jpg

    I have been assuming that I would want to use 3/8" or 1/4" 1 or 2 flute end mills for roughing at lower speeds and 1/8" or smaller for finishing passes at high speed. Would you guys use smaller diamater cutting tools for the whole thing? Or, to get more to the actual point, are you suggesting that I forget about looking for a spindle capable of low speed torque and do all my milling at 10,000 rpm to 18,000 rpm (or higher)?

    I found torque / power / hp / rpm charts for Colombo spindles and most seem to be constant torque between 6,000 and 18,000 rpm with a drop off between 18,000 and 24,000. Most of the vendors of the cheaper spindles don't provide any torque data at all on their affordable models. Is it possible to work out the available torque with just the power, speed and spindle diamater?



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Stop the press! I found a deal on a refurbished / remanufactured Colombo 7.5kw ER25 300hz / 400hz air cooled spindle. The seller is asking $1100 and it includes a 6 month warranty which should pretty much alleviate any concerns over receiving a turkey when you order a used spindle.

    That seems like a fairly good deal right? I'm feeling good about it. It's a CNC zone member approved brand. The bearings are new. It's light enough that I won't have to worry about upgrading my stepper motors. According to Colombo's helpful torque / power / rpm charts, it produces nearly 3x the torque of the Tormach 770 spindle at aluminum milling speeds.

    The only "concern" is that it is a much more powerful spindle than I had intended. I was looking in the 2.2-3kw range but, apparently, my Nema 10-30r outlet is more than capable of covering the 15a draw and the difference in noise is not significant. So... more power can't hurt, probably.


    So the lesson for me is that there are good deals occasionally, just not on ebay where the same list of over-priced spindles recycles indefinitely with sellers who are immune to reason and logic.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Are you sure it's not a 380V spindle? I don't know if you can run a 10HP spindle on 240V. You probably at least need 3 phase power?

    Although I think I saw someone the other day that's running a similar sized spindle from 240V single phase, and he posted a link to the VFD he's using.

    Gerry

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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Power is work over time. In our case power is measured in Watts or horsepower, work is torque, and time is your spindle RPM. So if you have constant torque along the entire range, then the power is a function of the speed. It should be clear that, if the motor isn't spinning, it is generating NO power, even though it has holding torque. Likewise, power ratings can be confusing, because you can have two motors that have the same rated peak power, but they achieve them at different speeds. So one motor can have higher torque at lower speed, and another lower torque at higher speeds. It is the reason why motors (and engines) are geared down; so that the power output fits the application at hand.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by ger21 View Post
    Are you sure it's not a 380V spindle? I don't know if you can run a 10HP spindle on 240V. You probably at least need 3 phase power?

    Although I think I saw someone the other day that's running a similar sized spindle from 240V single phase, and he posted a link to the VFD he's using.
    I'm sure. It's the first thing I checked as I usually find that deals that look great are often followed by the disappointment of finding out they have power requirements that make them worthless on the used market.

    Colombo spindles are available in 220/230v up to at least 16hp if you have the right breaker:

    RV Series Collet | Colombo USA

    The other thing that is often a source of disappointment is those spindle motors that have no collet. You think "ooh that looks like a nice price" and then you see that the spindle was used by a props company and instead of a collet, it has a large rotating rubber head, or something...

    oh, and don't get me started on those sellers who list them as "working" and then list all the ways in which it's broken.... or the ones who list them as "used" but then say "item is untested". I mean... what are we meant to do with that? Who is going to just take a chance on a $1500 purchase... or.... worst of all, those sellers who can't be bothered to put any info at all. You just have a price and a photo

    This one has power I can use and a collet I have heard of. Plus the seller is reputable. So far, so good.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by louieatienza View Post
    Power is work over time. In our case power is measured in Watts or horsepower, work is torque, and time is your spindle RPM. So if you have constant torque along the entire range, then the power is a function of the speed. It should be clear that, if the motor isn't spinning, it is generating NO power, even though it has holding torque. Likewise, power ratings can be confusing, because you can have two motors that have the same rated peak power, but they achieve them at different speeds. So one motor can have higher torque at lower speed, and another lower torque at higher speeds. It is the reason why motors (and engines) are geared down; so that the power output fits the application at hand.

    It would be far less confusing for me if all sellers provided a torque/ power / rpm chart like Colombo (and some others) provide for each model listed on their websites. As you said, Just saying "it's 2.2kw" doesn't tell you much. It certainly doesn't mean it will cut better than a 1.5kw spindle. It might remove even less material.

    It was incredibly frustrating trying to shop for one because many sellers provide useless and incomplete info like one power rating with no torque info. It gets even more annoying because most don't know very much about their products so you end up with a lot of conflicting info from people who all claim to be experts. It's the same reason why nobody knows which foods are healthy. Self proclaimed experts with opposition views presented as fact.

    I now assume, with all things CNC related, that if a seller can't or won't provide complete info, it is because there is nothing to be proud of. If they offer a choice of 10 spindles and only provide torque info for one, the others have an asthmatic toy motor that couldn't cut a wet paper bag.

    Also, sometimes, when they do provide info like "4 ceramic bearings", it doesn't tell us anything about the quality, apparently. It's really a horrible shopping experience.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    With a warranty that sounds like a great deal.
    You definitely won't get 7.5kW out of it running off a 30A 240V breaker though. Need at least a 50A circuit to use all of it, but even running off a 30A breaker you should be able to get full torque at lower speeds.
    I assume it's 18/24k RPM?



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by Goemon View Post
    It would be far less confusing for me if all sellers provided a torque/ power / rpm chart like Colombo (and some others) provide for each model listed on their websites. As you said, Just saying "it's 2.2kw" doesn't tell you much. It certainly doesn't mean it will cut better than a 1.5kw spindle. It might remove even less material.

    It was incredibly frustrating trying to shop for one because many sellers provide useless and incomplete info like one power rating with no torque info. It gets even more annoying because most don't know very much about their products so you end up with a lot of conflicting info from people who all claim to be experts. It's the same reason why nobody knows which foods are healthy. Self proclaimed experts with opposition views presented as fact.

    I now assume, with all things CNC related, that if a seller can't or won't provide complete info, it is because there is nothing to be proud of. If they offer a choice of 10 spindles and only provide torque info for one, the others have an asthmatic toy motor that couldn't cut a wet paper bag.

    Also, sometimes, when they do provide info like "4 ceramic bearings", it doesn't tell us anything about the quality, apparently. It's really a horrible shopping experience.
    The charts are out there, but unfortunately it's up to you to find them. A lot of the new import stuff are sold by resellers who don't care, because enough people buy them. And a lot of the surplus stuff is sold by liquidators, who just list part numbers and zoom in on the specs because they don't have the equipment to test.

    I still think this is a better decision than the milling head, since you'll be doing finish milling with smaller tools which has to run at higher rpm and feedrates...



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by skrubol View Post
    With a warranty that sounds like a great deal.
    You definitely won't get 7.5kW out of it running off a 30A 240V breaker though. Need at least a 50A circuit to use all of it, but even running off a 30A breaker you should be able to get full torque at lower speeds.
    I assume it's 18/24k RPM?

    It is an 18,000 300hz / 24,000 400hz model. I did have another 4 pole 600hz 18,000rpm option but reading about matching frequencies to material frequencies gave me a nose bleed.

    They don't show the chart for the 230v set-up for this spindle on the Colombo site but they do show it for the 8.9kw 36a model and they indicate that it achieves full power / full speed at 230v:

    http://colombospindles.com/wp-conten...-T-1355011.png

    The 380v and 460v models just use less amps. They don't deliver more power or torque according to the graphs. Or are you saying that I need at least a 50amp breaker to cover a 15 or 30 amp spindle?

    Either way, I was looking at 2.2kw spindles so even at half power the 7.5kw should deliver what I need.

    I am worried about noise but I keep reminding myself that I rarely regret having more power but frequently regret buying too little. It's all going in a walk-in closet and I can sound proof the walls like a recording studio.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by louieatienza View Post
    The charts are out there, but unfortunately it's up to you to find them. A lot of the new import stuff are sold by resellers who don't care, because enough people buy them. And a lot of the surplus stuff is sold by liquidators, who just list part numbers and zoom in on the specs because they don't have the equipment to test.

    I still think this is a better decision than the milling head, since you'll be doing finish milling with smaller tools which has to run at higher rpm and feedrates...

    I'm not sure there will ever be a consensus on this topic. There is definitely two camps that do not agree. There is the old school guys that say, to get a nice finish on aluminum, or any other metal, you need a large heavy column mill with a huge diamater milling head and spindle which is large and heavy enough to reduce all the chatter and whatnot. Then there is the new high speed machining guys that say you can't get a nice finish on aluminum without a super high speed spindle.

    I don't know who is right. I suspect that both of them are and neither. The larger milling heads definitely offer more flexibility. With a speeder, you can use any end mill, face mill or router bit you want and mill at 25,000rpm for smaller bits. The choices for affordable milling heads at my end of the market though... well they aren't that good. There is the Tormach, those 2.2kw 5000rpm induction motor / mechanical spindles from China off eBay, or the 550watt r8 mini milling heads from LMS.

    If I was buying a $150,000 machining center, I would have a 200lb 20hp milling head capable of peeing through diamonds with 5" end mills and I would have an awesome 50,000 rpm Datron spindle too. At my end of the market though, there is a compromise either way I think.

    Between a 7.5kw Colombo and the 1hp Tormach head, the Colombo looks better on paper for my needs. I still think the Tormach 10,000 rpm R8 spindle heads offer a lot for the money though. I have seen them deliver some very nice finishes on milled aluminum. It looks like they cut faster and deeper plus remove more material than most of the Chinese 2.2kw spindles you see demoed on YouTube.

    Anyway, for now, I'm feeling good about my decision. I listened to the advice of those that know and chose a brand that everyone says is good. I have never read anything anywhere that says anything bad about Colombo.

    Also, if it turns out to be all wrong for me, I'll be able to sell it without losing too much cash.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    2 pole high speed spindles are easier to get a drive for, as almost all the VFD's out there will do 400 Hz, but relatively few will go higher.
    I was just saying you'll need more current at the wall to run at full 7.5 kW. 30 A at 240V is only 7.2kW. Then taking into account power factor of the drive and efficiency of the drive and motor, you're probably down in the range of 5kW. That would give you full torque up to 12k RPM though, so still a whole lot better than a 2.2kW.
    For your reference, most 2.2kW spindles with a well programmed VFD should have about .65 Ft-lbs of torque from around 6k to 24k RPM. Yours should have around 2.9 ft-lbs from 1500 or 3000 to 12k RPM and it will drop off (constant power) above that and I'm not sure how it will behave at low speed. Need to be careful of overheating of course with the cooling fan spinning so slowly.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by Goemon View Post
    I'm not sure there will ever be a consensus on this topic. There is definitely two camps that do not agree. There is the old school guys that say, to get a nice finish on aluminum, or any other metal, you need a large heavy column mill with a huge diamater milling head and spindle which is large and heavy enough to reduce all the chatter and whatnot. Then there is the new high speed machining guys that say you can't get a nice finish on aluminum without a super high speed spindle.

    I don't know who is right. I suspect that both of them are and neither. The larger milling heads definitely offer more flexibility. With a speeder, you can use any end mill, face mill or router bit you want and mill at 25,000rpm for smaller bits. The choices for affordable milling heads at my end of the market though... well they aren't that good. There is the Tormach, those 2.2kw 5000rpm induction motor / mechanical spindles from China off eBay, or the 550watt r8 mini milling heads from LMS.

    If I was buying a $150,000 machining center, I would have a 200lb 20hp milling head capable of peeing through diamonds with 5" end mills and I would have an awesome 50,000 rpm Datron spindle too. At my end of the market though, there is a compromise either way I think.

    Between a 7.5kw Colombo and the 1hp Tormach head, the Colombo looks better on paper for my needs. I still think the Tormach 10,000 rpm R8 spindle heads offer a lot for the money though. I have seen them deliver some very nice finishes on milled aluminum. It looks like they cut faster and deeper plus remove more material than most of the Chinese 2.2kw spindles you see demoed on YouTube.

    Anyway, for now, I'm feeling good about my decision. I listened to the advice of those that know and chose a brand that everyone says is good. I have never read anything anywhere that says anything bad about Colombo.

    Also, if it turns out to be all wrong for me, I'll be able to sell it without losing too much cash.
    There are many VMCs out there that have a portal configuration, as much as there are many machines with a column configuration. These VMCs have high HP ratings, but that doesn't mean it's putting out that much, nor is that HP available at all speeds.

    You're also confusing two different operations - roughing/surfacing and finishing. Roughing and surfacing is more efficiently done with larger tools and higher torque/lower RPM. The opposite with finishing - largely done with smaller tools and higher RPM. You don't need a lot of torque to finish because you're removing very little material. The HP ratings on VMCs are high because they have to do both. It is kind of funny to see a 40HP spindle (which is what you'd see in a $150K machine) with a 2mm ball endmill on a shrink collet. But the spindle is only given enough juice as it needs to make the cut. Look at any video online of a VMC doing a finish pass on a mold. Tell me how many you see at a slow federate. Absolutely none - because for finishing of 3D contoured surfaces, they're using small tools with small stepovers at higher feedrates. It may not appear as such since the machines accelerate so fast and smooth. Then look at the same machine surfacing a billet. If it's using a fly cutter, it's likely traveling pretty slow. If it's using a shell mill, it's probably moving very fast.

    Also, a lot of how a tool cuts has to do with the rated chipload of the tool, which with the spindle speed determines the federate. The Tormach spindle head will cut deeper, because it is designed to have low end torque. It will take larger tools than an electric spindle. And some of those tools are not designed to run at high RPMs (like a fly cutter). The electric spindle uses smaller tools, but since its power comes at higher speeds, you're taking smaller cuts, but faster, so you could potentially have a similar material removal rate. And maybe even more, with the high-speed (adaptive) toolpaths now used in CAM such as Fusion360 (or are you buying a CAM software?) Then again, since you mention that time is of no concern when it comes to making the molds, why then have a need or want for deeper cuts?

    It's like this - say we both were given the task of emptying same-sized swimming pools. Only you have two buckets and I have one. Logic may say you would be faster or have more power (do more work over time.) But since I have only one bucket, I could walk twice as fast as you to the drain area. A similar thing happens in machining. See, both views are right. But the VMCs can actually do both.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    HP roughly equals MRR. Doesn't matter whether you're using a 2" face mill or a 1/4" end mill, if you're putting the same HP into the cut, you're removing about the same amount of material. The thing with the Tormach is that it can run near it's peak power at a fairly wide range of RPM's, so it can remove about 3 cubic inches per minute of aluminum with a 2" fly cutter, or a 3/8" end mill (or anything in between.) On a 3HP high speed spindle, first, that's probably close to peak power, so maybe 2 real hp, plus you only get that HP around 23k RPM. So you could only really use a 1/4" or 3/8" EM to max it out, and you're going to have to be able to run at 200+ IPM to do so with a 1/4" EM. Anything larger, and you'll have to run it slower and not have the HP, anything smaller, and you will be up against the loading limitations of the endmill.
    With that 10 HP Colombo anything up to 5/8" (largest that will fit in an ER25 collet,) should run fine in aluminum.



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    Default Re: Thoughts on buy a used Colombo spindle of unknown history?

    Quote Originally Posted by louieatienza View Post
    There are many VMCs out there that have a portal configuration, as much as there are many machines with a column configuration. These VMCs have high HP ratings, but that doesn't mean it's putting out that much, nor is that HP available at all speeds.

    You're also confusing two different operations - roughing/surfacing and finishing. Roughing and surfacing is more efficiently done with larger tools and higher torque/lower RPM. The opposite with finishing - largely done with smaller tools and higher RPM. You don't need a lot of torque to finish because you're removing very little material. The HP ratings on VMCs are high because they have to do both. It is kind of funny to see a 40HP spindle (which is what you'd see in a $150K machine) with a 2mm ball endmill on a shrink collet. But the spindle is only given enough juice as it needs to make the cut. Look at any video online of a VMC doing a finish pass on a mold. Tell me how many you see at a slow federate. Absolutely none - because for finishing of 3D contoured surfaces, they're using small tools with small stepovers at higher feedrates. It may not appear as such since the machines accelerate so fast and smooth. Then look at the same machine surfacing a billet. If it's using a fly cutter, it's likely traveling pretty slow. If it's using a shell mill, it's probably moving very fast.

    Also, a lot of how a tool cuts has to do with the rated chipload of the tool, which with the spindle speed determines the federate. The Tormach spindle head will cut deeper, because it is designed to have low end torque. It will take larger tools than an electric spindle. And some of those tools are not designed to run at high RPMs (like a fly cutter). The electric spindle uses smaller tools, but since its power comes at higher speeds, you're taking smaller cuts, but faster, so you could potentially have a similar material removal rate. And maybe even more, with the high-speed (adaptive) toolpaths now used in CAM such as Fusion360 (or are you buying a CAM software?) Then again, since you mention that time is of no concern when it comes to making the molds, why then have a need or want for deeper cuts?

    It's like this - say we both were given the task of emptying same-sized swimming pools. Only you have two buckets and I have one. Logic may say you would be faster or have more power (do more work over time.) But since I have only one bucket, I could walk twice as fast as you to the drain area. A similar thing happens in machining. See, both views are right. But the VMCs can actually do both.

    I've heard this point of view and the opposite one. I'm not saying you are wrong (or right), just that there are various opinions and I have no way of knowing who is right as everyone sounds like they could be when you know as little as me.

    I am not confusing finishing and roughing btw. I understand the difference and that high speed machining with smaller bits has been adopted by many manufacturers to improve efficiency and whatnot. As I said, in an ideal world, I would have both (and a super-model wife). The opposing opinions start when you have to choose one or the other for people like me...

    if if I was milling steel, everyone would agree I needed a CNC mill. If I was only doing wood, everyone would agree it should be a CNC router. Aluminum has the world divided like "fushion cuisine".

    Anyway, as I've decided to go with the high speed option, it sounds like that is consistent with what you would have recommended so there is nothing for us to disagree on (at least in this group). I have stopped asking questions on practical machinist as all the opposing opinions have started sending me a little insane. People can't even agree what high speed machining means.



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Thoughts on buy a used Colombo spindle of unknown history?

Thoughts on buy a used Colombo spindle of unknown history?