# Where to next?



## bakrch (Dec 4, 2019)

I purchased a "turnkey" CNC PM-25MV from ProCut CNC to make some parts that I had developed. There was much regret in that as the machine had to be torn down and reassembled properly before it was even usable.  I will spare the details, just beware of their lack of pride if you choose to deal with them.

A Chinese PM1236 was also purchased (directly from PM) to aid in making said parts. With the exception of replacing some cheap hardware it has served me quite well.

Sales have slowed just shy of 2 years later, machines are paid off and they even put a new roof on my house. Now looking at about $6k surplus to put back into the hobby shop that basically built itself out of need. Now I would like to focus on what I actually want.

*PM-25 CNC* - Not as rigid as I would like. The column had to be shimmed to a compound angle to get it square, close to 1/64" one way and about .0025 the other way. After it was dialed in my only issue was the control/electronics being somewhat unreliable. KL5056 stepper drivers would alarm from time to time and shut down usually the X-axis motor and on rare occasions the Y. Those drivers have been replaced, and the alarming only happened once since Sept. Forgive me here, but I am basically an idiot with anything to do with controls/electrical ... I do not have anything profound to say here. In short, I would definitely want to incorporate servo motors in the future build (_i.e._ Clearpath SDSK). It has been tempting to just add them to my current setup, but I have resisted so far knowing my next machine would likely not use Nema 23 like this one does.

It is quite a capable machine, but I do not feel great about putting more money towards it when I could just start over with something more robust that will suit me for many years to come. As Matt has mentioned before, the PM25 is great for the price point, but it is still at a price point. My vision sees me starting with a better quality base machine.

The *833T-V *and *728VT* are prime candidates, but obviously there is more support for the *940M* to aid me along at this point. I would look elsewhere, but as a professional moving into the hobby arena, I have to just stick with what I know at this point until more information comes along.  My goal is to also use this mill for CNC lathe work, including threading ... so I would probably be better off grabbing a gear head to start with. Not sure if there is a way to control the stock spindles as you could an aftermarket VFD.

As for Chinese vs. Taiwanese quality, I work with several Taiwan made lathes and knee mills on a daily basis at my day job. If I am to draw any parallels from these anecdotes, going with a Taiwan machine will probably net me something that is actually square from the factory but will still have most of the same quality issues as its China-made counterpart. This has me leaning toward the 833T or T-V over the 940M.

It would be great to buy a conversion kit, where I do really want to focus my learning is on the controls and electrical end of things. There is MUCH for me to learn, and my goal will be to become somewhat educated on that end. Right now I am totally lost, haha.

Mach 3 also sorta drives me insane, so I would like to move toward either Acorn or LinuxCNC (most seem happy with those) and learn how to get that set up as I am foreign to both.

I would love to hear thoughts if anybody can help nudge me out of decision paralysis!


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## JimDawson (Dec 4, 2019)

The first question is: How much room do you have for a machine?

If you can handle a full size BP clone then that's the way to go.  My personal preference for a single machine in the shop would be a manual/CNC machine.  There were a number of 10x50 table BP clone factory CNC/manual machines imported by Webb, Eagle, and a couple others in the late 80's. Most had Anilam controllers.  These were made by Topwell in Taiwan, high quality machines.  I picked mine up for $1000, mechanically near new, but a dying controller.  I see them on EBay and Craigslist occasionally.  Something like this is a very easy retrofit with modern controls, and most of the hard work is already done.

Any CNC machine that started out life as a CNC would be a good choice.  The controls is the easy and inexpensive part.

Now for the controls, Centroid Acorn or the other Centroid products are a good choice.

Depending on the application, the ClearPath or DMM servos https://store.dmm-tech.com/ would be a great choice.  For most applications DMM would be my first choice.  I have used both, and have DMM servos on my lathe.  I think the DMM units are a better value, and have more flexibility in how they are controlled.  Both are fully compatible with Centroid Acorn or LinuxCNC.

As far as turning on a mill, it's doable.  Just build a headstock, like a 4th axis, and attach gang tooling to the quill or head.  It's not a CNC lathe, but will certainly work for light turning.  If you power it with a servo motor you would have full mill/turn capability. For small work I have put a part in the spindle and clamped tooling in the vice.  For any real work, a lathe is the best, either converted manual or a small slant bed.  It is possible to convert a manual lathe to CNC and keep all original manual capability intact.


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## bakrch (Dec 4, 2019)

JimDawson said:


> The first question is: How much room do you have for a machine?
> 
> If you can handle a full size BP clone then that's the way to go.  My personal preference for a single machine in the shop would be a manual/CNC machine.  There were a number of 10x50 table BP clone factory CNC/manual machines imported by Webb, Eagle, and a couple others in the late 80's. Most had Anilam controllers.  These were made by Topwell in Taiwan, high quality machines.  I picked mine up for $1000, mechanically near new, but a dying controller.  I see them on EBay and Craigslist occasionally.  Something like this is a very easy retrofit with modern controls, and most of the hard work is already done.
> 
> ...



Space isn't really an issue as I do have a rather large garage.










The shop on the far side, and a forklift could easily  get inside with that sliding door open.

It isn't heated (ignoring the wood stove as it isn't ideal for machinery)  but insulated fairly well.  The caveat here is the floor. 100-year-old concrete that is likely too thin for a BP and finding spots where there are no major cracks does limit the large area that I do have.

Better shot at the floor. Not all of it is like this, but yeah ... don't think a big boy machine is doable unless I get the floor done.







Part in the spindle is my go-to, posting radial X code. Under 3" diameter by 3" OAL has been doable, but stainless takes forever.  I do have industrial CNC equipment that I can use for the occasional larger part, so limited capability is okay by me. 


__
		http://instagr.am/p/ByTNiwDnM1r/


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## JimDawson (Dec 4, 2019)

My machines are sitting on a standard 3.5 inch thick garage floor with no rebar in it as far as I can tell, the largest is 10,200 lbs.  My forklift has taken a toll on the floor.

Cutting out a 6x6 ft square and pouring a 6 inch footing for a BP would be my choice in your situation.


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## bakrch (Dec 4, 2019)

JimDawson said:


> My machines are sitting on a standard 3.5 inch thick garage floor with no rebar in it as far as I can tell, the largest is 10,200 lbs.  My forklift has taken a toll on the floor.
> 
> Cutting out a 6x6 ft square and pouring a 6 inch footing for a BP would be my choice in your situation.



I will have to price that out to see if it's feasible. That and power requirements would certainly eat into the budget, but having a machine like that would certainly be the dream!


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## JimDawson (Dec 4, 2019)

bakrch said:


> I will have to price that out to see if it's feasible. That and power requirements would certainly eat into the budget, but having a machine like that would certainly be the dream!



A large rented hammer drill, some gravel, a few bags of concrete, and a few hours of back breaking work shouldn't cost more than a couple hundred. (depending on how much the doctor charges to fix your back  )

Power requirement is pretty minimal, but you would need maybe 15 amps of 230V to run the spindle VFD.  If you already have 230V in your shop, then you should be good to go.


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## bakrch (Dec 4, 2019)

JimDawson said:


> A large rented hammer drill, some gravel, a few bags of concrete, and a few hours of back breaking work shouldn't cost more than a couple hundred. (depending on how much the doctor charges to fix your back  )
> 
> Power requirement is pretty minimal, but you would need maybe 15 amps of 230V to run the spindle VFD.  If you already have 230V in your shop, then you should be good to go.


Oh nice, yes I am good on power then. 

I know about as much about concrete work as I do about electrical.  But if it's that simple (minus the labor) I can certainly handle that much.


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## JimDawson (Dec 4, 2019)

bakrch said:


> I know about as much about concrete work as I do about electrical. But if it's that simple (minus the labor) I can certainly handle that much.



Just drill a series of 1/2 or 5/8 inch holes, about 4 inches apart, around the perimeter of the target square, then using the jack hammer function of the hammer drill break up the concrete in the square into chunks you can handle.  The finished cutout doesn't have to be pretty, the new concrete will fill in the ragged edge. Then dig down about a foot, put in about 6 inches of crushed gravel and tamp down.  Then fill the balance with concrete, throw in a couple layers of rebar as you are filling.  Space the rebar about 6 inches apart, one layer going one direction the other layer perpendicular to the first, so you create a square grid.  Then scrape off the excess concrete with a 2x4, working the 2x4 back & forth in it's long axis, then trowel smooth.  You can check the level by setting a level on the 2x4.  Let it set for about a month before you set a machine on it.  Home Depot has everything you need for this project.


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## bakrch (Dec 5, 2019)

Excellent! Thank you for the information, this is looking like a great option if I can find 3-axis.

I saw your Z-axis conversion on yours, amazing!

Not that I am even ready, but I found this one on ebay this morning.  








						EAGLE  CNC VERTICAL MILL  10" X 54" 11190940010  | eBay
					

Find many great new & used options and get the best deals for EAGLE  CNC VERTICAL MILL  10" X 54" 11190940010 at the best online prices at eBay! Free shipping for many products!



					www.ebay.com
				




Some concrete work, a drop deck trailer, and HF gantry crane would easily get me into this project. Even if I have to pay for freight when the time comes it doesn't look like it would be a budget buster.


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## rgray (Dec 5, 2019)

JimDawson said:


> Just drill a series of 1/2 or 5/8 inch holes, about 4 inches apart, around the perimeter of the target square, then using the jack hammer function of the hammer drill break up the concrete in the square into chunks you can handle.



I think I'd just rent a concrete saw, but if that concrete is real thin it may be overkill.


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## macardoso (Dec 5, 2019)

I agree on the Bridgeport, however if you want to stick with a benchtop machine, the PM940 looks to be an awesome candidate.

If you are annoyed with Mach 3, just take the plunge and get Mach 4. I was a huge Mach 3 fanboy and I have never looked back.

Depending on you needs (hobby vs production work) consider looking for some higher end servo controls. AB Ultra 3000 drives and the Delta A2 drives are really solid. They can be found used (and in great condition) quite cheaply. If you like new, I would go with DMM as well. There are quite a few people here that have experience in control and CNC panels, so ask questions and you will get answers!

Mike


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## bakrch (Dec 5, 2019)

macardoso said:


> I agree on the Bridgeport, however if you want to stick with a benchtop machine, the PM940 looks to be an awesome candidate.
> 
> If you are annoyed with Mach 3, just take the plunge and get Mach 4. I was a huge Mach 3 fanboy and I have never looked back.
> 
> ...



I generally like new stuff, so I would go with DMM it seems based on recommendations.  I will have to look into the used options you listed though, as I am unfamiliar. Used is certainly not out of the question.

I can live with most Mach 3 issues, it really is decent for most things ... but cannot get the 4th axis to feed predictably in any of the modes. I know the posted code is good as I have a Haas and Doosan at work that run smoothly with the same code (using either the Mach 3 post or Fanuc). But for some reason, the "use radius as feedrate" function does not work for me on my setup.  The problem seems to appear only when A runs simultaneously with another axis. A by itself is no problem. I've read everything that can be found, gone over my settings ... so unless it's a motor tuning issue that is beyond my understanding there seems to be no hope for me. Have just been getting by with using the "set maximum feed" feature though Cimco Edit.

Mach 4 industrial would be great, Macro B in the home shop would be super handy. The price tag for that is a bit high, especially when I can just translate a macro to G-code through NC Plot software. Hobby Mach 4, eh ... I just do not trust it based on what I have read.

The 940M certainly does have my attention still, that thing is an absolute unit!  I suppose I just need feedback from current owners as to whether the quality of the base machine is worth it. Reading through posts here I did find an owner that wishes he started with the 833T.

I would rather not lug around a 1 ton knee mill, but quality of machine is more important to me than ease of moving it around.


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## bakrch (Dec 5, 2019)

Oh, and this would not be a production machine ... more of a hobby type thing with an accuracy/repeatability that can be trusted.


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## macardoso (Dec 5, 2019)

My biggest complaint with doing a CNC conversion is the spindle. You either get stuck with a manual machine with a 3000 rpm (more or less) spindle, or you end up with one of those HF spindles that does 24000 rpm with no torque or rigidity or a large taper.

I have yet to find a spindle option that gives you 8-10k with appreciable torque, a large taper, ATC or drawbar options, spindle feedback, etc.

I did a custom job on my G0704 CNC spindle. I ended up with 2.5HP and 5000rpm but it is still limited for real CNC work. 

Larger machines use larger cutters and are less demanding on spindle speed, but you still want the capability to use small cutters effectively.

I really respect the engineers who design those 40k rpm HSK spindles on some of the newer machines. Crazy speed, crazy precision, and can still drive a 1 inch tap without issue.


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## macardoso (Dec 5, 2019)

Here is a build thread to my control panel on my G0704. Gives you an idea of what a system with AC servos might look like. I'll admit this is tremendously overpowered and complicated for this small machine, but it is sized to be moved onto a much larger machine like a PM940 once I buy a house. Maybe some of the info would be of help to you.









						G0704 CNC AC Servo Rebuild (Picture Heavy)
					

Hi All,  About 5 years ago I completed a CNC conversion of a Grizzly G0704 milling machine. Like everyone at that time I chose to go with the Hoss Machine style conversion as there were not many options on the market. I was not comfortable designing my own system at the time since I was just...




					www.hobby-machinist.com


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## JimDawson (Dec 5, 2019)

bakrch said:


> Excellent! Thank you for the information, this is looking like a great option if I can find 3-axis.



My pleasure



> I saw your Z-axis conversion on yours, amazing!



Thank you 



> Not that I am even ready, but I found this one on ebay this morning.
> 
> 
> 
> ...



Yup, there are a few around.  I'm guessing if you walked in the door with about $1500 cash that you could drag it home.  That looks like the heavier 4VK frame with square ways.  Same machine I have.



> Some concrete work, a drop deck trailer, and HF gantry crane would easily get me into this project. Even if I have to pay for freight when the time comes it doesn't look like it would be a budget buster.



Not sure if the HF gantry is going to lift that.  It's about a 3500 lb machine.  But a rented pallet jack would work well, except that your floor is a bit rough to roll a pallet jack.  A 5000lb short mast forklift with pneumatic tires would be the best option.


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## bakrch (Dec 5, 2019)

macardoso said:


> My biggest complaint with doing a CNC conversion is the spindle. You either get stuck with a manual machine with a 3000 rpm (more or less) spindle, or you end up with one of those HF spindles that does 24000 rpm with no torque or rigidity or a large taper.
> 
> I have yet to find a spindle option that gives you 8-10k with appreciable torque, a large taper, ATC or drawbar options, spindle feedback, etc.
> 
> ...



I hear you. I do a lot of engraving in Ti and SS at home, 2500 rpms have been killing me for that.  10k would be sweet, but 5000RPM and 2-2.5HP would be a great compromise to cover my basic needs. 

The floppy column on this size machine affects me with 1hp @ 2500RPM, can't imagine how much more of an issue that is for you now.



macardoso said:


> Here is a build thread to my control panel on my G0704. Gives you an idea of what a system with AC servos might look like. I'll admit this is tremendously overpowered and complicated for this small machine, but it is sized to be moved onto a much larger machine like a PM940 once I buy a house. Maybe some of the info would be of help to you.
> 
> 
> 
> ...



I am very familiar with your thread and have read through it a few times. Much of that is well over my head so I just have been watching in silence.



JimDawson said:


> Not sure if the HF gantry is going to lift that.  It's about a 3500 lb machine.  But a rented pallet jack would work well, except that your floor is a bit rough to roll a pallet jack.  A 5000lb short mast forklift with pneumatic tires would be the best option.



Ha, oh jeez ... just assumed it would be around 2k. Having a closer look it does look a bit thick. I have had my share of pallet jack failures on that floor. Getting the PM1236 crate into my garage was fun (not). Ended up having to push it the last bit in with my truck just so the door could be closed.


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## macardoso (Dec 5, 2019)

bakrch said:


> The floppy column on this size machine affects me with 1hp @ 2500RPM, can't imagine how much more of an issue that is for you now.



Honestly, the rigidity is my killer. Really the reason I want to upgrade to a bigger machine. For the most part, the torque and power of the spindle only get used when roughing or using large drills. I've done some cutting on this machine I never would have thought was possible. When I'm machining aluminum, every tool gets set to 5000rpm since I would be programming them much faster if I had the spindle speed.

I program with the rigidity issues in mind, so typically very deep depths of cut with very small step overs (dynamic toolpaths from MasterCAM). I can get a bit aggressive during roughing, but need to finishing passes very slowly otherwise the machine just bends around and can't keep tolerances.



bakrch said:


> I am very familiar with your thread and have read through it a few times. Much of that is well over my head so I just have been watching in silence.



Whoops  I've come to accept that I like working on the machine itself more than making parts on it. That page is just a good way for me to keep track and look back on what I've done with the thing. I really need to get some projects to build on it!


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## bakrch (Dec 5, 2019)

macardoso said:


> Honestly, the rigidity is my killer. Really the reason I want to upgrade to a bigger machine. For the most part, the torque and power of the spindle only get used when roughing or using large drills. I've done some cutting on this machine I never would have thought was possible. When I'm machining aluminum, every tool gets set to 5000rpm since I would be programming them much faster if I had the spindle speed.
> 
> I program with the rigidity issues in mind, so typically very deep depths of cut with very small step overs (dynamic toolpaths from MasterCAM). I can get a bit aggressive during roughing, but need to finishing passes very slowly otherwise the machine just bends around and can't keep tolerances.
> 
> ...



Honestly though, it's a good thing. Watching you, @shooter123456 and @spumco doing your thing is largely what has inspired me to begin learning the bits I am weak on.  It will take a few years to get where I need to be on the control/electrical end ... but I am certainly hooked.

I can design parts and machine them all day, been doing that for 25 years now ... time for something new!


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## bakrch (Dec 16, 2019)

The DMM kits are looking quite reasonable. 

Since a new machine is not 100% decided upon yet, I can just sit here and wait for a deal than I cannot be passed up.  

The 750w DMM kit utilizes Nema 34 mounts, which would obviously work for a larger machine when the time comes. There is no reason why I should wait to build the control. All it would take is new motor mounts to get this onto my PM25, so that is looking quite attractive as a first step.

The 1.8kW DMM motor looks good for the spindle, but I am unsure of the pros/cons in driving that with a VFD or using one of their drives?  AC bearings are already in my possession, but that was more as a precaution just in case the originals failed. This motor is rated for 1500RPM, is it unreasonable to count on the maximum 3000RPM to net me 6k via 2:1 pulley system? 

I do have a spare 2HP motor as my PM1236 was upgraded to a Baldor, but that looks like too much trouble to adapt to a mill configuration.


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## macardoso (Dec 16, 2019)

I would personally turn up my nose at the 1.8kW DMM motor. A speed increase through pulleys is possible but always more difficult than speed reduction. You would not be able to run that motor on a VFD as you would need to pull the commutation data out of their 17-bit serial encoder (likely impossible). When you go above the rated speed, the motor torque will drop off a bit so you likely wouldn't have the torque you would hope for at higher speeds.  

My setup is the best I have been able to come up with so far. 1:1 gearing of an Allen Bradley MPL-A330P-xxxxxx servo and an Ultra 3000 (2098-DSD-020x-xx) drive. The "xx" are characters which don't affect the performance of the motor. That is 1.8kW but a rated/maximum speed of 5000rpm. With a 1:1.5 gearing you could easily get 7500 rpm. These are available on ebay and I could help you set it up.

Think hard about if you really need a servo. They are great, very compact, and very powerful, but also very expensive. A 3600rpm inverter duty induction motor could be set up to run at 7200rpm within reason. You wouldn't get the stability in speed that a servo gives you, or any kind of rigid tapping/spindle positioning, but you could save some $$.

I would say that DMM is a great choice for the axis motors. 

All of this is just my personal opinion/experience.


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## bakrch (Dec 16, 2019)

macardoso said:


> I would personally turn up my nose at the 1.8kW DMM motor. A speed increase through pulleys is possible but always more difficult than speed reduction. You would not be able to run that motor on a VFD as you would need to pull the commutation data out of their 17-bit serial encoder (likely impossible). When you go above the rated speed, the motor torque will drop off a bit so you likely wouldn't have the torque you would hope for at higher speeds.
> 
> My setup is the best I have been able to come up with so far. 1:1 gearing of an Allen Bradley MPL-A330P-xxxxxx servo and an Ultra 3000 (2098-DSD-020x-xx) drive. The "xx" are characters which don't affect the performance of the motor. That is 1.8kW but a rated/maximum speed of 5000rpm. With a 1:1.5 gearing you could easily get 7500 rpm. These are available on ebay and I could help you set it up.
> 
> ...



Good to know, many thanks! 

I am fine with just the 5k rpm really, for now anyway. Maybe when I mount it all to the next machine we can shoot for more.

"need"?, heh ... noooo. This is more about building an optimal setup without getting too ridiculous.  Like you, my interest is something that can later be moved to a bigger machine and perform reliably.  Putting this on the PM25 would get me familiar with the control setup, and hopefully, make my inevitable mistakes cheaper. 

$3k is a reasonable budget for the entire control system I think.  If I go a bit over, not worried.


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## macardoso (Dec 16, 2019)

bakrch said:


> "need"?, heh ... noooo. This is more about building an optimal setup without getting too ridiculous. Like you, my interest is something that can later be moved to a bigger machine and perform reliably. Putting this on the PM25 would get me familiar with the control setup, and hopefully, make my inevitable mistakes cheaper.



I get that It is a bug!




bakrch said:


> $3k is a reasonable budget for the entire control system I think. If I go a bit over, not worried.



Sounds very reasonable to me. Figure adding in these rough costs. Spending a little more to do it "right" will make it much more painless. Can certainly go cheaper here though if you end up against a budget.

$100 - Electrical Enclosure
$125 - Disconnect, Breakers, etc
$200-250 - Motion Controller, Breakout Boards
$0-200 - CNC Software
$75 - Cable, Wire, Crimpers, etc.
$50-100 - Bulkheads or connectors for cables
$25 - Wire Duct


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## bakrch (Dec 16, 2019)

Okay, Mike already knows this but spindle servo motor and drive acquired!

I will update when everything is assembled for a bench test! 

The tapered roller bearings should be cowering in fear, because I plan to cook those first before replacing them.


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## JimDawson (Dec 16, 2019)

Spindle motors:  Using a small (1.8 KW) servo for a spindle motor would not be my first choice, especially when running on single phase power.  Take a look at the published torque curves.  Then divide that by your planned gear ratio.  Ok if you are running in the lower RPM ranges, but do not make for a good high speed system. Most of the small, good quality (Baldor, Marathon) inverter duty induction motors (<5 HP) are rated at 5000 - 6000 RPM max, and run very well, and will give you 100% torque from 0 to the motor rated speed when run with a sensorless vector VFD.  You want to get a 4 pole (1800 rpm) motor, they have double to torque of a 2 pole (3600 RPM) motor for a given HP.  You can get purpose built high speed servo spindle motors, but the cost is more than the rest your machine.  Just not practical for the home shop.

Rigid tapping is possible when using an induction motor driven by a VFD, just requires an encoder on the spindle and the controller must support rigid tapping.  The only thing I have not been able to accomplish yet is to index using VFD control, but not important on most mills without tool changers.

You were posting while I was writing this, I see that you have acquired a servo motor.  Your opportunity to prove me wrong, I have no first hand experience with servo spindles, only running the numbers.  I'm very interested in the results, you may cause me to change my mind.


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## macardoso (Dec 16, 2019)

JimDawson said:


> I'm very interested in the results, you may cause me to change my mind.



We were able to find @bakrch a servo that has a rated/max speed of 5000rpm, a flat continuous torque through the entire speed range of 3.5Nm and peak torque of 9Nm up to 2500rpm which tapers down to the continuous rating at 5000rpm. Should be a good fit for a machine like the PM-25MV since you cant really use much more power than that. That's all on 240VAC 1P. 

I've found that when I am roughing aluminum at the absolute limit of my machine's rigidity, I'm nowhere near maxing out that spindle (maybe 40%). I do use most of the torque for drilling at the lower speeds and roughing steel which is why I've kept the gear ratio on mine at 1:1. 




I will be interested to get his thoughts on the matter once it is up and running!



JimDawson said:


> Rigid tapping is possible when using an induction motor driven by a VFD, just requires an encoder on the spindle and the controller must support rigid tapping. The only thing I have not been able to accomplish yet is to index using VFD control, but not important on most mills without tool changers.



Good point on the rigid tapping. I was wrong on that!

If only induction motors weren't so big and heavy for these little machines


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## bakrch (Dec 16, 2019)

We have a Summit EVS349b (3hp 4300RPM) manual knee mill at work, I use it often and know (roughly) what to expect in the future when I move the servo motor to a larger machine. Wanting more than this would just be greedy, at that point it's time to get a HAAS TM1 or Mini Mill.


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## macardoso (Dec 16, 2019)

Boy that's a nice looking mill. Never seen a company selling modern manual machines at 26k lbs. Geez


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## bakrch (Dec 16, 2019)

macardoso said:


> Boy that's a nice looking mill. Never seen a company selling modern manual machines at 26k lbs. Geez



Yep, that's about what our HBM-110 weighs, apparently.

We have their 16",18",22", 42" lathes, the horizontal pictured below, EVS349B and EVS-550B knee mills. 

They had big shoes to fill (replaced Bridgeport, Giddings & Lewis and Monarch equipment) ... but they get the job done.


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## bakrch (Jan 8, 2020)

I still haven't messed with the servo motor testing, need to get on that within the next week or else I am out of the return zone should anything go wrong.

What I have been busy with, taking my PM-25 apart to diagnose chatter while climb cutting in X.

Nothing was loose, or even close to coming loose at all ... which surprised me.  All that stood out was shoddy work on the double ball nuts. Here is a short (crappy quality) video that I took.



https://imgur.com/UOkA1gd


My backlash has between  .002-.003  in X and Y since the day I got it, which is explained by less-than-perfect preload. Not the greatest but have been able to make decent parts using compensation.  I would have liked to take them apart, but the key screws are ground too far down.

I checked videos from Hoss from back in the day and I guess even that unbound lateral play is just normal for a Chai C7 setup.

The dovetails are still quite perfect, with incredibly smooth action throughout X and Y travel range.

Now I am going to look at the column again. It needed to be shimmed quite a bit in both directions, which had to impact the already weak rigidity. Next,  I may take all of the column shims out, run a few aluminum parts to see if there is an improvement.  I went ahead and put it back together, then checked tram from the head to the column ... it is still darn near perfect.

There is always the Stefan Gotteswinter epoxy method for the column shimming, but I do have machinery available to simply skim cut it square. The setup would be tricky, but it is doable.


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## bakrch (Jan 8, 2020)

For those who haven't seen it (was posted in another thread), here is an example of my "chatter".

This is about .62 axial, .02-.025 radial and 45IPM @ 2500 RPM ... with a 1/2" 3FL YG-1 alu-power end mill.  The same spec 3/8" end mill does the same thing.  This will even chatter on a finish cut if it is run too fast.

Apples to apples (same cut parameters above), I can rough 65 IPM with conventional cuts with little to no chatter. General vibration starts to limit me at that point.

Running across the fixed jaw area of the vise (X+) is where the sound is most pronounced. Difficult to get the visual, so crank the sound.

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		http://instagr.am/p/BwGGXRGl0GG/


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## macardoso (Jan 8, 2020)

Yikes. That ballscrew isn't looking very well fitted from the factory. Still a lot better than mine, but you'd think they could do a little better.

Did the aluminum parts run without the column shims come out any better?


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## bakrch (Jan 8, 2020)

macardoso said:


> Yikes. That ballscrew isn't looking very well fitted from the factory. Still a lot better than mine, but you'd think they could do a little better.




Yes, it is embarrassing. On top of that ... Pro-Cut CNC put it together with the screws bent to hell. I need to take them back out and maybe put some more time into straightening, but it just seems like a waste of time at this point. I saw @shooter123456 got a nice set of ballscrews/ballnuts in ... may have to upgrade to those!

What I have is doing the job though, so maybe not.



> Did the aluminum parts run without the column shims come out any better?



I only had time to get it back together and X Y axes dialed back in.

Column/head tram was checked and I also adjusted the Z gib as it was a little too tight. I was only getting indicator movement every .002 or so while jogging in .001 increments.  Sizes were coming out okay, so I left it alone for a bit. Pretty sure the chip cover is staying off now for easy access to the bottom Z gib screw.  I put a zeroed indicator on the spindle and backed the Z gib up until there was a smidge of nod movement, about 1/2 to 3/4 turn or so. Then I locked it down back at zero. I must have overtightened it when troubleshooting the chatter last time.

Next, most likely tonight I will get the column shims out, clean the surfaces, lock it back down and run some sacrificial aluminum to see what happens.


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## macardoso (Jan 8, 2020)

bakrch said:


> I saw @shooter123456 got a nice set of ballscrews/ballnuts in ... may have to upgrade to those!



I saw those and boy did they look nice. Quite pricy tho. Perhaps on my next CNC build 



bakrch said:


> Next, most likely tonight I will get the column shims out, clean the surfaces, lock it back down and run some sacrificial aluminum to see what happens.



Let us know how it goes.


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## bakrch (Jan 8, 2020)

macardoso said:


> I saw those and boy did they look nice. Quite pricy tho. *Perhaps on my next CNC build *


For sure, that is my thought on the matter as well.

Too bad I didn't get the original parts for the Pm-25, wouldn't mind converting it back to manual after my next build.



> Let us know how it goes.



Will do. Based on what I have laying around, cuts will be something like .31 axial, .04 radial, 60IPM 2500 RPM with the 3/8" end mill.  I will take videos with the shims in and out, same cut parameters.


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## bakrch (Jan 8, 2020)

With shims. (Metal clanging is just my spindle wrenches in the chip pan).

. 31 axial, .05 radial, 52ipm,2500 rpm

This would not chatter at all cutting conventional direction. 


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		http://instagr.am/p/B7E64NvgSax/

Without shims. Just a hair better, judging by the finish. 


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		http://instagr.am/p/B7E7FQKAvXm/

I didn't film it, but after this I really leaned into the column to counteract the cutting forces, got a few clean passes with no chatter.


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## shooter123456 (Jan 9, 2020)

bakrch said:


> For sure, that is my thought on the matter as well.
> 
> Too bad I didn't get the original parts for the Pm-25, wouldn't mind converting it back to manual after my next build.
> 
> ...


My old ones may fit your machine.  If you are interested, we can talk about rehoming them.


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## spumco (Jan 10, 2020)

bakrch said:


> Nothing was loose, or even close to coming loose at all ... which surprised me.  All that stood out was shoddy work on the double ball nuts. Here is a short (crappy quality) video that I took.
> 
> 
> My backlash has between  .002-.003  in X and Y since the day I got it, which is explained by less-than-perfect preload. Not the greatest but have been able to make decent parts using compensation.  I would have liked to take them apart, but the key screws are ground too far down.



Late response (just noticed the thread again), but those ballnuts are terrible.  You've got to do something about them!

Measure the distance between the ball nuts.  Then drill out the key screws with a cobalt drill and get some belleville washers from CrackMaster Carr that make up a stack just slightly longer than the nut gap.

Put the ballnut back on with the washers between them.  Should just_ barely_ not line up the keyways.  You then preload the nuts by compressing the springs and install new (unshagged!) keys and screws.  Even if the keys waller out a bit the springs will take up the slack.

If the screw holes are too damaged during removal you can use roll pins & loctite to anchor the keys.  Anything would be better than what was in the video you posted.

-R


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## bakrch (Jan 10, 2020)

shooter123456 said:


> My old ones may fit your machine.  If you are interested, we can talk about rehoming them.



My machine has a production date of 5-2017. If yours is reasonably close to that I think it's worth a shot!



spumco said:


> Late response (just noticed the thread again), but those ballnuts are terrible.  You've got to do something about them!
> 
> Measure the distance between the ball nuts.  Then drill out the key screws with a cobalt drill and get some belleville washers from CrackMaster Carr that make up a stack just slightly longer than the nut gap.
> 
> ...



I should just throw them in the bin!

I suppose that doesn't sound too difficult. I need to run a few parts (and test my new spindle motor), so when I am done it will come apart for some measurements.

Thanks for the help guys!


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## bakrch (Jan 22, 2020)

Finally got a few minutes to snap a video conventional milling.  Everything is trammed and shimmed. Absolutely perfect.


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		http://instagr.am/p/B7o-JMynp4j/

Physically pushing/ twisting  the column helps on the climb cut,  so my theory is the backlash slightly bouncing the table in climb direction + floppy column(torsion) = synergistic effect of chatter. Remove or improve one of  those elements and it goes away.

Also,  starting with 0 chip and it ramping to full chip load(conventional) is helping stabilize it relative to starting full chip and decreasing to 0 (climb).

Time to fix with belleville washers like @spumco  mentioned above to test the theory.


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