[Goodwood]

What are the major differences that make Minitech more accurate, more expensive and more rigid than Sherline ? In a watchmaking aspect of machining, why is Minitech better than Sherline ? I have no experience with Minitech, looking at the pictures they are slightly bigger than Sherline,using Sherline motor, and making of aluminium with some alloys ? But does that make Minitech so much costlier, and is Minitech so accurate and precise as compared to Sherline ?

Last question, I couldn't find any accessories for Minitech. Like the rotary table, tilting angle device Sherline has. If the user have to use this toolings, do they modify Sherline's and fit it onto Minitech ?

[rowbare]

The Sherline is quite small, it weighs under 40 lbs. The various Minitechs are bigger and heavier.

The Sherline rotary table is the way to go for these small mills. If you get a 4th axis from Taig or Minitech it will be using the Sherline rotary table.

bob

[awerby]

Are we talking about lathes here? The rotary table is a mill accessory - I'm not sure how you'd use it on a lathe.

There are various companies called "Minitech", so it's hard to make a comparison without saying exactly which machine we're talking about. This CNC lathe: Desktop CNC lathe appears to be based on a Sherline (on riser blocks), with some linear rails used instead of the normal dovetail ways. (It's hard to say for sure, since they only provide a very small picture, and hardly any other information or specifications).

Those rails might help somewhat with linear motion, but whether they're worth another $5k or so is debatable, and I don't think they'd make much difference in overall accuracy. I doubt it's more rigid than a Sherline that's not up on blocks, and you don't need all that swing for watchmaking. If you give Minitech another $10k, you can substitute a Levin spindle, if the very low runout of the standard Sherline spindle is too much for your purposes. Whether it's worth it or not is for you to decide.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[Goodwood]

Are we talking about lathes here? The rotary table is a mill accessory - I'm not sure how you'd use it on a lathe.

There are various companies called "Minitech", so it's hard to make a comparison without saying exactly which machine we're talking about. This CNC lathe: Desktop CNC lathe appears to be based on a Sherline (on riser blocks), with some linear rails used instead of the normal dovetail ways. (It's hard to say for sure, since they only provide a very small picture, and hardly any other information or specifications).

Those rails might help somewhat with linear motion, but whether they're worth another $5k or so is debatable, and I don't think they'd make much difference in overall accuracy. I doubt it's more rigid than a Sherline that's not up on blocks, and you don't need all that swing for watchmaking. If you give Minitech another $10k, you can substitute a Levin spindle, if the very low runout of the standard Sherline spindle is too much for your purposes. Whether it's worth it or not is for you to decide.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

Hi, sorry for not being specific here. I am referring to the Sherline mill and the Minitech mini cnc 2. Sherline weighting 36 lbs, while Minitech mini mill 2 65lbs.

[awerby]

Goodwood wrote:

Hi, sorry for not being specific here. I am referring to the Sherline mill and the Minitech mini cnc 2. Sherline weighting 36 lbs, while Minitech mini mill 2 65lbs.

OK; that makes things clearer. Since you posted this in the lathes forum and talked about watchmaking, I thought you meant lathes, not mills. If you go to the other Minitech site: Minitech Machinery , they have some information about their offerings and a handy price calculator which adds things up as you select the controller, rotary table, part-holding provisions, etc. Going for the cheapest options on all that (and no part-holding), I got to $10,950 for the MiniMill2, which has travels of 10"X, 5"Y, and 8"Z. Considering that a similarly-equipped Sherline 5400 mill (with travels of 9"X, 5"Y, and 6.25"Z) goes for $2700 or so at list, you'd hope there were some advantages to the Minitech2.

What are they? While the site talks about their heavy granite-epoxy frames, on the #2 model you don't get that; the Minitech 2's $8000 frame is made of aluminum and I don't see it weighing very much more than the Sherline. (The granite/epoxy frame is offered with the MiniMill GX, which goes for $16k just for the bare frame). It does have anti-backlash springs on the leadscrew nuts, which would reduce backlash, at least until cutting forces overcame the spring tension. The site talks about using square-rail linear slides instead of the Sherline's dovetail gibs, but again, you don't get that on the #2 model, which runs on unsupported round rods.

They seem to be using Sherline parts rather liberally in these machines, at least until you get into the (even) more expensive options, but they're marking them up considerably. The 4" rotary table, for instance, which Sherline lists for $675 with a right-angle mount, tailstock, motor, and 4-jaw self-centering chuck goes for $1850 if you get it from Minitech, and appears to be exactly the same unit on a different mount that lacks the angled buttress of Sherline's right-angle mount . Their 10,000 RPM spindle also appears identical to Sherline's, but they want $650 for it, while Sherline charges $400.

So the Minitech2 (here's a picture: Minitech Machinery ) is a little bit bigger in X and Z, it has antibacklash nuts, the controller uses 16x microstepping instead of Sherline's half-stepping, it runs in Windows instead of EMC, it has round rods instead of dovetails with gibs, and it has a bellows on the Z axis to keep chips out. Instead of T-slots, it has a table with an array of tapped holes for workholding. Aside from that, it's pretty much (or exactly) the same machine. It might be a little more rigid due to its beefier column, but that column is also higher, which detracts from rigidity. I don't see why it would be any more accurate, except that the backlash springs would help somewhat. If these factors add up to $8250 worth of improvements for you, then you should get the Minitech2 instead of the Sherline 5400.

It seems like there would be a more significant contrast between the Sherline and Minitech's higher-end offerings, but those are larger, heavier and much more expensive machines, so it would be an apples-to-oranges comparison.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[bebob1]

is there a performance enhancement of using the minitech 1 and 2 mills compared to the sherline, considering that neither of the minitechs 1 and 2 models are actually ballscrews to benefit from improved backlash? Sure they are acme screws with spring loaded anti-backlash, but it is still no ballscrew. Maybe it can handle higher loads before experiencing damage to the mill, so longevity may be one advantage, but it costs a lot more? Also, with acme screws and the low pitch ratings, the resolution of movement may be worse than the sherline that have fairly high pitch threads on their axis?

[swarfman]

Hi Goodwood,

I'm really just getting started in the world of CNC. I've just reached the 2 year point of learning how to design parts, create tool paths and cut. So far so good. I've owned a Minitech Mini Mill II for 2 years now. While Minitech doesn't have the accessory catalog Sherline has - which frustrated me in the beginning as well - you'll be able to get what you need from different sources (including Sherline) or make some of it yourself.

I'd like to offer some random thoughts I think might make the process easier for you.

Try to determine what tolerances you're going to be machining/designing to and what materials you'll be working with. It will be much easier to compare machines and their capabilities if you know what you're going to be doing exactly. In shopping for mine, I had the good fortune to meet a few folks who were able to get me thinking correctly about how to spec out and purchase a mill and software.

While the weight of the machine is some indication of it's strength, if it's not assembled and setup correctly you're going to struggle. I would take a properly aligned lightweight mill any day of the week over an improperly setup boat-anchor.

What sort of experience are you expecting when you walk over to the mill and want to start machining? Are you comfortable with having to manually zero (home) the machine or would you like it to have limit switches so this is done automatically? Seems like a small thing until you need to walk away from milling a part in the evening and finish it the next day.

If you need high precision - say tolerances of .001 mm for example - can any of the standard spindles shipped on many of the mini mills hold this tolerance? You'll find this much run-out in some of the cheaper spindles. A 500 lb mill can't fix this. The tolerances stack up in multi-axis machines. The more complex the cut i.e. 4 axis v.s. 2 axis the more exposure your part has to the stacked up tolerances in the machine.

How rigid does the machine really have to be? I cut a lot of machinable wax and use it as tooling for making silicone molds to cast parts. The side loading on my Z tower is small but I wanted to hold a tight tolerance as I make a lot of small parts. What's the point of creating tool paths with a tolerance of .001 mm when your mill can't hold .005 mm, right? I needed something like the Minitech Mill II with a high speed, high precision spindle and a frame rigid enough to achieve the tolerances I was going to be working with.

I spec'd out a machine with everything I could to minimize the impact of my lack of experience. I have limit switches, zero backlash screws and a high speed, high precision spindle so I can focus on making parts. Learning the CAD/CAM side of CNC was/is challenging enough.

I hope this helps in some way. Try to determine what you need and the market will narrow up giving you a better view of what is really available to suit your needs. From there you can decide where to make compromises.

[johnohara]

Nice post swarfman. Thanks for taking the time.

~john

[Goodwood]

Hi Goodwood,

I'm really just getting started in the world of CNC. I've just reached the 2 year point of learning how to design parts, create tool paths and cut. So far so good. I've owned a Minitech Mini Mill II for 2 years now. While Minitech doesn't have the accessory catalog Sherline has - which frustrated me in the beginning as well - you'll be able to get what you need from different sources (including Sherline) or make some of it yourself.

I'd like to offer some random thoughts I think might make the process easier for you.

Try to determine what tolerances you're going to be machining/designing to and what materials you'll be working with. It will be much easier to compare machines and their capabilities if you know what you're going to be doing exactly. In shopping for mine, I had the good fortune to meet a few folks who were able to get me thinking correctly about how to spec out and purchase a mill and software.

While the weight of the machine is some indication of it's strength, if it's not assembled and setup correctly you're going to struggle. I would take a properly aligned lightweight mill any day of the week over an improperly setup boat-anchor.

What sort of experience are you expecting when you walk over to the mill and want to start machining? Are you comfortable with having to manually zero (home) the machine or would you like it to have limit switches so this is done automatically? Seems like a small thing until you need to walk away from milling a part in the evening and finish it the next day.

If you need high precision - say tolerances of .001 mm for example - can any of the standard spindles shipped on many of the mini mills hold this tolerance? You'll find this much run-out in some of the cheaper spindles. A 500 lb mill can't fix this. The tolerances stack up in multi-axis machines. The more complex the cut i.e. 4 axis v.s. 2 axis the more exposure your part has to the stacked up tolerances in the machine.

How rigid does the machine really have to be? I cut a lot of machinable wax and use it as tooling for making silicone molds to cast parts. The side loading on my Z tower is small but I wanted to hold a tight tolerance as I make a lot of small parts. What's the point of creating tool paths with a tolerance of .001 mm when your mill can't hold .005 mm, right? I needed something like the Minitech Mill II with a high speed, high precision spindle and a frame rigid enough to achieve the tolerances I was going to be working with.

I spec'd out a machine with everything I could to minimize the impact of my lack of experience. I have limit switches, zero backlash screws and a high speed, high precision spindle so I can focus on making parts. Learning the CAD/CAM side of CNC was/is challenging enough.

I hope this helps in some way. Try to determine what you need and the market will narrow up giving you a better view of what is really available to suit your needs. From there you can decide where to make compromises.

Thanks swarfman for the details, I am in the horology field doing watchmaking. I will be cutting mostly brass materials, tolerance must be precise to 0.01mm +/-.
As I have rather limited working area living in an apartment, I could only afford desktop mills. I cannot take up big bench mills that are very heavy as well like the sieg x3.

Noise factor is another concern. Actually I hardly mill, the only time I did was some lessons with Sherline mill. It was very limited. I spent more time on lathe than mill. But I must learn milling, and very committed to learning mill as it will be a great help in the future.

The working field will be generally less than 5cm by 5cm square as it will be mostly small parts. I have no experience with CAD, CAM or CNC. But I am willing to learn and grow with it. Knowing if it is a good mill to invest, I would buy it now and take my time to learn since eventually I have to get one CNC in the future. And if the price is right (used minitech), I will get it.

I think if I get a minitech or sherline, I will spend most time cutting brass and sometime on mild steel. I will not be cutting wax, or plastic.

Lastly, and the most importantly cost is another concern. I don't have a huge budget, but if the cost for a used minitech 2 cost as much as a new sherline I can get it. But the killing will be upgrading the screws and the spindle. I saw those NSK spindles can get as much as $5000. Which is way over budget for now. But as my funding get more, I can eventually pay for it in the future. But not now.

[bebob1]

The problem with the minitech is that you really are not getting any ballscrews until you get their third best (minitech 3) offering which is more than $12K barebones before adding a milling spindle. Without the ballscrews there isnt a huge benefit of the minitech that I can tell, other than arguably machine rigidity, which probably isnt really true either, especially when comparing it with the Taig. But machine stiffness can be overcome on these smaller mills by changing the way you machine your part. Leave skin thickness when doing roughing, then do finishing passes that takes really light cuts. It will make your machining time longer, but with this strategy you really dont need a super stiff mill to do tight tolerance stuff.

For your requirements taking into account cost you probably want a sherline or a taig, which will get you the +/-0.01mm tolerance if you are skillful enough wtih the machine. These machines can handle brass and steel without issues. The downside is the wearing of the leadscrews which makes backlash worse over an extended period of time. You can modify your mill to make them anti-backlash or use backlash compensation which is often ok.

You only really need the NSK high speed spindles if you do a lot of work with small features which uses small end mills or engravers. The smaller the diameter tool, the higher the RPM you need to keep up with the feed, otherwise you can use the slower spindle options provided by sherline and simply make your feeds lower (i.e. takes longer to finish milling). The NSK spindle may get you better radial runout too, potentially, but you can factor radial runout into your G-code programming. Unless you get down to really small endmills, then runout can cause issues with tool breakage but it is doubtful you will be using those end mills, say 50um diameter ones.

Noisewise there isnt a huge deal difference between what youd reasonably get from a minitech vs a sherline or taig. Noise source comes from cutting action, spindle and stepper/servo noise. There isnt any difference all things being equal between minitech and sherline then. Perhaps you can look at difference between NSK vs sherline spindle, but both are reasonably quiet. No matter what you will want to make an enclosure for your mill for noise and dust control. You should expect to spend maybe $500 give or take depending on how good your enclosure is. Obviously if you are taking heavy cuts into steel it will be loud. But light cutting may be ok.

[Goodwood]

The problem with the minitech is that you really are not getting any ballscrews until you get their third best (minitech 3) offering which is more than $12K barebones before adding a milling spindle. Without the ballscrews there isnt a huge benefit of the minitech that I can tell, other than arguably machine rigidity, which probably isnt really true either, especially when comparing it with the Taig. But machine stiffness can be overcome on these smaller mills by changing the way you machine your part. Leave skin thickness when doing roughing, then do finishing passes that takes really light cuts. It will make your machining time longer, but with this strategy you really dont need a super stiff mill to do tight tolerance stuff.

For your requirements taking into account cost you probably want a sherline or a taig, which will get you the +/-0.01mm tolerance if you are skillful enough wtih the machine. These machines can handle brass and steel without issues. The downside is the wearing of the leadscrews which makes backlash worse over an extended period of time. You can modify your mill to make them anti-backlash or use backlash compensation which is often ok.

You only really need the NSK high speed spindles if you do a lot of work with small features which uses small end mills or engravers. The smaller the diameter tool, the higher the RPM you need to keep up with the feed, otherwise you can use the slower spindle options provided by sherline and simply make your feeds lower (i.e. takes longer to finish milling). The NSK spindle may get you better radial runout too, potentially, but you can factor radial runout into your G-code programming. Unless you get down to really small endmills, then runout can cause issues with tool breakage but it is doubtful you will be using those end mills, say 50um diameter ones.

Noisewise there isnt a huge deal difference between what youd reasonably get from a minitech vs a sherline or taig. Noise source comes from cutting action, spindle and stepper/servo noise. There isnt any difference all things being equal between minitech and sherline then. Perhaps you can look at difference between NSK vs sherline spindle, but both are reasonably quiet. No matter what you will want to make an enclosure for your mill for noise and dust control. You should expect to spend maybe $500 give or take depending on how good your enclosure is. Obviously if you are taking heavy cuts into steel it will be loud. But light cutting may be ok.

Thanks bebob1, it seemed the extra cost to get the minitech 2 is not very significantly great difference compared to sherline. I probably have set my mind on getting sherline now. Thanks for the advice.