Thoughts on cnc converted MH22 for hobbyist ...

[steff_dk]

Hi all - first post, but have been lurking on and off for a while.

I am a hobbyist/tinkerer and all-around amateur.
I have a software developer background, but through my tinkering with Arduinos and Beaglebones I found an interest in making brackets, cases etc. for my electronics projects.

I have an EMCO Compact 5 with the milling attachment which is "okay" for turning/milling small plastic/aluminium parts but it is too small for the parts I want to make.

I would like to mill aluminium parts up to 280 x 150 x 50 mm and within better tolerances than the EMCO can achieve.
I have been looking at some cnc converted Optimum machines and the MH22 looks like a good option:
German seller here -> MH22 sets

I am partial to getting the machine in Germany due to prices, shipping cost and (God forbid) warranty cases. I live in Denmark.

I am curious about your thoughts on the Optimum MH22 (or alternatives) and also if investing in the extra options of the Hiwin ball screws and brushless spindle are justifiable for a discerning hobbyist such as myself.

Hope to get some good inputs on this pleasant dilemma

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[Pardonmebuthelp]

As far as price is concerned, its always going to be cost effective to build your own cnc. Your alot closer to china so it shouldnt be too expensive to get mill castings to convert.

[dazp1976]

The mill itself looks ok but I don't like the conversion kits it has fitted.
Motor systems it has seem under-powered too. I see at least 4nm on this size machine at a minimum when belted. 8nm when direct drive.

Better off getting one similar to a PM25MV and converting it yourself.

[steff_dk]

Thanks for the replies - really appreciated.
I will admit to being the type of guy that start pondering how to build a fence for a cow if I need a glass of milk - and consequently have a shed full of half finished projects
So even if there is $$ to save on converting to cnc myself I'd rather buy something turnkey.

I suppose I could ask for an upgrade on the steppers for the MH22 set to get more torques. Good point.
However, I can see that even the MH25 SV ships with 2.2 Nm on X and Y and 4.2 on the Z axis from the factory ...

Again, thank you all for your inputs!

[ninefinger]

the stepper motor torques are fine. 2.5 Nm is plenty for the cutters and speeds you will run. Anything bigger is just helping you break tools and the machine faster when you make a mistake.
Those steppers coupled to a 4mm lead ball screw can generate 300 Kg force easily, plenty for X and Y. Sure the torque drops at higher speeds but you don't need lots of torque at higher speeds as you are not cutting then.
In this case I feel confident the manufacturer has put together the kit in a responsible way that will work well for you. Don't get sucked into the bigger better faster mentality for a hobby machine, you'll save more time (and money) with a machine that is well balanced.

Mike

[dazp1976]

the stepper motor torques are fine. 2.5 Nm is plenty for the cutters and speeds you will run. Anything bigger is just helping you break tools and the machine faster when you make a mistake.
Those steppers coupled to a 4mm lead ball screw can generate 300 Kg force easily, plenty for X and Y. Sure the torque drops at higher speeds but you don't need lots of torque at higher speeds as you are not cutting then.
In this case I feel confident the manufacturer has put together the kit in a responsible way that will work well for you. Don't get sucked into the bigger better faster mentality for a hobby machine, you'll save more time (and money) with a machine that is well balanced.

Mike

True.
With a 2:1 belt system you'll get 5nm from the 2.5 motors.

I'm going direct drive with my PM25 clone and judging by how my 3nm perform on the X2 I'll probarbly need to bump up to 6nm.
I lose most of my torque by stepping at 1/16th.
Prob won't need more than 1/8th when I'm finished with this new one so that will help.

[skrubol]

I will admit to being the type of guy that start pondering how to build a fence for a cow if I need a glass of milk - and consequently have a shed full of half finished projects

Lol, love this one!
Unfortunately I know the feeling. My latest project has been getting shelving units built so that I can organize my half-finished projects.

I lose most of my torque by stepping at 1/16th.
Prob won't need more than 1/8th when I'm finished with this new one so that will help.

If you're referring to what I think you are, torque loss from micro-stepping is a myth. There is some torque loss from going from full-stepping to any micro-stepping if you don't adjust the peak current, but with modern drives this shouldn't be an issue. Torque loss from high micro-step ratios is completely false though, you lose incremental torque, but that only means you don't get the additional resolution you should with the higher microstepping, there's still just as much torque to move the workpiece/cutter.

[jschoch]

Thanks for the replies - really appreciated.

start pondering how to build a fence for a cow if I need a glass of milk

I also suffer from this condition. I found my self researching strain gauges, HX711 amps, load cells and eventually velostat last night as a tangent from a diy tool setter!

[DLF]

for a little more money you can get the MH25V. It is bigger than the MH22 and overall better suited for CNC conversion