A Cheap and Capable CNC Mill?
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- Опубликовано: 31 июл 2024
- In today's video I am going to put my relatively cheap Chinese Milling Machine to the test and see if it will accurately machine steel.
I purchased the mill new and converted it to CNC. The machine was $2,800 NZD shipped about 2 years ago and the kit for the conversion to CNC totaled about $1,700 NZD. The machine uses 2005 Taiwanese Ball Screws on the X and Y axis and 2505 on the Z axis. The stepper motors are all 8nm Nema 34 closed loop units, these came in a kit with power supplies and drivers.
The spindle motor I now have fitted to the mill is a 1.5Kw servo, this is not included in the $3,000 USD ($4,500 NZD) cost total as I added this to the machine after it was finished for a few more RPM, this cost around $500 NZD.
This machine obviously involves a fair bit of work to convert to CNC but it is still cheaper than any alternatives, namely the offerings from Tormach like the PCNC440 coming in at around 7,000USD ($11,000 NZD) which is: a similar weight, far less powerful and has a smaller work envelope. The work envelope of this mill is slightly larger than the more expensive Tormach 770M although the 770M will be far more rigid.
If you have any questions feel free to ask in the comments. 
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You can easily adjust step count in software and reduce that "inaccuracy" number's. In every software there is a value for the step count for the amount of movement. For example default for certain model is CNC is 800. What you do is you move the X axis for 100 mm an measure how much did it actually moved. Then you use that distance to calculate the needed step count. It turns to be, for example, 807 steps. Than you enter that value in the software and repeat the process. Once you are getting close number's you are done with calibration of the X axis. Do same for Y and Z axis. You will be calibrated and parts will be way closer to the needed size. This works when you have constant size difference per axis. Like X axis size is always bigger or always smaller. Will not improve anything if part is once bigger and once smaller. That is than inherent runout of the machine or shows some issue that needs to be addressed. BTW do calibration with lower feed rates because you do not want machine to lose steps and you to hunt those. Also do it at the part od the bed where you do your most work. Namely things are never perfect and same thing might be behaving different on the other part of the machine due to the imperfections of the parts. I have had to return some ballscrews because they were ground so poorly that they would even stick on some part's of their travel. So not only that I was getting different size but inconsistent sizes as well. So calibrate your CNC machine in software and you will be golden. Good luck.
Thanks for the advice, the set up is definitely worth revisiting as I did it so long ago. Originally I set the step count as per the Mach 3 software with my dial indicator on the x and y the ball screws are only C7 grade ‘Taiwanese’ , and I have been able to machine aluminium to within 0.05mm or better with a high degree of repeatability. I honestly think this was just fault on my part with a machine that isn’t particularly rigid and a poor machining strategy. Like you can see the column flex on a dial indicator when applying pressure to it by hand, not a lot but worth noting.
@@OddsandEndsMachining I see video is two days old so I though let me try to help. But I am barking at the wrong tree. You already know that part. Sorry didn't wanted to be Captain Obvious just tried to help.
No worries, for all you know I could have been oblivious and any help or insight is appreciated.
@@OddsandEndsMachining I hear you about the flex. I've been messing with my round column mill. Using an indicator it is close to perfect alignment in X & Y. However when cutting it appears to have errors particularly when I have used a boring bar as a small fly cutter. The finish was pretty good but the pattern indicated a tilt. I'm pretty sure it's simply a lack of rigidity and tool loading during the cut causing deflection. I also have noticed the indicator moving when applying pressure to the head of the mill when I was adjusting alignment. .05mm deflection wasn't difficult. I recently purchased a tool steel boring bar and inserts from BB, the same place you purchased from. Very nicely finished. I also bought end mills from Yifino. Supposedly HRC70, and happily mowed through a piece of tool steel when tested.
@@kwaka140 It's amazing what you can get for relatively little money from Aliexpress. In regards to the flex, all you can really do is take smaller cuts and use smaller tools where possible.
I do plan on revisiting testing the mills accuracy at some stage.
Good demonstration, great insights and interesting results. Thanks 👍🏼
I'm in chch and have done a similar but not quite as good cnc build. Enjoyed seeing your work and results!
Thanks, I’ll definitely have to revisit this at some point and see if I can get a more accurate result though. What mill did you start off with?
I want one of those! :-)
Great demonstration of the capability of your machine, do you have a link for the carbide cutter ? I am really enjoying the progress with your motor, super impressed with the quality of your crankcase casting
Thanks, I impressed myself with the castings, I never dreamt they would turn out how they did. Here’s the link for the cutter, they have plenty of different sizes. m.aliexpress.com/i/4000007777520.html
I'm in the middle of converting my Hbm bf 28 to cnc myself, they look the same, all made in china with slightly different spec according to the end sellers requests. I think they are a slightly bigger version of the PM 25mv, similar castings but bigger brushless 2 step belt driven variable speed motor and a few other odds and ends.
It definitely helps the conversion if you can get away without having to use another mill. Not quite the case for me.
If you have a look on Ali express and look at some sfu1605 or maybe sfu1204 ball screws and nuts, under the description the sellers will have all of the dimensions.
This is awesome for planning the build and seeing how much space you have without spending any money. Although I think 16mm screws would be fine for the build I probably went a bit overkill.
Nice build, the HM-46B is probably more rigid at the same price point. I nearly bought it but Hafco ran out of stock and I ended up buying a Sieg SX3L instead. No CNC plans for now though.
Thanks, It was definitely a learning curve. When I bought this mill I knew very little about rigidity and weight being such an influence as the only mills I had used previously all weighed over a ton and I hadn’t any experience with bench top mills. The main reason I went with this mill was because of the ‘large’ Y axis travel. The extra weight of the HM-46 would’ve been ideal though if it had the travel.
You’re not missing out on much, I would definitely appreciate another Manual mill for when I can’t be bothered programming.
@@OddsandEndsMachining one ton mill, lol if only I had the space in my tiny tin shed I'd love to get a Schaublin 53 😁
@@HM-Projects I bet if you had a bigger shed it would never be big enough as you’ll always find more stuff to fill it with. At least that’s the case for me.
@@OddsandEndsMachining haha, truer words have never been spoken.
Duplicate finish pass for vertical wall and use strategy 2d pocket
I’ll have to try that next time, I’m only getting started and I have a lot to learn.
Really nice👌👌
If you dont plan on using the swivel base, remove it, it increases stability.
Which spindel/Servo are you using for cutting
I probably will remove it if I need to do any ‘heavy’ cutting (if that’s possible on this mill). The spindle motor is a generic 3000rpm 1.5kw AC servo from aliexpress.
I ended up burning out the stock 1.1Kw DC spindle motor early on by gearing it from its stock 2,500rpm max to 5,000rpm and it was not happy with this to say the least. It worked well up till the gearing change.
@@OddsandEndsMachining Did you have any significant issues setting up the speed control? I have a similar spindle motor (the 1.8kw one) thats is going to drive a bt30 cartridge on my impending router, and I would like to be able to drive it in step/direction mode for rigid tapping, and seperately with a 0-10v for normal milling - I would appreciate you sharing any learnings during your setup (I see its also geared up, have you had any torque issues?)
@@88TheLuke1 I haven’t used it or set it up for rigid tapping as I can’t do that in Mach 3. I understand you need Linux cnc for this. Although the 0-10v set up is very straight forward and only requires two pins to be wired to the breakout board. Then all of the settings on the controller are in the user manual and fairly straightforward. I’m more than happy to help if you run into any trouble.
I’ve had no issues with the torque with the unit geared to double the rpm to 6000 max. Although I have yet to push the machine to it’s limits and rarely use any endmills bigger than 12mm, usually I stick to 6-8mm endmills.
Hi There
I am also converting a MH-28V to CNC, Where did you get the belt drive conversion gear from?. Thanks Murray
For the spindle? I made the servo mount out out of some 30x5 flat, 12mm plate and 30mm round stand offs. All aluminium.
The pulleys are nylon because i didn’t have any aluminium at the time and planned on re making them but they have since held up fine for the last year. I am using a PK series belt sourced from a local shop. I do have CAD drawings of the aluminium pulleys if you want them.
What motor and motor controller did you use?
@@goldoneday
a.aliexpress.com/_mN5NGqc
Let me know if you want the drawings for the mounts I’m pretty sure I’ve got them still.
I'm about to convert my mini mill.
It's called a Fervi T061 here in Italy, but it's one of the many similar ones, and it seems very similar to yours.
Mine is over 15 years old and I think I'm going to forget the dovetail slide in favor of linear ball guides, it have some play and the X axis isn't sliding evenly, so probably dovetails are going in the chip bin.
What size of motors and torque are you using for the axis?
Are they closed loop or open loop?
Closed Loop Hybrid Steppers, using a Novosun controller.
They are 8 nm NEMA 34 steppers, i probably could have gotten away with 4nm motors to be honest.
adding rails might also stiffen up your frame which wouldn't be a bad thing and allow faster rapids.
@@OddsandEndsMachining Thanks for the reply! I'm probably buying the 12Nm motors because maybe in the future I can use them for a bigger machine.
Maybe they're too big?
What screws are you using?
I need to take some measurements, but I think if there's enough space I'm going for 2005 ones.
I need accuracy and fast rapids since I need to use the machine to make plastic injection molds for my precious plastic workspace.
@@dadoVRC As I understand larger motors wont necessarily allow faster rapids, I am using 2005 on the X and Y and 2505 on the Z. Complete overkill, 1605 probably would have been fine for a machine of this size, I suggest if you want faster rapids to go for 2010 ball screws if you can get them and to use double nuts to reduce backlash.
I used single nut screws and have to live with 0.02mm in Y and 0.04mm in X of backlash.
@@OddsandEndsMachining Thank you!
I want to put the motors laterally on the basement because of space issues and the table since the mill has an enclosure made for flood coolant , so I can play with transmission to achieve faster speed.
I have to find double nuts ballscrews... suggestions?
I got everything on aliexpress from a Taiwanese company they were very good at replying and sent the products quickly, custom made to length. @@dadoVRC
what is the name of this machine?
Optimum MH28V, converted to CNC using an aliexpress 3 axis kit and 2005 single nut ball screws.
Your bore gauge technique looks a little suspect. Roll it through once and in one direction after locking it.
Also, verify the diameter of that endmill. The chinese ones can be undersized which might explain some of that offset.
You’re quite right I should’ve definitely checked the endmill size. And yeah it was pretty hard to get a good measurement with the hole only being 6mm deep, usually I can roll the bore gauge through but it was barely in the hole. I’ll have a look next time I’m in the shed.
@@OddsandEndsMachining I hear ya on that shallow hole. Note you can use it as well for slots if there is an open end rather than have to wiggle around calipers for high spots. Given the surface finish, I'm guessing you're probably right with the spring pass though .3 seems a bit much for just that. Something else at play! Something subtle. Fun puzzle for you to solve at least.
When checking the endmill, do it on the actual cutting edges not the shank. They can be different. You can rotate it backwards through caliper jaws to keep everything from getting damaged and get a good measurement. Nice job overall.
I’ll give measuring the endmill a go, I’m thinking .2-3mm width on the square is only .1-.15mm off deflection on each wall. The only way I can test this is to re run the part on the other side with a better finishing strategy.
That is too much for tool deflection.
By tool deflection I also meant to say some deflection in the column too. About .1-.15MM on each wall doesn’t seem to extreme for a combination. The only way to find out will be to re-run the part and do a proper finishing pass.