Author Topic: Sienci Mill One  (Read 6764 times)

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Offline Tin Duc Vo

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Sienci Mill One
« on: September 06, 2016, 10:16:01 pm »
     Hey, what does everyone think about this CNC machine on Kickstarter? They seem to be able to do aluminum milling and have a decent build height. I'm backing one, but would like to hear everyone elses' thoughts before I commit.

     Some of the concerns I have about the project are the fact that it seems to be produced by a team of undergraduates (I just think that it is a lot of work), there aren't any T-slots, and the machine is built out of MDF, but is advertised to mill aluminum.


     The project: https://www.kickstarter.com/projects/sienci/sienci-mill-one-simple-and-affordable-desktop-cnc?ref=activity
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #1 on: September 07, 2016, 12:39:34 am »
Hi

It seems very expensive for what it is. It should do a fine job on foam or cardboard. The frame will go to pieces trying to do anything solid with reasonable cuts. If you want to spend two weeks of machine time on a part you *might* get a small chunk of metal through it.

You can get a variety of small mills that will handle metal for about the same cost....

Bob
 

Offline george graves

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Re: Sienci Mill One
« Reply #2 on: September 07, 2016, 01:23:40 am »
"A fun and easy to use program...."

Errrr.  That makes it sound so limited. I have a feeling when people make kickstarter videos now-a-days, they just copy and paste the verbiage from other videos or something.

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #3 on: September 07, 2016, 12:16:16 pm »
The MDF looks pretty thick. I thought cutting wood would be no problem at least. I'm not a machinist, so that's why I thought I'd post here. What would you recommend for a small mill, uncle Bob? I found one on AliExpress that's all aluminum/steel and claims to be able to cut aluminum, but it actually gives you a transformer and bridge rectifier as the most sketchy part of the kit, meaning I'd have to deal with mains and create a case for it so no one geta shocked.

I have no intention of using their software.
 

Offline Koen

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Re: Sienci Mill One
« Reply #4 on: September 07, 2016, 01:40:34 pm »
Well, what do you want to mill ?
 
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Offline Jeff_Birt

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Re: Sienci Mill One
« Reply #5 on: September 07, 2016, 02:02:26 pm »
It is a pretty flimsy machine to be honest. From a quick overview I can see that they lead nut mounts are not very secure, they use SOLID couplers to couple the stepper motor and lead screw and have NO bearings supporting the leadscrew. Only the stepper motor bearings support the leadscrew and the entire lateral force of moving the carriage which the stepper motors were NOT designed to do.

Many of the parts are 3D printed, while it is great for some things it is lousy for others. I have 3D printed stepper motor mounts myself for different applications. When it is a very light duty application where the mount does not have to align the motor to what is being driven. i.e. is you are using belt drive, then it works OK. I should caution it is OK for light duty and should not be counted on to last forever. When you are directly driving a leadscrew the motor mount must be rigid as it serves to align the motor to the leadscrew. A zero backlash coupling, like an Oldham style, should be used to couple the motor to the leadscrew. The coupler serves to account for the slight misalignment between the motor and shaft. the driven end of the leadscrew must also be supported by bearings (support for both rotational forces and thrust). Relying on the little bearings in the stepper motor for this will quickly destroy the motor.

Not to toot my own horn but I do know a lot about this sort of thing as I do motion control related applications at work and sell desktop CNC machines  on the side. I won't link to my website but if you are interested in a well built CNC mill Google 'Taig' (not my company but one of my suppliers.) if you Google my name you will find my website. If you are interested in more of a small router type machine look up routakit.com. His SD machine is about the same price as the one you linked to and much better built.
 
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Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #6 on: September 07, 2016, 02:40:10 pm »
I see that they only use one external bearing per lead screw. Wouldn't the axial forces be shared by the bearings also? I will see if they will be able to fix these issues and if not, I will have to find something else. Thanks for all the insight. I looked up Taig machines and they're too expensive for me. His SD machine is $1800USD + shipping + tax while the Sienci one is $660CAD and I can pick up. My budget is under $1000CAD.
« Last Edit: September 07, 2016, 02:41:56 pm by Tin Duc Vo »
 

Offline kosine

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Re: Sienci Mill One
« Reply #7 on: September 07, 2016, 03:27:10 pm »
Ok, a nice student project, but probably not a very good workhorse.

I'd also recommend something like a Taig or a Seig, though there are many similar brands out there. They sell secondhand for not much more than the Sienci asking price, and it's not too hard to add your own CNC conversion kit. (Or buy one prebuilt...)

I've had an Axminster for over a decade, have clocked up over 10,000 hours on it (yes, I use it a lot!), and it'll still hit 25micron accuracy all day long. (I make aluminium moulds for short-run plastic injection moulding, so accuracy is critical.)

I've no doubt the Sienci "works", but I wouldn't expect wonders from it. There are plenty of cheap Chinese CNC machines on ebay that would offer similar performance. If you're just wanting to dabble with CNC, maybe start with one of those.

There's some pictures of assembling the Sienci on Instructables: http://www.instructables.com/id/How-to-Assemble-the-Sienci-Mill-One/

Some critical points to note (in addition to those mentioned already in this thread):
- table size is quite small. If you added clamps, your work space will be very limited.

- table has no T-slots - not sure how they clamp the workpiece. Heavy cuts need more than sticky tape. The cheap Chinese CNC machines do at least have a reasonable size bed and clamping slots.

- table may not sit 100% flat. This is a big problem for etching PCBs. You only cut about 100microns deep, so if one end is 0.1mm higher than the other, you'll have problems. (You can always skim it first to level things up.)

- 3D printed parts do not instill confidence.

- the box enclosure will make it hard to align the workpiece. Double-sided PCBs would be tricky. An overhanging spindle (like Taigs have) gives much better access, and larger workpieces can overhang the bed if necessary.

- rigidity is critical if you're trying to machine metal. If you're after their stated 250micron accuracy (which is actually pretty terrible for a CNC machine), the frame and spindle must be rigid to some tens of microns. This is why commercially available machines (again like the Taig) are made from cast-iron.

- no drip tray. You can dry-cut aluminum if using cutting bits above 3mm diameter, but smaller fine detail cuts (I use dental burs!) need cutting fluid. If that gets on the MDF frame - and it will - it'll swell and their goes your accuracy.

- steppers. They don't say, but looks like they're using 4-wire bipolar. I've build a few CNC machines and always use 5,6 or 8-wire unipolar motors. They run smoother and can offer better accuracy. (Ok, you get less torque, but speed isn't everything...)

- electronics is probably OK, but not sure how much current can be delivered to the steppers. My primary system has 3A per coil, and then I have 5:1 reduction gearing to boost the torque and accuracy even further. I doubt this machine would like doing heavy cuts in aluminium or even hardwoods.

- I can't find any pictures of anything made from metal, though I expect they've done some tests. The kickstarter page says 80-100micron depth of cut in aluminium. A good machine should be capable of 1-2mm even with small cutting bits (1-2mm diameter). You'd have to do multiple passes to get anywhere at 0.1mm depths, and then we're back to accuracy issues.


On the plus side, I think it's great that the group are working on an accessible CNC system, but this initial offering has some serious limitations.
 
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Offline Jeff_Birt

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Re: Sienci Mill One
« Reply #8 on: September 07, 2016, 03:48:45 pm »
- steppers. They don't say, but looks like they're using 4-wire bipolar. I've build a few CNC machines and always use 5,6 or 8-wire unipolar motors. They run smoother and can offer better accuracy. (Ok, you get less torque, but speed isn't everything...)

Uni-polar vs. bi-polar has nothing to do with the smoothness of operation, that all has to do with the stepper driver and drive reduction of the machine. Most affordable stepper drives used to be uni-polar as it as a lot less expensive to build. The trade-off is that you only get 80% or so of the torque of the motor. These days building bi-polar drives is less expensive so you see them most often as they will let you get full torque from your motor.

The smoothness of operation has to do with the stepper drive and gearing. If you drive a stepper motor in full steps at low RPMs it will not be very smooth, which makes sense as you are going fully from step to step so you get a cog/detent effect. To combat this you micro-step the motor, i.e. increase resolution by stepping between full steps. You will see micro-step level from 2x to 16x commonly, but micro-stepping is also a trade-off, while you get smoother low speed operation with higher micro-stepping amounts you also get less power from the motor at higher RPMs. Modern stepper drives do some form of 'step morphing', they might expect a 10x micro-stepping input which is used at low RPMs. As the RPMs increase they 'morph' to a lower number of micro-steps and them to full steps. The morphing is done internally and is transparent to the control. This gives you very smooth low speed operation and all the power of the motor at higher RPMs. (Some very new drives do up to 256x micro-stepping.

With the higher micro-stepping rates you have to pulse the stepper drive faster and the old PC parallel port is just not up to the task in most cases. An external motion control/step generator board makes a world of difference.

What ever type of machine you are looking for do comparisons on price, performance and what you are actually getting. I see a lot of 'low cost' machines that don't include all the needed bits. On Ebay there are a slew of 2040 / 6030 CNC routers. The mechanicals are OK but the control box is junk. If you can get just the machine and build your own control they work fine.
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #9 on: September 07, 2016, 03:59:21 pm »
What do you guys think about these?

http://www.aliexpress.com/item/200W-Three-axis-Ball-Screw-CNC-Router-Engraver-Engraving-Milling-Drilling-Cutting-Machine-CNC-3040-Z/32712744259.html?spm=2114.13010208.99999999.267.WpIIXg

http://www.aliexpress.com/item/Free-ship-1pcs-DIY-CNC-Wood-Carving-Mini-Engraving-Machine-PVC-Mill-Engraver-Support-MACH3-System/32672216454.html?spm=2114.13010208.99999999.276.WpIIXg

Another option is getting a used Shapeoko for $1100CAD before haggling.

The second one provides a transformer and a rectifier instead of a full-blown power supply for the spindle, so I will have to pay $80 more for a proper supply/higher power spindle while I'm at it.

They both look a lot more than the Sienci Mill One. I was also wondering about how you would use cutting fluid on top of MDF like that. I saw a video of them milling aluminum and to clamp that down, they had to bolt down into acrylic with like 20 bolts, which I find very inconvenient. The concern I have for the chinese ones is the power of the spindles, 230W and 500W. Also, the support seems like it would be a nightmare if I needed any. I'm thinking that either of the Chinese machines would work, but then again, I don't have any experience, so all of this is very appreciated.
 

Offline Koen

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Re: Sienci Mill One
« Reply #10 on: September 07, 2016, 09:56:17 pm »
Well, what do you want to mill ?
You can't receive a valid answer on the suitability of any machine without stating your goals.
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #11 on: September 08, 2016, 04:03:20 pm »
Hi

What country are you in? Shipping and import issues will have a lot of impact on how far your budget will go. If you would turn on your country ID that would be a big help.

How big an item do you want to mill?  One meter by one meter by one meter will cost more than 10 cm x 5 xm x 5 cm.

Do you have an enclosure / mount for the mill already? They throw up an awful lot of "stuff" and need to be solidly mounted.

What sort of material do you want to work with? These machines quickly break into categories in terms of:

1) Foam (but maybe something else in a dream world)
2) Wood (and foam)
3) Metal (and wood and foam and plastics)

Do you really have to have CNC? A manual device will do exactly the same thing for less money.

How much time are you going to put into this? There *is* a learning curve. A CNC is actually more work than a manual machine at first.

How much are you willing to spend on added tooling? How much tooling do you have already? A good guess is that you will spend roughly 1/2 the cost of the mill up to the cost of the mill on tooling before you are done.

What sort of precision do you require? Is +/- 10 mm ok? Do you need +/- 0.1 mm?

Is price the only criteria? In other words, any mill will do as long as it's under $1,000. Does tooling and the enclosure have to come out of that budget?

How much work are you willing to do on the machine to get it working? A full kit is one thing. A basic machine that needs setup is something else.

There are a lot of Chinese outfits that will sell you a basic machine. There are a lot of places that will sell you add on parts. A drill press based machine will do one set of things. Other machines will do other stuff. There are literally tens of thousands of options out there to pick between. A used Bridgeport in need of a major overhaul for $1000 might make a lot of sense to me. Having a manual machine that weighs > 500 Kg takes up 5 meters in every direction might not make sense to you. (As in, do you have 3 phase power?)

Bob
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #12 on: September 08, 2016, 04:10:35 pm »
Well, what do you want to mill ?
You can't receive a valid answer on the suitability of any machine without stating your goals.

Sorry about that. I'm looking to milling aluminum, acrylic, and PCBs. I'm looking at this machine right now: http://www.aliexpress.com/item/500W-USB-CNC-Router-Desktop-CNC-Router-Engraving-Milling-Machine-ME3040-Air-Cooling-3-Axis/32717051510.html?spm=2114.13010208.99999999.261.XuJIgV.

I'm wondering what wattage of spindle I'll need as an estimate without going into the torque-speed curves.
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #13 on: September 08, 2016, 04:23:08 pm »
To Uncle Bob,

I'm in Canada. I'm finding that I'm actually using this forum, so I'll go through the country ID and stuff later :).

I think a 3040 machine would work for me. I'm intending to use it for those little metal parts I need machined and PCBs. 3040 seems like a comfortable size for this application. I'm not planning to use it for big builds.

I have a desk I can totally wreck, but no enclosure.

I don't absolutely need a CNC, but I think it's good to have to be able to produce PCBs without busting out the gloves and chemicals. I will need to produce many PCBs and do not want to wait and do not have the money to use express services. I'm willing to put in as much time as necessary.

+/-10/10mil for PCBs is what I would like.

I'm willing to put in the time to build and around $1000 just for the machine is okay. Thanks for the help by the way.
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #14 on: September 08, 2016, 04:33:34 pm »
Hi

If your focus is on pcb's, you should look at an engraving machine rather than a mill. It is better suited to the task and at a given budget level will give you better results. You will need a high speed hole drill either way. My suggestion is to go with the cheap PCB houses or simply use perf board. Perf board will do as well as a single sided board. It will give you the same density, the same performance, and it is *much* faster than a pcb.  Double sided without plated through holes is a major pain to assemble. Unless you have a very unusual machine, most modern IC's will be a problem with a mill style pcb....

Bob
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #15 on: September 08, 2016, 04:40:33 pm »
I don't want to wait a month for a board though. I'm working on my own projects and will need boards pretty rapidly and I'm using surface mount mostly. With double sided boards, I'm okay with making my own giant vias. Let's say it was for aluminum milling, do you think a 200W or 500W spindle would be okay?
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #16 on: September 08, 2016, 04:51:31 pm »
Hi

I think that for proper milling of metal, you need a variable speed drive so you can match the cutting speed of the tool to the material being milled. For an engraving style machine you just run the spindle as fast as you possibly can and tolerate the problems you create. For a two dimensional object (like a pcb) you do not need much Z travel or Z axis stability. For a three dimensional milling process, lateral force on the cutting tool makes Z stability *very* critical. For a mill you put more metal into this and that. If you have a fixed budget, that takes down the size of the work area. On a mill, the same lateral forces mean you need a lot of drive power on the X and Y axis. To do this without spending a fortune, you gear down the drives. You trade off speed for power. On an engraver, you don't need the power. You put in wimpy X and Y drives and run them fast. That saves you money.

There are places in the US that will do a "one day fab" double sided board with plated holes for < $30 and get it to you in a couple of days .... No solder mask or silk screen, but a better board than you will do on a mill.

Bob
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #17 on: September 08, 2016, 08:39:59 pm »
The one I'm looking at is variable speed with a 12000rpm max. What do you think of the latest machine I posted? I don't have any PCB fabrication options like that here in Canada. It's 200$ for a 2 layer 32sqin board with a mask. I can't afford that when I'm not making any money yet.
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #18 on: September 08, 2016, 08:48:08 pm »
Hi

I believe that the US outfits will ship to Canada without much trouble. Courtesy of NAFTA there isn't any hassle with duty.

=====

On a CNC, you want the spindle to go down to a few 10's of RPM on the low end. The "router" motor heads just don't go down that low. You also need full power at the low end, so some sort of "gear shift" process is essential.

For PC boards, you aren't going to run real high speed. I would bet that the 200W motor will be ok for what you are doing. Either the 3020 or the 3040 version will do the job. Exactly which of the multitude of sellers to buy it from .... who knows.

Bob

 
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Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #19 on: September 09, 2016, 12:52:41 am »
Thanks, everyone. As a student, the lowest price I found was $33 for a board, but then I'd also have to pay shipping, which is at least 15USD. On top of that, there's the possibility of shipping fees, so I would rather just produce my own boards. I'll update on how it goes with the Chinese CNC if there's interest :).
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #20 on: September 09, 2016, 01:09:59 am »
Hi

As a student, Advanced Circuits will sell you full up solder mask / silk screen boards for $33. They take 5 days to fab. Their "bare bones" process is cheaper still. It does not have mask and silk screen, but does have plated through holes. shipping is roughly $10. They are *not* the lowest price out there. They are a high quality outfit.

Bob
 

Online blueskull

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Re: Sienci Mill One
« Reply #21 on: September 09, 2016, 02:54:46 am »
As a student, Advanced Circuits will sell you full up solder mask / silk screen boards for $33.

And they have a minimum order number! You can not just order a single board for $33.
Also, their expedited service is very expensive. We once built a board from them, 1 week lead time, single layer, 1 square inch, just 3 pads (interconnection board), it costed us $1000.

I highly recommend OSHPark for small boards without time constraint, but quality is a must.
I recommend PCNWay for larger boards or expedited services where general Chinese quality is acceptable (poor silkscreen, besides all as good as OSHPark).
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #22 on: September 09, 2016, 03:50:41 pm »
As a student, Advanced Circuits will sell you full up solder mask / silk screen boards for $33.

And they have a minimum order number! You can not just order a single board for $33.
Also, their expedited service is very expensive. We once built a board from them, 1 week lead time, single layer, 1 square inch, just 3 pads (interconnection board), it costed us $1000.

I highly recommend OSHPark for small boards without time constraint, but quality is a must.
I recommend PCNWay for larger boards or expedited services where general Chinese quality is acceptable (poor silkscreen, besides all as good as OSHPark).

Hi

For a "normal person" they have a minimum order of 4 pieces x $33 on the full up process @ 5 days. For a student (the OP is a student) they wave the minimum order and it's just 1 piece @ $33. No idea if that deal comes and goes or if it is always there. The
one day stuff on a small board with no mask (bare bones) usually runs me about $10 to $20 before shipping.

If you go with a custom process board and the full blown approach, their prices are inline with other US based PCB houses.

I have no issue with waiting for boards from overseas. The OP has a problem with the delay and I just wanted to be sure that he was not under the impression that "all quick boards are > $200". That was the case 30 years ago, it isn't anymore.

Bob
 

Offline Tin Duc Vo

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Re: Sienci Mill One
« Reply #23 on: September 10, 2016, 05:24:05 pm »
That is to Canada shipping though. And it's not definite that I'll only be making small boards. For small boards, it's getting closer to affordable, but with big ones, I'd be like ... I hope I didn't mess anything up at all...
 

Offline uncle_bob

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Re: Sienci Mill One
« Reply #24 on: September 10, 2016, 05:48:08 pm »
That is to Canada shipping though. And it's not definite that I'll only be making small boards. For small boards, it's getting closer to affordable, but with big ones, I'd be like ... I hope I didn't mess anything up at all...

Hi

The bare bones process only makes sense for little stuff. For big boards, the full blown approach is actually cheaper.

I don't think you made any mistakes here. I just wanted to be sure you were aware of the options. The student deal is a nice thing while you are a student. Shame on me if I don't mentioning it while it applies :)  It's been ... errr ... a while.... since I qualified for a student discount.

One thing to put on the list while you are shopping is a high speed PC Board drill. Also collets for the router body => milling heads along with drill collets. You might as well order a ton of drill bits. You will go through a lot of them.

You may be tempted to do drilling with the 3040 / 3020. To do so, you need to rig a substrate under the pc board. Most people's experience is that it's more trouble than it's worth. You just set up a drill had go to it manually.

Bob

 


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