OpenBuilds MiniMill Review (mostly for cutting aluminum)
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- เผยแพร่เมื่อ 16 พ.ย. 2024
- Think of the OpenBuilds MiniMill as a CNC router with a small (5 inch square) work area. It doesn't have the mass or rigidity of a mill. If you think you'll need a larger work area, get a CNC router with a larger work area instead. If you think you'll need the rigidity of a mill, buy a mill instead. If you're not sure what you want, or can work within its limitations, it's a good inexpensive introduction to the world of CNC.
We are always working on ways to improve and we thank you for your honest review as well as sharing your modifications. We will take these thoughts in review in future developments.
OpenBuilds® if you were to supply this mill with these linear rails I would buy one for sure.
@@shawnlund Yup, I have a MiniMill myself, and would definitely buy the rails as an upgrade kit if OpenBuilds sold them! In the meantime, I will look for rails in my area.
It appears you didn't really even test it.
The problem with Openbuilds is they are so stuck on the V-Wheels and for anything that will apply any force to them they suck. I almost bought this and glad I didn't because wheels, no matter which ones, is not the way to go for these machines. Even in the 3d printing world people are moving away from the wheels into the linear bearings and blocks and their quality has come up.
The wheels, especially the plastic ones, are not suitable for these machines. My machine had over 0.1" of deflection on the vertical axis with only light pressure. It has been relegated to an oversize 3d printer.
Just seeing this video now in 2020 as I've been contemplating making a Mill or router via openbuilds stuff. This was very helpful and well presented. Thanks for taking the time!
This is a PHENOMENAL review!!! Thank you for taking the time to go through all of this.
2021 and this is still a great review and the mods you have done totally transformed the machine. Great job! With spindle RPM like that, Single flute endmills are the way to go. Good job and thanks for making the video
Very interesting. At one point I had a Hurco KMB1M 3HP Mill. It weighed North of 2,000 pounds. I wouldn't have done some of the cuts in aluminum that you are doing with a small router on a light mill. I thought for sure you were going to break the end mill on the first cut. I'm more impressed that it held up to the abuse.
Taig makes a small micromill. It's a good source of information on how to work these light machines. You need to use small bits and very light cuts and be exceptionally patient.
You did discover the mass and rigidity rule the day with mills. The roller wheel and narrow stance of the linear rail assemblies don't contribute to rigidity.
nice work though and please don't take this as an attack. Hopefully this will help manage expectations for others interested in the same things.
Oh and that Chinese mill you showed is only good as a door stop. :) Better to buy a Grizzly benchtop mill and convert it to CNC or buy a full on Bridgeport :)....
Wow, thank you for this review. You just made me realize that I need a real mill and not a router!
Just FYI you can utilize fixtures or location pins to machine parts larger than the working area of the CNC in the X axis. It's not always practical and with an enclosure the parts might not fit but I've done it myself at work before when I had to cut some keyways into a really long shaft.
Impressive piece of development work. You could cast a 3" slab of concrete to mount it on with buried studs as a lo-cost alternative to the aluminum block.
The guides are not rigid enough.
A cheaper mass to use for anchoring the mill would have been to use a block of concrete with some anchors in it. Lot cheaper (and effective) than the block of aluminum.
Hi, I would try adding sand inside the aluminum profile to dampen the vibration
really cool video 👌keep up the work 💪
also you once you have your first cnc , the hard part is done, if you ever want to upgreade you can now build exactly what you want
Great video, very interesting. Nice to see the mods and how they improved the machine.
Mass is the cheapest way to achieve rigidity, but form.. There is something to be said for form. We have yet to see ultralight machines made out composites like carbon fiber. You could have a machine with a rather large cutting area that just two men could carry that could easily machine titanium. Cost prohibitive I guess.
In the video, he has had to make due with mostly form, and just a little bit of mass (outside of that enormous block of aluminum). These are really my favorite kinds of machines. To me, they are more incredible than the big ones because they are making due with so much less. I want to see this field, this hobby, propelled into the future, and it's happening right before my eyes. Great build, great modifications. I hope to have one soon.
Totally agree. I think the structural design and engineering behind the aluminum extrusions is more impressive than just trying to oversize everything with steel. For hobbyists (like myself), having an inexpensive yet capable machine that is able to mill aluminum for parts now and then is invaluable. I see folks DIYing these impressive yet excessively expensive CNC Mills but for what purpose? They aren't going to be running a machine shop. The mini mill with it's upgrades like the video is perfect for the hobbyist.
Best review, you saved me time and money by learning your mistakes, don't get me wrong very good video
Insightful video. Learned a lot. Thank you!
Cool little mill and documentation of your improvements, i know you already did these improvements but with that 125 for that big block of aluminum a cast iron plate would have helped alot more. Cast iron transmits vibration to heat and aluminum just transmits the vibration, but still congrats on your findings and improvements.
I would have loved to use cast iron, but I wasn't able to find an affordable source. The aluminum was $125 with shipping... the few places that I found cast iron were at least twice that after shipping, even with half the thickness.
Great job documenting the whole process.
Try conventional milling instead of climb milling to reduce vibration, also lighter cuts, or slower feedrate.
Conventional is good for roughing if you don't have a particularly rigid setup, but climb gives a better finish on a light cut from what I've worked on. But I've only got experience on a prototrak smx and an old Bridgeport with EZ-trak add-ons so I've never used this kind of machine.
I was watching this for a second time and realized you were climb cutting on almost all the cuts. You should see a massive improvement in vibration and resonance by simply going to a conventional cut.
If you look @18:13, I do conventional and climb. There's not a lot of difference in terms of the vibration. I've done other tests, and conventional is a bit worse overall on this machine, presumably because more chips are getting recut. Someone else was surprised at that too, I guess because climb cutting can be difficult even on large machines if you have a lot of backlash. The delrin anti-backlash nuts on this machine work well to eliminate backlash, enough so that the rigidity in the structure is much less than the backlash, so climb vs conventional doesn't matter too much.
I was watching your other videos and came to the same conclusion. It's very odd to me that your machine does better in a climb cut rather than conventional. I wonder if it has something to do with the router itself? I think you can probably change your name from "'I'm no expert, but" to "I'm a self-taught expert" now. : ) Keep the video's coming, they are excellent both in content and presentation. Cheers
20:08 FWIW, you can use center cutting end mills to make holes.
Cool I have unimat db200 lathe, mill . You mill on your upgrade machine better than I can on mine . I’m going try get. Cnc kit for mine see what I can do. Anyway cool setup just keep chips flying
Amazing job all around! I built a miniMill myself and ran into the same issue with the wheels. Now waiting for mgn rails to come in. Looks like I'll need a giant block of aluminum as well! That cutting calculator is pretty nifty! Did you make it yourself?
This build video has me thinking of a few other improvements now:
* Filling the extrusion cavities with gravel/resin to add mass & rigidity
* SuperPID to keep the router spinning at the designed RPM
* Diy 2 nozzle mister (fogbuster) to help with chip evacuation & keep the cutting tool cool. It also has the added benefit of improving surface finish.
The Makita router seems to have good speed regulation already. I have also thought about a fogbuster, or maybe a simple gravity feed drip system -- as I get more aggressive with cuts there is a tendency for the aluminum to get gummy if I don't spray on WD-40 occasionally. I'm curious about filling the extrusions -- if you do that, make a video and let us know how it goes!
day and night after your improvements, thinking of Frankensteinig a mpcnc or something fro my next project
Great video! Excellent actually!
Great video. 👍🏻
Did you experiment with conventional milling? It looks like all your cuts are climb cutting. Chances are this machine has a very low end backlash eliminator and it's certainly very flexible compared to a real mill, in that scenario I wonder if you might be better off with conventional cuts. Maybe not though - just a thought.
The delrin anti-backlash nut is actually pretty good -- it requires some tweaking but once you get it set right, it is fairly rigid and does a good job at eliminating backlash. Conventional cuts were worse than climb cuts because conventional cuts resulted in a lot of chip recutting, which is even worse when you're already getting chatter & lack of rigidity. I've started making my own versions of the openbuilds anti backlash nuts, I'll probably make a video about them soon.
Very good review and you just saved me money and told me what needs to be done as well. Only one issue I see for me is that 120 dollar (aluminum has gone up since your video was made) aluminum block. I wonder what could take its place that would be cheap and allow a spritzer to be used?
Epoxy granite block or maybe concrete block?
@I'm no expert, but I was thinking a cinder block but it would need some sealant on it and use concrete in the holes if it were long enough and if not it would take two. I wonder if that would be heavier? Anyway the weight then gets to be an issue for the table.
I wonder if in the end a 3040 CNC from China wouldn't be better?
@@thebeststooge For cutting metal? I don't think so, the ones I've seen just use unsupported smooth rods, which aren't very rigid compared to square linear rails.
Thanks so much for your video. I am wanting to custom engrave/mill brass for use with old fashioned style wax seal stamps - where you stamp the brass into molten wax to make an impression. Do you think this machine would be suitable? I need a machine that can A. handle brass and B. be good for very fine detail - to about 1mm depth. Thanks again. Christine
PS - price isn't really an issue (well it is, but isn't) so if you have a better recommendation please let me know :-)
@@chrisf4627 I haven't ever milled brass, so I can't say for sure. I can say that this machine is able to mill fine detail accurately when the milling loads are low, which they may be for your case, where you're making very tiny cuts.
Great work! Could you provide the files that you printed that hold the accordion covers to the minimill?
Aluminum milling at high spindle speed sounds like hell even on very expensive CNC machining centers made for aluminum.
Not really, I mill aluminum at 24k rpm with a chinese spindle. Works really well as long as the machine is rigid/heavy enough and you got enough feedrate (mine is 148kg and bolted down).
@@exol511 yes really. I spent entirely too many days in machine shops feeling the floor shaking from a cnc milling aluminum. I never said that the machine suited the job, some salespeople had convinced the shop owner that they were adequate for the job. The owner was in his office a quarter mile from the shop he wasn't subjected to the sounds.
@@wtchr6883 in my case only the 300kg table its bolted to shakes haha. Its still a toy machine, but its better than most routers using those cheap hf spindles, so I can actually get some use out of the 2,2kW one I have.
I beleave you can get much better solutions with the Base Machine.
The Aluminium you use sucks it is lowcost - use 7075 Aluminium AlZnMgCu1,5 - do not feed directly into z always feed z and xy at the same time - the axial force decreases and the cutter no longer wobbles out of its axis - feed less into z and increase the feed instead - there is a cutting öl available made from rapeseed oil which evaporates after some time - the heavy vibration (and sound) is cause of the backlash of the 8mm spindle - use an adjustable spindle nut - Do you know the difference between climb milling and up-cut milling? With such a soft machine, please use only up-cut milling - at least for roughing.
would using a bigger Z axis gantry plate with the bigger clear wheels on the outside of the 80mm Al extrusion be helpful?
That's how the stock X and Y axes work. It'd be an improvement, but the rigidity of that arrangement isn't great either.
Great vid.
wow, great work on those upgrade! That sounds like a really decent mill now. How satisified are you with your upgraded setup after some time now?
oh and have you considered getting one of those chinese VFD spindles? They got some really high power ones for 100-200€
Having precise electronic RPM control over the manual router setting sounds like it could improve things as well as going with a lot higher rpm to compensate the lack of rigidity.
@@timonsku I have a couple of upgrade videos after this one, and now I'm satisfied. Replacing Z axis/head of the mill in the later videos made a lot of difference. I did switch to a chinese VFD; it's a lot quieter, easier to find collets for, and easier to mount rigidly to the head, but didn't make too much difference to the capabilities besides the extra convenience.
@@imnoexpertbut thank will check them out! Did you ever made plans/guides for those modifications? I'm sure quite a few in the community would be interested.
would this work with nema 17 instead?
Yes!
for the metal base why not just use a 1x6"x20" long block of steel. Would of been half the price, weigh about the same and be just as stiff?
I computed similar rigidity with a 1.5" thick piece of steel. All the steel places around me have horrible prices for small orders, and if I bought online the shipping for 50 lbs of steel would put it at about the same price as the aluminum. At that price, I went with aluminum so it'd be easier for me to carry around and work on (I don't have great tools for working on a heavy piece of steel).
so how much did it cost to upgrade this? $100 for all the linear rails and $120 for aluminum block $100 for 3 custom mounting plates, about $320 total? plus the $500 cost of the machine to begin with and you are up to $820?
Pretty much, although the mounting plates were around $25 total: they're just 1/2" thick plate that I manually laid out and drilled on my drill press.
It's too light?
How did you fasten that alu plate that you cut at 17m30s of the video, to the wooden block? Great build, I have a minimill and I will probably add these additions to mine!
Blue painter's tape on the wood block, blue painter's tape on the aluminum plate, and superglue in between. Works like double sided tape but MUCH stronger. If you search for NYC CNC superglue you'll find more info.
How did you mount the plate after adding the linear rails? I assume it added a gap between the plate and the anti backlash nut. Did.you make a spacer to attach the two? This is great information thank you
Yes, I 3d printed a rectangular spacer that had 2 through holes for the screws.
@@imnoexpertbut do you have the stl file for the spacer? Or step? And also what's the length of the linear rails you used? Thanks again
@@Mainstream818 I don't, but it should be easy to model, just a 15mm tall rectangle. I used 250mm rails for X and Z and 300mm rails for Y. MGN12C bearings.
@@imnoexpertbut perfect thanks again for the information
Hi thx for all. Where can i buy it?
Excellent Video
Very well done review, your insight has helped
Where did you purchase your bellows (part no.), can you print me some fasteners, too?
You expect a project like this is perfect in timing because when open-builds had a special when I purchased mine, so now everybody has hopefully assembled them, I have not yet since I was waiting on ideas such as yours so I may skip ahead to yours right?
I bought them on amazon; if you search for "CNC Machine Black Rubber Shield" you'll find them. If you don't have a 3d printer, you should try cutting fasteners for them from plastic or wood sheet.
Once u get cut more than roughed in. U can always polish by hand or dremel.
Better than using a file , hacksaw, etc. to make the part. Lol.
I built my own minimill and ended up with a mill that is twice the machine this one is for about half what Openbuilds is screwing people over with this one for!
I'm currently trying to do this myself, sourcing the parts myself with linear rails just like this video. Any tips or things you've learned you could share? Thanks
With all the advancements in power electronics we are still stuck with a large power supply.
you just went too aggressive with that cut. literally bit off more than it could chew lol. less stick out will help and more rigidity. weld a thick walled metal tubing frame together for it. maybe even pour a cement base..?
Yeah. Rails.
what kind stepper motor are u using?
I'm using the 175 oz*in nema 23 steppers that they sell on the openbuilds part store.
Thank you so much for this, it will save me time and disappointment.
My daughter bought a cheap 3W laser etcher which was good for name tags then came the need for bigger area and odd thickness that the unit could not straddle.
I started project 'Will it ever be finished' as a 600mm x 600mm x 20mm frame with a 15W blue laser with seconds of thought spent on centres and rigidity when moving the unit.
Part way through I looked at it and thought "If I had a 3D printer then some of the parts could be a bit better than being produced by hand power tools and files." maybe it should be a dual 3D and Laser... Hmm need to make the Z axis at least 200mm.
Next it has to be rigid or to phrase it in real terms, heavy. The gantry has raise not a platform because I may want to drop this on a full sheet of ply.
I have collected 3 - 400mm ballscrew with edge wheels not linear slides and saw a bit of wobble on the DTI.
Today I connected to OpenBuilds for inspiration which brought me to here, now I feel like I am not being over cautious.
(non-surprising)Conclusion - keep v wheels away from metal and stick to wood/plastics/composites
those nylon rollers are a crap solution for CNC, aren't they? Why is Openbuilds even using those as a solution for their products, one might start to wonder ;-)
Also: how about aluminium versus steel beams? Isn't aluminium a weak point too?
3/4 n video sounds good lot better
Did you try slower travel speed? Depth of cut seems ok but it looks like you're cutting awfully fast.
I used a 0.001 inch feed per tooth to compute the feedrate. Too much lower than that and you risk doing more rubbing than cutting, which can make the cut behave even worse. I did play around with the feedrate override a bit and it didn't make too much of a difference. Lowering the RPM lets you lower the feedrate and keep the feed per tooth up, but lower RPMs seemed to generate more resonance in the system. :(
you have a lot of room to buy some more aluminium construction profile and cheaply turning this machine into a decent CNC.
Maybe figure out some stiffened braces
This actually brings up an important issue. I own a C-Beam and it does everything I ask it to do, but I am cutting Baltic Birch plywood, plastics, MDF, and other softer materials. Given the flexible nature of some of the materials these machines are made of, and the natural vibration you get with hand held routers, It may not be the best idea to cut aluminum or other soft alloys. Half of that misinformation goes back to Open Builds and the claims they make about these platforms. The other fault is ours as consumers. I could probably make something fancy using a hacksaw and a couple of files, but should I really? Unfortunately, the elephant in the room is the extensive body of information showing how to purchase and assemble these machines, but there is very little showing what is actually made with them. I don't want to be a wienie, I just don't think it's prudent to cut aluminum using a holding fixture made of.....aluminum.
I make model rocket fins, drilled brackets and plates, circle cuts in plywood, etc. Just be sure you are not making stone soup here.
Is the vise mounted on PLASTIC?
Lol.
nope
@@imnoexpertbut What are the orange things? I suppose it's kinda rudimentary but it is bolted? Looks like uhmw.
@@imnoexpertbut painted orange steel bars? 1/4-20 machine screw?
Oh, I see what you're asking. The vise is mounted on an anodized aluminum plate with steel bolts, but the orange square washers/spacers are plastic (PLA or PETG, can't remember which). They just need to get compressed, which plastic is fine for.
POS , never was any good new. Someone gave me one, I'm giving it back. Not worth replacing all the electrical components, servos are Bipolar 1.55 amp 65 volt and there are no affordable drivers, spindle motor is old school AC/DC combo. Body is weak and 1/4-20 lead screws are pathetic. Don't waste your time and money on one, even if its free.
Well, if it's free I won't waste money on that by definition. =)