OpenBuilds MiniMill Review (mostly for cutting aluminum) 

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.

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

Wow, thank you for this review. You just made me realize that I need a real mill and not a router!

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 :)....

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.

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

Your presentation was first class. Keep up the good work. Your voice is easy to listen to and very smooth. I did learn about this machine. Like the title indicated, it was about this machine on aluminum. This machine on plastic and/or foam would obviously be outstanding. Great job, I enjoyed the review, especially showing the improvements after every change.

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.

Great video, very interesting. Nice to see the mods and how they improved the machine.

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

Best review, you saved me time and money by learning your mistakes, don't get me wrong very good video

Great job documenting the whole process.

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.

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.

Try conventional milling instead of climb milling to reduce vibration, also lighter cuts, or slower feedrate.

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.

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.

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.

Great video! Excellent actually!

20:08 FWIW, you can use center cutting end mills to make holes.

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?

day and night after your improvements, thinking of Frankensteinig a mpcnc or something fro my next project

Great vid.

Aluminum milling at high spindle speed sounds like hell even on very expensive CNC machining centers made for aluminum.

Great work! Could you provide the files that you printed that hold the accordion covers to the minimill?

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

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..?

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.

Excellent Video

would this work with nema 17 instead?

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?

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!

Very well done review, your insight has helped

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?

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?

would using a bigger Z axis gantry plate with the bigger clear wheels on the outside of the 80mm Al extrusion be helpful?

With all the advancements in power electronics we are still stuck with a large power supply.

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

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?

It's too light?

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.

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

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!

Hi thx for all. Where can i buy it?

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?

(non-surprising)Conclusion - keep v wheels away from metal and stick to wood/plastics/composites

Did you try slower travel speed? Depth of cut seems ok but it looks like you're cutting awfully fast.

what kind stepper motor are u using?

you have a lot of room to buy some more aluminium construction profile and cheaply turning this machine into a decent CNC.

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.

3/4 n video sounds good lot better

Yeah. Rails.

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.

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.