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Homebuilt CNC in Tokyo

Well.

Doc's someone with a breadth of experience, and to take his well meaning advice and twist it such that you need to reply in full-snark has told me I can go to lurk-mode on this thread.

Fair enough. I think his doubling down didn't help my attitude. Telling someone to abandon all their work and just buy a machine and get a shop isn't really helpful, even if well intentioned.

Maybe useful information will be found later.

Maybe you'll actually make something.

I appreciate your suggestions, I'm working to implement some of them in the final design. Still can't find any rails with higher preload, but will likely upgrade the gantry rails to a stronger pair of 30mm that are a bit longer so I can space out the blocks a bit more.

Maybe you'll realize that trying to fight everyone who walks through the bar's doors unless they're of "you're right, boss!" mindset isn't productive.

Whatever.


But you chose your name poorly.

It's Bakaraba...

That's pretty funny! Thanks again.
 
Fair enough. I think his doubling down didn't help my attitude. Telling someone to abandon all their work and just buy a machine and get a shop isn't really helpful, even if well intentioned.

Bakafish, HONESTLY, I did EXACTLY that, after futzing around with trying to build a machine, I ended up establishing some space (1.5 hour drive away from home one way, FYI) and bought a commercial machine shown here:
AG0P1327.jpg
This machine has a SMALLER work envelope than you are trying to handle, and weighs 4500 lb...this is what a professional machine looks like.
 
Bakafish, HONESTLY, I did EXACTLY that, after futzing around with trying to build a machine, I ended up establishing some space (1.5 hour drive away from home one way, FYI) and bought a commercial machine shown here:
View attachment 345212
This machine has a SMALLER work envelope than you are trying to handle, and weighs 4500 lb...this is what a professional machine looks like.

Okay, I hear that you're being sincere about it, and I came down pretty hard on you. But I hope my points, despite being exceptionally pointy, were understood. I'm not actively looking to fight people, despite the appearances, I'm just not used to this level of S/N, as the GJ is so much more supportive.

Keeping the costs low until I can find utility from the experiment seems the most prudent course for me at this time. I have already solved all the problems in implementing this plan, I've got all the specialized parts, just waited to order the extrusions as that's when I have the design as locked in as possible.

I readily agree the machine may turn out to be crap, but there's no reason not to find out at this point. I have a full time engineering role at a giant company (fortunately from home) and want to have something to pivot to when I retire in the next few years, this is the best way I can see getting up to speed. I want the machine close for now, if it becomes a business, I have the finances to do it the official way and the Kaiju will be unceremoniously kicked to the curb.
 
Okay, I hear that you're being sincere about it, and I came down pretty hard on you. But I hope my points, despite being exceptionally pointy, were understood. I'm not actively looking to fight people, despite the appearances, I'm just not used to this level of S/N, as the GJ is so much more supportive.

Keeping the costs low until I can find utility from the experiment seems the most prudent course for me at this time. I have already solved all the problems in implementing this plan, I've got all the specialized parts, just waited to order the extrusions as that's when I have the design as locked in as possible.

I readily agree the machine may turn out to be crap, but there's no reason not to find out at this point. I have a full time engineering role at a giant company (fortunately from home) and want to have something to pivot to when I retire in the next few years, this is the best way I can see getting up to speed. I want the machine close for now, if it becomes a business, I have the finances to do it the official way and the Kaiju will be unceremoniously kicked to the curb.

I could be wrong, but my prediction is that you will have a lot of vibration in your machine due to insufficient mass, and this will seriously affect your accuracy. In addition, I predict that you'll be unable to cut anything more than aluminum without torquing the machine.

In a side-bar, I had a discussion with another machinist on this forum, and we both agreed that if we were trying to build a very small high precision machine, we would build it out of granite...not just the base, but possibly an entire box. His suggestion was something akin to an Hermle, possibly hanging the grantry from the bottom of the upper slab of granite. This kind of design could rival any modern commercial machine, albeit for very small parts.

Anyway, good luck with your project.

FYI, I was impressed with the remodelling you have done on your house.
 
Just to add, those Speedio's are sweet, as are the little Datron's... and my wife would be supportive if I bought one. We don't have kids and we own a successful business, the money is there. I just come from a background where you don't spend that much money (to be fair we didn't have money) in the hope it will be useful. And I want to get my crash experience on something cheaper and easier to repair or replace...
 
Just to add, those Speedio's are sweet, as are the little Datron's... and my wife would be supportive if I bought one. We don't have kids and we own a successful business, the money is there. I just come from a background where you don't spend that much money (to be fair we didn't have money) in the hope it will be useful. And I want to get my crash experience on something cheaper and easier to repair or replace...

Speedio is in a different class from Datron, Datron Neos are effectively a 2D machine and quite limited, speedios are full out production machines....mine has 4th axis as well.
 
I could be wrong, but my prediction is that you will have a lot of vibration in your machine due to insufficient mass, and this will seriously affect your accuracy. In addition, I predict that you'll be unable to cut anything more than aluminum without torquing the machine.

I can't say I'd be super disappointed if I could only cut Aluminum. I understand and agree that would put this in the hobby category, but let's see what it will do.

In a side-bar, I had a discussion with another machinist on this forum, and we both agreed that if we were trying to build a very small high precision machine, we would build it out of granite...not just the base, but possibly an entire box. His suggestion was something akin to an Hermle, possibly hanging the grantry from the bottom of the upper slab of granite. This kind of design could rival any modern commercial machine, albeit for very small parts.

I totally agree, I actually pointed at two projects that did exactly that. My concerns over weight were sincere, this house has wood floors, and while it is better built than most, it would be a mistake to put that much weight on anything but cement and steel.

I've also kept a close eye on granite parts and although big surface plates are often very inexpensive, smaller components are typically quite dear. One of the exceptions in this market, most of these metrological tools are dirt cheap. I don't know why, likely just rarity.

So all those parts would need to be custom ordered, or I'd need to slice up a couple of smaller plates.[/QUOTE]

Anyway, good luck with your project.

FYI, I was impressed with the remodelling you have done on your house.

I appreciate that, it was way more stressful puzzle than this simple machine build :)
 
Speedio is in a different class from Datron, Datron Neos are effectively a 2D machine and quite limited, speedios are full out production machines....mine has 4th axis as well.

You have my interest! In what way are the Neo's 2D? I've seen the videos of them running (and with a 4th axis), what was I missing? I'm a Brother fan as that's the 'home' team, but I've never heard that the Datron's were limited.
 
You have my interest! In what way are the Neo's 2D? I've seen the videos of them running (and with a 4th axis), what was I missing? I'm a Brother fan as that's the 'home' team, but I've never heard that the Datron's were limited.

I found your original shopping thread on it, good info there. I guess I bought the Datron hype :) I didn't want to deep dive these machines because I worried I will sell myself an expensive box before I needed it.
 
You have my interest! In what way are the Neo's 2D? I've seen the videos of them running (and with a 4th axis), what was I missing? I'm a Brother fan as that's the 'home' team, but I've never heard that the Datron's were limited.

Just look at the z limits. In general, folks that buy these machines are doing stuff that has very little z, and from talking to folks that have bought the machine they view these as targeting products that are more 2D in nature. Also, the neo has similar work envelope (other than z) as the Speedio S300X1 but weighs 1500 lb versus 4500 lb, its just not in the same category. Also, in terms of speed, Speedio knocks the socks off Datron, and is I believe the fastest CNC in the market currently.

Plus, Speedio is made in Japan, where you live !!!
 
Just look at the z limits. In general, folks that buy these machines are doing stuff that has very little z, and from talking to folks that have bought the machine they view these as targeting products that are more 2D in nature. Also, the neo has similar work envelope (other than z) as the Speedio S300X1 but weighs 1500 lb versus 4500 lb, its just not in the same category. Also, in terms of speed, Speedio knocks the socks off Datron, and is I believe the fastest CNC in the market currently.

Plus, Speedio is made in Japan, where you live !!!

Yep, the Speedio will be the first on my list to check out when I'm ready to pull the trigger. You have some other nice looking machines too. Those 400v 3-phase cutoff boxes were just taunting me. :(
 
Yep, the Speedio will be the first on my list to check out when I'm ready to pull the trigger. You have some other nice looking machines too. Those 400v 3-phase cutoff boxes were just taunting me. :(

My machines are built in Japan, Germany, and Switzerland....thus 400V transformer....also a 208V transformer for the Speedio as it didn't like the 230V from utility. And yes, lucky to have 3-phase service. Do a search on Studer S20, thats my most recent and most prized machine.
 
My machines are built in Japan, Germany, and Switzerland....thus 400V transformer....also a 208V transformer for the Speedio as it didn't like the 230V from utility. And yes, lucky to have 3-phase service. Do a search on Studer S20, thats my most recent and most prized machine.

Yes, I know it, would love something like that someday. You have great taste in machines! ;-)
 
Back to the concept- building better machine with locally grown organic free range product. Aluminum is obviously not first choice, but not bad choice. Bolted connections and always in flexed tension under load is bad, very poor for material choice. Aluminum does transfer load in compression (shock) fairly well, use that to an advantage and run arch shaped bridge (like two dams back to back). Bolted connections need beefy wing plates, and lots of bolts to get compression to near welded stiffness.
To bad japan doesn’t have native controllers other than brother, Fanuc, Okuma, Sony, toshiba, and I know I missing some others... I run a Slovenian controller- no need to reinvent the wheel on a mill control unless you have some very unique improvement/concept.

If you are making a tool it is either a quick and dirty one to work, or an elegant product. Even if it doesn’t work try for the second- you are not on the clock for this job.
 
Are the Oriental Motors Alpha series closed loop steppers and NEMA 34 motors underpowered yak's vomit?

You can put all those fancy names in front of it, but at the end of the day its still just a stepper motor. Which is still garbage for any kind of serious CNC. Im aware the closed loop steppers are much better then normal steppers, but they are still garbage.

Have a look online and see what type of "steppers" are used on Okuma, Mazak, Doosan, even Haas machines...
 
Back to the concept- building better machine with locally grown organic free range product. Aluminum is obviously not first choice, but not bad choice. Bolted connections and always in flexed tension under load is bad, very poor for material choice. Aluminum does transfer load in compression (shock) fairly well, use that to an advantage and run arch shaped bridge (like two dams back to back).

I just don't have the equipment to get this creative with the structure, one of the reasons I chose the Al profile that can be drop shipped to my door. I suspect that additional damping will mollify some of the worst of these spars behavior, but the bolted connections will certainly be a weak point.

Bolted connections need beefy wing plates, and lots of bolts to get compression to near welded stiffness.

I will be trying to integrate as much steel as possible in this way. I hope to make all the wing plates and backing plates out of steel.

To bad japan doesn’t have native controllers other than brother, Fanuc, Okuma, Sony, toshiba, and I know I missing some others... I run a Slovenian controller- no need to reinvent the wheel on a mill control unless you have some very unique improvement/concept.

I've seen some used domestic controllers sold pretty cheaply, but trying to understand and adapt a full enterprise controller with what I have would massively complicate this project (although would be really useful knowledge.)

If you are making a tool it is either a quick and dirty one to work, or an elegant product. Even if it doesn’t work try for the second- you are not on the clock for this job.

Yes, you get it. This is obviously a bit of a hack, but I take pride in my work and I'm trying to make it as best I can.

You can put all those fancy names in front of it, but at the end of the day its still just a stepper motor. Which is still garbage for any kind of serious CNC. Im aware the closed loop steppers are much better then normal steppers, but they are still garbage.

Have a look online and see what type of "steppers" are used on Okuma, Mazak, Doosan, even Haas machines...

This smacks of, "How many small block chevy V8's do you see in Porsches, Ferraris and Lamborghinis?"

They may be crude, we all know Servos are better, but these steppers will do the job I am asking them to do. I don't think it makes it any less serious, the parts this machine will generate would be identical, irrespective of the motors used. Their biggest practical drawback is speed, which has little impact on someone making parts for himself with a low speed spindle on a timeline of his choosing.
 
This smacks of, "How many small block chevy V8's do you see in Porsches, Ferraris and Lamborghinis?"

They may be crude, we all know Servos are better, but these steppers will do the job I am asking them to do. I don't think it makes it any less serious, the parts this machine will generate would be identical, irrespective of the motors used. Their biggest practical drawback is speed, which has little impact on someone making parts for himself with a low speed spindle on a timeline of his choosing.

Sorry but your parts will certainly not be identical. Steppers move in steps. Dont forget that. You will never get perfectly smooth motion from a stepper motor compared to a servo. Interpolated moves will never get the same surface finish you will get from a servo. Even in single axis moves the steppers will introduce vibration that could affect surface finish. Its not just the difference in top speed, although that is huge factor too. Steppers use much more power too. Servos are way more efficient, run cooler etc. Just night and day better all around. If this project is really worth doing dont even think about it, just ditch the darn stepper motors and get servos!
 
Sorry but your parts will certainly not be identical. Steppers move in steps. Dont forget that. You will never get perfectly smooth motion from a stepper motor compared to a servo. Interpolated moves will never get the same surface finish you will get from a servo. Even in single axis moves the steppers will introduce vibration that could affect surface finish. Its not just the difference in top speed, although that is huge factor too. Steppers use much more power too. Servos are way more efficient, run cooler etc. Just night and day better all around. If this project is really worth doing dont even think about it, just ditch the darn stepper motors and get servos!

Okay, I'm doing best to not sound combative, I like that you are listing actual concerns here rather than generalizing that they are "bad." I'm not trying to 'sell' you on cl-steppers, just make it clear why I think that they should work here.

As far as discrete steps, you are of course correct. Micro-stepping, while it trades off torque and is less consistent than native steps, does overall improve the accuracy and reduce cogging errors. But I will get back to this point when we run some numbers below.

Your point about power usage is much more true with open loop steppers as you have to just set a baseline current and there is no intelligence behind the power flowing into them. Since the potential loads are so high, and the penalty for losing steps is so great, you need to run them as close to their heat dissipation limits as you can. However this is one of the advantages that closed loop steppers have, that they can continuously analyze their actual position, their load and the desired position and dynamically adjust the current to adapt to those conditions. Due to the difference in the motor construction of steppers, specifically for things like holding torque and extremely low speeds, they can actually be more efficient than a servo. Overall I would suggest to you that efficiency is pretty much a wash here, and at worst the closed loop steppers are competitive on power utilization for the speed ranges I'm expecting.

So many of my motors are actually geared (OM claims 7-10 arc minutes max backlash) and the ones that are not, may be connected to the ball screws via timing belts to improve the packaging and tweak the final ratios that I want. I haven't finalized the actual values here as there are a lot of tradeoffs I'm still balancing and steppers are much harder to design speed envelopes with than servos. Changing the gearing ratio of a stepper can often be a pointless exercise as any torque you gain from the gearing advantage is just thrown away by increased motor speed, so you really have to decide up front what you care about. Obviously the higher gear ratios reduce the amount of cogging error, my 25:1 motors have 0.0144°/Pulse resolution using the standard 1000 pulse per rotation encoder settings (the native encoder is 1,800 rev.)

But since I don't have these ratios locked down, let's just use the worst case scenario of a 1:1 motor directly coupled to my 6mm lead X or Y axis ball screw. This plain motor has a quoted 0.36°/Pulse step and (again at defaults) if we run the basic numbers (ignoring the many other motion errors) it means that one step would move the ball nut 6 microns. Not great, but again this isn't what I actually will be using as I have 7.2:1 motors lined up for these screws (which gets us in sub-micron step territory.) Will it be slow? Yes, it is going to be dog slow, I've said this.

Will the surface finish directly suffer because of the steppers? I don't think so, my expectation is that backlash, ball screw tolerances, bearings, spindle runout and the infamous aluminum frame are all in the same ballpark of error domains, and I'm hoping that like Montgomery Burns' immune system, they will all miraculously cancel each other out :D I just don't think that throwing the best servos in the world at this would result in enough of an improvement to justify even a moderate cost (although it would speed the machine up for sure.)

But in reality we will find out how well these work when I start making parts and if I'm wrong I will be man enough to come here and say so.
 
Any chance you have part numbers for your motors/drives handy? I'd look closely at that backlash figure and work out what it means in terms of position error after it's converted to linear motion. 7-10 arcminutes is a pretty large amount of backlash and may cause issues when interpolating holes or otherwise changing directions. Which is a twofold problem: 1) accuracy and 2) sudden increases in chipload that can break small endmills. But if your 6 micron number is correct, the gearbox backlash would be roughly half that figure. Not the end of the world in that case.

Personally I don't think steppers are nearly as bad as it's being portrayed here. There's a big difference between an Arduino + a $15 Amazon stepper (aka the experience of 99% of the people who have used steppers) and a closed-loop industrial stepper + matching drive. I also doubt there is enough rigidity in the structure and control authority in the steppers for the individual steps to be visible on the part unless you're running glacial feedrates where the motors actually come to a complete stop (or slow significantly) between micro-steps.

As you said: servos are definitely better but does it really matter for this application with this machine? I doubt it. Motors are also the easiest thing to replace so if you do decide you need them, you can spend the money and replace them later.

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One suggestion (with some caveats) that may help improve the rigidity of the aluminum structure: don't bolt the end plates (which support the ballscrews) into the track of the aluminum extrusion directly below them, if you can avoid it. It'd be better to bolt them all the way through the extrusion. I.e. run a threaded rod all the way through the extrusion to the opposite side and put a nut on either end. This distributes the load a bit so it's not all just getting levered against a nut held in place by a thin lip of aluminum. A given load concentrated into a small volume = higher strain = higher stress. It'll also serve to pre-tension the aluminum a bit. Both will reduce the deflection of those supports in response to applied loads.

Crappy illustration here that should get the idea across. The green lines would be threaded rods (and inside the extrusion) with nuts on either end.

2022-03-23 03_18_22-Homebuilt CNC in Tokyo.jpg

Speaking of pre-stressing, I think it's a pretty neat idea. It's something I would try if I was building this. Run several threaded rods through each extrusion (one per opening in the cross-section) and tighten them all an equivalent amount to compress the extrusion. Since you have steel plates on the ends of all your extrusions, you can just pass them through those and use them as bearing surfaces for the nuts.

The big upside of this is that it can substantially increases the rigidity of the structure. It will deflect less for a given external load. Perhaps not as much as as cast iron or steel...but more than the original aluminum. The big downside is that more care in assembly and more upfront calculation will be involved to settle on an appropriate amount of pre-tension, and crucially to minimize tweaking the members and distorting their shapes which will happen and may make your alignment task harder. That's always a risk when you intentionally add stress. Ideally you'd do this before it's assembled. Even more ideally you'd also send the individual members out, pre-stressed, to have reference surfaces for each member post-machined. Removing as little material as possible - just enough to get a clean reference surface. Goes without saying that the internal rods should be considered permanent and can never be loosened/tightened/disassembled or it's all for naught.

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One thing I didn't see in your OP are locating features. Take for example your ballscrew supports for the X-axis. How will you align them to one another? If you're using the standard extrusion t-slots/holes to do it, you don't really get any say in the alignment - it is what it is when you assemble it. Maybe they can tolerate the potential misalignment, but if they can't then consider separating those brackets into two parts - one bracket that bolts to the extrusion, and another bracket that contains the ballscrew support and is bolted to the first bracket. That way you have some ability to align the ballscrew supports independently of the attachment to the extrusion.

Another crappy picture to make it clearer - red lines are the potential separation points.

2022-03-23 04_00_15-.jpg

It looks like you have a couple areas where you have extrusions bolted to one another. Those would be weak points for sure. Hard to tell without more CAD views!

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Personally I'm not on board with the idea that the smart businessman thing to do is to turn your <$10k side-project into a mound of obligations and debt by 10-xing your budget and signing a multi-year lease on an industrial space that's an hour+ away. That might make sense if you were trying to make this your primary source of income ASAP and have no issue paying those expenses out of pocket for the next couple of years.

I get a similar thing when it comes to housing as I also live in a ludicrously expensive place. "There's gotta be a cheaper place! You're just not looking that hard!" I just tell them you know what...hop on Zillow or Craigslist and find one. They never do. They just say it and then carry on believing there are heaps of houses sitting around here that are equivalent to mine but 50% below market value. Likewise I've been told "just rent an industrial space" for the sake of saving 100 square feet in my garage, as if those spaces don't cost $30/SF/year around here.

This is a common line of questioning/lecturing when it comes to those living in expensive areas. There are those who can't wrap their heads around the idea that not everybody wants to completely upend their life, quit their jobs, move their SO/kids, leave their friends, etc. just for the sake of moving to Wisconsin to score some cheap real estate. It's easier to just...do the thing and try it out. If you love it and want to pursue it, great. If you don't, you're only out the money you spent + what it'll cost to have someone pick up your machine and haul it to a scrapyard.

To each their own I guess. I wouldn't stress about it though.
 
Thanks for the thoughtful comments.

Any chance you have part numbers for your motors/drives handy? I'd look closely at that backlash figure and work out what it means in terms of position error after it's converted to linear motion. 7-10 arcminutes is a pretty large amount of backlash and may cause issues when interpolating holes or otherwise changing directions. Which is a twofold problem: 1) accuracy and 2) sudden increases in chipload that can break small endmills. But if your 6 micron number is correct, the gearbox backlash would be roughly half that figure. Not the end of the world in that case.

The 6 micron figure is for a direct drive gearless motor, so no backlash from the motor itself, although the coupling and ball screw are still contributors. For the geared drives, this is the max figure and Japanese are very conservative in under promising and over delivering. I'll keep my eye on it, but the gear boxes seem super tight.

Personally I don't think steppers are nearly as bad as it's being portrayed here. There's a big difference between an Arduino + a $15 Amazon stepper (aka the experience of 99% of the people who have used steppers) and a closed-loop industrial stepper + matching drive. I also doubt there is enough rigidity in the structure and control authority in the steppers for the individual steps to be visible on the part unless you're running glacial feedrates where the motors actually come to a complete stop (or slow significantly) between micro-steps.

As you said: servos are definitely better but does it really matter for this application with this machine? I doubt it. Motors are also the easiest thing to replace so if you do decide you need them, you can spend the money and replace them later.

These are basically the most evolved steppers currently made. They are designed for industrial use and a single controller and motor set with cables sells for $1000-2000, they are intended to compete with low end servos for specific applications. Japanese stuff like this is admittedly overpriced, but very high quality. I was lucky to get them very inexpensively, pennys on the dollar. I wouldn't have paid retail for them, and if I had I would understand getting grief over spending that much money and not getting servos, but they are not really what people are picturing when they hear 'stepper.'

One suggestion (with some caveats) that may help improve the rigidity of the aluminum structure: don't bolt the end plates (which support the ballscrews) into the track of the aluminum extrusion directly below them, if you can avoid it. It'd be better to bolt them all the way through the extrusion. I.e. run a threaded rod all the way through the extrusion to the opposite side and put a nut on either end. This distributes the load a bit so it's not all just getting levered against a nut held in place by a thin lip of aluminum. A given load concentrated into a small volume = higher strain = higher stress. It'll also serve to pre-tension the aluminum a bit. Both will reduce the deflection of those supports in response to applied loads.

Crappy illustration here that should get the idea across. The green lines would be threaded rods (and inside the extrusion) with nuts on either end.

View attachment 345290

I've thought a lot about this and what it comes down to is the question, how strong is the rod, how much will a compressive force across the height (of an unfilled) structural member distort it and how much strength is the aluminum spar losing due to the through holes? Even a large diameter rod or all-thread that is 250mm+ in length is going to have some stretch to it, and the rails are only designed for M6 (which is fine for conventional mounting.) So I honestly worry that the through bolting (without some kind of non-compressible fill, will end up distorting the profile and be susceptible to bolt stretching. I could be wrong, but it's a big non-reversible commitment to drill those through holes, and despite it being aluminum, such long holes centered through the bottom of the T slots are actually going to be a pain in the ass to get right. The inside surfaces of the profile makes it more difficult than you might expect.

What I'd like to start with, is instead of individual nuts, a single piece of mild steel (like a long T nut) that slides into the profile slot that distributes the load of the individual rail screws across the whole slot and helps stabilize it.

Speaking of pre-stressing, I think it's a pretty neat idea. It's something I would try if I was building this. Run several threaded rods through each extrusion (one per opening in the cross-section) and tighten them all an equivalent amount to compress the extrusion. Since you have steel plates on the ends of all your extrusions, you can just pass them through those and use them as bearing surfaces for the nuts.

I thought of this too, only using fairly large steel tubing :) These profiles have pretty big voids, plenty of room for something that not only allows for compression, but if set in granite epoxy could actually directly contribute to rigidity. No premature optimization though! Got to test it before going crazy.

The big upside of this is that it can substantially increases the rigidity of the structure. It will deflect less for a given external load. Perhaps not as much as as cast iron or steel...but more than the original aluminum. The big downside is that more care in assembly and more upfront calculation will be involved to settle on an appropriate amount of pre-tension, and crucially to minimize tweaking the members and distorting their shapes which will happen and may make your alignment task harder. That's always a risk when you intentionally add stress. Ideally you'd do this before it's assembled. Even more ideally you'd also send the individual members out, pre-stressed, to have reference surfaces for each member post-machined. Removing as little material as possible - just enough to get a clean reference surface. Goes without saying that the internal rods should be considered permanent and can never be loosened/tightened/disassembled or it's all for naught.

Yes, I suspect it would be easy to induce unintended curvature doing this. The reality is, Aluminum is being chosen primarily because of its ease of use in this application. If it can't do the job, there is only so much effort I'm willing to throw good after bad. Granite epoxy will basically ruin them for easy reuse and recycling (unless I can make it removable some how, a whole other kettle of fish.) And that's likely as far as I will go, if I even go that far. I mean, if the doubters are right, they are right. Just have to move to steel and be done with it.

One thing I didn't see in your OP are locating features. Take for example your ballscrew supports for the X-axis. How will you align them to one another? If you're using the standard extrusion t-slots/holes to do it, you don't really get any say in the alignment - it is what it is when you assemble it. Maybe they can tolerate the potential misalignment, but if they can't then consider separating those brackets into two parts - one bracket that bolts to the extrusion, and another bracket that contains the ballscrew support and is bolted to the first bracket. That way you have some ability to align the ballscrew supports independently of the attachment to the extrusion.

Another crappy picture to make it clearer - red lines are the potential separation points.

View attachment 345291

It looks like you have a couple areas where you have extrusions bolted to one another. Those would be weak points for sure. Hard to tell without more CAD views!

This is an older rendering, and a lot of that detail isn't clear. All extrusion to extrusion interfaces are through steel plates, no direct contact. All the ball screw mounts have interstitial plates as well, they are actually not tall enough to reach the extrusion even if the hole spacing fit (which it doesn't.) I should be able to get things lined up pretty accurately, assuming the extrusions are as good as I expect.

Personally I'm not on board with the idea that the smart businessman thing to do is to turn your <$10k side-project into a mound of obligations and debt by 10-xing your budget and signing a multi-year lease on an industrial space that's an hour+ away. That might make sense if you were trying to make this your primary source of income ASAP and have no issue paying those expenses out of pocket for the next couple of years.

I get a similar thing when it comes to housing as I also live in a ludicrously expensive place. "There's gotta be a cheaper place! You're just not looking that hard!" I just tell them you know what...hop on Zillow or Craigslist and find one. They never do. They just say it and then carry on believing there are heaps of houses sitting around here that are equivalent to mine but 50% below market value. Likewise I've been told "just rent an industrial space" for the sake of saving 100 square feet in my garage, as if those spaces don't cost $30/SF/year around here.

This is a common line of questioning/lecturing when it comes to those living in expensive areas. There are those who can't wrap their heads around the idea that not everybody wants to completely upend their life, quit their jobs, move their SO/kids, leave their friends, etc. just for the sake of moving to Wisconsin to score some cheap real estate. It's easier to just...do the thing and try it out. If you love it and want to pursue it, great. If you don't, you're only out the money you spent + what it'll cost to have someone pick up your machine and haul it to a scrapyard.

To each their own I guess. I wouldn't stress about it though.

Well I should be understanding that the feelings of many of the members here is that this forum is for 'professional' use, and I do not have a business using machinery that I'm willing to talk about or that is making me any money yet. And the machine is certainly unbuilt and unproven and has a lot of the red flags that inevitably are going to draw criticism. So I should have been less defensive about it, I just am not used to some of these guys way of 'interacting' and as it has been noted I do like a bit of a rumble. (@Milland: Maybe Sakanaraba is an even better name than Bakaraba?)

But as I said from the beginning, this thread was just trying to keep the discussion of this machine out of the thread that I actually cared about :) I was trying to get specific advice from someone that in reading his previous comments, it seemed that keeping him focused would improve the quality of the answer. I knew this project would get a lot of 'friendly advice' and derail everything.
 








 
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