Milland
Diamond
- Joined
- Jul 6, 2006
- Location
- Hillsboro, New Hampshire
Ya' got me - Goggle says "If it's a slope", and I'm sure you didn't intend the pejorative use of "slope", but I'm not catching the meaning.
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Homebuilt CNC in Tokyo
- Thread starter Bakafish
- Start date
- Replies 203
- Views 18,939
Ya' got me - Goggle says "If it's a slope", and I'm sure you didn't intend the pejorative use of "slope", but I'm not catching the meaning.
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
Sakana means Fish. Sakuraba... Sakanaraba.
SVFeingold
Aluminum
- Joined
- Aug 7, 2015
- Location
- Santa Clara
To elaborate I'm not talking about doing this to the linear rails, but rather to your custom endplates to which your ballscrews are mounted in your original CAD image. The hypothetical rods would run lengthwise through the existing cavities in the extrusion and compress the extrusion "axially." A picture would make it much more clear but I'm feeling lazy today.
Bolt stretch is good! That's usually what you want. A longer bolt is even better. Longer bolt = more stretch = lower bolt rigidity relative to the structure = less variation in bolt tension due to applied loads and thermal expansion of the extrusion = more stable structure. Probably skipped a few steps and oversimplified a bit, but the basic idea holds.
Take some time to read through (and understand) this series. "How do bolts work?" (in many more words) was a favorite question of mine to ask engineers during technical interviews. It's somewhat counterintuitive and many (most?) engineers haven't fully internalized it.
This being said, I'm certainly not trying to push you in that direction. I just think it's a cool idea that I've never seen done in this space. Could end up being a terrible idea, but it's still stuck in my brain. Maybe I'll try it one day and save you the trouble!
I thought of this too, only using fairly large steel tubingThese 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.
Epoxy granite as a bulk material isn't very stiff (i.e. low Young's modulus) - less than half of regular old 6061. That's why in commercial epoxy granite applications you see see steel/iron reinforcement as well as huge cross-sections when compared to cast iron. But it does do a great job of damping vibrations and adding mass. Laundry list of other benefits too, but they don't all apply to filling up extrusions like this. But it won't hurt!
Totally fair. Of course, they are right in the sense that even the best aluminum extrusion won't be great - unless it's designed for CNC purposes - and a custom steel/iron/EG structure would be better, but one step at a time. Plenty of people run routers and small mills built out of extrusion and make money doing it - which can then be spent on better equipment.
I'm looking forward to your progress and I hope you'll keep this thread active with it. If you want to post more detail (cross sections, exploded views, etc.) I'd love to see it and give any relevant feedback that pops up.
To OP, the following are some excellent references you may find useful, with the first reference giving you the tools you need to evaluate the performance/accuracy of your machine, and the last providing many calculations to allow you to evaluate design trade-offs:
"Machine Tool Reconditioning" - Edward F Connelly
"Precision Machine Design" - Alexander Slocum
"Engineering Mechanics and Solids" - Egor P. Popov
"An Introduction to Mechanical Vibrations" - Robert F Steidel
"Design of Machine Elements" - Spotts, Shoup, Hornberger
"Machine Tool Reconditioning" - Edward F Connelly
"Precision Machine Design" - Alexander Slocum
"Engineering Mechanics and Solids" - Egor P. Popov
"An Introduction to Mechanical Vibrations" - Robert F Steidel
"Design of Machine Elements" - Spotts, Shoup, Hornberger
A classic, thx for posting.
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
Yes, I understood that, I just misunderstood that you were also suggesting through holes for the rails as well (which is obviously something I've been pondering.)
I understand that, bolts are happiest when properly torqued and stretched to pre-yield conditions. But I've not done any real structural analysis, so what worries me is deviating from standard usage. I expect that rails mounted with standard ~30mm M6 bolts with full thread engagement is likely to be a lot more stable than with 250mm all thread floating mostly in space traversing the whole extrusion. But it seems you weren't suggesting that, so you can ignore my concerns.
Take some time to read through (and understand) this series. "How do bolts work?" (in many more words) was a favorite question of mine to ask engineers during technical interviews. It's somewhat counterintuitive and many (most?) engineers haven't fully internalized it.
This being said, I'm certainly not trying to push you in that direction. I just think it's a cool idea that I've never seen done in this space. Could end up being a terrible idea, but it's still stuck in my brain. Maybe I'll try it one day and save you the trouble!
I've been thinking about it too, which is why I came to the modified solution using a single tube. My concern about just using some beefy all thread was that you basically have a bunch of identical length, identically tensioned 'strings' that are going to resonate together, possibly in a really unfortunate way. That's why I started to think about just substituting a single piece of large diameter tubing with threaded plates on either end running in the upper and lower cavities. The epoxy granite would be intended to fill the void between the tubing and the extrusion to transfer any deflection of the extrusion to the tubing via compressive forces, I wouldn't expect a lot of strength gained from this, the tension of the tubes on the endplates would likely be a bigger contributor, but maybe it would help.
Yes, filling them would be for damping and counteracting any compressive forces of through profile fixtures. I know it won't improve the stiffness, filling tubes never really does, but I suspect that bolting 4-8mm thick steel plates acting as sheering on some of the outside surfaces of the extrusions could help there.
Yes, I'm just working out my big materials order. The steel plates I need are more expensive than I expected, mostly because I'm pricing it from the Big suppliers. But the alternative, starting up a business relationship with a specialty steel supplier, is a bit daunting and will probably not save me much money anyway. Those kinds of business want nothing to do with small orders and don't list pricing, so they'd likely quote high just to avoid having to deal with some strange Gaijin. Since the plates are above my 'painless' cost threshold, I want to make sure I don't make any mistakes and have to reorder them. I also need to see if ordering larger pieces and doing some of the cutting will save me enough to be worth it. I will upload the updated drawings when everything has been finalized.
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
Unlike the Moore book, I've not read any of those, they all look interesting. I will see what I can do to get my hands on them, unlikely to be available locally. I fear that they may be more expensive than my machine though
If you think dealing with suppliers is "daunting", just what till you start dealing with customers..
Why can't you just order your parts from one of the hundreds of online fabricators like sendcutsend, etc and ship to japan? Really don't understand why this is all that hard or expensive, its just small steel parts ?
SVFeingold
Aluminum
- Joined
- Aug 7, 2015
- Location
- Santa Clara
@Bakafish it might be helpful for you to give a quick overview of the processes/challenges involved in shipping components to where you live in Japan, for those who don't know. It'd be interesting for those of us not in the know to give you better advice. What's the VAT? Any arbitrarily low weight limits that necessitate freight shipping? How does freight shipping work? Etc.
Unlike the other issues you mentioned, shipping is a little more straightforward. Size/weight/VAT/import restrictions/cost are the usual considerations. As far as I've experienced, as long as all that checks out it doesn't really matter what's in the box or where it comes from.
When you say the steel plates are more expensive it'd be helpful too to know what those plates look like, and what you were quoted. If for example you're getting quoted $100 per flat steel part cutout, that could be reasonable. If you're getting quoted $1000/ea, maybe not so much and we can point you to a better supplier that will save you $$$.
Lots of interesting and capable suppliers out there, I learn about more of them every week. Fabrication capabilities are improving at a rapid clip, stuff that was crazy expensive even 5 years ago is reasonably priced now. Some stuff that was unobtanium 10 years ago is cheap today. Flex and HDI PCBs are an example that shocked me, literally a 10x+ cost reduction over the last decade for prototype quantities, and more advanced capabilities to boot. Promise I'm not badgering you here! Genuinely think you could pick up a few great tips/new suppliers to play with, if we had some idea of constraints/BOM costs/etc you're working with. The people who get a high from saying "toy machine har har" will get bored soon enough.
@Bakafish it might be helpful for you to give a quick overview of the processes/challenges involved in shipping components to where you live in Japan, for those who don't know. It'd be interesting for those of us not in the know to give you better advice. What's the VAT? Any arbitrarily low weight limits that necessitate freight shipping? How does freight shipping work? Etc.
Unlike the other issues you mentioned, shipping is a little more straightforward. Size/weight/VAT/import restrictions/cost are the usual considerations. As far as I've experienced, as long as all that checks out it doesn't really matter what's in the box or where it comes from.
When you say the steel plates are more expensive it'd be helpful too to know what those plates look like, and what you were quoted. If for example you're getting quoted $100 per flat steel part cutout, that could be reasonable. If you're getting quoted $1000/ea, maybe not so much and we can point you to a better supplier that will save you $$$.
Lots of interesting and capable suppliers out there, I learn about more of them every week. Fabrication capabilities are improving at a rapid clip, stuff that was crazy expensive even 5 years ago is reasonably priced now. Some stuff that was unobtanium 10 years ago is cheap today. Flex and HDI PCBs are an example that shocked me, literally a 10x+ cost reduction over the last decade for prototype quantities, and more advanced capabilities to boot. Promise I'm not badgering you here! Genuinely think you could pick up a few great tips/new suppliers to play with, if we had some idea of constraints/BOM costs/etc you're working with. The people who get a high from saying "toy machine har har" will get bored soon enough.
Just ship the stuff via DHL/Fedex, I know for a fact that these services work fine in Japan.
CarbideBob
Diamond
- Joined
- Jan 14, 2007
- Location
- Flushing/Flint, Michigan
Quit all the thinking and get your butt building.
Things will be wrong and things will be right. Along this path is learning.
Unless you are god I can flat out guarantee your first build will have holes in it.
I look at my first builds from 50 years back and I did all the math I could. ...They where not so great but each generation taught me something.
Just go for it. If it has flaws it has flaws and we learn.
Bob
Things will be wrong and things will be right. Along this path is learning.
Unless you are god I can flat out guarantee your first build will have holes in it.
I look at my first builds from 50 years back and I did all the math I could. ...They where not so great but each generation taught me something.
Just go for it. If it has flaws it has flaws and we learn.
Bob
I generally agree with you, BUT sometimes it is very helpful to look at what others have done before and understand why they took the approach they did and not re-invent the wheel. AND, it is very important to understand up-front what your goals are: a) fiddle around with a gantry machine made out of aluminum built in the least costly manner to learn what it can/cannot do, b) build a machine that can produce parts of x tolerance/accuracy that will cut aluminum and mild steel so one can get into some new business making stuff, etc.......of course goal a here could lead to goal b in future iterations....but again, all about expectations that drive design decisions.
Was thinking more about (aside from renting some space and buying a used CNC) how I would approach the problem the OP has: small space, limited 1-phase electrical, limited budget. A bit wild but I wonder whether aquiring an old small horizontal mill like a Burke No 4 and converting to CNC might be interesting. The work envelope would be smaller than OPs current plans, but the machine could cut anything....those little guys were very robust within the work envelope they presented. There is a challenge to having sufficient power to raise/lower the z/knee that would need solving. One could put a very nice head on it such as a Bridgeport M or Rusnok. Also, one gets a universal mill, both vertical and horizontal spindles.
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
This is a fair question. There certainly have been items where importing them results in a net savings. Many of my Festool (battery powered so I didn't need to worry about the local voltages), Incra and Veritas tools were imported due to local unavailability and/or higher local costs. But shipping to Japan tends to be expensive enough that, for most things, it wipes out any cost savings or makes them more expensive.
I just started pricing out the plates, and when I say 'expensive' I mean they were higher than my admittedly uninformed expectations. They may be totally reasonable (for example Misumi-Vona is cheaper domestically than the same exact part sold from them in the US) I just was caught a little off guard. I didn't put the pricing up because I worried I would be attacked either way, either "That's cheap, what did you expect?" or "What kind of idiot buys from Misumi-Vona?" and I didn't want to give the impression that I couldn't afford the costs, which I certainly can. It just made me take this part of the build (materials acquisition) a little more seriously and do more price comparisons, which is a good thing.
So let me do a bit more research here to make sure I have a reasonable baseline cost locally to compare to what it costs to import. As far as importing, my experiences have varied a lot, and some of that experience has certainly made me hesitant. The Japanese customs fees are usually ~10-20% of the indicated value, but they can be extremely hostile to even allowing the importation if anything in the paperwork doesn't meet their standards. I literally had to stop ordering from Banggood (probably a good thing) because my orders just kept being rejected at customs (who clearly do not like Chinese imports.) So importing really leaves me at the mercy and experience of the supplier, or I have to ask my connections in the US to receive and forward the items, which I typically reserve for really unobtanium stuff that isn't inconvenient (doesn't weigh a million pounds and is smaller than a breadbox.)
Another reason I don't import often is handling any issues or returns is just that much more difficult. Japanese customer service and quality spoils you, I know dealing with inevitable issues is baked into the low margins and cheap prices in the states, but having to pay freight back and forth if some of these plates were made wrong could quickly ruin all the effort, and that worries me. But an informed decision means at least knowing the price differential, so I'll try and be transparent with the pricing differentials (if any) I find.
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
Part of the WAF is that I built it myself, and that it looks more like a robot than an old industrial machine. I love the looks of old iron, but I can understand my wife's feelings on that. So converting an existing machine (if a good set of bones could be found) is certainly a more straightforward approach, but it just would put a lot more pressure on me to 'get that thing out of the house' if you understand. Due to the big castings it would also be much harder to move, support and dispose of. My machine's largest parts (other than the base plate) are all 30kg or less, and are small enough in size that they can be disposed of without special handling. I plan for success, but I plan for failure too.
Requirements for the machine:
- small
- not too noisy
- 1-phase, low amperage power
- not too expensive
- must appear modern/robot like, not classic machine/industrial look from WWII
- components must be lightweight so can be easily moved around and disposed of
- must be built from scratch, not allowed to utilize previously created cast iron bodies
Good luck!!!
Bakafish
Hot Rolled
- Joined
- Feb 21, 2022
- Location
- Tokyo Japan
That's a pretty good summary
although I planned on mitigating the noise after the fact, it isn't one of the initial primary criteria, I suspect it will be really loud to begin with. I'd also add to that list that I am doing everything I can to use domestic parts, and ideally recycled/salvaged stuff. Save the planet and everything. To be honest if I had come across something that was well built enough to serve the purpose and meet my needs I would have (will) buy it. Being built by me is not as important as doing what I need it to do, I was just saying that my wife will have a softer place in her heart knowing I put it together myself. I hope that's understandable. And as far as the expense, I wanted to keep it under $10k, which is cheap compared to a Brother Speedio, but reasonable compared to hobbyist machines. I've not spent anything like that much so far, but I think the impression that I'm cheaping out or making crazy compromises over costs isn't really fair, I just feel like I've been fortunate to find what I need cheaply.
I get the sense (although I've misread you before) that you may not think these are reasonable pre-requisites, or achievable goals, and I can understand that. But I've said before that defining the constraints helps focus the details, and even though I may not have done a good job of communicating them, they have been clear enough in my own head to guide my design.
This is something I've been thinking about for years, and actually committed to working on seriously for the last year, so I've made a lot of decisions that may look arbitrary from the outside or sound like I'm just making up excuses when I try to explain them after the fact. You will have to trust me when I say, I believe I've thought of the same solutions you guys are coming up with along the way. I know I sound defensive, a lot of it is getting annoyed that I feel condescended to that I haven't thought of these (obvious?) things, or don't understand my own situation better than someone who just jumped into a post for the first time. I'm not trying to make this harder than it needs to be out of whimsy. The fact that I dismissed these suggestions doesn't mean they are wrong, just that I considered them and they didn't work for me. I'm not saying I've thought of everything, or know everything, or even that I know this will work, one of you may blow my mind and change my direction entirely. I just hope those of you who are actually trying to be supportive can understand my attitude, and why I'm doing it this way.
The requirements I would always start with when designing a machine are:
- what materials do you want to cut?
- what tolerance do you require?
- what repeatability do you require?
- what surface finish quality do you require for each target material?
- how fast do you want the machine to be in terms of cut through speed for any given target material?
- how deep do you want your cuts to be for a given pass and target material?
- how will you handle tool changes?
- how will you handle coolant? do you plan on using coolant?
- how will you handle swarf?
- how will you handle maintenance of the machine, e.g. lubrication?
- what is max noise level you are willing to tolerate noting that this will change with different materials?
- what materials do you want to cut?
- what tolerance do you require?
- what repeatability do you require?
- what surface finish quality do you require for each target material?
- how fast do you want the machine to be in terms of cut through speed for any given target material?
- how deep do you want your cuts to be for a given pass and target material?
- how will you handle tool changes?
- how will you handle coolant? do you plan on using coolant?
- how will you handle swarf?
- how will you handle maintenance of the machine, e.g. lubrication?
- what is max noise level you are willing to tolerate noting that this will change with different materials?
