4'x8' CNC Router

[Charles Jenkinson]

Or 5'x10', for the 5x5 sheets.

Just wondered where those interested in the CNC router technology / asset, are up to with it all... thinking of dabbling still?, at what size and price-performance point? or given it up as not a cost-effective return on investment....? For speaker building obviously.

Personally, I've been thinking about them, for hobbyist reasons, but with future business potential. Commercial offerings seem to be in the £10k to £20k+ (or dollars) arena, but people seem to be able get the american Blackfoot / GreenBull (google: build your cnc) wooden machines to perform admirably with cutting speeds of up to 100 IPM, for an initial kit outlay of $3k to $4k.

My other interests are boat building (stitch & glue) which uses profile-cut plywood, and possibly machining high efficiency aluminium propellers for human powered water bikes. Airfoil (hydrofoil) profiles all possible aswell.

Just interested.

Charles

[sine143]

I have a good friend who has put together a number of cnc machines.

His most recent feature a 4x4 table.

https://scontent-a.xx.fbcdn.net/hphotos ... 1754_n.jpg

In my opinion, for the sake of speaker building (horns at least) you need 2 things. Fullsheet capability, and at least 4 axis (for angles). As long as the angles are not parallel (sheet looks like this / \ not like this / /) you can get by with 3 axis and edge profiling, but this is rarely the case with horn speakers.

when going beyond 4x4 ft tables, the rigidity of your cnc parts becomes an issue so you have to go with super thick metal pieces.

[Charles Jenkinson]

That's a nice machine your friend has made there.

I agree about full sheet capability - anything less is a compromise. A possible compromise is just 4x8 capability as opposed to also 5x5 aswell. It would be reasonably expedient to cut mitres by other means, if EVERYTHING else is right, including dadoes and mortice/tenon locators.

It's the stiffness of the gantry and the vertical (z) bearing sysyem that people rave about for good accuracy, repeatability and cutting performance. All systems, whether home built hotch potch or fancy schmancy have to be set up well to give performance commensurate with the best they can give.

I saw Kronos Robotics yesterday ( http://www.kronosrobotics.com/krmx02/ ) and thought it looked well screwed together - a 50" x100" for $5580, they say. That sort of money can roll off the tongue easy (if you say it quickly) but for what it could do, its not much. Of course, its not as straightforward in the uk, and I dont have the room yet for one, so it'll have to go on the just pondering / researching backburner.

[LelandCrooks]

Nice. I'd never seen that one, and thought I'd researched every DIY cnc on the net. Still, estimated build time is a shade over 2 weeks. But it's the first diy I've seen that looks as robust as a commercial machine.

[sine143]

I somehow expect they are grossly underestimating the costs... 8020 extrusion is not very cheap, and those kronos builds use A LOT of it (a whole table out of it????). even with the limited amounts of extrusion in the 4x4 foot table I pictured build cost was around 2500 I believe.

[Charles Jenkinson]

Nice. I'd never seen that one, and thought I'd researched every DIY cnc on the net. Still, estimated build time is a shade over 2 weeks. But it's the first diy I've seen that looks as robust as a commercial machine.

TBH, I had you in mind Leland, as I've been looking, from previous CNC references I've read in various threads. I guess the build time is the extra dollars for a commercial offering.

I somehow expect they are grossly underestimating the costs... 8020 extrusion is not very cheap, and those kronos builds use A LOT of it (a whole table out of it????). even with the limited amounts of extrusion in the 4x4 foot table I pictured build cost was around 2500 I believe.

Ok Sine. I hadn't had validating the price or any other parameters (like which and how much extrusion) at the forefront of my mind with it being a US site, but I guess the next stage would be access to some kronos builders who might be able to verify matters. 5580 is rather a precise number for a cost estimate, especially when it seems one has to commit before verification commences. I'd certainly want estimated cost verifying against a BOM.

Anyway, I'll stop harping on about this soon - I was only throwing it out there again as a powerful productivity solution, ...though I believe when one gets the cnc bug things can get out of hand in terms of creativity as well. Overall, and within my multifarious constraints, I've found a uk website that is gonna probably be my research base for moving forward, however slowly - mycncuk. I'm thinking longer term. There's a number of blokes on there who appear to give unreserved amounts of time to the whole cnc idea, both as work, hobbyists and fellow forum community members - like here. They reckon if you can weld, and fabricate a frame up, there are big savings over aluminium extrusion straight away, and the gantry can be made that way as well. One of the gurus, JAZZCNC, even has his stacked up against a wall (80 degrees or so) for space saving and chip fall away.

http://www.mycncuk.com/forums/forum.php

[sine143]

I've been toying with the idea now for about 6 months, but without being able to literally plop a 5x5 sheet down and have it processed to the point of installation... a tracksaw looks like it might be a more worthy investment at this point.

I've even considered just a small cnc table for bracing only lol.

[Charles Jenkinson]

I gather they're initially a fairly big investment in time/money/effort, , whatever size of table you go for. But, for commercial, purposeful use, they probably are a no-brainer, after the fact. & ...I also think of the biblical mandate to 'multiply and subdue' - a CNC router helps fulfil it, I feel.

The important thing is keeping the main thing the main thing. One's main thing can be defined in many ways and with many different components. But I hear that if one gets taken by the CNC bug, that's generally it.

[LelandCrooks]

I've talked to these guys a couple of times. http://probotix.com/FireBall_Meteor_cnc_router/
It's smaller, 25x50, but big enough to be useful. They say it will stand up to production work, they have many machines out doing that.
I don't really need big sheet capability. With my saw setup I can rip up a 5x5 very quickly. 5ft fence, 5x5 outfeed table. What I need is more speed in baffle cutouts, handle cutouts, small parts. I think this will fit the bill.

[Harley]

I don't really need big sheet capability. With my saw setup I can rip up a 5x5 very quickly. 5ft fence, 5x5 outfeed table. What I need is more speed in baffle cutouts, handle cutouts, small parts. I think this will fit the bill.

Spot on there Leland. I've been investigating CNC machines too and as we discussed during my visit last May, it's just a matter of going through all the plans and looking at what parts are square/rectangular and discounting those for CNC immediately. After that you're left with the 'oddball' shapes and most of those are not large.

For the square/rectangle parts, I'd build either one of those vertical/horizontal cutting cutting tables or some roller equipped out-riggers for my table saw.

I would not invest in CNC machine capable of cutting angles either. The extra complication and cost is just not worth it. For the angles I'd use a 'buzzer' after the shapes are cut, either by the table saw or CNC machine.

Quick and effective and useful for other tasks.

The other alternative for angles is a jig made for use on the table saw.

[LelandCrooks]

Hmm, never thought about using my jointer. I may have to give it a try.

[Harley]

Hmm, never thought about using my jointer. I may have to give it a try.

Sam and I spoke at length about it and I showed him how to set various angles for various thicknesses to make them accurate, and make up a reference table. I wish I had a buzzer right now, makes the builds much quicker.

[Charles Jenkinson]

Still thinking about this.

I feel there's more to it than the perceived economies of ripping up big sheets and cutting mitres on other 'better' machines. Apart from the complex parts with awkward shapes and milled pockets and recesses, bits can be changed to do mitres, either negative or positive angle, and joint setting features can be engineered in. Either I've been reading too much Deming, or I'm imagining that a more engineered or systemized approach to assembly is where gains can be made. Eg. Flat pack furniture.

[sine143]

True, bits can be changed for angles, but that pretty much means 4 or so tool changes per sheet. (At about $40 or more a piece). This is a major time sink. Imo it would bw easier to rip the angles with a table saw on to the cnc panels while sheet 2 is bein processed. a 3 axis can also e configuredto "profile" positive angles

[David Raehn]

I know it's just another complication, but why not add a 4th axis to the machine (head tilt)? Keep the same tool bit in the head and let the computer handle the trig to offset the carriage.