Hello from Lancs

Hello there,

I'm Charles, from Ramsbottom. :-) My interests are to ultimately build a CNC router, 4'x8' bed, plywood work, with small scale aluminium capability. I have an engineering background, mainly design/stress analysis/machine performance optimisaiton, but some (non hands on machine) shopfloor experience from my days at David Brown (Huddersfield), so I've seen how it's done but without the practical experience myself - no electrics experience though. I can weld - good enough to make a frame and gantry, am interested in the 'vertical' JAZZ orientation for space saving (but would like to build in horizontal plane!, :-)). My interests in terms of usage are potentially cutting out speaker cabinet parts, plywood boat parts (stitch and glue), foil profiles (i.e. centre boards /rudders), and possibly machining high efficiency (long and narrow with high pitch) aluminium propellers for human powered boat type craft, ...and I'm sure the list will grow. I'm not sure how much Z-axis I want because the option to 3D mill blocks of foam for hulls might be useful - this could be kept to a minimum since the hull could be sliced up and layered (in Z), and stuck together afterwards, and 8ft long is a slight limitation anyway, ...but 400mm Z will probably be an acceptable compromise - I'm wondering if this can be achieved by a bed that can be removed/lowered (a head in hands moment), so the gantry doesn't have to be high up for the majority of (panel) work or the Z working at the bottom of the stroke - is it possibly for the bed to be in the middle???, so the split is 200mm above the table, plus another 200mm below when table is removed. Timescale - nothing required quickly - this is a longer term project - just need to determine design spec and typical equipment BOM & costs, spending the money ideally needs to be spread out over time if possible - budget will be whatever is required to sensibly meet the spec. - I need to avoid fixing spec and obsolesence kicking in for parts that I haven't obtained yet. I'd initially like to connect up with some other local people to go and see what they're doing - may try and contact a few. Thanks for a great forum.

Best regards,

Charles

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Originally Posted by CharlesJenkinson

400mm Z will probably be an acceptable compromise - I'm wondering if this can be achieved by a bed that can be removed/lowered (a head in hands moment), so the gantry doesn't have to be high up for the majority of (panel) work or the Z working at the bottom of the stroke - is it possibly for the bed to be in the middle???, so the split is 200mm above the table, plus another 200mm below when table is removed.

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My machine has a Z-axis with 400mm travel and the bed height, so you might want to have a look how I did it in my build log:
http://www.mycncuk.com/forums/gantry...html#post35482

The frame/X-axis is OK, but don't take too much notice of my gantry as there's plenty of room for improvement there.

Thank you Jonathan. I will read that. Am reading as much as I can, as soon as I can. All pointers welcome. I like to discuss things, but there's a hell of a lot of information to read first before that, which is slightly frustrating, but the way it is. Cheers, C.

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Originally Posted by CharlesJenkinson

but there's a hell of a lot of information to read first before that, which is slightly frustrating, but the way it is. Cheers, C.

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That is true, I had the same problem, but as soon as I started to get some ideas together and crucially got some drawings uploaded from Sketchup it made my way clearer and gave other forum members something tangible to discuss and tear to pieces, which thankfully they did to my benefit.

Welcome :) was near you yesterday in Bury .. it rained .. about all I can say on that subject.. have a good stay !

Not to try putting you off or saying your not capable but what your proposing at the size your proposing is very ambitous for a first build.!! . . . .Be very truthful with your self regards your abilty's and don't be afraid to ask for advise or help if at all unsure.

After some research and when you feel you have a handle on what you want then Be patient don't rushout and buy stuff before running it by us because it's very easy to get wrong stuff.
At the same time and contry to above "Be patient" advise Don't get to hung up on drawing stuff to the last degree just the basic design layout to check fitments etc and materials to used is all you really need then get stuck into building. Often doing too much research can have a negative affect and fry your noodle.
Often you'll see people take months or years on design never to see it come to fruision and if it does it rarely resembles the paper design when finished.!!

Good luck, if done correctly and patiently then it's a very rewarding journey.!

Thank you Gents. Love the pragmatic advice Jazz - many things are a compromise of two contradictory ideas. I'm getting the feeling it's ambitious from reading other build/use/buy threads - but if I can't spec it to do the potential jobs, I'll never be satisfied. When my noodle is approaching fry off temperature I'll be on here, asking stuff. The timescale is the tricky one - it's normal for me to end up taking years on projects, but with an analytical eye, rather than a doing hand (which I'm trying to change), it usually ends up right first time. ...there you go, I've gone and walked right into the trap - well, you laid the bloody gauntlet, I just had to pick it up didn't I. :-)

...there is one thing. My gut feel is this is going to cost £4k to £5k. Am I in the right ball park?; because that, I.e. The spending rate (and space plus other commitments) as well as the learning curve will dictate the progress rate. If that cost is right, and I can keep momentum, I feel it'll be a 2 year (minimum) project.

Hi Charles, welcome to the forum. I used to work in Rammy...at Drury Adams the foam converters, there's now a co-op i think where the factory used to be. Now live in Gloucester but come up to Accy to see the kids every other weekend.

If you do as Jazz, Jon and Eddy say and do a bit of research then put up some designs in a build log then you'll get constructive comments (there are sometimes a few warm debates thrown in for good measure) and you'll find your understanding growing until you're confident in doing it. As jazz says don't get hung up on design as it'll waste time...read my build log if you want to see that! I'm now just getting on with the build as I've been reading others build threads and chipping in so have the confidence. Anyway enough ramblings, good luck with the build, I'll be following it with interest!

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Originally Posted by CharlesJenkinson

...there is one thing. My gut feel is this is going to cost £4k to £5k. Am I in the right ball park?; because that, I.e. The spending rate (and space plus other commitments) as well as the learning curve will dictate the progress rate. If that cost is right, and I can keep momentum, I feel it'll be a 2 year (minimum) project.

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Spot on in both cases.
2 years is a very realistic goal for someone new to fully learn what's required to correctly design, source and build to a high standard a fully finished machine that will do everything they require without wasting money or compromising on features.!! . . . .Yes it can be done much quicker and with savy buying done cheaper but that's a good conservative time frame and budget.

I know how easy it is on Forums to miss read what's being written and of late it seems many of my posts are being taken or twisted by some differantly to how they were intended so please don't think I was being Negative or doubting your abilty's. My words where purely to help try get over the significant task you would be taking on with this size machine has a first time builder. (I hate the word Newbie, Noob or any other way of spelling it.!!)

I help many many people and most of those that fail or become disillusioned are those that have rushed and tried to build too large machine. Often if they do succeed in getting a machine built they are dissapointed with the results because they rushed and cut corners.

I've said this before again thru helping many people from all walks of life.!! Those that often succeed in building the best machines are people who you'd least expect with very little to no practicle engineering experience but a desire to succeed and willingness to take advise on board.!! . . . . From the approach and words seen so far I'm sure you'll be fine. . :thumsup:

Thanks to all who've posted so far. If this is something more/different than an 'Introduction', apologies and please advise - I haven't got my head round all the forum chapter-categories yet, but felt I need to explain myself, ..for the reasons people explain themselves, etc.

Time for a reality check. I foresee this as being solely a design activity for some time, rather than a 'some design, then enter a concurrent design & manufacture phase + ongoing problem solving & upgrading (i.e. the proverbial "building machine number 2")' experience. The latter is not my style, for one, however the reasons are: current family circumstances - 3 small boys, garage not big enough and the concept of commiting to the costs associated with the genre / spec of a machine I'd like to build. The remaining pressing issues: we need to move into a bigger house & I would need a dedicated workshop, or at least a bigger (double) garage to get going. A bigger income wouldn't go amiss. What I do have is a healthy amount of thinking time, but not quite enough doing (design & CAD) time to match against it. I'm already finding it a balancing act to make enough time to get up to speed on the wealth of forum info. - it's a full course dinner, and some. Being prone to Displacement Activity, I've probably done some of my best stuff when I was supposed to be doing something else, ...so, the best I can make of that little lot is to work on the design and figure it all out such that when the doing comes along it'll go smoother and be pretty much spec'd. I think I've figured also that the objective has migrated to the substance of the rewards of just designing & making a CNC machine, but not dreaming about what I can do with it, just yet - the former is enough of a draw, and when the workshop with CNC machine has manifested, the ideas, projects and jobs will also come, but based on the idea that I'm probably doing enough bits and bobs now to justify it and my wife is an ex Design Tech teacher and is always raving about "laser cutter this and that" I think we'll be OK for dreaming up some future shed time. ...that's the theory.

So, for a while at least this is going to be a good look at the philosophy of CNC router design for a 1220x2440 vertical (Y upright) cutting bed, for wood and aluminium; the process of doing that design; generating some design output, fixing part spec's (incl. costs), & specific component sourcing options. It's for me, but I'm happy for it to be as generic (as possible) and open source - then it's repeatable, with all info in one place - a spec/design doc of some description.

I'd put my initial ideas down, but I'm wary of entering into detail whilst I have unanswered concept-type questions, ...because there's no sense in folks poring over stuff where I haven't thought about it myself, and especially given how wrong the initial concepts might be - so until concepts have passed an internal credibility / sanity check, against the background of reasonable research one could do on here or elsewhere, I'm better not going public.

Once again, thanks for a great forum, and the staggering talent.

Ok, here's the initial budget for a 1250x2500 bed, gantry router. I would be interested in lumping all the rails, screws and spindle together in one China order, with someone like solar jean. Sorry, still not sure where to put this on here - it's not a build thread, nor design - it just gives an idea of the big spend points and the overall project delivery philosophy. What I'm interested in is where it's right/wrong, needs adjusting...? I'm hoping this is a mid-term realisation and not hypothetical, but I figure the order of things is fix design/spec first, then purchase the big lumps all together, and weld together frame and get parts made and assemble near the end, when all components have arrived and any dimensional differences can be accounted for without waste/rework. Bearing in mind it's early days on design / spec., and spec relates to cost, I've tried my best to write something down, ...this is mainly a budgeting exercise.

X; 2 pairs of: screws (25 dia. - non rotating) + end housings & nuts; rails + brgs (hiwin profile 20mm)£1200
Y; 20mm dia rotating screw + end brgs & nut, pair of rails + brgs (hiwin profile 20mm) £450
Z; 16mm rotating screw + end brgs & nut, pair of rails + brgs (hiwin profile 20mm) £250
2.2kW spindle + vfd + collet/s £250
4 (Nema 23) motors + leadshine drivers (UK supply) £600 Control panel + cabling + energy chain £250
Software £200
Steel + weld consumables £350
Fasteners £100
Other tools; epoxy, taps, straight edge, square, spirit level £200
Bespoke machined parts/assy's: motor mounts, Z plates, rotating ballnuts, pulleys & belts £500

total: £4,350

You might get away with 20mm screws on X if using rotating nuts. The only reason for using bigger screws is if you cant tension them sufficiently to avoid too much sag over the length. Smaller screws also means less inertia in the (smaller) ballnuts, but this is not so critical. The tension you apply will depend on the amount of distortion in the frame ends you're prepared to tolerate and that will depend on the cross-section of the frame material. What do you plan to use for the frame?

Thanks Irving. I can make provision for screw tension - how's tension measured? Natural frequency or so many nut turns? 80, 90, or 100 box for frame, 3mm thick. I think torsional (cross corner) vibration mode is important given it'll be vertical mounted. It will be braced back to a brick or block wall.

if the X screws are vertical then sag is less an issue. Tension is measured in Newtons and the tension applied can be calculated from the pitch of the thread used for the tensioning nut and the torque applied to the nut. Google nut torque and bolt preload for the formulae.

X screws will be horizontal and probably about 2900+ long. I forgot about nut torque and bolt stretch, doh! I can't imagine screws get particularly hot, but it would be temperature differential between the steel and frame steel screw that might reduce tension, and then vibration potential if the nut is near the ends, I.e. not supporting near the middle. I don't have a feel for temp differential, but I read a figure of 3 degrees the other day, gives a large change in tension, so maybe 3 degrees is the number to base a nut torque calc on, but that still leaves 1st bending natural frequency, which I also don't have a feel for the permissible lowest natural frequency for a screw. It's not going to be much different between a 25 dia or a 20 - they are both long and slender at nearly 3 metres.

I'd be surprised if you got that much a temp difference between screw and bed rail given they're only going to be a couple of 100mm apart or so.I'd turn the screw end down to say 15 or 12mm depending on root depth and put a similar clearance hole through the end box section with an anti-crush tube inside and thread the last 20mm of the screw for the tensioning nut and thrust washer. You could look at back to back Bellevue washers to get a defined preload.