Comments sought on new build: A CNC Router for RC Gliders and Planes

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Originally Posted by jcb121

I've ordered these other ballnut housing and in total I bought 4 for about £26~
just purchase but don't pay and then say you want 4 or however many.

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I think they're the same as I've ordered...

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I've been welding my frame up and now that I have gas it's going pretty well! though i wish i had as much space as you do!

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It's the works so not really mine, wish it was though!

I'm away for the weekend so nothing getting done until next week now :(

Was wondering what to do with the left over steel I've got so had a play at lunchtime with Sketchup...
https://www.youtube.com/watch?v=sNnnq6yOfus

Looks good Niel (I love fixed gantry). I think you could move the gantry back further if you wanted slightly more travel, and am not even sure you would need the back diagonals. Do it !!! G.

Hi G, there's only one slight problem if I built this...where the heck would I put it, going to be tight on space in my little shed as it is!! The design as it is allows maximum travel of the bed so I can cut the whole area (500 x 400) I've got the raised sides (sealed with gaskets/sealant) so I can flood the bed with water when cutting the CF so the dust doesn't go everywhere. TBH I doubt I'd need any of the diagonals for cutting CF and Trafolite but I've got the steel so better safe than sorry!! This could use up all the left over bits I've got from when I bought the rubbish TB6560 control board and steppers, might even be able to use it for engraving labels for work. Spec for this one is very much as per my first post on here with the exception of SBR12 rails and blocks.

Well I finally managed to get back onto the shop floor this lunchtime and re-cut the 40° angles to 45°on the supports.....tomorrow I'm going to try to do some more tacking up...depends on if I can get anywhere to weld as the shop floor is a bit busy at the moment. Really want to crack on with this now so I can hopefully have it running before Xmas.

PROGRESS.....today I managed to tack up the last of the angle supports and start some of the welding up of the frame. Can tell I've not welded for a couple of years!!!!!:hysterical:

Attachment 10539Attachment 10540

Oh yes, judicial use of the angle grinder I think will be needed...

Nothing managed today as the area I was using has been set up for SS so I can't go welding and grinding there!! Spent a little time getting the fixed end blocks onto the ballscrews as the screws were a little oversized so couldn't get the bearings on the screw. Have managed to get one on but there's some play in the bearings which will need looking at...disappointing.

Nice to see the bed taking shape Neil. It's a shame the screws/bearings from Chai don't fit properly :( Hope you manage to sort it out.

Si.

Cheers Si, I'll put them in the lathe and take some emery paper to them to get them to fit.

Fitted the 2 solar panels to the shed roof and wired them in series into the charge controller and wired the 2 x 115Ah leisure batteries again in series into the controller and.........it works!! Have a small 600W inverter coming next week so should be able to run small things like soldering irons, radios etc. until I decide what my power requirements are.

Installation has loose wires all over the place as I was running out of time this evening but I wanted to prove it all worked. Shed desperately needs tidying as I've been bringing stuff back from storage and just dumping it in there.

http://img.tapatalk.com/d/13/11/04/gy8a9ute.jpg

First time out to the shed since installing to see if its working ok and it is, just need to run the batteries down a bit to see if it charges them as they're topped up now so not being charged.
http://img.tapatalk.com/d/13/11/08/juhehahu.jpg

Looks like yours are working better than mine the day after I mounted them:

Attachment 10618

That's after I'd wiped the snow off!

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Originally Posted by Jonathan

Looks like yours are working better than mine the day after I mounted them:

Attachment 10618

That's after I'd wiped the snow off!

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They seem to be pumping out voltage and you can see it fluctuate as the sun comes out. Just bought a plug in electricity cost meter to see what some things consume to see what I'll need. Booked a day off this week so I can sort out the shed as it's a right tip with boxes and RC models scattered and piled up everywhere.
Put the ballscrews in the works lathe and had it on slow today at lunch and took off a couple of thou off the shaft with some emery cloth as it would have been a tight interference fit. Now a nice tight sliding fit on the shaft so happy. Still unhappy that there is play in what should be a fixed bearing, anyone else have this?

Well after another couple of months of inactivity I finished welding up the basic frame. I've still got to attach the side rails (and ends) but am unsure whether to bolt them (so I can adjust them so they're level) and then weld them or just weld them as near as possible as I'm going to do the epoxy levelling on them. I presume that It's doubtful that they'll be level enough to mount the linear rails directly on them without some form of levelling? I've no straight edge to measure them with mind...

Attachment shows the frame tacked up previously not welded up before the eagle eyed point this out...!

Looking good Neil.

I think I'd just weld rails in place if you're going to epoxy level them. I can't imagine that bolting them first would improve the final outcome by more than a mm or two for fair bit of work. I've got some brackets if you need them though ;-)

Cheers Graham, preferred method is to weld them rather than bolt and weld!

Today in lunch I finished off a couple of welds on the frame that I missed last week and put the first of the side rails on and tacked the back upper beam on.

Used my bevel box to set the top rail level with the bottom rail. The second rail will be referenced to the first rail later this week when I get back in the workshop.

Attachment 11333Attachment 11332Attachment 11331Attachment 11330

Although you can't see the first reading on the bevel box that well it does say 0.0 and 0.0......much like the second one!!

Once all the rails are welded up then I'll be getting the grinder out (and the welder again to fill any holes etc...!!) to smarten up some of the welds and also to get the bed rail welds flat so the base will sit flush with the frame.

I've still got to cut some squares out to weld in the upright tops for when I do the epoxy levelling. Also got to weld on a couple of stops on the ends to park the gantry up against when not in use.

Well after being off sick with stomach cramps for the last 3 days I got into the workshop at lunch to weld the second side rail on and start tidying up the welds. I am quite pleased with the accuracy I got (hopefully) on the rails according to my level box. I referenced the first side rail from the base frame and then using the level I clamped the second rail and referenced that from the base frame front and then kept tapping the rail down with a soft face mallet until it was showing 0.0 & 0.0 all the way from the front to the back. I checked the level again before tacking the rail in place and then checked it again before doing the final welds. I'm still going to epoxy level the rails I think...

I started cleaning up some of the welds but there's a lot of that to be done as my welding is rubbish! I also put on (at Jazz'z suggestion) a piece of 50x6 flat on the end of the rails to act as a stop for the gantry when it goes vertical.
Attachment 11352Attachment 11353

Looking good, I like the look of the smaller box section for the bed and triangulation. Are you going to block off the ends of the box with those plastic caps ?

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Originally Posted by njhussey

I started cleaning up some of the welds but there's a lot of that to be done as my welding is rubbish! I also put on (at Jazz'z suggestion) a piece of 50x6 flat on the end of the rails to act as a stop for the gantry when it goes vertical.

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At the moment my machine is back on it's feet for some recent repairs and I can tell you I really miss it being vertical.?
Not just for the space but for my Back has leaning over the bloody thing to fasten material has been killing me. Didn't realise just how easy it does make fastening and accessing material while it's working.
Also having to deal with clearing chips again is a pain in the arse and again you don't fully appreciate how much differance it makes until you have to go back.!!

You haven't experienced using flat so you maybe won't fully get what I mean but you will if you ever use it horizontal after being vertical. . .Lol

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Originally Posted by EddyCurrent

Looking good, I like the look of the smaller box section for the bed and triangulation. Are you going to block off the ends of the box with those plastic caps ?

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Thanks Eddie, I'm pretty pleased with how it's turning out...no I'm going to weld plate the ends and grind the welds smooth. Will probably put 20mm thick bits in the bottom and drill and tap M12 for adjustable legs just in case I do leave it horizontal at any time. :)

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Originally Posted by JAZZCNC

You haven't experienced using flat so you maybe won't fully get what I mean but you will if you ever use it horizontal after being vertical. . .Lol

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I'll take your word for it jazz lol I'm beginning to wonder if I'll ever get it finished. I just never seem to have any free time...

Looking forward to finishing the frame off next week, getting quite into the fabrication side of things again!

Question for people. How is the best way to DIY cut 20mm Ali accurately? I'm running out of money (wedding is end of March so bills are coming in fast!!). I was thinking of cutting the Ali for the gantry myself to save a couple of quid (plus I like the challenge!) as I don't like the prospect if telling the wife to be that we're not having a cake as I spent the money on machining... ;)

I cut 20m Ali plate full depth on my table saw using a carbide tip blade that is so tired it complains at cutting hard woods yet munchs thru Ali.??
(Wear eye protection and cover all exposed flesh has the chips are red hot and hurt like hell.!!)

For shaped parts make some MDF templates and use large router with bearing guided carbide cutter with very shallow passes.! That's how I made my first machines gantry sides and that was with a 12mm cutter.!!!! . . . Which wouldn't recommend so go for 6 or 8mm max.
Other than being a little daunting it worked a treat.!. . . . Thou I will say I was very very experienced with using a Large router free hand so if not used to routers then be careful has they can be a handful.!

Couldn't be bothered to set up the bench to do grinding today so though I'd get out the linear rails for the X axis and see how flat they were. Took a quick video (apologies for it being upright!) and the rails are pretty flat.

My question is.....do I need to epoxy then level as they seem pretty damn bloody flat to me as they are now!!!

http://www.youtube.com/watch?v=rIkyrg0vw4s

I'm not sure your test of flatness on the x-axis bars is valid because the rails weren't bolted down. If there's a dip in the bar the rail will probably span it but get pulled into it (slightly) when bolted firmly down. I think you'd need a long straight edge and feeler gauges to really figure out if it was flat enough.

As for cutting aluminium my SCMS went though that 10mm you gave me like it wasn't there using a positive rake cross cutting blade - about the worst blade you could use for metal cutting - and left a mirror finish. With a negative rake aluminium blade I'm sure you could do 20mm easily. Watch out for those chips though, as Jazz says, they are bloody hot. As for routing to shape you might want to try a router table instead of a free hand, I think you'd probably get better control over the depth of cut and a finished face this is more perpendicular. The downside of of a router table is that the chips will fall onto and potentially into the router which may not end well. You can pick up a router table insert for very little as long as you don't mind the height adjustment being completely manual.

Forget the spirit level thing - it's nowhere near accurate enough to provide useful readings for rail alignment. When I measured the error on the rails in the recent build log, we were measuring height error to 0.01mm and angular error (rail twist) to 0.003 degrees...I'm not saying you have to do that, but it gives an idea of the tolerances that can be involved if you try and do it properly.

The rails will conform to the surface you bolt them to, so regardless of how straight the rail is to start with, if you bolt it on to a surface which isn't flat, the result will be a rail that isn't flat. Hence you should use epoxy to level the surface.

Oh well.....still quite chuffed that I managed to weld them pretty damn level :eagerness: Will carry on grinding and welding and getting ready for pouring the epoxy (best buy some I guess!!) OK another question :) Is it better to drill and tap the holes before epoxying or after? I was thinking before as we have a mag drill at work and that would make drilling the holes much easier first, but then would need to fit the bolts and make sure epoxy doesn't stick to them and then there's the question of the miniscus round the bolt?

Now playing devils advocate here....how much accuracy do I need? There's a CNC router I know of that looks a bit like this.....
Attachment 11387
which has supported round rails bolted straight to what looks like steel rectangular section and that machine seems to put out some nice accurate shiny aluminium bits :wink: :wink: :wink: :wink: :wink: I'm mostly going to be cutting balsa, ply, carbon fibre, wood engraving and the odd piece out of aluminium (probably upgrades for the machine itself if most build threads are to be believed...!) so just wondering to what degree I go to with the levelling? I've got nothing to measure the accuracy of the epoxy once it's set and have no way of accurately telling if the rails are flat. I don't want to go out and spend a small fortune on a surface plate or engineers bevelled edge 1300mm long sop suggestions on a postcard please?

These lot, make you think too much.... think less........

Just do the best you can do with the tools & experience you have. I spent ages in my build worry about this very point, in the end I just got one rail spirit level flat, and set the other one up off that. BOSH

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Originally Posted by njhussey

Now playing devils advocate here....how much accuracy do I need? There's a CNC router I know of that looks a bit like this.....
so just wondering to what degree I go to with the levelling? I've got nothing to measure the accuracy of the epoxy once it's set and have no way of accurately telling if the rails are flat. I don't want to go out and spend a small fortune on a surface plate or engineers bevelled edge 1300mm long sop suggestions on a postcard please?

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Excellent point and your 100% spot on.!!. . . . He's talking Bollocks.!! . . . . Measuring to those tolerences needs expensive highly calibrated equipment which I doubt he has either.!

For what you want to do then if those rails are on the same plane then you will be perfectly fine.!! . . . . Fact is this is DIY Level precision and to attain higher level precision cost's lots of Money or Lots of time and frustration.!!. . . . . .KEEP IT REAL. . . it will be PERFECTly fine for wood.!

Cheers Jazz ;)
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My cunning plan is to get some of my 10mm 6082 plate I have and make a plate to go across the X axis and bolt it to the carriages like so....then put some 100x50 section on it to stiffen it....
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Attachment 11390
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Then I can drill one hole one end of a rail and then using digital callipers (accurate enough???!!!) get the hole at the other end the same distance from the rail side, move the carriage to one end and drill a hole on the opposite rail at that end, slide the carriage up to the other end and mark the hole and drill that. Then by sliding the carriage up and down and nipping the bolts up I should be able to get them parallel to each other. I can then move the carriage near the middle and mark, drill and tap those holes. Once I've a sufficient number of holes drilled and tapped (every other hole?) I should be able to see if it slides freely or if it binds? If it slides freely......happy days, if not then epoxy it is! Sound like a (convoluted) plan?
P.S. I know the bolts should be allen head socket bolts and counter sunk but I couldn't be bothered to draw any.....sorry!

although the amount of deflection mentioned by jonathan may seem small, it would be noticeable over a large machine base, or if your surfacing or engraving anything bigger than 500mm.

In his build, he shows you how to use epoxy to get it level, as close as you would need it.

I also fly RC planes. If you considering cutting wing profiles, you will notice even a small deflection. All depends on what your doing.

IMHO, for the sake of £ 45 for the expox, and a few hours ( no expencive tools needed ), do the resin thing, get it as accurate as possible.

Imagine doing a glider wing profile from foam, 1000mm long each, a small amount deflection on your rails would ruin the wing.

Understood George, however I think we're all knit picking here! I cheekily pointed out Jonathan's build as he has done what I was (maybe still am??!) thinking of doing and putting the rails directly on the steel. The sort of deflections I'm possibly looking at are in the magnitude if 0.5mm which is one stroke of sandpaper on a wing rib to put it in context. I've built some large and small planes by cutting out round paper templates so there would already be larger errors than what I think these rails will give.

I do think doing the epoxy levelling is worth it, after all why put in the hours on the design, the hours fabricating the frame only to not let it reach its full potential? However Jonathan's "Sufficiently strong" machine (a superb machine) was built with parts made (nested out of one large sheet of Ali) on a machine using supported round rail (I'm sure you've read on different build threads Jazz's comments on what he thinks the linearity of those rails is like!) on non levelled beams ;). Is that a chicken and egg situation??

Anyway, enough fun. I'll have a look at the rails tomorrow and poke about with some feeler gauges to explore...

The critical point to bear in mind my old machine uses round rails on the X-axis, which tolerate a lot more misalignment than profile rails. The required tolerances go up a lot when you start using profile rails.


If you can get the rails to run smoothly without the epoxy, then that's probably fine for what you want to cut. The issue is it's hard to tell when a rail is misaligned by only a small amount, as this just applies a large quite large force to the bearings, but they can tolerate that temporarily. The problem is if you don't spot the slight change in smoothness caused by this, then your bearings could wear prematurely due to the increased load. Compare that to epoxy, where unless something goes seriously wrong it guarantees better accuracy and sufficient flatness. The £45 for epoxy is not much in the whole scheme of things when building a CNC router, so I'd strongly recommend it, although it's not mandatory if you can get the rails to run smoothly without.

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Originally Posted by JAZZCNC

Excellent point and your 100% spot on.!!. . . . He's talking Bollocks.!! . . . . Measuring to those tolerences needs expensive highly calibrated equipment which I doubt he has either.

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I'm not sure if I should dignify that with a response, but I will for now. Are you referring to the angular resolution I quoted? If so then it really should be obvious to you how I measured that from the photos.

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Originally Posted by njhussey

However Jonathan's "Sufficiently strong" machine (a superb machine) was built with parts made (nested out of one large sheet of Ali) on a machine using supported round rail [...] Is that a chicken and egg situation??

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The mounting surfaces for the Y rails were milled using the bridgeport mill at school, since it wasn't reasonable to expect the required accuracy from my machine.

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Originally Posted by Jonathan

The critical point to bear in mind my old machine uses round rails on the X-axis, which tolerate a lot more misalignment than profile rails. The required tolerances go up a lot when you start using profile rails.

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The point I was cheekily making was that we get hung up on fine tolerances when your machine is perfectly good for cutting aluminium!

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If you can get the rails to run smoothly without the epoxy, then that's probably fine for what you want to cut. The issue is it's hard to tell when a rail is misaligned by only a small amount, as this just applies a large quite large force to the bearings, but they can tolerate that temporarily. The problem is if you don't spot the slight change in smoothness caused by this, then your bearings could wear prematurely due to the increased load. Compare that to epoxy, where unless something goes seriously wrong it guarantees better accuracy and sufficient flatness. The £45 for epoxy is not much in the whole scheme of things when building a CNC router, so I'd strongly recommend it, although it's not mandatory if you can get the rails to run smoothly without.

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99.9% sure ill epoxy it but will prob drill and tap the holes first. As you say the £45 or so for the epoxy is insignificant compared to the total price of the machine, its a no brainier. I'll still bolt the rails straight down though...just because!! ;)

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The mounting surfaces for the Y rails were milled using the bridgeport mill at school, since it wasn't reasonable to expect the required accuracy from my machine.

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Again the rest of it was machined from nested parts on one sheet showing that with round rails on steel it's perfectly fine for cutting Ali!

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Originally Posted by njhussey

Again the rest of it was machined from nested parts on one sheet showing that with round rails on steel it's perfectly fine for cutting Ali!

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Within reason the accuracy of your rail mounting wont affect what the machine can cut - it affects how accurately the material is cut and how long the machine lasts.

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Originally Posted by Jonathan

I'm not sure if I should dignify that with a response, but I will for now. Are you referring to the angular resolution I quoted? If so then it really should be obvious to you how I measured that from the photos.

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Wasn't referring to any specific area I was saying the whole measuring and graphs etc to the level your quoteing was bollocks because unless you measured and worked from a calibrated reference point with calibrated and accurate measuring devices you couldn't possibly know for sure.!

End of the day the quality of the pie is in the eating so bolt it together and see how it tastes.!! . . . . . Looking at the care taken so far I'd put a small wager on that if just left untouched no epoxy etc it will quite happily cut wood to a very high standard and do it all day long without any grumbles from those bearings.!!

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Originally Posted by JAZZCNC

Wasn't referring to any specific area I was saying the whole measuring and graphs etc to the level your quoteing was bollocks because unless you measured and worked from a calibrated reference point with calibrated and accurate measuring devices you couldn't possibly know for sure.!

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The measurements I was taking were relative, not absolute. That is sufficient for the purpose, if you accept that the flatness of my surface plate as an adequate reference point.

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Originally Posted by Jonathan

The measurements I was taking were relative, not absolute. That is sufficient for the purpose, if you accept that the flatness of my surface plate as an adequate reference point.

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Unless you could fit the whole machine on the surface plate so have base reference then no I don't.! . . . . . . But to be honest I don't give F@~£ all I know is that for cutting wood then with enough care and attention which has obviously been taken here it will be fine even without epoxy.

He's quite correct that If your machine and Mine for that matter can cut aluminium his will easily cut wood.!!. . . End of discussion.!!

Hi Neil,

I think in all that energetic exchange no-one picked up your enquiry in post #189. You were asking about getting the rails parallel to each other (in plan view). In building mk3 (WIP) I did something similar to you in fixing the 'primary rail' and using the gantry to help set the other rail before marking, tapping and bolting it down. In addition to that to make sure the first rail was straight I clamped a flat hard plate of steel against the outside of the extrusion (with a bit sticking up) to form a stop to push the side of the rail up to.

It turned out that the secondary rail fitted gently against the edge of the other extrusion so all that time spent cutting the crossmembers carefully etc. and building the squarest bed I could had paid off.

I also design and make RC planes - so balsa, liteply, and ply are the usual materials being cut. Will be watching your build with interest.

Hi Barry,
Yes that's the way I was thinking of, seemed to be the easiest option but will rely on getting the bearing carriage mounting points dead accurate as Jonathan says you have to get it accurate or it puts stress on the bearings and rails and will lead to premature wear. I'll look at getting a local machine shop to machine the carriage mounting points on the ali so there are reference shoulders to butt the carriages up to...

I've ordered the Reactive Resins slow curing epoxy (like the West System stuff hopefully but cheaper) and the viscosity doesn't seem too bad. Here's a quick video of me swishing it about in the bottles!!

https://www.youtube.com/watch?v=WRajBSEwFWw&feature=c4-overview&list=UUX_ImztPc6hUkKDfklSSdBA