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

[njhussey]

If I had a big enough shed I would!! Only in rented accommodation (moving from Hereford to Gloucester) so no where to put a big machine like yours :(

[njhussey]

Just got another bargain bit of Ali on fleabay...20 mm Aluminium Plate | eBay

Might have to think about re-designing my router now to take into account the 20mm thick Ali

[njhussey]

Guys, I'm now in a quandary as to which direction to go in my build. I'm going to have to have the router in a shed (10' x 8' it's grown since my previous post as I've been looking at how much "useful stuff" I've recently acquired!!) so space will be at a premium. As I'm mostly going to be cutting balsa, 3mm thick ply, the odd bit of plastic and thin Aluminium (for control horns etc.) do I go for a bigger design I've been working on or stick with the original design? The original design gives me 700mm x 300mm cutting which is ample for what I need it for (not thinking of future expansion though) with 1000mm 20mm rails and 16mm ball screws and the new design gives me 995mm x 500mm with 1300mm 20mm rails and 16mm ball screws. I've been considering also mounting the new design vertically to save space (after remembering Jazz mounting his, almost, vertically.) For the original design I've already fabricated the base but seeing as I have access to getting hold of cheap steel through work, fabricating a new frame will not be that hard or costly.

I'd appreciate your thoughts as I'm in two (possibly more) minds....

[JAZZCNC]

I've been considering also mounting the new design vertically to save space (after remembering Jazz mounting his, almost, vertically.)

If your space challenged then it's a no brainier to me go vertical. There's no down sides only gains, space being the biggest gain.
My machine mainly (99%) cuts aluminium and other than the space saving the other benefits are below. Wood cutting will be similar and possibly better with vacuum for chips.

Better quality of finish due to gravity helping to clear chips.
Much Longer cutter life due to less re-cutting chips, over 50% less wear.!
Greater DOC can be used for roughing again due to less heat and work re-cutting chips.
Less air required for blown air/mist cooling again due to gravity and less chips to clear. Down from 50-70psi to 10psi and obviously much less volume of air required.
Less chips flung around shop again due to gravity and cut chips being cleared more efficiently so not getting re-cut and thrown about with 80%+ falling into bins below machine.
Much easier access and loading/clamping of material due to bed being directly in-front of you, no more back aching bending over fastening material.
Better access to spindle and tool loading.

Has you can see other than the major space saving there's quite a few other decent quality benefits and I can honestly say there's been NO down sides.

Yes there's things I've learnt from being vertical about design that I'd build into a purpose built vertical machine. These would mainly deal with lessening chip collection on various surfaces.
The Z axis would be one area I'd look at and build more shielding around. Ball-screw bearing blocks would be another and I'd build shielding to stop chip collection.
Both of these are only minor things and don't affect the machine in anyway also my machine has NO protection of any kind for belts,ball-screws so they would be things I'd do anyway if was building again and it was horizontal.

The other thing I'd do with MY particular machine is raise the whole thing up higher than it is now.?
At the minute it's just in the same spot it was when first tipped up, sat on same axle stands. This means the bottom area of the bed lower than I'd like also the gantry when parked at top is not quite above head height and I bump my head on it when removing material. Also it's just makes fitting tools into spindle a bit more awkward than could be.
Both of these things are Still much better than when horizontal but if machine was 12" higher they would be perfect.

Now before folks comment on material holding etc other than requiring holding on first placement until clamped then it's absolutely no different to when horizontal.
This initial holding is easy over come with a simple temporary holding shelf I slide into position to place against material edge, which I then slide out the way while cutting. The slight incline of bed then holds it hands free against bed while I clamp or screw it down.
Just like when horizontal both cut parts and waste material needs to be clamped for safety's sake. To be honest it's actually safer regards waste because it mostly falls away from cutter and off the bed so with thought about placement of material cutting entry IE: always starting/exiting at top then there's far less chance of material being pulled back into cutter. That said I also have and do fasten waste material has it's just best practice.

Hope this helps.!

[njhussey]

Jazz, in your opinion would the router be better at a slight angle (15° in this case) or at 90°?

I can see the slight angle as better for work placement as the work will "fall" against the bed and the chips will still fall away into the collection tray at the bottom. I've added some sheet steel sides (that might need more support to stop resonance) so those will stop the chips from being flung all over the place. Just need to work out some shielding for the ball screw lower bearing mounts, and the stepper mounting arrangements and a few other details and I should be good to go I hope?

[njhussey]

I might go a single stepper on the X axis and use belt drive for both ball screws then.

Got a quote from Chai today for the SBR20 rails/carriages and the 1610 machined ball screws, ball nuts, BK & BF bearings etc. and its very reasonable (just a bit over half the price I worked out getting it from the UK would be) so will get those on order soon. Am moving house this week so will wait till the end of the month till I have done that and unpacked a bit!

Should give me time to go through the design and make sure all dims etc are correct and print cutting lists off for the steel.

[njhussey]

Another question. I was planning on using 3" x 2" x 1/4" Aluminium box for mounting the rails on (X & Y axis) but noticed that others have used steel in their builds. I was always under the impression that steel was not straight enough? I'd prefer to use steel as it's cheaper and I can weld the frame up and I need 3 lengths of it for the existing frame so wouldn't have as much waste.

[JAZZCNC]

Another question. I was planning on using 3" x 2" x 1/4" Aluminium box for mounting the rails on (X & Y axis) but noticed that others have used steel in their builds. I was always under the impression that steel was not straight enough? I'd prefer to use steel as it's cheaper and I can weld the frame up and I need 3 lengths of it for the existing frame so wouldn't have as much waste.

Man wish I'd got £ for every time get asked this.. .Lol

What makes you think Ali box is any straighter or flatter than steel.?. .. It's not.!! Also contrary to popular belief often neither is Alu profile.! . . Steel is far stronger and cheaper and with careful selection can be very straight and flat. It's also very easy to work with if it's not perfectly flat.

There's very few off the shelf materials that you can use without some form of correction for inaccuracies and that includes Alu profile. People think profile is straight and flat but in reality it's often not, yes it can be better than extruded profiles like Alu box but it will still need some form of correction to the surface at some point. It's also 5x the price.

The main area of concern is for the rail surfaces being straight and flat. Extruded Alu like Box is rarely straight or flat enough to use without work so will need some form of correction, either filling or sanding high spots.
This also the same for steel but the difference being steel is quite easy to scrape,file,grind,sand than Ali has being harder it doesn't clog tools etc.
In my experience steel box has just the same inaccuracies that Alu box does but steel is much easier to correct. Often all it needs is a quick run over with grinder knocking off any high spots, Low spots can be filled. Then just shim the rails to get perfect.

If your using the Chinese round type rail then I can tell you with 99% certainty the base will not be flat or straight and will have more error than the steel your fastening it to.!!. . And thats without correcting the steel.!!

Have no fear of steel, it's cheaper,stronger and very easy to work with and manipulate to your needs. Other than being lighter Alu has just the same issues steel does and unless you have special welding equipment is actually harder to work with.
If you bolt together while bit easier to drill alu suffers from crush and hole deformation much more than steel does. Unless it's thick material doesn't hold tapped threads very well like steel does. Steel will easily hold fine threads in 3mm thickness for fastening rails etc and allow decent torque on bolts, try that in Alu.!

[njhussey]

Man wish I'd got £ for every time get asked this.. .Lol

That's £ I owe you then

What makes you think Ali box is any straighter or flatter than steel.?. .. It's not.!!

Just presumed that as lots have it for the Y axis that it was straighter, never used it really so presumed others knew best!!

In my experience steel box has just the same inaccuracies that Alu box does but steel is much easier to correct. Often all it needs is a quick run over with grinder knocking off any high spots, Low spots can be filled. Then just shim the rails to get perfect.

Can do all that in our works, Was thinking of welding some 50x5 flat to the 50x50 box and get a local engineers to skim the surface so it's flat.

If your using the Chinese round type rail then I can tell you with 99% certainty the base will not be flat or straight and will have more error than the steel your fastening it to.!!. . And thats without correcting the steel.!!

Nice, I look forward to that!

Have no fear of steel, it's cheaper,stronger and very easy to work with and manipulate to your needs. Other than being lighter Alu has just the same issues steel does and unless you have special welding equipment is actually harder to work with.
If you bolt together while bit easier to drill alu suffers from crush and hole deformation much more than steel does. Unless it's thick material doesn't hold tapped threads very well like steel does. Steel will easily hold fine threads in 3mm thickness for fastening rails etc and allow decent torque on bolts, try that in Alu.!

I have no fear of steel, it's my preferred material of construction as that's what we use at work to build the oil systems I quote, see the pic of a system we did for Ratcliffe Power Station ID fan blowers.

[m.marino]

Neil,

Nice power station reminds me of the days when I worked as pipe-fitter in Industrial tool trade in the Detroit area. I use AM882's and unless you are planning on going to the feed back loop stepper motor/drive combo I strongly suggest them. They run well and stay cool even after a good long day of cutting (14 hrs). Unless you have access to industrial power supplies I would suggest building one with a toroidal transformer, I get a really nice smooth power off my set up and once the transformer got charged it has been running very nice (looking at adding a fan to cool everything down just a bit, for safety measure).

Nice design and should do everything you are asking of it and more. Hope the move goes well. -Michael