Thread: Chris's 2nd Build "Big K4huna"

Hello Blueray / Rodm

I had an idea of what I would be routing on my machine, thing is though I was asked to rout / carve a nosecone from blue foam that tested the limits of the machine, I ahd moved the X motor so it wasn't a problem but it would have been if I hadn't moved it earlier.

I have " heard " figures of ally having 1/2 the strength of steel, I also have a mate with a CNC machining business that machines Ally that is stronger than steel. For me ally is good as it is easy to work with but that is also a downside, normall milling machines don't ( well my Hare and Forbes one ) have enough RPM's for it so it cuts poorly, on a CNC router we have the RPM's but less rigidity.

At the risk of getting my head bitten off......hasn't stopped me before, the recent debate about welding / bolting could also be seen as personal preference, mine is to weld as I hate drilling holes in steel, with planning the stress bending can be negated, the other thing that helps is to ask for help, I'm not a welding professional but those I know who are don't mind sharing thier secrets, much the same way as we would help new chums here.

BTW, I have had some fair cock ups when welding, I welded a 1400mm length of 40mm by 15mm to a 50mm SHS by 5mm section and had it looking like a banana, not to worry, I'm getting it machined, when the machinist clamped it up he did it so tight he flatened the assembly, which sprung back when he released the tension, got it right the second time - much like us.

Ed

Hi Chris
20 mm long shaft for a Nema23 and 37mm for a Nema34. Manufacturers specs so it can vary a bit on that.
The 15XL pulley does not have enough meat in the hub to fit a 1/2 inch shaft to it. You will get the hole but there is not enough left for a grub screw. I have just measured a pulley from Hubbard CNC.
I hope you didn't take me seriously on my last couple of posts as I played up a bit this afternoon.
In Perth we have Scrap Metal Yards more popularly named recycling centres that buy all sorts of metal. I have a couple of yards I visit every couple or three weeks and they have brass, aluminum and steel. If they buy it they sell it and if they get to know you they will hold it for you. I have got quite usable aluminum plate up to 40mm thick as well as solid bar for lathe work. I have no idea of the grade of this stuff but I make it work for the tinkering I do. You will not get lenghts for building stands, etc but the offcuts I get are suitable for gantry sides, motor mounts, etc. Sometimes I get lucky and get larger sizes. Ring around or visit their yards and you might get surprised at what you find. I find ebay prices high and if they are charging more than $6 per kg for ally then chances are they beat you to the scrap yards.

Hi Ed,
I will never knock anybodies posting on technique as we all work with our own set of skills, knowledge and materials. It would be silly not to keep an open mind and all suggestions should be taken seriously otherwise how do we improve?
Everyone has something to offer.

To anyone elses interest You dont see many prices so it might be interesting to anyone thinking of starting a build.


0.0.416.30, 120 x 80 heavy profile is $196.50/m + GST and any local freight cost. (LinearBearings)

Estimated $315.579 + GST for a length 1606mm

And prices for Aluminium Plate from a local mob who cant cut it (ie a reseller) Should be cheaper from a place that actually stocks it.

12mm plate - 1200,2400 = $736 + gst
15mm plate - 1200,2400 = $980 + gst


I think the price did go up on the 120x80. {Edit = It did }


{EDIT}
WOOT some good news

$5 kg for aluminium (he said sheet but I said plate should be the same price regardless)

He also said there is alot there. Hoping some 12mm I can play with on my router, ill see if I can grab some tommorow. Biggest sheet I need would be 220x380 so not sure if I can get that there but all the smaller stuff I should be able to.


Just a little maths here but found out the weight is 2.7g/cm3 does that mean in a 1000x1000x10mm sheet there is only 270 grams? Just trying to get a idea on how much I can get for $5 a kg. The website must have been a decimal off at 27g/cm3 instead of 2.7.

Also Rod about the alu to steel strength

Originally Posted by wikipedia

Aluminium has about one-third the density and stiffness of steel,

But then again different grades different strength, just like hardened steel ect.

and has ~1/3rd of the weight.

I too am a fan of welding items, but to achieve a solid penetrating weld you 9 out of 10 times distort the metal shape. So for things like these cnc machines, bolts and threads are the better option, also as pointed out allows for a greater degree of shimming and finess.

As far as hardness in metals, alluminium will do the trick for cnc routers, but on a side note, aluminium and most non aviation alloys have a hardness of 23 brinell, whilst old fashioned steel from the steel merchants has a reading of 110 brinell for the same cross sectional area, so its more like a 1:5 ratio for strength, "for info I inspect metals for a living".

Quote - 2.7g/cm3 does that mean in a 1000x1000x10mm sheet there is only 270 grams?

Nope unfortunatley its 27kgs

A strip 10mm wide by 10mm thick by 1000mm long = 270 grams

My maths isn't great, but by my reckoning, 1000mm x 1000mm x 10mm = 100cm x 100cm x 1cm = 10,000 cm3.

10,000 x 2.7 = 27,000g = 27kg.

Cheers

Hi Steve,
Should have thought to ask you on the different strengths of ally and steel.

We are flying out to Gold Coast, Newcastle and Melbourne in February so I'll give you the flight number and you can stress check the aircraft before we leave. No destruction tests either.

Hi Chris,
Is the $5/kg from a scrap merchant? If so compare the pirce on ebay and you will see where I am coming from there. Nice profit for those blokes.
I think sheet refers to thinner material while plate is for thicker section. I have no idea where one stops and the other begins but I call sheet up to 6mm thick and plate 8mm onwards. Happy to be corrected on my thinking.
Hope you score a heap of good stuff and let us know how you get on.

Originally Posted by rodm

flying out to Gold Coast, Newcastle and Melbourne

Lucky bugger, whats the special occasion.

Originally Posted by rodm

Hi Chris,
Is the $5/kg from a scrap merchant? .

Recycling center. If any difference.

Taking a holiday with the kids. Should be fun but not sure if I can keep up with the nightlife they have planned.

Hi Chris,
Nah just a more fashionable term. Same old dirty yards and clutter.
Good luck with your find.

Still waiting on my rails but I will be ordering the steel next week regardless of if its in or not, so I can drill and tap the holes for the linear slides (I just cannot weld anything)

I will be getting the 1160oz-in nema 24 from ms-motor if they ever reply to my emails. , Was going to order 4x 425 oz-in, 3x 1160oz-in and 1x 1160 oz in with 3:1 gear on it as I am not sure if I will need it for the Y axis or not, and getting a extra 3x nema 24's just for the sake of it.

I am also going to get some gecko 201's for the nema 34's and 1x 251 for the Z axis.


I have been trying to find a suitable power supply but I cannot does anyone know where you get more powerful power supplies? best I found on ebay was 58V 20Amp for ~ $150USD.

Hi Chris,
I am fairly sure you can have more than one power supply in your machine - in fact I think you can have a seperate power supply for each motor. If you are slaving X axis I would make sure both of those are on the one supply as you would not want one axis driving and the other one stopped. You could then drive Y and Z on another power supply.

This is not my strong area so somebody chime in if I am out of order.

Having separate power supplies for each motor can also be an advantage as the voltage out of the transformer can droop under high current draw which is most likely to happen with big motors all running simulataneously.