Ideal base plate thickness...?

Basically, as per the title.
I'm after opinions on the thickness of a base plate for my case.
I'd initially thought 12mm (1/2" ish), but then I saw the cost! :eek:
I'm going to have the case with 2 'floors':
Bottom: 300x500mm
Top: 180x500mm
With cylindrical support posts on both sides scattered down the 500mm length, probably at 100mm intervals.
Optics + Laser heads downstairs, and power supplies t'upstairs.

It's going to cost around £8 per mm thickness for the overall material required.
So my choices are: 6mm, 8mm, 10mm or 12mm
What would you all suggest?

Obviously 12mm would be the ideal, but I suppose my question really is: could I get away with less at those dimensions, while maintaining a rigid construction?

Cheers,
Dan *retardo

Hi Dan

The only thing i'd throw in on this topic is to have the metal laser or water jet cut as it will be much more thermally stable than guillotining.

Personally i'd go for the 10mm or 12mm.

Cheers

Jem

Cheers Jem
Just one question: Any chance you could explain a bit more about the thermally stable part? :confused:
I was planning to bandsaw it to close to the right dimensions, then file to shape, and finally mill the angle required on the side.

Ta,
Dan :)

Quote:

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Originally Posted by danielbriggs

Cheers Jem
Just one question: Any chance you could explain a bit more about the thermally stable part? :confused:
I was planning to bandsaw it to close to the right dimensions, then file to shape, and finally mill the angle required on the side.

Ta,
Dan :)

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Well, speaking from experience... I had my baseplate chopped with a large guillotine at Metal Supermarket in Leeds, this seemed like a good idea at the time. However, when the plate warms up, due to the stress invoked into the metal with the guillotining it tends to warp ever so slightly. Under normal circumstances this wouldn't be a problem, but when you need precise alignment of three laser beams it becomes a problem.

If you perfectly align all your lasers when the plate is cold, when it warms up the alignment shifts slightly. Likewise if you align your lasers when the plate is warm they move slightly as the plate cools. This means that next time you switch on the alignment is off... Can you see a pattern emerging here? :rolleyes:

If you carefully cut the metal with a method that doesn't put stress into the metal this doesn't happen and your lasers remain aligned whether the plate is warm or cold. This is one reason why proper optical breadboards are so expensive.

Since I made mine i've also found out that there are different types of aluminium and different methods of extrusion / rolling, all of which have an effect on thermal stability. Obviously the better metal is more expensive... How deep is your wallet? :D

I'm not quite sure how bandsawing will affect the metal.

Hope this helps.

Jem

Yep, cheers Jem
I didn't twig with that guillotine thing before - makes sense though.
I'm guessing it's the work hardening process going on at the edges. But I wasn't aware this would have such a pronounced effect.
I'll mull over this a little more then over Easter before I jump out and buy £100 sheet of Al. I might have a word with my materials professor to see what he thinks would be the best way to machine a plate and to minimise thermal warping. I might be able to get access to the special cutting machines they use if I ask very nicely! ;)

Again, thanks for the help Jem - much appreciated.

Dan :)

i've built monster projectors with never using more than 1/4" allum. I usually made it very rigid and stable by welding a frame of 1" square steel tube. If you are building a small projector say 1'x2' you might get some twisting but a 1'x1' is very stable.

I vote for 10mm alu baseplate.
Since from my first prototype of RGB projector, I always used 1cm baseplate.
Largest baseplate I made was 60 x 40cm: no problem.... solid like a rock.
Until now I had not ANY problem with this kind of thickness.:)

Steves no twist classic.

One, Ask for jig plate, its polished on one side and destressed.

12" wide by up to 36-48 inches long. allen screw every 3" to hold a 1x1" AL stringers along the long length, at the edges.

____
[] [] cross section view.

with 3/8ths plate (1/4" in pinch) this is remarkably stiff because you just made half a I-beam.

If not, solid , use association channel, but try to make sure its the same alloy as the plate

http://www.industrialmetalsales.com/1895.html

Steve

i have used 10mm aluminium plate, but unless you have a good saw it will be difficult to cut.
i had mine cut to size using a water jet cutter

you could drop to 8mm to save a bit of cash but if you spending loads on laser is the saving worth it at the end ?

dave321

Thanks all...
I tempted to say what the heck and go for the 12mm... I'm only likely to do this once (he says!)
And if it's worth doing, it's worth doing properly :D
I'll put a word in a uni and see if I can get my plate cut on the water jet cutter.

Ta,
Dan :)

Quote:

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Originally Posted by danielbriggs

Thanks all...
I tempted to say what the heck and go for the 12mm... I'm only likely to do this once (he says!)
And if it's worth doing, it's worth doing properly :D
I'll put a word in a uni and see if I can get my plate cut on the water jet cutter.

Ta,
Dan :)

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If you get it waterjetted, have them do the hole grid about 5 drill sizes down from your final tap drill, makes it far easier to do the 1" grids.

Steve

Thanks I'll bear that in mind.
I was planning to 'tap on demand' where and when. But we'll see how the design goes.

Cheers,
Dan

I believe the cast aluminium plate is better than the rolled stuff ( but it is a lot more expensive )


I find drilling and tapping on demand the better, faster way to go..

Has anybody tried the Alucobest paneling from 8020? It's a composite of two 0.020" aluminum sheets bonded to polyethylene, 6mm think sandwich. I have a tendency to think space-age when bronze age will do just fine.

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Originally Posted by Agent C

Has anybody tried the Alucobest paneling from 8020? It's a composite of two 0.020" aluminum sheets bonded to polyethylene, 6mm think sandwich. I have a tendency to think space-age when bronze age will do just fine.

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Heatsinking issues?
And although a composite, wouldn't the polythene be more flexible?
Also the £££/$$$

Dan :)

Water-jet cutting? Well, I suppose if you've got free access to the equipment it makes sense, but otherwise...:eek:

I've cut 1/2 inch aluminum with nothing more exotic than an electric jig saw with a standard metal-cutting blade. Sure, you have to go slow,(otherwise the teeth will get plugged up with the relatively soft aluminum), but it does work... It you've got a band saw, or even a carbide-toothed blade, it will work quite well.

Considering that you're only talking about a few cuts, it seems overkill to go to the expense of a water jet... Why not cut it yourself?

Adam

When I was making telescopes instead of laser projectors, I was cutting 1/4" aluminum plate with several passes of a router with carbide cutter.

Loud! :eek: But it works well.

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Originally Posted by buffo

Water-jet cutting? Well, I suppose if you've got free access to the equipment it makes sense, but otherwise...:eek:

I've cut 1/2 inch aluminum with nothing more exotic than an electric jig saw with a standard metal-cutting blade. Sure, you have to go slow,(otherwise the teeth will get plugged up with the relatively soft aluminum), but it does work... It you've got a band saw, or even a carbide-toothed blade, it will work quite well.

Considering that you're only talking about a few cuts, it seems overkill to go to the expense of a water jet... Why not cut it yourself?

Adam

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I have a couple of tools I could use in the garage, however the CNC mill doesn't have the capacity for a 500x300mm job :(
So this would have to be done by hand (unless I do some tedious multipart cutting+aligning process, but actually I don't think the table size would accommodate such a plate - it's only a small machine)
The only sticking part is the 60 deg chamfer needed on two of the sides - I don't really want to file that. I'd rather mill it or otherwise.
Waterjet cutting is relatively new to me, and I've never used one, so would be a good learning experience. I think they have a couple of 5-axis water jets at uni - so I'll enquire. (I'm not going to get my hopes up, as just because they have the tools doesn't mean I will be able to use them - especially for a non-course related project)
But I've been in contact with my materials prof. and he suggested EDM as an option too. I'm back there in a couple of weeks, so will probably have a quick chat in person to see if I can sort anything. ;)

As for cost; the material is the only thing I need to fork out for, as it's going to cost the same whether I use EDM, water-jet or a hacksaw and a jar of elbow grease :D

Thanks all for the input - much appreciated.
I still have a lot of planning to do first though!

Ta,
Dan :)

I've just realised - I should try and get it laser cut! *retardo
The irony...
Muhahah! >:)

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Originally Posted by trwalters001

When I was making telescopes instead of laser projectors, I was cutting 1/4" aluminum plate with several passes of a router with carbide cutter.

Loud! :eek: But it works well.

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HSS is actually preferable to carbide for Aluminum. It can be made sharper then carbide for endmills and typically provides a cleaner cut. I would use a HSS mill with a really steep flute line. Get one with 3 flutes as it will reduce chatter.

re: baseplate thickness

I used 1/4 inch due to the price/weight but it does have plenty of flex in it. Definitely a problem for precise alignment of multiple lasers. Bolt/weld a small frame of 1/2" - 1" aluminum or steel square tube around the bottom and it should be very solid. Also if you have it securely bolted to your case, it should help with the flex problem.

I'm thinking of using this for my base. Anyone else think that this is just a tad bit overkill? Also, with it being that thick, how will this affect the cooling of my scanner amps?

http://cgi.ebay.com/Precision-Cast-A...3A1%7C294%3A50

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Originally Posted by redgoat

I'm thinking of using this for my base.

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You realise that the 12" x 12" base plate will weight almost 10Kg on it's own, right? :eek:

Quote:

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Originally Posted by redgoat

I'm thinking of using this for my base. Anyone else think that this is just a tad bit overkill?

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Forget that auction. You're wasting your money, and risking a bad back in the process. That plate will be *way* too heavy. For a 12 inch square piece, you would be fine with 1/4 inch plate. If you are really paranoid, then go up to 3/8ths of an inch. But 1.5 inches? You've got to be shitting me! Way too thick. That's not overkill, that's overkill cubed!

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Also, with it being that thick, how will this affect the cooling of my scanner amps?

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It won't have much of an effect at all. So long as they're bolted to a metal plate and you have some air circulation, they'll be fine no matter how thick or thin your baseplate is. They don't get all that hot.

But seriously - look for something thinner. That plate will give you nothing but headaches. (And a backache!)

Adam

Quote:

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Originally Posted by danielbriggs

I've just realised - I should try and get it laser cut! *retardo
The irony...
Muhahah! >:)

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Mate if you know anyone with a co2 laser big ass enough to cut Ali plate do let me know and I'll throw some business their way also!! :)

I got my base plate from a retailer on ebay here in the UK (Clickmetal I believe) 500x500x10mm was not cheap (£60ish I think) but it seems to be the dogs balls.

I've just been cutting it with a jigsaw and appropriate blades and yep obviously you have to go slow and it's best to cut it outside of your house (garage is good) and yep! the neighbors think you are a mad scientist popping in and out of the garage all the time making loud cutting noises.. but hey ! worth it.

I also got a drill press for £40 from .. dare I say it... Aldi's not the most amazing bit of kit and a bit small for large base plates but does the job.

Only issue I have had so far is nuking my tap's on the ali - I assume it's because I end up buying cheap ones as opposed to the more expensive ones - but learnt my lesson on that and have a nice Draper one arriving shortly.. hopefully make the difference!!

:D

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Originally Posted by gashead

Mate if you know anyone with a co2 laser big ass enough to cut Ali plate do let me know and I'll throw some business their way also!! :)

I got my base plate from a retailer on ebay here in the UK (Clickmetal I believe) 500x500x10mm was not cheap (£60ish I think) but it seems to be the dogs balls.

I've just been cutting it with a jigsaw and appropriate blades and yep obviously you have to go slow and it's best to cut it outside of your house (garage is good) and yep! the neighbors think you are a mad scientist popping in and out of the garage all the time making loud cutting noises.. but hey ! worth it.

I also got a drill press for £40 from .. dare I say it... Aldi's not the most amazing bit of kit and a bit small for large base plates but does the job.

Only issue I have had so far is nuking my tap's on the ali - I assume it's because I end up buying cheap ones as opposed to the more expensive ones - but learnt my lesson on that and have a nice Draper one arriving shortly.. hopefully make the difference!!

:D

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Well... my uni has a few cutters. However due to bad timing on my part, I couldn't use it (right near the end of term :( )

I know EXACTLY what you mean about neighbors and noise. I leave the CNC running in the garage on its own for hours at a time, and the slightly hypnotic noise of the servos moving around sends them potty next door.>:)

Any TiN bits/taps are ace for ally. They are like a hot knife through butter. Slightly more expensive, but will improve the job 10 fold. Any carbon steel bits should be binned... :D

Dan

Using a fluid such as "Tapmagic" is mandatory on AL. Makes taps go at least 2x longer.

Steve

Spot on Steve.
If you can't get hold of tapmagic, a really good alternative for us UK folks is from Chronos.
http://www.chronos.ltd.uk/cgi-local/...ml%23aMT1#aMT1

Look for 1 Litre Multispec Cutting & Tapping Fluid (3rd one down), about £7 inc. P&P
A bottle will last years if you just use it for tapping.
(Don't dilute it, it's not soluble)

Ta,
Dan

That is also cast tooling plate. Not only will it be slightly more difficult to work with, it will look like shit when you finish cutting it if you use a mill.

Quote:

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Originally Posted by redgoat

I'm thinking of using this for my base. Anyone else think that this is just a tad bit overkill? Also, with it being that thick, how will this affect the cooling of my scanner amps?

http://cgi.ebay.com/Precision-Cast-A...3A1%7C294%3A50

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Quote:

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Originally Posted by danielbriggs

Spot on Steve.
If you can't get hold of tapmagic, a really good alternative for us UK folks is from Chronos.
http://www.chronos.ltd.uk/cgi-local/...ml%23aMT1#aMT1

Look for 1 Litre Multispec Cutting & Tapping Fluid (3rd one down), about £7 inc. P&P
A bottle will last years if you just use it for tapping.
(Don't dilute it, it's not soluble)

Ta,
Dan

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Jubbly Dan!

Just what I was looking for :)

Cheers for that mate.

Nige.

Quote:

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Originally Posted by trwalters001

When I was making telescopes instead of laser projectors, I was cutting 1/4" aluminum plate with several passes of a router with carbide cutter.

Loud! :eek: But it works well.

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You can actually use a table saw (works for large pieces, this was even done in some R&D labs I know of) no kidding just keep the alcohol spraying on the aluminum cut, it is rough but even a wood blade works (a two person job)... Tomorrow I am cutting a plate but using a jig saw and metal blade (ear plugs too).

-Adam

Our comany always uses circular saws to cut thick alu. The blade has 4tpi for this purpose. Makes a really neat finish.

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