Need Help in Finding an Economical Alternative for CNC Plasma/Laser Cutting

Define "utmost accuracy". What are the tolerances?

You only say the thickness is 3mm -- What about the other dimensions? Cutting a 10mm piece is much different than cutting a 1 meter piece.

How many pieces -- 10, 100, 1000... ?

Dear Pantaz,

Thanks a lot for the response..

Tolerance : 1mm

Thickness of the sheet : 3mm

Other dimensions : Width - 20mm & Length - 1500mm

Quantity : 300 such pieces

Material : Mild Steel

Having a templete, how about a hand plasma and a person that is experience to use one.

Its not hard to use one, but one has to understand the setup and technique

Thanks a lot phoenix911 for your advice

That is one good solution. But the problem would be finding one who is well worth doing it

well the training can be straight forward and short.

I was just putting it out for considerations.

good luck

Good answer. I've never used a plasma cutter myself but, with a little practice, I'm sure my plasma cuts would be more accurate than my sawing.

OP, Google 'plasma cutting with template', here are a couple of hits:

http://www.thefabricator.com/article/plasmacutting/cut-it-out

http://www.offroadfabnet.com/forums/showthread.php?t=987

Another thought - I can't tell the exact final shape from the drawing, but could you start with a straight piece and bend it?

Hi bigg,

Thanks a lot for the search results..It is of great help for me...Going through them

If the tolerance is 1mm, a bandsaw would do it.
Or if it's the shape you've shown on the screen maybe it could be bend from straight strip if the two edges are parallell?
Del

Yes, the two edges are parallel. I am going for cutting process but not bending to get high accuracy...though I mean by saying the tolerance of 1mm but we want better than that.

Just guessing that the important side is the concave side: what about stacking up 10 pieces; bending them in a jig; cutting off the convex side straight, then, allowing the pieces to relax again.

How about a die and stamping press?

Really people, just shear the pieces off the end of a sheet of material and hand form as required.

Nyah nyah na na nyah I said that at 6#
But of course, having said the tolerance was 1mm OP now says 'he' wants it better... or maybe it's a 'she'
Del

Nyah nyah na na nyah, you didn't say how to make the strip.

Sounds like the OP doesn't know what they want, nor how to get it. They just want it cheap.

lynn, here is my GA. Also mild steel 20mm X 3 is available in 6m lengths (20 feet)

Just cut and "parabolise" it in a mould and press or roller set.

The most economical method is to have a pattern cut - but not plywood.

On this thin material, the two fastest, best, most accurate methods are laser or waterjet. Either method will cut extremely fast. You may find that for this many pieces, it is less expensive to have them all made than to have the pattern made, buy a machine, and pay a person to hand cut following a pattern, unless you have "free labor" and lots of time.

You need the pattern cut from non-flammable material. Plywood would not last for plasma cutting for this many pieces. Your edge will burn away and you will lose the accuracy you need. Aluminum may be good choice because it is easy to waterjet cut and will give you a very smooth pattern edge and be lightweight for shifting on your stock material.

Rent or buy a hand held plasma torch with edge following template guide to cut the 3mm material.

You will achieve much tighter tolerance than 1mm and much much tighter than cold saw. The sales person who sells or rents the plasma machine can teach the user how to use the machine and the template. Even non-skilled worker can learn this in hour or less.

I see most difficult part of project in maintaining tight connection of template to the thin material - which is actually very simple but because it is so thin you will need a very flat backing support to hold the material against the bottom of the template. 1200 mm piece is not very large.

I should have said " a very flat backing cone table support" of course you can't just use a flat table and then plasma through the material and the table. Unless you have a lot of cheap, very flat tables to ruin.

Sorry for the unclear comment.

How about using this: www.multiplaz.com

The rest is up to you...

Vince

Are you guys being serious with the forming, band saw, plasma cutting BY HAND nonsense?? OP is asking for 1mm or tighter total tolerance !! There's no freakin way that's going to happen by hand!...and he wants to cut 300 pieces! C'mon seriously?

Machine cutting by water jet as an alternative to CNC, laser, or plasma is the only way to get that accurate and get it done in a short amount of time. Nadam, listen to Pantaz. He had the only good answer. It's cost effective and efficient. If you can find a water jet in your area it's your best bet.

C'mon boys. Give Pantaz your votes for good answer.

Are you guys being serious with the forming, band saw, plasma cutting BY HAND nonsense??

TerraMan: You have to realize that the precision didn't come out till later, as usual.

I agree with you, this is rediculous

And OP, there is no cheap alternative.

heat shrinking the edge of a strip may be the easiest. Order out some 20 x 4 mm strip stock, heat one edge with an oxyacetylene torch, cool right behind, and check the curve against a go - no go gage. A few pieces will be spoiled getting the needed timing of fire and water. For 300 pieces, two days for a weldor and a helper should be plenty. If it were a deep curve, forming around a jig would work, but it appears that there is only a few degrees curve in 1500 mm, so heat shrinking the one edge should suffice. Drill the indicated holes last.

2 days??? So 16 hours = about 1 every 3 min for 1 guy non stop. Heat shrink accurately within 1mm, check with gage, then drill holes in 3 min??? I doubt it... but I would be impressed if you could pull that off even with a helper.

Why don't you clamp a few sheets together and use a CNC to cut them out? Leave a few sections not cut of about 5mm every 100-200mm to hold everything together. Basically cut a dotted line all around. Then separate them from the waste material with a metal saw and finish the edge with a file / sander.

Many sheets can be clamped together by welding the ends or riveting them outside the work area. Plan your clamping points to help with the separation process.

If you cut many in a sheet, place rivets / welds in the waste material between parts to secure the sheet stack.

Using wood for such a long and narrow profile is not a good idea as it will easily be bent out of shape and will be subject to distortion from change of humidity / water...

Marcot, Thanks a lot for an awesome advice. Stacking and cutting is a great way to reduce the running cutting length thereby the costs of cutting also..In this way I can go for plasma cutting as the net cost wil be very low coz of less running length. One small doubt I had is that will i be able to get the same accuracy/edge finish of cutting if i stack 3mm sheets by using rivets at waste areas on the workpiece!!??

I just spoke with one of the plasma cutting service providers and asked about the possibility of cutting by cnc plasma by stacking together sheets by rivetting or clamping....He said plasma cant work as there will definitely be some space between the sheets even after clamping/riveting...So any other way to work it out??

Stack & water jet.

Yes there is another way to work it out and it's been suggested a few times. WATERJET! You can also stack and waterjet as Pantaz/Snave suggested. Is there a reason why you won't consider it? Is it not available in your area? The CNC is not a bad idea but but you need to clamp the pieces together carefully and make sure they don't move during machining(vibration, force, etc). These are thin pieces and it won't be easy. You don't have these issues with water jet.

The CNC is not a bad idea but but you need to clamp the pieces together carefully and make sure they don't move during machining(vibration, force, etc). These are thin pieces and it won't be easy. You don't have these issues with water jet.

No, actually with water jet, you also have issues with the pieces moving. the piece can move when water gets between the pieces. Whether from the residual waterjet, or if you drown the pieces.

You're right...with stacked sheets. We would typically stack say three sheets 4' x 8' and making a first pass to cut out the holes. Sheets are too heavy to move. Pop rivet the pieces together using the holes then make the final cutting pass.

I'm concerned about water getting between the layers, too, and maybe eroding the metal. But I don't have any direct experience with cutting multiple layers.

Ya I kinda lost interest and stop paying attention some of the info came in as to what material...... Seems this thing got way out of hand as the info rolled in.

I'm surprised I'm still here.

AS far as eroding the material.....yep that how a wj cuts.

like terraman talked about it is better

I had done it was 5# 3x8' copper sheet I had cut. the sheets shifted right at the end, fortunately it shifted the cut to the drop, all I had to do was shear a little off.

As far as cutting time, it save on setup, but you speed decreases proportionally to the thickness, but it does save time thou.

Was in a guy's shop once and he showed me a section of RR track that he had cut half way through top to bottom. The kerf (If that's the right term for waterjets) was twice as thick at exit as it was at entrance.

Just a consideration when stacking.

Flow International came out about 10-12 ? years ago on thier water jet what was called a dynamic head, The head tilts so that the kerf on the part side is straight and the fan kerf is on the drop as it goes around cutting the part.

Of course the problem that you have is the jet stream lags, from the top of the peice to the bottom. and depending the the thickness of the material even though the after the cut, the tip of the head finishing cutting out the top of the piece from were it started, the bottom of the piece can be an inch away. Leaving what I call a tit. of uncut material. A real pain in the ass if not compensated.

I don't know if the dynamic head also tilts the head to creat a lead for the cut, if it doesn't it should. That might be a good accessory for LynDoor to sell. Atleast that would be one useful item LynDoor can claim, and your welcome.

Ha...LynDoor! I went to the link and for a few seconds I thought it was legit...then I saw the extension cord....good one. Lyn, you have way too much time in your hands. :-)

What? the job you are describing is a cnc laser job. What is the problem? In the uk a sheet of 3mm 1220 x 1600 would retail at about £100, you would get about 45 out of it.

7 sheets £700

The metal would cost less if you were buying laser cutting compared with buying it and hacking at it yourself with plasma-the job might be done for £1000.

You have got the file already to output as .dxf .eps whatever....

I know you ask for economical - I am reading 'cheaper' because laser is the most economical. Shop around. He who pays less more will pay, to quote another cr4 member.

Cnc jim

I was at a trade show last week and OMAX had their machines cutting tweezers with serated edges and thumb grip ribs. They were fyling through these things and giving them to everyone. I took a few pics and measurements for shits and giggles. Might be of intersest. There is a slight taper from one side to the other and it's about .006 on a .120 thk plate.

Hi Nadam,

Let's see if we can try one more time to figure this out!

Your post says you need an "economical alternative" to "CNC plasma/laser". Because of your (we are all assuming +/- .05mm) tolerance for the curvature and the 20 mm width of the piece, I am presuming flame cutting is not a possible solution.

Water Jet is a very good and very accurate alternative, but may not be economical.

Other posters don't think you can get a handheld plasma torch jig and template that will hold the tolerance. I think you can, but let's look further.

Is the 3mm thickness also a +/- .05mm tolerance? And the holes? And the length?

Which is most critical, the 20mm width or the parabolic curve, or both?

Not to be ridiculous, but if we really have to think out of the box on this - Do you have access to any large metal working equipment - and by large I mean like a 500 ton shear? Can you get 20 mm plate?

Can you roll 20 mm thick stock, accurately?

Do you have any CNC machinery or is all of your shop manual - meaning that each piece has to be measured manually and you don't have automatic repetition for anything unless you make templates or jigs?

If this is the case, then we need to help you come up with a method that relies on templates and jigs, or you will never be able to make 300 of anything that are the same to the +/- .05mm tolerance you say you need...

I dare say if you don't have excellent templates and jigs or at least x/y machines you could not drill 900 holes in one single sheet of 3mm plate and maintain that tolerance. Trying to do it in 300 separate pieces just multiplies the error.

So if this is truly your requirement, I think you must re-examine your specification for "economical solution/alternative for CNC"...

Otherwise, get some 20mm sheet. Shear that in your really big shear into 3mm strips - if the 3mm is not a tight tolerance. Tell your boss that's economical, somehow... Shear those to length. Roll them in your bender the hard way... and very carefully. Now start drilling, but make a jig first.

That, or the heat and cool method which will drive you nuts, or the hand bend, but none of these is going to be repeatable to 1mm... not unless you have a guy with OCD and only need one a day???

Nadam, I really think there's been a lot of good and different suggestions made here on CR4. Your best bet if you want these to come out right is to WaterJet or Laser, and at 3mm, you just don't need to worry about stacking. You won't gain anything on machine time. WJ will FLY on 3mm. So will laser. You will waste more labor time drilling and riveting and trying to edge weld or clamp plates and trying to fight float and flare that it's just not worth it to mess with that. Just load the plate and start cutting. The parts will fly out. You'll have the whole job done faster than you can find the guy who will sell you the template making machinery.

But, if you just can't do the project that way - maybe you are contractually forbidden to use CNC or something... then tell us what you CAN use and I'll get the shop guys to argue about it at lunch some more.

So, tell us more about why these need to be so precise, and why you can't do CNC plasma/laser and I bet a bunch of guys will come back with some more ideas.

Dear tcmedic3338,

Firstly thanks a lot for a detailed brainstorming of my requirement

After reviewing all the valuable suggestions as well as enquiring from various suppliers out here, I finally got down to either cnc plasma or laser cutting. This is coming out to be the best, clean and economical option compared to all the other methods.

CR4 really is helping me a lot at all the times whenever I get stuck with any problem. The greater accuracy am looking for is with the parabolic section of the template. Now that it is decided to go with cnc cutting, there is no worry of getting accuracy and fine edge cut.

Thanks again for all for the help esp. pantaz, phoenix911, bigg, Del the cat, Randall, ronseto, lyn, dvmdsc, txmedic3338, Vince GEntile,TerraMan, drbobwoolery, marcot, Snave, cnc jim

Wow! A personal thank you to everyone who contributed. Never seen that before. Nadam, you sir are a gentlemen. Good luck in your project. Best regards.

Good luck!

Can you send a photo of a finished part, when available?

I think we'd all appreciate that.

Sure lyn..that would be pleasure in sharing it with all...i will definitely do it when once completed

Thank you for listening.:)

cnc jim

i should say thanks to all for such a lively active participation in the discussion. i have always got the best solutions to my problems here in Cr4 .....

What is your budget?