Laser cut plates

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[Former MemberParticipant @formermember19781]

[FMESParticipant @fmes]

Hi Bill,

Its so that the dimensions can be entered directly into the computerised cutting machine whithout the company having to do any design work.

Only problem is, if there is a mistake its the CAD artists fault and not the cutters.

Regards

[egaParticipant @ega]

Is there some way a laser cutter can do a dummy run to check?

[Cornish JackParticipant @cornishjack]

Re. laser cutting, yesterday I received a completed order from 'Original Forgery Ltd.' . It was just a simple set of decorative windvane direction letters but the quality was outstanding and the delivery lightning fast. No connection etc. but they will certainly be first port of call for any further work.

rgds

Bill

[duncan webster 1Participant @duncanwebster1]

Posted by 34046 on 01/08/2019 10:58:27:

Asked for some plates from Model Eng Laser and was told drawing no good it had to be in CAD.

Googled Cad so realise what it is.

Interested to know, in simple terms, why they insisted on CAD

I ask as computers are still a mystery to me

Thanks

Bill

Laser cutting machine is computer controlled, so it needs CAD drawing. If you send a pencil drawing someone will have to convert it to CAD which will cost as much as doing the actual cutting, if not more, and introduces the possibility of the CAD man getting it wrong

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[Dave Smith 14Participant @davesmith14]

Bill

Email me your drawing and I will produce you the dxf file which Malcomn needs. I will message you my email address.

Regards

Dave

[Paul LousickParticipant @paullousick59116]

Is there some way a laser cutter can do a dummy run to check? You would have to cut the plate to be able to check it. The laser profile cutter could trace out the path it would take to cut the plates without cutting but it would be imposible to measure.

In the days prior to laser cutting and CAD systems, steel plate was cut with machine with an oxy torch which traced the outline of a hand drawn template, drawn at a scale of 1:1. The finished size of the cut plates depended on how accurate a drafter could draw the profile with an ink pen, usually on plastic film which did not expand or contract like paper as it absorbed moisture. Steel plates could be cut with a 1mm – 2mm accuracy.

The advantages of doing everything in CAD (Computer Aided Design). is that the models and drawings can be drawn to a much greater accuracy. (eg. 0.00000001mm). Mating parts are assembled in the computer drawing and it is here that dimensional checks are made. Some CAD systems can automatically check for interference problems with mating parts. Much cheaper and easier to fix before it is cut from steel.

Most oxy, laser, water jet cutters use a computer program to cut the profile and if a CAD file is not supplied then someone at the cutting company has to make one. Some profile cutting machines have built in programs which can cut basic shapes without a CAD file but are limited to rectangles, circles, etc.

I had laser cut spokes made for the steel wheels on my traction engine and they were cut to within 0.2mm accuracy.

Paul.

Edited By Paul Lousick on 01/08/2019 13:36:01

[Ben CharltonParticipant @bencharlton53151]

Bill,

Depending on how complex the plates are I could potentially sketch them up in CAD for you over a lunch break or 2, Obviously if they're fully detailed side plates for a 7 1/4" mainline engine I might shy away!

 

Regards,

Ben

 

Edit: I see I've already been beaten to it!

Edited By Ben Charlton on 01/08/2019 13:36:33

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[David JuppParticipant @davidjupp51506]

Posted by ega on 01/08/2019 11:27:13:

Is there some way a laser cutter can do a dummy run to check?

Kind of; the g-code prepared to drive the machine can be plotted in a simulation program (many cnc controllers will plot the toolpath on screen anyway before starting, which can give a quick check). If using a simulator program, it has to be set up to mimic the controller being used (they vary in the fine detail). And of course an on-screen 'check' is only useful if the person looking at the screen knows what it should look like…

[egaParticipant @ega]

Paul Lousick:

Thank you for the explanation.

I suppose I had in mind that it might be possible (if not economic) to run the laser using some suitable cheap material to produce a result which could be checked by the customer; all being well, the real job could then proceed.

[Ian McVickersParticipant @ianmcvickers56553]

The cad file, either dxf or dwg, will be run through a post processor to convert it to a cnc file, g code or essi for example, which the machine controller will understand. The post processor will also add the necessary auxiliary function codes for beam on, beam off, kerf, speed etc.

[Paul LousickParticipant @paullousick59116]

Hi ega,

Laser cutting services use expensive machines and their charge out rate has to cover the cost of labour and business overheads and to cut a sample would be expensive. It's not just for cost of the material used.

Not many firms have a service where you could wait at the counter for a job to be done. Instead it would be scheduled into their work program and made at a later time after placing an order. Then you would have to come in and check the job and if OK, re-scheduled again for the final cutting. It is a different matter though, if you need hundreds of the same part and the cost of a sample part is justified.

Paul.

[Neil WyattModerator @neilwyatt]

Posted by ega on 01/08/2019 14:45:01:

I suppose I had in mind that it might be possible (if not economic) to run the laser using some suitable cheap material to produce a result which could be checked by the customer; all being well, the real job could then proceed.

Usually the material is one of the cheapest elements of the process, especially if you are using steel.

Also bear in mind that if they used card, they would probably have to cut it on another machine as I doubt you could 'tune' a steel cutting laser low enough for it!

Neil

[egaParticipant @ega]

Thanks for the further enlightenment.

My only experience of this sort of thing was when a friend produced some large artworks in steel and roped me in to help him erect them. I don't remember the process – they might have been flame rather than laser-cut – but I do recall acquiring some of the circular offcuts.

 

Edited By ega on 02/08/2019 11:33:01

[Ian PParticipant @ianp]

Posted by ega on 01/08/2019 14:45:01:

Paul Lousick:

Thank you for the explanation.

I suppose I had in mind that it might be possible (if not economic) to run the laser using some suitable cheap material to produce a result which could be checked by the customer; all being well, the real job could then proceed.

I have had many parts made by laser and waterjet cutting and every one was correct and exactly to the drawing I provided (a DXF file). The only ones that were not suitable for use were ones that I had made a mistake on the drawing.

Basically there is no need to make a sample or test cut because the part will what you ordered. Any checking needs to be done before the part is cut.

Ian P

[John McNamaraParticipant @johnmcnamara74883]

Hi Bill

Can you post a scanned copy of your scale drawing with written dimensions and the accuracy required.
For say 5mm plate a typical laser should be able to cut to within 0.1mm. sometimes better.
I also would be happy to make a DXF file if it is not super complex.

Regards
John

[Dave Smith 14Participant @davesmith14]

John

I am already doing the job for Bill, in fact it is finished I just need to send the dxf and pdf for Bill to check he is happy with it.

Dave

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[Fowlers FuryParticipant @fowlersfury]

34046 – Have you checked with Malcolm what excess – if any – he requires to be added to your required dimensions? He's done several laser-cut items from my CAD dwgs and he's queried some of my dimensions thankfully !

The laser-cut edges from the company he used for my items were "rough" and hard. They needed draw filing smooth with a diamond file, I accept that techniques may have moved on in the last couple of years but a small dimensional excess was incorporated to allow for the smoothing-off.

[S.D.L.Participant @s-d-l]

Posted by Fowlers Fury on 02/08/2019 20:50:12:

34046 – Have you checked with Malcolm what excess – if any – he requires to be added to your required dimensions? He's done several laser-cut items from my CAD dwgs and he's queried some of my dimensions thankfully !

The laser-cut edges from the company he used for my items were "rough" and hard. They needed draw filing smooth with a diamond file, I accept that techniques may have moved on in the last couple of years but a small dimensional excess was incorporated to allow for the smoothing-off.

If you find a laser cutting company that cuts a lot of stainless steel they wil use a purge gas and the edges will be clean with no oxide.

Steve

[Bruno TaylorParticipant @brunotaylor21701]

My two-pennyworth on this subject is that if you want parts cut nice and accurately by CNC you really need to get to grips with CAD drawing, either by your own ability (a CAD literate Engineer) or via trusted CAD Jockey who can turn your sketch into a digital drawing. Which is how the professionals do it.

If you have a CAD drawing then print it, that is your dummy run and check it for fit, suitability or whatever.

Next important thing is to speak to your intended supplier for their input on what can be achieved and what limitations may effect the end product. In this Malcolm at MEL is excellent, especially for us as he is a model Engineer.

Finally the cost of the parts is generally low, little more than the material price with no wastage. So if unsure have it cut in thin material. But fundamentally if you drawing is correct so will the part.

I think if you look imaginatively at the components you may make them quite differently with CAD/CNC in your armoury.

Edited By Bruno Taylor on 04/08/2019 21:50:28

[Author]

Posts