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Laser cut plates

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3404601/08/2019 10:58:27
689 forum posts
7 photos

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

FMES01/08/2019 11:19:50
598 forum posts
2 photos

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

ega01/08/2019 11:27:13
1226 forum posts
103 photos

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

Cornish Jack01/08/2019 11:28:01
919 forum posts
120 photos

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 webster01/08/2019 12:20:24
avatar
2197 forum posts
32 photos
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

3404601/08/2019 12:31:29
689 forum posts
7 photos
Posted by duncan webster on 01/08/2019 12:20:24:
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

Thanks Duncan - I think that rules it out.

Bill

Dave Smith 1401/08/2019 13:29:06
76 forum posts
7 photos

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 Lousick01/08/2019 13:34:32
1149 forum posts
492 photos

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 Charlton01/08/2019 13:35:22
14 forum posts
1 photos

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

3404601/08/2019 13:47:58
689 forum posts
7 photos

Dave and Ben - my sincere thanks to you both

Bill

David Jupp01/08/2019 14:43:28
691 forum posts
17 photos
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...

ega01/08/2019 14:45:01
1226 forum posts
103 photos

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 McVickers01/08/2019 22:14:32
134 forum posts
69 photos

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 Lousick02/08/2019 00:23:27
1149 forum posts
492 photos

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 Wyatt02/08/2019 10:01:08
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Moderator
16415 forum posts
685 photos
74 articles
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

ega02/08/2019 11:31:40
1226 forum posts
103 photos

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.

insulator sculpture 033.jpg

 

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

Ian P02/08/2019 13:41:13
avatar
2138 forum posts
89 photos
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 McNamara02/08/2019 13:45:55
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1306 forum posts
113 photos

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 1402/08/2019 15:48:48
76 forum posts
7 photos

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

3404602/08/2019 19:56:27
689 forum posts
7 photos

A very sincere THANK YOU to Dave Smith 14 who has sorted it all out for me .

Well pleased.

Bill

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