Where do you start with CNC?

[Stuart Z]

Just speculating at the moment?

What do you need to buy / learn to get into CNC cutting? I’m curious about getting a plan and translating into CNC cut parts. But as a hobby, wanting to do this economically.

Interested in how this can be done.

[Paul Marsh]

At 0,0...

[Stuart Z]

I think that sums up how much I know about the subject.

S

[Martin Harris - Moderator]

One of my clubmates taught himself to program and cut balsa and ply with a laser cutter last year. He's a regular poster here so may pick up on this but I'll see if I can get some info if he's otherwise engaged.

[Stuart Z]

Thanks Martin

It may be useful for a wider audience as well.

Many thanks

S

[Martin Gay]

The difficult bit is the software to convert the drawing into a format that can drive the CNC machine.

I use Vectric Aspire, which allows me to import most pdf files and work with them. It is expensive but they also do a cheaper 2d version of the software.

It will allow you to output the drawing via the correct "post processor" direct to the machine.

Martin.

[Alan Hilton]

I have had great service from SLEC .They can scan a plan and cut parts for a very reasonable price .Being an old gi@ and somewhat technophobic I find this a good solution

Alan

[pete hammond 1]

Not a recommendation as such, just what I do-

I use CAMBAM to draw and generate the .nc gcode file for my amateur bench top CNC machines. More complex drawings drawn in Nanocad -a free download program, then import drawing to CAMBAM to create the .nc gcode file.

If I was smarter I would make more use of Fusion- I find it is rather daunting in the number of variables it offers, I am learning slowly!

Actually manually generating very simple programs in gcode is not that hard for start/stop and speeds plus straight line cutting but arcs require thought to locate the centre of the arc. CAMBAM solves that for you for a £100 downloaded perpetual licence BUT you get 40 sessions free to see if you like it- if you leave the program open for a couple of days each time you can really get to grips with the program -or not - before spending the licence fee.

Of Course mach3 or mach4 is another popular option as a code generator and operating system, again free for assesment/trial use (has program limitations during this stage) then a £100 perpetual licence which gives the bells and whistle features.

Each gcode program starts in a very similar way so you soon learn to read the language.

Anyway its all part of the challenge to make parts that fit together! (CNC machines can/do make scrap -quickly)

I am always on the lookout for drawing (DXF) or program (.nc or text) files to try cutting/learn from.

Pete

[kevin b]

If by "economically", you mean build models cheaply, then the costs involved in setting up a CNC machine (router, or laser) are far greater than having somebody, such as SLEC do the job for you. You need to be a serious modeller, or looking at it commercially for that sort of investment. If you are looking at it as part of your hobby (learning and developing models), then by all means get involved. I would suggest though that first of all learn the use of CAD to produce the required files to use for cutting. Then get someone who has a machine to cut them for you until you have that part of the process mastered. Then you can jump into the minefield of obtaining the machinery. To do the job properly it is not "cheap" and CNC cutting can be a whole new hobby in itself.

The question you have to ask yourself is "How do I want to spend my time" bearing in mind that it the most valuable commodity there is.

[FlyinFlynn]

Posted by Paul Marsh on 20/12/2020 15:57:19:

At 0,0...

Actually 0,0,0

As far as getting from a plan to a cnc file goes I find it easiest to 'trace' the outlines from an imported picture in LibreCad. The 'pictures' come from taking a photo of the wanted profile from your plan. You don't need to worry about the scale of your part at this stage, you can set the sizes later. Once you have the shape you save it as a .dxf From there I use Vetric Aspire, import the .dxf, set the size of the piece (measure from the plan) place the shape on your stock and configure your cutting (or lasing) parameters and generate your toolpaths. It obviously isn't quite that easy...but it's fun getting to know how to drive.

*WARNING*....learning this will seriously impact your leisure time!

[Stuart Z]

Well, thanks for all the input! I think that based on the time factor and apparent costs it appears to be not something for me. The valuable input may help someone else that wants to have a go but for me it looks like SLEC or a self drive scalpel will be the methods of choice.

Thanks everyone!

S

[David Hall 9]

I wondered about how I might CNC cut sheets and have seen the results of many many hours of the work of others, and given up.

But, just lately, I've been playing with 3D printing. The movement of the "hot end" is very similar to what I would want in a laser cutter except that it has an extra movement in the vertical direction. I have even managed to import airfoils in a PDF file to the (free) software that allows me to easily manage size and modifications. I used this to produce more than a few wing ribs at minimum (some one layer) thickness while attempting to find a good balance between strength and weight. For the most part, if I had a laser in place of the hot-end, I would be most of the way towards a viable laser cutter..... less restrictions due to bed size, a little extra work in controlling the laser output etc.

I didn't go any further with it as I am probably thinking more about 3D printed plastic parts than cut balsa.

 

Edited By David Hall 9 on 21/12/2020 15:34:21

[Broken Prop]

David

Geoff Gardiner did a series of helpful posts on here a little while ago. They included his work on converting his 3D printer into a laser cutter.

Search under 'Anet A8'

Good luck!

[Piers Bowlan]

Being able to CNC cut one's own balsa parts has been of interest to me for years but there seems to be a considerable investment in hardware, software and time required, to make it happen. People who do so have my admiration for mastering this aspect of the hobby, which has it's own challenges and rewards. Not least for me is getting the software to work on a Mac! I know that Parallels and Virtual Machine can enable this sometimes or, if all else fails, Boot Camp, which I have run on my computer in the past. At the end of the day I rather enjoy chopping up bits of balsa with my trusty Swan Morton so why get a machine to do it, even if it can do so much more accurately and quickly than me? If I did take up the challenge I am sure that I would soon get hooked but to get there I would undoubtedly waste vast quantities of virgin balsa, which could otherwise be put to good use building several models! - Assuming I could actually buy the balsa in the first place. 

I am surprised that there haven't been articles in RCM&E on 'getting started in CNC cutting', like there have been for 3D printing. Perhaps Geoff Gardiner could write one?

 

Edited By Piers Bowlan on 22/12/2020 06:06:19

[Shane Sunday]

CNC your own kit is such a time saver and if you're a voracious builder like me then the cost is reasonable.

Stepcracft CNC kit - @1200

dremel -@ 60

Adobe illustrator- 9.99 per month

cut 2D- @150

Mach3 - @ 150

1mm end mill - 10

6 watt diode laser - @ 660

I purchased the laser years later as I knew I would want it.

scan your plan and redraw in Illustrator. it takes some getting used to but youtube can help greatly here.

Save your drawing as an EPS file.

Open EPS file in Cut 2D. edit cut peramiters and save to Gcode

open Gcode file in Mach3 and cut parts.

I know that over the years of building models this setup has saved me thousands. I went through a period of crashing a lot of models due to a bad ( used ) transmiter. Also once you are set up to CNC parts and know what you are doing things come together so quickly. You might need a part and rather than order it and wait for the post man you can cut it right there for the cost of materials.

Greatest investment I've ever made. aside form my kids ofcoarse.

[Mark Turner 12]

Google Dremel cnc and you will find a cheap cnc build which like Geoff gardiner you can add a laser. I’ve used a cheap eBay frame and added a laser and a z axis. If you are prepared to do a bit yourself you can build something quite nice for not much money. The advantage is by building it you under stand it far better.

[Martin Gay]

I built my first CNC machine by hand from MDF, then used the machine to make more accurate parts for itself!

[Bob Smitham]

Posted by David Hall 9 on 21/12/2020 15:33:28:

I wondered about how I might CNC cut sheets and have seen the results of many many hours of the work of others, and given up.

But, just lately, I've been playing with 3D printing. The movement of the "hot end" is very similar to what I would want in a laser cutter except that it has an extra movement in the vertical direction. I have even managed to import airfoils in a PDF file to the (free) software that allows me to easily manage size and modifications. I used this to produce more than a few wing ribs at minimum (some one layer) thickness while attempting to find a good balance between strength and weight. For the most part, if I had a laser in place of the hot-end, I would be most of the way towards a viable laser cutter..... less restrictions due to bed size, a little extra work in controlling the laser output etc.

I didn't go any further with it as I am probably thinking more about 3D printed plastic parts than cut balsa.

 

Edited By David Hall 9 on 21/12/2020 15:34:21

I'm looking down the same path David.I can manage rudimentary CAD work and 3D prints.Printed wing ribs being my initial use on a build .A few 3D printers can accept a laser head The Creality range(I'm running an Ender3) have a laser unit that simply sticks to the metal fan shroud on the hot end using magnets for £40.But it's only 500mw so I'm not sure how it would cope with thicker ply and you are of course as you pointed out limited to the size of your print bed.And like Mark and Martin I have thought about building one .I have been tempted by the budget  cutter engravers.Around £150-200 for 10-20w units with a working area of 13x7.5 inches. I have been watching a few youtube channels on them. So that means if my 3D printer is anything to go by I will end up buying one in a few months after justifying the outlay and usefulness to my self.

 

Edited By Bob Smitham on 24/12/2020 03:14:00

[FlyinFlynn]

Something to bear in mind when considering using a 3d printer with a laser is the 3d printer runs on Marlin firmware and a laser performs better with GRBL firmware. 

Among other reasons,GRBL has a feature whereby it can dynamically control the  power of the laser whilst the laser assembly accelerates and decelerates during a change in direction, this is important in laser work as without this feature it will burn the workpiece in the corners. This is less of a problem when cutting than engraving but it still is noticeable.

Marlin devs are currently working on Marlin to add a feature similar to this but AFAIK it is not properly integrated into Marlin at this time.

I would not recommend using a 3d printer for this reason. A cheap eleksmaker frame laser engraver or, if you already have a 3d printer, a cantilever type (https://www.modelflying.co.uk/forums/postings.asp?th=147510) would in my view be a much better option.

Edited By FlyinFlynn on 24/12/2020 10:20:57

[FlyinFlynn]

Posted by FlyinFlynn on 24/12/2020 10:03:25:

Posted by Bob Smitham on 24/12/2020 03:11:03:

Posted by David Hall 9 on 21/12/2020 15:33:28:

I have thought about building one .I have been tempted by the budget cutter engravers.Around £150-200 for 10-20w units with a working area of 13x7.5 inches

Edited By Bob Smitham on 24/12/2020 03:14:00

Just be very sceptical about the quoted power of these lasers. The power quoted is often the DC electrical input power - not the optical output power, which is the value you are really interested in. The cheap '10 Watt' lasers are, in reality 2.5 or 3W optical laser diodes. Currently I believe the highest power 445nM laser diode has an output power of 6 Watts (Nichia NUBM44). You can get higher output powers by pulsing the input but it has to be done extremely carefully or you risk blowing the diode. You can also add more diodes to form an array.....but not at the prices quoted.

We are also dealing with the Chinese here..... Chinese Watts are not necessarily the same as the SI Watt!!

Given a decent lens and an air assist, a 2.5W laser diode is capable of cutting 3mm plywood with multiple passes....500mW, not so much. I wouldn't expect a 500mW laser to cut through much more than paper. OK for engraving lolly sticks but that will be about all.

[J V R]

Here's my CNC cut wing ribs all 3mm lite ply, weight is 4g per rib. Ribs were taken from a PDF copied into Vetric Cut2D and traced around to genarate the G code for the cnc machine cut in a single pass with a 2mm end mill around 90 seconds per rib

[Stuart Z]

Absolutely amazing results and the depth of knowledge on the forum on very technical subjects is great to hear.

S

[pete hammond 1]

Tracing,

Please-

A few more details on quite how you trace from an image would help me a lot.

If you have an example you could 'walk' through I am sure it would be much clearer how and what can be achieved.

Is it a 2d image from the phone perhaps- of say a wing rib that has straight and curved lines?

I downloaded Librcad yesterday on recommendation of Flying Finn, already have nanocad that I use prior to using Cambam to create gcode. so getting there slowly. I like free software. and was disappointed to lose autocad by another name last year.

Learning Fusion for 3D slowly- just so many options in the CAM part of process!

Merry Christmas and keep safe in the workroom, garages, sheds lofts and basements (should I include bedrooms?) -wherever you have fun -enjoy yourself!

Pete

[J V R]

Pete

You can download a free trail of the Vetric programs scroll down to the bird symbol ''trace bitmap'' use this tool to trace or there is an auto function, but this will trace all of the bitmap image...

[FlyinFlynn]

Posted by pete hammond 1 on 24/12/2020 15:15:43:

Tracing,

Please-

A few more details on quite how you trace from an image would help me a lot.

If you have an example you could 'walk' through I am sure it would be much clearer how and what can be achieved.

Is it a 2d image from the phone perhaps- of say a wing rib that has straight and curved lines?

I downloaded Librcad yesterday on recommendation of Flying Finn, already have nanocad that I use prior to using Cambam to create gcode. so getting there slowly. I like free software. and was disappointed to lose autocad by another name last year.

Learning Fusion for 3D slowly- just so many options in the CAM part of process!

Merry Christmas and keep safe in the workroom, garages, sheds lofts and basements (should I include bedrooms?) -wherever you have fun -enjoy yourself!

Pete

Depending on how good your bitmap is will decide on how good the auto tracing does...If you need to trace a bitmap manually I can help you with that Pete.

Open LibreCad.

you need an image file to start with, (it accepts about 20 different formats inc. all the common ones) and you select File - Import - Insert Image . The crosshairs will change and you place the image anywhere, don't worry about the size of it at this stage, use the mouse scroll wheel to get the image size comfortable.

Look at the Layer List ,top right of LibreCad, select the '+' and the next box opens - give it a name 'tracing' and a bright colour and a line size, I select 0.13ISO.Click OK and the new layer appears in the Layer List window. The eye button make it visible/invisible. click on the wording of the title you gave it and ensure the background to the word is darker than the other layers wording, then oyou can start tracing.

Click on the top 'line' icon on the left hand side - actually click on the little down arrow on the line icon and select the top item '2 points', your curser will change and zoom in with the mouse scroll wheel to your first (any) corner, left click and a point will be made,move to the next point using the zoom as needed, once there, left click again and the point will move and your 'trace should show...continue the outline until you arrive back at the starting point. Right click to finish. You can use circle, box, spline and other tools to get your shape. If you click on the '0' layer 'eye' to hide it you will get a better look at your new shape. Once happy with it click on 'file/save as' and you have your first dxf former (or whatever). I have bound to have missed something and I am by no means an expert but chirp back if you have problems