CNC plasma cutter


#1

not entirely sure where topost. i chose here since i am using pro version. if t needs to move, thats cool

ok, so i may be getting a cool new cnc plasma cutter to gain more experience and to learn new things. But before i make that decission, especially as a student, i am needing to know how to take a 3d bracket i mae in sketchup and somehow tell the cnc machine to cut it out. A person told me that they think you make drawings of all 3 views then send it to the cnc software.

Is this were layout comes in handy? I use layout to generate my 2d drawings then send it over? or is there another way that i can accomplish this?

Take for example, :

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwioz5jnsOjbAhVqCDQIHWGgAN8QjRx6BAgBEAU&url=https%3A%2F%2Fwww.pinterest.com%2Fkknezic%2Fsheet-metal-design%2F&psig=AOvVaw00blYM7Hqk5pHvzoQ70utC&ust=1529795026361634

or this:
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwi58LyHsejbAhX6HzQIHRg2Ds0QjRx6BAgBEAU&url=https%3A%2F%2Fus.misumi-ec.com%2Fvona2%2Fdetail%2F110302711470%2F&psig=AOvVaw00blYM7Hqk5pHvzoQ70utC&ust=1529795026361634

i know it cant cut the depth and what nbot, so i will have to bend or weld. as long as i know where to bend it or weld it haha

thank you much for the help:)


Create 3D Wireframe 2D Projections?
#2

Here’s a thread that might provide some answers. Of course our beloved forum bot has closed the thread.

https://forums.sketchup.com/t/polylines-with-real-arcs-for-cnc-router/64342

Shep


#3

Dang, that is alot to take in haha. thanks for that link. i will continue to read it. Man im excited though haha


#4

Don’t feel bad, I participated in the thread and understand about half of it. :smile:

Shep


#5

Lol, yeah, im feelin the brain cramp haha. Im just lovin the stuff i can do on my 3d printer and now i can wait to hooefully, soon, get a cnc plasma cutter. Maybe even a glowforge pro one day. Could do some cool ■■■■ with that haha


#6

My curiosity has been the possibility of cutting architectural parts from pvc with a waterjet. We’ll see…


#7

For one of the brackets you show, here’s a idea I had. By using a “weld” extension to weld one of the edges together you can find out the total blank length using Entity Info. You can use this length to create a flat rectangle with the holes in the same positions as the final bent bracket. This is the flattened part to cut on a machine ready for bending.

As for knowing where to bend the flat, you can copy the end profile of the bracket and then flatten that down too to cut out a pattern shape for the bending maybe.

It might sound a bit long winded but it doesn’t take very long to do it. I would make a copy of the original file and create the flattened parts in that though, deleting the 3d model before exporting.

Hope it gives you a few ideas anyway.


#8

@Shep That would be way cool to be able to cut pvc with a waterjet. Man, its been a LONG time since i have talked about a waterjet.

@IanT
so the weld extension is an actual extension installed into sketchup? i did not know entity info would tell me total length, including the bends and curves. I assume that is called blank length? That video was very informative. thanks for that

also, i assume i would remove the 3d model from the pic above, save the file as a dxf and send to the cutter and it will do what it needs to?

Then once cut out, ibend and match the bends o the pattern. thats a great idea. thanks for this info.


#9

You have to install it of course, the one I use is by “Smustard” I believe, but there are others. Its available from the Extension Warehouse from within SketchUp.

I say that meaning that is the full length of the “blank” of steel (as I would call it) that is required for the bracket.

Yes, remove the 3d from that copied file, select Top View and Parallel Projection camera for the export. Then go to: >File>Export>3d Model and probably save as DXF file from the choice of formats. In the options dialog choose an early DXF version such as “release 12” for maximum chance of machine compatibility. Check with your CAM software if you can to find out if there are any preferences on this or what file formats they require if
not DXF.

I’ve never used a plasma cutter, but I imagine there will be a little setting of work height and number of passes maybe before cutting. But again that will depend on the particular software you use.

Doing the 3d export as opposed to 2d should give you true circles in the export as opposed to Sketchup segmented ones.


#10

ok, cool. i will try oput the extension oyu mention.

I see what you mean by blank length now. Now, the little till-dee mark in front of the 393mm, how accurate is that? i know it means roughly, but how roughly is roughly?

I will find out what software it uses, i know they have installed fusion 360 on the laptop that comes with it. I have never used fusion. i am a solidworks and sketchup user haha. One thing i wish SU had was the ability to do parametric dims. So if i change one dim, it will update the others to fit.

thanks for the info.


#11

Your welcome

In that example thats less than 0.1mm, I would say it’s pretty acceptable considering you are going to have to bend that piece to shape. I would think that would be the main challenge of accuracy for this one.


#12

ok, thats good to know. thats pretty accurate for what i need it to be


#13

Hi IanT,
This is only true if you have an equal amount of left and right bends of the same radius! (whitch in this case is true…)
If you have say one bend, the length of the inner bend will be shorter than the outer bend!
The only way to measure your “blank” is to measure the length of the “midline” because thats were the material will bend around. The outer bend will stretch and the inner bend will schrink.


#14

Yes I suppose it were pure coincidence that the suggested bracket worked out that way. I were just trying to show ideas of how to find the total length and figure it out. You are very right though, using a centerline would be accurate for all cases.


#15

The key to getting this more accurate is to increase the number of sides in your arc or circle. By default a circle in Sketchup has 24 sides yet you can change the number of sides in an arc or circle by selecting the arc or circle tool and typing in the number of sides required and pushing enter. In general 24 sides is sufficient, however, if you are exporting to a dwg and you want to be exact then increase the number of sides as the CNC will cut the sides as flat until the intersection of the next side. Basically it is all about the scale of the project 24 sides is sufficient if the circle radius is around 50mm, yet, if the cut out was 5m you would need many more sides for the circle to look round.
Note the maximum number of sides that can be input into a circle Sketchup is 999 and by doing this you will increase the size of you model due to increase geometry, so use it sparingly.
I hope that helps


#16

Very tiny segments that approximate an arc or a curve can be potentially harmful to CNC equipment. The real solution is to export a dxf where the actual curvature (circle or arc) is maintained. This turns into a very simple CNC instruction which is much easier on CNC equipment.

In this example the GKWare_Simple_DXF plugin preserves arc information when exporting

Here is the DXF imported back into Sketchup with the same plugin without loss of arc info. Additionally when using CNC routers direction of the polyline is important.

In this example you can see that this results in a clockwise direction.


#17

so how does exporting it as a dxf, not cause issues with the cnc machine? when you sayharmfull, do you mean as in damage to the machine because of how curves haev to be cut(cnc plasma) or dawn(3d printer)and it can screw them up?

I might be confused to what you mean by how dxf preserves arc info. does a dwg not preserve info for arc or circles?

tahnks


#18

A smooth arc allows the controller to run the cutting head at a consistent (hopefully optimized) speed.

An arc can be made up of many small straight lines which can burn out router bits since the controller moves so slowly between each operation. I’ve had reports where this has caused the head to literally start vibrating back and forth since each movement is so small. That just can’t be good for the CNC.

The issue is how good is the DXF import. In this next example here is SU 2018 DXF import of the same file as in the previous post. Notice that SU did not honor the direction of the polyline and the Import LOST all the arc information and converted the arcs into very rough line segments.


#19

Oh, i see what you are saying. I always make my circles or arcs 48 sides, sometimes larger. So the dxf export recognizes that those SHOULD be arc and curves, therefor keeping them smooth. But SU sees them as just 48 lines making an arc or a curve.

I have not looked at the supplied files or images since i am replying from the email on my phone. I will look at those when i jave a chance.

On a side note, does export stl keep arc data because i dont want to burn out my 3d printer since it is a cnc machine as well.

Thank you for this info.


#20

My plugin writes out the DXF with circle and arc data. Most CAM software will read it and produce G Code that will end up in a pure Circle or arc.