What is Luban doing to this file?

Hello all; Luban 3.8 appears to be producing a problem. I still am not sure why it is giving me variable results with .svg files and I am trying to chase that issue down. I thought I could use a .jpg file for my test carving and was surprised to see the file image getting broken up in Luban. I know a bit about .jpg file resolution and the algorithm for saving files so I am at a loss to understand what happened inside Luban.

The file I created as a .jpg file was created at the exact size I wanted to work with in Luban… that is 37mm square. The screenshot shows a very clean file on a background that is exactly 37mm square. This program will print images out to the exact size specified in the set-up so I know it to be accurate.

When the file is taken into Luban, it should look similar to the first image at a maximum density of 10. What can be seen is that the file has lost its integrity.

I cannot tell what has happened to it. Luban appears to have misplaced some of the points in the file and placed them outside of the image. Any thoughts would be most welcome because I have not seen this problem before with any file transfer into any other software that can accept the file being transferred. Thanks.

I forgot to mention that the background to the original file is transparent and unless one uses .jpg 2000 files, the background becomes white when the file is saved. The density setting of 10 in Luban normally makes the file a dense black in colour when it is viewed at the original size (37mm square in this case)

It’s showing the tool path. It’s a representation of how the tool is going to travel. You have a 2mm target depth set, so it’s showing the bevel/edge of that depth. If you rotate the image around the various axis, it will be clearer what you’re seeing.
Depending on the hardness of the material you’re carving, 2mm is a pretty large step-down. I would probably set it to 1mm at most.

What’s the resolution of your jpeg file?
I can’t remember what the resolution capability of the snapmaker is in laser printer terms. But it’s much less than a normal printer (think of it as dot matrix compared to a laser or inkjet printer). Also you’re dependent on the size of the bit for how finely it can carve. With a 1.85mm diameter bit the narrowest line you can cut is 1.85mm and all of your inside corners will be rounded with a .925 radius. A smaller bit will mean a smaller radius but it’s always going to be slightly rounded.

Luban is very primitive in what it does for CNC. To really be able to adjust settings and to see what’s actually happening and going to happen, you need fusion 360 or simplify3d.
I’ve only used fusion (free to home users). It’s incredibly powerful but the learning curve is steep. One advantage is that it will simulate the tool path and will actually create a 3d representation of the outcomes of the tool paths. It will also warn you if there are any potential problems with how it’s going to be carving.

-S

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Thank you @sdj544 for a very helpful and illuminating response. First, I know that the depth set is way too much but this version of Luban 3.8.0 is producing some odd issues so I was trying a deliberate adjustment to see its effect. I agree with you that Luban is a really primitive software application and it needs a whole lot of love. My first brush with tool paths, being completely new to CNC carving, was that the density control was effectively the method for controlling the workpiece space that the end of the milling bit covered. At first, my SM1 was running for about 14 hours to carve a 40 x 40 x 10mm square hole. I was running over each spot many times with a cut that was shifting by 0.1mm with each new cut. I could eventually see that setting the density to 1 was the way to have the software move the tool bit laterally by half of its diameter.

The jpeg file is saved at a 300 dpi resolution. Your helpful illustration of a dot matrix printer is instructive. It helped me to understand that all inside corners will be the radius of the bit diameter. I guess that was obvious really but I had not thought about it in those terms. I have looked at Fusion 360 and I need to sit for many hours to understand the main principles. You could give me any software for graphic design and because I understand what methods can be used to achieve an endpoint, I can use any package freely. Fusion 360 has a few of those elements but in general terms the design language it uses is unknown to me. At these early stages of my CNC use, all I want to do is find examples that I can work with and see how the different parameters affect the outcome. Known example pieces with known outcomes (where settings are duplicated) would go a long way to being instructive.

I found an online software (Easel) that is very easy to use and really visual so it helps one to
pre-visualise the endpoint. The g code it generates moves the project to the top right quadrant of Luban so the SM1 does not do what is actually wanted. Easel can generate grbl code and I have tried to adjust the code by hand editing it but without success. Its visual interface is what Luban ought to provide for those of us who are new to the world of CNC/Laser/3D printing. If I could speak to my machine with certainty, then I could potentially sit down and try and understand how to use Fusion 360.

All of my work inside Luban has been a bit of a struggle because it appears to have no internal logic that I can understand. Some settings are persistent, some get adjusted even though nothing was done to adjust them and some cannot be entered unless a sequence is followed. The user interface leaves a whole lot to be desired and for a product that is as mature as Snapmaker, the Luban software is lagging behind by a considerable margin. Using third party software is the logical response to Luban.

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I feel the same way about visualizing what the software is doing. The whole world of fusion 360 and cnc 3D takes a little bit to get your head around. One of the big differences is thinking about it as being a subtractive process - taking away material - vs. 3D printing being additive. When you’re designing something (in tinkercad, fusion etc.) you’re still usually being additive. You start with a shape and add features. When you flip around to the manufacturing part then you have to change your mindset to being subtractive. You have to think about ‘stock’, the piece of material you’re starting with and what and how you’re going to remove in what order and with what tools to get the final product.

Fusion 360 is designed for the professional with an emphasis on metalworking. It’s super powerful but also super complex and doesn’t have the most polished interface. It has little features that are great for someone who knows what they’re doing but for someone who’s starting out they can be baffling. For instance, when you’re choosing your stock size it automatically wants to round up. For a machinist who’s working with standard sizes of metal this is great. For someone who’s using scrap wood of various sizes to play around it’s one more thing to have to understand and know to turn off. Then of course there’s all the new terminology and processes and ways to calculate the tool paths and why to choose a certain way for each project. Figuring out how to use a series of bits for several passes and how the settings for each pass relate to each other takes some time. Fortunately fusion 360 has a really good simulation that you can run that will show tool paths and give warnings about problems and give a pretty good rendering of what the finished piece should look like.
Unfortunately it took a couple weeks of playing around and not having tests turn out how I thought they should to realize that it could do this. A big part of this was realizing that my 2009 MacBook wasn’t going to cut it and couldn’t show these simulations because it couldn’t handle them and they were turned off. Now that I have a brand new laptop it’s made all the difference.

It probably would’ve been wise for me to start with some trial projects that people have had success with. Instead I decided to jump into one of the main things I want to do, which is take logos and grayscale images and convert to depth maps. There is a lot that goes into the prep process and design even before trying to bring it into cad/cam programs. Image2Surface (within fusion), image to lithophane website or even rastercarve all handle those differently. I did create a test to help me understand what they were doing and how the different settings affect everything. I’m attaching the png version of my test file and the link to the stl results. On the stl you can see the difference between how I2S and ITL handle the same file.

There are a number of different programs (Camotics) that will take your g-code file and show you what the outcome will be. One thing I didn’t realize going into this is how much time I’d spend downloading and trying different software. There isn’t one ‘do it all’ solution. I settled on fusion because of cost and capability. None of the interfaces are great or simplified. Fusion has pop-up help menus for every choice which is great, but still need to look up terms to see what they actually mean. I still like tinkercad to model something quickly for 3d printing.
happy making!

-S!

https://drive.google.com/drive/folders/1G4XgBkUvK4BSzg7Ir1oAhEWQ-Ojd3OV1?usp=sharing

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Hi S; Thank you very much for the links to the files and the really valuable insight into what I am likely to find. I am running a reasonably capable quad core Macbook Pro from 2015 and I don’t particularly want to give it up just yet. I have always used Apple from the early 80s right up to now. I have no understanding of Windows machines and if I was pushed then I can use Linux/Unix with some facility. Happily, I discovered CAMotics right at the start of my experiments with CNC and I do check all of my files before trying to run them. That software has a lot of very useful settings and I like its simple to understand and follow interface.

I don’t yet have a complete picture in my mind of how the process of thought, design process and machining works together. It has not helped that Luban does not handle many .svg files at all. Vector illustrations are essential if the resolution is not to be destroyed by magnification. Trying simple layer manipulation has been a nightmare. I suppose if Luban is not going to be improved beyond its current capability and user interface then I had best move to software which I can learn and use for my intended projects.

My growing suspicion is that SM1 is somewhat less able than I had thought at first. The chattering of the end mill bits appears to be related to the quality and configuration of the bit selection available for the fixed 1/8th of an inch collet. I am going to try one fairly expensive 1/8th of an inch end mill and if that solves the chattering issue, I may well go ahead and convert the motor. I noticed that someone on the facebook SM group had managed a motor and collet conversion job so that their SM1 now takes an E11 collet.

I have been looking at several different software solutions. Without knowing an awful lot about what I really do require I have been trying the fit. Cura, Simplify 3D and a look at Vectra software (not Mac compatible I think). Easel online has been the only piece that has been instantly understandable but I cannot understand why it places the work at the top right, despite its own design program placing the 0,0 point at bottom left. I want to centre the workpiece so that is in line with Snapmaker’s methods of work.

I will take a look at Tinkercad and another longer look at Fusion 360. It appears to be the only game in town from what little I have read and heard. Thank you for taking the time to inform me and stop me blundering around.