Virtual Zero Like Shark CNC?

[George B.]

Does shopbot have something like the Shark's virtual zero software which looks at 4 or 5 z points to develop a combined z zero for a variable thickness board? will the shark's z zero work on the desktop? if not, how should the variable thickness of 3/8" thick acrylic be handled when making a LED lited sign?

[willnewton]

I watched the video to see what they used. Basically, they have a touch sensor integrated into the Z axis. The software then uses mesh based leveling to plot points around the bed or workpiece. It will touch down in a grid and save the Z-zeros, then builds a multi-plane surface based on those grid points.

I have built and used a mesh based leveling system similar to this for my large 3dprinter. It does work, but is not some amazing process that obsoletes every other machine that does not have one.

For a 3D printer, the build plate and print head relationship is VERY important to get critical first layer down. The larger the machine, the more difficult it can be to keep things aligned. 3d printer frames tend to be built a bit more lightly than machines for metal and wood cutting and a large format printer can have difficulty keeping thing perfect over large bed. It needs to hold under 0.05mm tolerance for most first layer operations. Mesh bed leveling has been a huge help in that area.

You what else it is good for?

1. Making cheap mass-produced or poorly constructed homebrew machines that can barely stay in tram lay down a decent first layer.

2. Lets operators with no concept of how to maintain a squared up machine run their machine in an adequate fashion.

3. Allow operators with no sense of how to secure a workpiece so it maintains flatness move ahead despite poor clamping procedures.

Basically, it has its moments, but enables a lot of **** workmanship too.

I have felt absolutely no need to have this type of mesh based system installed on my other 3d printers and is not necessary on the SB. My machines are well designed and maintained, and the SB has a substrate leveling procedure that gives a flat surface and it has a 3-point zeroing setup that is more than adequate for 99% of everything most folks will ever use it for.

Now, that being said, the shopbot DOES have the capability through the digitizing probe to capture surface variations and to digitize 3d items for use later. So if you want to machine something onto a substrate with variations, it is no problem. The system the SB uses is similar to the mesh-based leveling start-up protocol, but has more control over the setup. It is not limited to a start-up procedure, but is an actual valuable function that can be used at any time and configured as needed, and serve as scanning tool that can perform on three axes instead of just one. Basically, the 3d SB probe is a lot more than the one-trick pony Z-setter.

So, in the end my opinion is that it is nice, but unnecessary on a CNC router. I would not make that feature carry any true weight in my comparison any more than the color of the machine would. If you must have the ability to scan and cut uneven surfaces, the SB has the capability already and the chances you will find it necessary to do it as part of the startup procedure are low to none.

[willnewton]

Sorry for the long post, but if I just put up the answers without an explanation, it would not be very informative.

Here is the TL;DR.

1. Yes, they have something similar, but different.
2. No, as in you can't just plug it in. There is firmware/software that needs integrating, not just plug and play hardware.
3. By choosing an acrylic supplier that does not make such a poor tolerance product. :p

[Burkhardt]

I have a similar surface scan function on my (non-shopbot) machine controller and never use it for reasons willnewton mentioned. The feature was originally designed to allow machining of traces on printed circuit boards that are often slightly warped and need a few 1/1000" precision. I tried it once as an experiment (V-carving on a curved natural surface board) but the process is time consuming and there are other ways of getting results.

[Gary Campbell]

George...
As stated above there will be difficulties implementing that system and ensuring that it would be effective. Your time, and possibly dollars, might be better served by preparing the best, most coplanar machining surface to fixture your material and developing a toolpath strategy and tooling that would minimize any surface irregularities.

As CNC operators we sometimes get caught up in the "decimal points". Meaning that some of these "magical" operations are often unneeded and possibly simply marketing hype to position one brand above some others. Remember that there are thousands of pieces of acrylic being cut and engraved every day on CNC machines, the vast majority without the aid of a "virtual zero"

[George B.]

Thanks for the information. I'm a little unclear about what a what a 3-point zeroing setup is? Is that just the normal x-0, y-0, z-0 zeroing? With a board say 20" x 10" is there anyway of doing an x1 in lower left corner and x2 in the lower right corner, and y1 in the lower left corner and y2 in the upper left corner?

[willnewton]

https://store.shopbottools.com/collections/accessories/products/3-axis-zero-plate?variant=7825832513