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Old 05-09-2019, 08:24 AM
Tim McKnight's Avatar
Tim McKnight Tim McKnight is offline
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Join Date: Oct 2005
Location: Morral, Ohio
Posts: 5,263

Originally Posted by Quickstep192 View Post
Very cool stuff. Not surprising from an engineer become luthier!If time and willingness permit, I'd love to see more about the machine itself (I want one!
Sorry for the delay in posting more information about our CNC Quickstep. We use a ShopBot "Buddy" model. The bed of our machine measures ~24" x 36" which is the perfect size for guitar makers. Shop Bot makes MUCH larger machines that can handle 5' x 10' sheet goods for cabinet and sign makers. They also make smaller table top models which are perfect for hobbiests or inlay work. I know of several prominent inlay artists who are using the smaller table top machines with great success!

The CAD software, which came with our machine is made by Vectric and our version is called "V-Carve Pro". Vectric also makes another popular version called "Aspire". Shop Bot also includes 3-D software and a CAM package. We purchased our machine when they were first released at a cost of $4,995 well over a decade ago. Now the same machine is nearer $20,000.

This is a screen shot of the V-Carve pro software:

I am NOT a software guru by any stretch and I learned the software rather quickly. Initially it was rather intimidating but after I was shown the basics by a local High School Vo-Ag teacher, he had me up and running within 30 minutes and I learned the rest on my own. Shop Bot has an EXCELLENT forum and I was able to go there to get answers to every question that ever arose. Their forum is one of the main reasons I bought a Shop Bot because they answered all of my questions before I ever bought a machine and they patiently support newbies like myself with trivial questions without making me feel like an idiot. They also sponsor "camps" which are held in basements, garages and shops of other Shop Bot owners around the country. We attended a couple locally and it was a great way to meet other users and see examples of how they use their machines.

Our machine occupies about 3' x 4' footprint of floor space and quietly resides in a corner of our shop. The machine framework is made of 3/16" thick, powder coated, steel and also uses 80/20 aluminum members bolted to the steel frame. Every one of the three axis' of the machine smoothly glides on V shaped ball bearings and hardened steel ways and I have yet to see ANY wear or looseness on our machine.

The 3 HP water cooled spindle, which turns the carbide steel cutting tools, moves vertically up and down which is called the "Z" axis of the machine. The spindle assembly moves left and right, which is called the "Y" axis of the machine. Below the spindle is a brown 2' x 3' sheet of MDF (Medium Density Fiberboard). This is what the material which we are cutting is mounted to. This "MDF bed" of the machine moves front to back, which is called the "X" axis of the machine. The MDF board itself is called a "Spoil Board" and is meant to be consumed as the machine often times is programmed to cut through the work piece. The MDF starts out as 3/4" thick but as parts are cut it becomes necessary to resurface or flatten the spoil board's surface with a cutting tool. Its common to take a .010" - .020" depth of cut from the surface of the spoil board periodically to expose a new flat surface.

The most difficult task of using a CNC is trying to figure out how to hold the work piece down securely to the bed of the machine so it doesn't move around or slip while you are cutting a part. I have tried all sorts of methods over the years from screwing the work piece down to the spoil board, using a series of toggle clamps or hold down clamps, jigs, fixtures, double sided carpet tape, glue, small dedicated vacuum puck clamps and the method I have finally settled on to hold [most] work pieces, a vacuum bed.

Under the sheet of brown MDF, is a sheet of 1/2" thick plastic and under that is the actual factory supplied bed of the machine, which is an 1/2" thick 2' x 4' aluminum plate. Since you don't want to ruin the aluminum bed of the machine, most users bolt a MDF spoil board on top of the aluminum bed to protect it from "accidents" which can happen (please don't ask).

We bolted a sheet of 1/2" thick white plastic over the top of the aluminum bed and then machined a series of shallow interconnecting grooves in the plastic sheet which resembles the face of a waffle. Next we cut a 2" hole, through the center of the plastic sheet and aluminum bed and mounted a 2" flexible hose in the hole on the underside of the bed and finally connected the other end of the hose to a vacuum pump. Over the top of the 1/2" thick plastic grid is mounted the brown sheet of MDF which you see in the picture. This is not your regular grade of MDF but rather a material which is called Trupan which is a very porous variation of MDF. When the vacuum pump is turned on, it pulls a vacuum in all the channels of the waffle grid of the 1/2" thick white plastic sheet and then the entire face of the MDF becomes a vacuum or suction surface.

Lets say that we want to cut a rosette in a spruce top we would simply lay the spruce top on the surface of the MDF, turn the vacuum pump on and it becomes nearly impossible to move the spruce top on the bed of the machine. We can then program the software to cut the rosette channel precisely the size, depth and location we tell it to in the CAD software. The CAM software then converts the CAD picture into code which the CNC machine understands. The code is a complex series of exact moves to tell the CNC which axis to move in the X, Y or Z direction. The CAM software does this conversion all automatically in the back ground and you don't have to understand that language to use the machine, thank goodness!
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