SHOPBOT
While this page is primarily of interest to current owners of Shopbot CNC machines, we hope that it will provide information to anyone interested in incorporating CNC technology into their field of work/play..
Alignment tabs
I've come up with a simple way to align sheet goods on my table without having to use permanent "corner guides" which have previously gotten in my way when I was lowering the "Z " axis to make through cuts from the "Y" side of the sheet.
As you'll see from my first picture I am now using pieces of plywood which have slots cut in them so I can adjust the height of the guides according to my needs. My earlier "tabs" worked well, but did NOT handle heavy weights being pressed against them repeatedly, while this version can..
In the following picture, you see how the guides look when in use. Their larger size gives me a better bearing area, and they simplify, and speed up changing out sheet goods on my table..
Vacuum Clamping
There are times when regular clamping of parts is either impractical, or impossible. In situations such as these the use of vacuum works very well to hold down anything from very small parts to full sheets of plywood. I've been playing around with the idea of a simple, "all purpose" pump that will allow me to utilize vacuum to do everything from lithophanes, to kayaks, and this is what I have come up with....
The pump is a 1/4 HP , 230 volt Gast model # 0523-P335-G509DAX which I ordered from www.surpluscenter.com (their part #- 4-1540) It costs $89 plus shipping. And I got the 3 gallon "surge tank" there as well,( but I believe if you look around you may find a better deal locally without having to pay shipping costs....).
I am able to "pull" about 25"of mercury, and using the vacuum switch I purchased from www.mscdirect.com ( part # 56499197, $40) when I start to lose vacuum it kicks back on again at 18". This is easily sufficient to hold down any non porous item I have tried so far.
All of the assorted brass fittings and barbs can be purchased at any well stocked hardware, plumbing, or home supply store. The final cost of this unit should be under $200 depending on how resourceful you are.
Please see the note below regarding the use of a "one way check valve" (in the photo above it is the first brass fitting coming out of the vacuum pump body, and it is then followed by a "90 degree" fitting). You NEED this part and it is simply called a "heavy duty check valve" on the www.vwneersupplies.com web page....It costs about $13....
Above you see how I wired the switch to an extension cord (yellow). The middle lug on the switch is NOT used at all. In the center of the switch is a plastic cap you pry off to gain access to an adjusting screw inside the barrel.
On the other end of the extension cord we wired in a 220 plug and we run the pump through a dedicated outlet which has a switch on it. When adjusting your switch use your vacuum gauge and when the pump seems as though it is straining to gain much more holding power (as indicated by a "stalled" arrow on your gauge ) that is about the best you can expect to pull from that pump. Set your upper switch to a little below that number (probably going to be somewhere between 22-25 "), and the pump automatically will shut off when you reach that level of vacuum. It will not kick on again until you lose enough vacuum (leak, or porous materials) so that it drops 7-8"of mercury, and then it kicks back in until you are back up to 24". On my pump that process takes less than a minute so I'm not running the pump very often..
As with ALL vacuum setups, the nature of your material can make or break your system. Porous materials are not very well suited for this kind of process, and you may have to make adaptations in conjunction with other mechanical fasteners to obtain the positioning power you're looking for...
The key to much of the success of my vacuum work is the use of "pods/pucks" made of 1"thick PVC sheets. I get them from www.nappyproducts.com . They sell pod materials as well as completed units which can be purchased with single barbed fittings, or double ended units for working in a "daisy chain" of pods when holding down larger sheet goods. The PVC is impervious to air leakage, so I have no problems with porosity or loss of vacuum.
In the above picture I am using a larger pod unit to cut a lithophane. The pump/pod combo hold vacuum well enough that the pump does not have to run more than 30 seconds initially to build up enough vacuum to hold the Corian in place throughout the cutting process.
To facilitate switching from pods to vacuum bags, etc. I have adapted simple "quick connect" fittings as normally seen on nail guns, etc. I'm finding the brass versions work better than the aluminum ones, and they are readily available at any tool supply store. So far I have not noticed any air/vacuum leakage, and the time saving in moving from one project to another is major.
The gasket material which is vital to containing the vacuum is available from www.allstaradhesives.com It is available in a variety of thicknesses, but so far I think the 1/16" thickness has given me the best results. The general rules for gasketing are; "thinner is better than thicker", AND "harder is better than softer"...All Star has a complete line of gasket tapes and sheets for almost any application.
I am using the pump setup for vacuum bagging as well. Instead of building a vacuum bag from vinyl materials, I opted to buy a welded commercial unit with a fitting that can be adapted to the end hose on the pump. All of the materials for this phase of the operation are available from www.veneersupplies.com which was also where I purchased the vacuum "check valve" for the pump unit. It is VERY IMPORTANT that you use a check valve, or similar "one way" valve in your vacuum system, or else you will lose vacuum as soon as your pump turns off, and your vacuum switch will oscillate as it tries to hold the vacuum .
Here is another pump I have been using lately to test some pods/pucks as well as vacuum bagging. It is a reciprocating unit which is smaller, and therefore a little less powerful than the rotary vane unit shown above. I am getting a consistent 19"of mercury when running this setup. Yet even at that lower power I am able to crush metal coffee cans placed in the vacuum bag.
This pump also comes from the Surplus Center, (part # 4-1692) and costs about $60. Pictured on the right is a foot switch that I added from Veneer Supplies ( $25) as the pump does not have an on/off switch.
Using this pump I am now vacuum bagging veneer, and clamping parts as well. You can see in this picture how well the bag will allow parts to adhere to the shape of their substrate.
And here is an example of just how powerful even only 18"of mercury can be. I had to stop the pump before the can got totally crushed as I didn't want to tear the vacuum bag.
Dust collection attachment
A lot of people have modified their dust collection sytems to their own specific needs, and I'm no different. Borrowing heavily from Bill Young's designs at www.seasidesmallcraft.com I have made a simple unit which works better for my needs than most designs I've tried before.
It begins with a simple "ellipse" made of pine, or some other soft wood, and it's walls are about .25" thick, and .75" deep. Nothing fancy, as this piece is going to be right near the "business end" of things...As you can see in the picture below this attachment has a lot of stories it could tell...
On top/bottom of the ellipse I glued (silicone, liquid nails, etc.) two thin (.125") sheets of plexiglass.
I then added a hole on the TOP of
one side, and also attached a "donut" of wood with the same adhesives.
Then we glue a "wand" from any standard shop vacuum unit into the donut...
Here is the piece from the bottom so you can see how the hole looks from below...
Then I added a hole in both the top AND bottom on the other end of the ellipse and screwed/glued a piece of "garage door brush" from a home improvement store. The goal here was to seal up all airflow so you can see we used a LOT of glop to do so...
And then to maximize the flow of debris from the router bit to the "wand" at the other end we will seal
the UPPER hole on the business end with masking tape. This allows the bit to plunge through with no damage, and minimizes the opening so the majority of air flows directly back towards the wand....
I like this unit because we do
mostly 3 dimensional carving in this shop, and the unit always stays on the
surface of the material, rather than rising/plunging with the
"Z" axis. It also allows your router to collect dust AT THE BIT instead of 8
inches away, so this means you can now have complete collection, even when your
machine is at the "0,0" position. Other units collect ONLY at the "wand" end
because their bottoms are open, and when you are in this position your suction
is actually off the table, and no where NEAR the bit...
Then we simply used a 4" angle bracket, bolted to the frame of the machine for attachment of the 2" hose.
Taking the piece on/ off is a matter of loosening two hose clamps...
And then the unit is connected to the dust collector by 10'of 2" hose, which then further connects with 10'of 4" hose using the "gallows swivel arm" mentioned in the modification section of this page.
SIMPLE VACUUM JIG(S)
I have been using a version of Bill Young's vacuum table for over a year now. It is exactly what I need for full sheet projects, but it has limitations when it comes to anything other than a sheet goods project. SO, I decided to make a more adaptable setup to suit my needs. I wanted a rig that would be easily convertible from one size to the next, and it had to be accurate in it's positioning capabilities. After seeing how everyone else is running PVC pipe manifolds, or multiple chambered tables, I decided to simplify the process of vacuum pumps, valves, etc.
As you can see in the first picture I am using this jig setup on a standard PRT 96(Alpha now) steel table, but it will work on anyone's table. (For more info on the main vacuum table go to Bill Young's page www.seasidesmallcraft.com for the details).
Note; If I were to build a new table from scratch today I think I would create a multiple zone (12+ zones) and a PVC manifold. I run SO many different types of projects that the ability to start with a VERY small zone (4"by 4"), and work my way up to larger zones as needed ( leading to full sized table capacity..) would be a major asset.
It would also mean I didn't have to build new "sleds" as the projects changed. The current system works, but as with all techniques I think it needs to evolve as my needs have...Just another thing on the "to do " list..
When I need to do projects that are smaller such as cutting sign blanks, I can use a number of clamping systems such as the "back to back" variety pictured here; and they fit nicely over the vacuum table as well.
But in many cases I also need to get my blank totally flat to the table ( for engraving, or cutting out Tiff files, etc.), and these clamps will not help me there. This led me to start building "modules" of different sizes, which can be used for either single purpose, or gang cutting.. The module pictured below is able to hold a 2 foot by 4 foot piece tightly.
Here you can see a smaller module made to accomodate pieces that are roughly 1 square foot in size.
The key to making this all work easily is that instead of using different "zones", or different "ports"I am using the SAME vacuum port as for the entire table...This means I can build to any job that I need, (OR if I were clever, I could make adjustible modules that would allow me different setup capabilities..).
And to keep the accuracy I need for the engraving work, I have installed small "tabs"at each corner of the jigs, which will just slip into the existing table slots. This keeps the jig from slipping in any direction, and it ensures that my edges are parallel with the plane of the machine. Everything is pretty basic; I used a 1/2 inch piece of MDF as the base. Then I glued strips of 3/4 inch Laun plywood on top of that. The "plug"is 2 inch PVC pipe. After epoxying in the "plug" piece, I set it into it's "position" and planed the surface using the Shopbot with a morticing bit. Then I gave it two coats of water based poly to seal it. All of this is "powered"by a 4 h.p. "shopvac"machine that costs about 70 bucks at the Depot.. It works fine, and I'm now adding to my "fleet "of modules as I get time. If anyone comes up with a logical modification to allow ADJUSTABLE modules, please let us all know..
Alpha Modifications
When I recently upgraded to the new Alpha model, I decided to make life a little easier for myself during the initial setup of the machinery. One issue I have always had to deal with has been the routing of all of the wires and cables running from the machine/router/spindle to the control box. In all of the promotional materials advertising the Alpha the new airtight/dustproof control box is shown being placed UNDER the table itself. This would NOT have worked very well for me as it presented a few issues;
I do NOT want to have to crawl on the floor under my table anytime I need to get to/into my control box, and it seemed counterproductive to place the box in the SAME place most of my dust/debris always seemed to fall. Then I would have also been forced to run the wires in some convoluted fashion to get to the electrical circuits on my shop walls. So I mounted the control box chest high ( to make access VERY comfortable) on the wall, using 2"by 4" lumber as "standoffs" for air circulation (as the new box has NO fan for cooling). Then I ran all of the wires to the machine via a "skyhook" ( alias bicycle mounting hook) from my ceiling directly over the center of the table. This allows all of the cables to reach the furthest travel of my machine, and also allows me to do a complete circumnavigation of my table without having to trip over any wires. Having the luxury of 12'ceilings in my shop it only seemed logical to use the air space afforded me.
And then when it came time to run my dust collection system to the spindle I also wanted flexibility. So I set up what resembles a "gallows" mount for the 4"hose coming up from my dust collector, and using a few scrap pieces of HDPE ( for it's incredible lubricity) I made horizontal "spacer/washer/bearings" which allow VERY easy movement as the gantry travels from one end of the table to the other.....This ensures that the "lead" of the hose is always clear, and I have yet to see a situation where I get hung up in any position I might be cutting...
The Gallows arm
The HDPE bearing
