Newbie needs help for a quick start

[srwtlc@tds.net]

Hello to all:

While I'm awaiting the delivery of my new toy (ah err ah)I mean tool, I have been trying to learn the software and programing of the Shopbot, but my time has been quite limited lately. I understand the basic principles, but I really need to make this tool do one item as soon as possible and am not sure of how to write the file.
I really want to learn how and have no doubt that I can, but I need some help getting started.
What I need to make, either one at at time but preferably ten at a time or more, is a 5" x 8" box made from two pieces of 3/4" x 5" x 8" walnut hinged on the 8" edge, the bottoms have a 1/8" deep recess on the inside and the top has a 1/2" deep recess on the inside, both 3/8" from the front and sides and 1/2" from the back. My thoughts are to first make a series of shallow recesses in a piece of plywood to place these 5" x 8" blanks into and probably hold them down with a vacuum, then rout all the 1/8" recesses in the bottoms first then put in the tops and rout the 1/2" recesses in those in two to three steps
with a 1 1/4" bowl bottoming bit. Any thoughts or comments? I would greatly appreciate some help in getting the needed files started.

Thanks
Sincerely,
Scott Worden TLC

[rgengrave@aol.com]

Scott get with Ron he will be able to help you.

rgengrave@aol.com (mailto:rgengrave@aol.com)

Tom

[bill.young]

Scott,

Sounds like you've got some good ideas already. Here's how I think I would cut the recesses in the bottoms and tops if I was doing it, but there's lots of other ways as well. I'll make some assumptions for numbers and dimensions, but they can be easily changed.

First I would make a holding jig that will hold as many pieces as you want to be able to cut. Vacuum would work great, or you could make a clamping jig that will hold all the pieces by their edges with pressure; that's how ShopBot holds the aluminum blanks when they machine the motor mounts. Whatever way you do it, take care in making your jig so that all the parts will be an equal distance apart. This will be the fussiest part of the job.

I think the easiest way to actually cut the recesses would be to use the (CR) command with the pocketing feature turned on. If I understood your posting, it looks like the recesses will be 7.25" x 4.125". I would set your ShopBot's zero point to the corner of the first blank (maybe with proximity switches), and then write a file that was something like this:


MZ, .5 ' lift to a safe height

J2, 0.375, 0.375 ' move to the start point

MZ, 0 ' drop to blank surface

CR, 7.25, 4.125, I, 1, 4, -0.125, 1, 2 ' cut the recess

MZ, .5 ' lift to safe height

J2, 12.0, 0 ' move to the start of the next lid


Look at the parameters for the CR command in the command reference (HC) to see what it's doing, but in this case the (I) cuts the recess on the inside, the (1) cuts clockwise, the (4) picks the lower left corner as the start point, (-0.125) is the cutting depth, the next (1) is the number of repetitions, and the (2) turns on pocketing.

After the recess is cut, the final J2 command move you to the corner of the next lid ( assuming they are 12" apart). Save the file as something like botmrecs.sbp, then write another file that calls botmrecs.sbp in offset mode as many times as you have parts to cut. This new file is the one that you would run.

You would use basically the same files to cut your top recesses, since the only difference is the depth of the recess. All you would need to do is to change the depth-of-cut value and number of repetitions and then save with new names.

I hope this hasn't been too confusing (and that I understood what you are trying to do correctly), but the process is really pretty simple. Oh yeah, make sure you change the bit diameter setting to 1.25" with the (VC) command or your recesses won't be the right size.

Hope this helps,

Bill Young

[srwtlc@tds.net]

Bill,

Thanks much for the help. I think I'm catching on some now, and studying your files for the saw horses and workstation has helped also. The whole process/project does seem to be a relatively simple task for the ShopBot, I should be able to get it figured out. Stay tuned, I may have some more questions. We will see how many of these things I can or have to get out by Christmas/New Years. So much to learn and so little time.

Thanks again,

Scott

[bill.young]

Scott,

Here are a couple of more thoughts on creating part files that I hope will help. First, I've found that the simpler you can make your files, the better off you are. You don't always have to use a CAD program to create a file; you can do a lot with ShopBot's built-in commands like CR and CC. Drawing the parts out on graph paper can be really helpful in deciding how to make your part and visualizing how things should flow.

Second, use variables for things like cutting depths that you may need to change in the future. It makes it easier to edit and refine your files; you only have to make changes once.

Third, add comments for things that aren't REALLY obvious. This is advice that I don't always follow myself, but it comes back to haunt me when I'm trying to figure out what a part file I wrote three years ago does.

Last, spend a lot of time creating your holding jigs. As with parts files, usually the simpler your holding jig, the better off you are. No matter how accurate the tool is, if your parts aren't held accurately and securely you're going to have trouble. If you can figure out a way to machine the holding jig using your ShopBot, you're that much better off.

Bill

[srwtlc@tds.net]

Bill,

Thanks for the added insight. I think I've got the bottoms and tops figured out, but I have a question on making the holding fixture. I can make the 5 x 8 recesses to hold the blanks in the same manner,but I need the corners to be opened out to accept the corner of the blank(take out the fillet), using a 1/2" bit for all cuts. What I tried was to go back to each corner and make a plunge cut to take out the corner. I can only run it in preview and it looked like it was making those plunges outside the rectangle. Maybe it's just the way the preview shows it. I'm pretty sure I have the corner coordinates right. Maybe there is a better way to do this. I'll have to see what happens when I actually get my ShopBot setup.

Scott

[bill.young]

Scott,

You've got the right idea. If you plunge your bit at each corner of the rectangle it will make a little pocket that removes the corner fillets. You might even think about cutting them a little bit bigger to make it easier to remove any dust that collects in your jig.

Preview is a big help in seeing what your file is going to do, but the resolution is sometimes too large to get much detail. You can customize your preview screen with the (VP) command, changing things like the zoom factor, the area of the table top that you're viewing, and the speed that the preview is drawn on the screen. This last setting, the delay, is really helpful if you want to see how your parts will cut and the preview is drawn too fast.

Good luck with your files, and let us know how your parts turn out.

Bill

[Nancy]

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