Cutting a taper

[cbradshaw]

Can some one tell me how I can program the bot to cut on a taper on a 4 x post per the attached pictue. It needs to start at -1/8 and go down 1 3/8 over a 5 inch span.

Any ideas would be appreciated.
6852

[Brady Watson]

It will depend on how much Z-height you have to work with and the length of you bit. You can either do it from the side, like a profile cut (and get 2 sides at once) or do it from the top. It's a toss up...from the top is slower and you can use a short bit. From the side is faster, but you need a 3" CL (probably 6" OAL) to do the cutting.

-B

[cbradshaw]

Brady,
I planned on doing it from the top because of the bit length required to cut it from the side. I know how to cut ir from the side but I do not have a clue how to make it cut from the top. Can you give me some ideas?

Thanks,

Carroll

[Brady Watson]

Take a look at Bill's Extruder program over in ShopBot Labs. This will allow you to take a 2D vector and make it 3D.

If you felt particularly crafty, you could just write a file in notepad that tells the tool the XZ moves needed to make the part. You already know all of the distances, you just need to tell the tool where to go. IE:

MZ, .5 (safe Z)
MZ, -0.125
M3, 5,0,-1.375 (1st pass)
MY, .1 (move up in Y for next raster pass)
M3, 0,.1,-.125

etc...

This does NOT take into consideration the radius of your tool, and my programming is rough. Try out Bill's extruder and see what you come up with. If you don't have ArtCAM it's an easy way to do it.

-B

[jhicks]

Not too scientific or program intensive BUT one could simply create a fixture to hold the post at the proper calculated angle, then machine a flat surface across it with a bottom clearing bit. Just like surfacing the table or any stock flat.

If you set up a clamp fixture to hold all posts on the same angle (perhaps off the end of the table) you could simply machine as many as you can fit at once by running back and forth up the Y axis 1/8" deep over the 5" span, rotate 4 times and they are all done. Need to control depths in multiple passes to avoid too much cutting depth at the highest end though so one would need to start at the highest point and do multiple passes down to -125".
Should work and be fairly quick to set up rather than lots of design and set up time.

[beacon14]

I second Jerry's approach


6853

[myxpykalix]

Wouldn't it be easier to just cut them on a bandsaw? Sometimes with this stuff i'm remined of that old boardgame called "mousetrap" where the ball rolls down, tripping a lever, which in turn flips a mechanism, that jogs the cage down a pole to catch the mouse, when a simple "snap" will do the trick!
But then again, we like to figure out complex solutions to simple tasks don't we? I guess thats our justification for spending all that money on the bot in the first place right?

if you want to make it on the bot Davids picture seems to be the quickest easiest way to go.

[Brady Watson]

Jerry,
That's a great idea, as long as he can get that 1/8" step in there. I would be inclined to make a jig and just buzz them off with the table saw...provided that I could get the step in there as well.

-B

[garyb]

I would use the bansaw as Jack suggested, quicker set up & cut time.
Table saw is a double set up if you don't have the depth of cut for one pass, 4" in this case.

If you must use the Shopbot then Jerry's outline with David's photo would be the next best.

If you must lay them flat on the table, goup together and create or have someone create a simple relief in AC using the "fade Relief" will work just as well

6854

[ryan_slaback]

Is there any chance you can change the angle slightly? If so you could use a 15 degree bevel bit and machine them still from the top. You would probably have to take the bearing off and grind down the stub though.

[cbradshaw]

Everyone,

Thanks for responding! I never thought of using a Jig. I did think about the band saw, however the post is 10' long and is hard to manage that's why I wanted to use the bot. I had someone model it for me so I am going to try and cut it tonight.

Thanks again for all of the responses.

Carroll