longer pieces

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lenny
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Joined: Fri Jan 07, 2011 7:26 pm

longer pieces

Post by lenny »

Hi,
Can anyone help me understand how I can use my CNC Shark machine to do longer pieces? I am looking at wanted to do a piece that is 42" long. Thanks

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Consultingwoodworker
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Re: longer pieces

Post by Consultingwoodworker »

You'll need some way to "index" the part.

VCarve allows you to "tile" a project, automatically breaking it up into pieces to allow for larger parts. I've not tried it, but it should prove useful.

But any way you do it, you need to index the part. Mill one section, then move the part and mill the next section. The trick is figuring out where to set zero for the second run.

I'd use a fixed rail along the Y axis, and at the end of the first program you could mill a small mark on the bare area that will be the zero point for the second program.

Ralph

tonydude
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Re: longer pieces

Post by tonydude »

Check out my bench which is 48 inches long. http://cncsharktalk.com/viewtopic.php?f=4&t=51 I did mine in 3 steps, first I did the lettering in the middle then I measured the distance from the edge of the lettering to the end of the board, took that measurement and calcalated the maple leaf to fit in that area. I positioned the board so I have room to carve out the maple leaf. Thats the way I did mine.
Buffalo,NY

"What will matter is not what you bought but what you built; not what you got, but what you gave”

Aspire 11.015, photo vcarve, cnc mako shark extended bed with the new upgraded HD 5 gantry with Led pendent.

jeb2cav
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Re: longer pieces

Post by jeb2cav »

Ralph is absolutely spot on about VCarve's ability to tile the project for you with version 6 - that is a great add. I've set up these tiles so that they are not the maximum of the table top, this then enables me to use the following -

What I have done is to drill a hole along on edge about 1/2" or 1" from the bottom, and then one more hole that distance along Y "above" the tile edge - using a tool path and typically an end mill. I set the depth to enable this hole to also be cut into my scarf board. Then I use a peg to hold this in place. "tile" has the holes in the same place, so when I move the work piece for the next "tile", the peg can be used in the hole cut "above" the first tile. You need a hole "above" every tile you are using. This provides a very sound index. I also have a fence like setup along the y axis to ensure the piece is square to the gantry.

Here's a pic to explain what I think I may not be explaining clearly in text.
One Index Method
One Index Method
Using this kind of method to index means you don't change the x0,y0 - and only have to change z0 during a tool change. I've found that if I have a pocket or 3D object in play, it is best to run each tile through for each bit/tool, then start over for the next bit/tool. That way the same z0 is in use for every tool across every tile.

If you're a little unsure about cutting the hole for the peg along with everything else, you can run a separate set of tap files to cut the holes for each tile first, then start into the "real" cuts.

Having a table that is level to the gantry across the entire work surface is pretty important for indexing in my experience. While you may not notice that the upper left side of the table is 1/16" higher than the lower left when making a single cut across the entire, single, workpiece - when you are indexing and move that workpiece down, that upper left side that is 1/16" higher is now directly against the now lower left cut - so you'll end up with a ridge or some sanding if the table isn't level.

If you don't have any overlapping 3D objects or pockets, and you create the tiles so that any lettering isn't on the tile boundary, I've also had good success by careful measurement and moving the workpiece along a fence I've setup - as Tony describes in his post. Always go for the simplest solution to the work flow.

Lastly, I found that trying this out with some scrap and working up to the hardest case - pocket with 3D object across the tile boundary - was worth the time before moving to the first product.

There are a lot of good questions and answers/ideas on the Vectric forum for tiling - including 3D on both sides of the workpiece. I look forward to seeing your project in the showcase.

lenny
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Joined: Fri Jan 07, 2011 7:26 pm

Re: longer pieces

Post by lenny »

Thanks for all the reply's; appreciate it. Yes, I was able to use the tile toolpath and able to create longer pieces. Thanks again.

hdtheater
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Re: longer pieces

Post by hdtheater »

Have you ever had any issues where the X axis does not line up. I have done a few tiled jobs and on each of them the second tile's X axis is off by the diameter of the bit. I have indexed my tiles and have had success with the Y and Z axis.

-Eric
Thanks,

-Eric

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jeb2cav
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Re: longer pieces

Post by jeb2cav »

Hi Eric - I haven't indexed in z - so haven't had an opportunity to see this (or not). You may want to check on the Vectric forum for this and/or ask there as well.

hdtheater
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Re: longer pieces

Post by hdtheater »

Sorry, let me clarify my previous post. When doing tiled jobs, my Y and Z axis never give me trouble. It's the X axis that is always off by the diameter of the bit being used.

-Eric
Thanks,

-Eric

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jeb2cav
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Re: longer pieces

Post by jeb2cav »

Hi Eric - I haven't run into this, but I haven't been "carving" across tile boundaries either (so far). I double checked one this morning and it was spot on in X across the project. Are you running a pocket toolpath, 3D carve, or something where you notice this? Can you send a pic?

hdtheater
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Joined: Mon Aug 23, 2010 8:14 am

Re: longer pieces

Post by hdtheater »

This was just a profile tool path I ran for cutting out objects. The first was just a test to see how it worked. The second time, I made the deck for a skate board. I managed it by using a 1/16" bit and just sanding it smooth. Not as easy when using a 1/4". I did not take a photo of it. :(

Next time, I get the chance. I'll be sure to take a photo of it.

-Eric
Thanks,

-Eric

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