Shopbot as a plotter

[sparker]

Is there a pen attachment which can be placed in the shopbot so it may be used as a plotter.

I design boats and before cutting panels I do a 1/10 model first.

Seems it would be a very simple attachment.

[billp]

Larry,
I know of one person who took a pen and "threaded" the outside of the barrel with a standard tap/die. He then formed the mating internal threads into a piece of hardwood. Then he simply attached the block of wood to his Z axis and by adjusting the pen up/down (by turning the barrel) he was able to get the exact height he was looking for.
I suggested to him that he might also want to add a "set screw" into the side of the hardwood block so he could lock that position in place.
Seems simple, and accurate...

[hespj]

Hi Larry, I design the occasional boat too, and I have made scale models of some of those hulls. But I haven't plotted them, I've just cut them out of a block of wood. Not sure why you'd want to plot.

I've done a lot of "plotting" too. Well, not really plotting - I've never drawn on paper, only onto plywood or MDF. Initially I made a pen and a pencil holder, but these didn't work very well. Since then I've used a Vee bit to engrave boards with drawings. Usually 0.5mm (say 1/50") deep.

[hespj]

Interseting post Bill. Initially, before making a pen holder I just put a 1/2" dia pen into the router. Having a pen at a fixed height wasn't very good. So I made an attachment which let a pen slide up and down (a tube). A firm contact was maintained by having a weight on top of the pen. The weight was attached to the top of the pen so that when the router was raised the pen didn't slide out. Better, but not brilliant. I think the idea could have been made to work well, but I decided engraving was best for my purpose.

[billp]

Larry,
I think John and I will both agree that any method you attempt will ONLY work if your table is really flat and true...

[hespj]

Yes, unless the pencil is able to slide up and down as I described. And if you're drawing on sheet material like MDF you might (will) find that it's not a consistent thickness, resulting in no lines in some places and a snapped pencil in others.

I also remember drawing on a painted surface with a fixed pencil (not sliding). A little nib of paint broke the pencil.

[rhfurniture]

Could you set up a single nozzle ink-jet? Maybe it's a way of utilising your old printer.

[bill.young]

Back in the ShopBot "Stone age", when we didn't have any toolpathing software and a very rudimentary DOS preview, I used to draw all my files on a sheet of tileboard with a dry erase marker so that I could (in theory at least) see my mistakes BEFORE I started cutting the expensive imported marine plywood!

Here's a picture of one of panels from Marc Pettingill's "Sweet Dream" canoe (I think).


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Bill

[norm]

Larry,

Check with Ron Varela. I think he used to have a spring loaded pen attachment he used on the Bot. I was going to use something like that to draw stained glass patterns. Worth a try.

Norm

[myxpykalix]

Thats where i saw it! I knew i just saw it the other day. He took a brass tube, stuck a spring inside the tube, then the sharpie. I assume to apply downward pressure to keep the tip on the material. When i tried this long ago I recall that because of the nonlevel surface it pushed the tip of the marker up into the barrell. So try to get a marker that is designed not to be able to to that.

[scottcox]

I saw something last month that I liked but didn't bookmark it, so now I can't find again. These folks carved large terrain models (on the cnc) and then "printed" aerial photos onto the surface using inkjet type nozzles/cartridges. During the print phase, the z heights of the ink nozzles were relevant to the model.

Very cool stuff. I'll try to find it again.

[sparker]

Thank you all for your comments. John, I build kayaks which have 2 panels which make up the deck. So, I never thought about a solid model. I also build whitewater dories. Models help with a dory design also since you we can see the inside space.

On the pen ideas. I was already thinking of a pen in a spring loaded barrel of some kind so I think the problem of tracking a non-flat surface should not be a problem.

Thanks
Larry

[myxpykalix]

Hey SCOTT!

Here is the link for what you described.

http://www.solidterrainmodeling.com/NGS_movie.htm

[scottcox]

Yep. That's it!

I'm very intrigued by this. There's got to be a way to adapt something like that to the bot.

I picture the shopbot software communicating location data to a separate "printhead computer" which then dispenses ink accordingly.

Any ideas?

[dmdraper]

This pen holder is a thing of beauty. So simple, yet so effective. After building a few spring loaded types, I see now that I totally over designed the thing and put way too much time in the effort!

http://www.youtube.com/watch?v=1-B1FKpjtiA

[john_l]

Can't get much easier than that.

[jay_p]

David,

So what are we seeing here? Is that simply a weight on the top of the sharpie?

Jay

[jseiler]

How accurate does it need to be? How about a 1/2" piece of spring steel attached to a sawed off shoulder bolt and taped to a sharpie. If the spring steel is mounted like a diving board, then it would flex enough to cover differences in spoil board thickness, but it might drift half a tenth of an inch.

[dmdraper]

Jay,

You are correct. The weight attached to the top of the Sharpie applies the down force to keep it on the paper. The diameter of the bottom washer is such that the tip of the pen fits through, but it catches on the shoulder (where the cap attaches) to lift the pen up when you pull up to a given z.

[hespj]

That's pretty much what I was describing in post#4 of this thread, except mine was even simpler - the tube was 1/2" dia and fitted in the collet of the router. It did limit me to small dia pens/pencils, but I did want a sharp line.

[denver]

Unless you have a tight fit in the holder, isn't the pen going to wobble when changing directions? And if you do have a tight fit, then that presents other problems. In the video it does look like the pen wobbles at some points, but perhaps that's just the video. And maybe a little wobble doesn't matter for some drawings.


Thanks,

Denver

[hespj]

Denver, the tube I used was about 3" long, so the difference in size between pen and internal dia of tube created minimal wobble. Even so, it did wobble, and this was one of the reasons I abandoned the idea.

By the way, Larry, the original poster on this thread said "I build kayaks which have 2 panels which make up the deck". Why not just cut them out Larry? I assume you're drawing them then cutting them by hand?

John

[zeykr]

Here is an off the shelf mini sharpie holder constructed from brass plumbing fittings.

All parts but the lead weight came from Lowes plumbing department and it just screws together and fits in a 3/8 chuck. A version could probably be made for a 1/2 or 1/4 chuck with different top components.

Parts used from the bottom up are a Watts #A-765 3/8" FIP x 1/4 FIP reducer, a Watts #A-787 3/8" MIP x 2" pipe nipple, a Watts #A-762 3/8" x 1/8 FIP reducer, and a Watts #A-717 1/8" MIP x 2" pipe nipple.

The A-717 and A-762 could likely be changed out to fit other chuck sizes than 3/8".

The mini sharpies came four to a package and were part number 35113.

A small lead weight was sized to the inner pipe diameter by driving it through another piece of 3/8 MIP pipe and slightly sanding the edges so it would move up and down easily in the tube. The bottom was drilled out slightly to fit the back end of the sharpie to keep the pen aligned in the tube to reduce wobble.

The pen has around a 1/4" of movement in the tube, so I just zero with the pen tip slightly above the material surface and set up a machine along vector toolpath with a depth of .1".

Not laser accurate, but good enough for most purposes.



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[eaglesplsh]

I just posted info under the "Product/Supplier List and Requests" category about the Plotter Pen Bit that we have for sale. The thread is titled "Plotter Pen Bit for Drawing w/ ShopBot – Fits in 1/2" Chuck"

I believe that this product is exactly what the original poster was looking for - an off the shelf plotter pen bit that fits in the 1/2" collet of a ShopBot router.

If you're interested in a full description, pictures, and a video of the pen bit in action, feel free to take a look at our other post and/or visit our website: www.WidgetWorksUnlimited.com (http://www.WidgetWorksUnlimited.com)

[sagreen83]

This would be very cool for CAD drawings... It would be awesome if you could "print" to your shopbot. i.e. emulate a large format plotter like an HP760C or something like that...

[myxpykalix]

Seems like with this attachment you should be able to do just that. If you had some smooth surface like melamine (or not) and tape down your paper wouldn't it "print" just what you wanted (your dxf file)? If you were real creative you could change colors for different layers or toolpaths.

[eaglesplsh]

FYI - the video of the pen bit drawing the skull was done just as you describe. We placed a piece of MDF on the CNC table and scotch taped a piece of paper onto the MDF. Because the pen doesn't use a lot of force and because the drawing surface doesn't have to be perfectly flat you don't really need to clamp down the MDF of Melamine - the 24"x24" piece was held in place by it's own weight without any locator pins, etc.

[knight_toolworks]

what stepover do you use? save me having to play to find it.

[knight_toolworks]

got my tool yesterday and it is simple and works well. it should help out quite a bit on some projects. here are some pics and video's
http://s154.photobucket.com/albums/s266/knighttoolworks/drawing%20on%20the%20cnc/

[myxpykalix]

Steve,
heres a question..when you created your toolpath to cut the images in your link what type/size tool did you input was cutting the file? Also i wonder about plotting something other than a "line drawing" type file. You couldn't plot a 3d carving type file could you?

[knight_toolworks]

I think the tool size recommended is .015 I also made a v bit to match. but I did not have time to run it. I think a 3d file would just be a solid pattern since it is just a x or y movement and depth atleast from cut3d.

[dana_swift]

I would like to be able to plot out standard engineering drawings, and the SB is a logical tool to adapt to the purpose. C and D size drawings should be no problem.

It occurs to me that my vacuum system could be very hand for holding the paper down wrinkle free and eliminating the need for tape which only holds the edges.

Has anyone built a vacuum system to hold a sheet of paper in the bot? My first thought is it would look like an air hockey table in reverse. Vacuum distributed through a zillion little holes.

With a modest CFM it should hold paper and tolerate the loss from around the edges. Then again I an imagine a hold-down with a few ball valves to enable only the ports under standard engineering drawing sizes.. A, B, C, etc.

Ideas anyone?

D

[ed_lang]

Dana,

The normal vacuum table with Trupan for the bleeder would work real nice. Nothing new to have to make.

[knight_toolworks]

I agree you would not want holes that may suck the paper down or the pen may go through them.

[carve3d]

Attached is the photo of of the pen attachement Bill Palumbo was talking About in his post

[carve3d]

forgot to attach pen

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[curtiss]

This is a handy software site for a creating PDF files in larger sizes (24x36) that you could print at Kinko's if you need to.

http://www.pdfill.com/