Elevating Parts On Pods and Cutting Linoleum Tiles

[Matt Barinholtz, Covenant House Washington]

This is a copy from a posting in the Cutting Techniques area from 6/7...

We've been making a lot of birch ply children's furnishings, and have been rounding over all the edges with a hand held router. We'd like to make this happen (at least half of it) on the 'bot. After visiting a couple of big shows, witnessing huge cnc centers that do doors and door edges, we'd like to create "pods" that would elevate the workpieces and allow us to cut the part (minimixing flex), and then run a bullnose profile cutter around the edge.
We are building part files in PartWizard, and wonder how we compensate for a bit profile that is not "built in" to the program...We're wondering what folks have done to automate rounding edges on top AND bottom edge in one pass, and what problems you have faced and solved... Onsrud has a straight / roundover cutter in their new product line for a top side radius we're considering for the time being.

Anybody using these techniques? Any suggetions on where to look elsewhere on the forum?

Also, anybody cutting vinyl or linoleum floor tile? Curious.....

Thanks!

Matt Barinholtz
Covenant House Washington, D.C.
artisans(at)chdc(dot)org

[rgbrown@itexas.net]

Matt,

Woodbits.com has "plunging roundover" bits at a reasonable cost on page 6.

I can't tell you how "Parts Gizzard" does offsets as I don't have the program but, I would think just defining "cut on line" as if you did not want an offset with the proper bit would give you the "island" you need.

[pjweber@insightbb.com]

Looking at the catalog that Ron Brown mentioned, .
Page 7 has an adjustable "Double Corner Round" bit that looks like it would do both sides of the edge at once if the part were elevated off the table. This is where the "pod" comes in.

I don't think Part Wizard is smart enough to handle this type of bit automatically - you will have to do your own programming at the beginning and end of each cut to handle the fact that you need to bring this bit to and from the work horizontally, not vertically. I've done this for the case of cutting grooves on the edges of parts with slot cutting bits.

[gerald_d]

Rounding over with a ShopBot is a real pain!

Any slight variation in flatness of the workpiece on the table is immediately visible when the rounding over cutter is following the ShopBot's rails instead of the workpiece's surface. If your table is not perfectly surfaced, or there is a grain of sawdust between the table and the workpiece, or if the workpiece sheet is not exactly the same thickness at all points, then you quickly see a bad rounding over job.

Rounding over in a ShopBot will only become attractive if there is a "surface-riding" system where the z-depth is continuously adjusted to follow the surface under it.

[graphicmetals]

As usual, Gerald is right-on (or is "spot-on" the term in South Africa?). Everything would have to be perfectly (or very near so) flat and square (and stay that way!) to make this method viable.

We cut the profile on the ShopBot, then using a jig, we hand rout the round over(s).

-Kevin

[bill.young]

This may not give you the look that you want, but what about using a bullnose bit that's bigger than your material? It will have a "rounded" look but can stand a little variation in thickness or flatness.


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[toys]

Of course there is the Virtual leveler. Its sort of a pain to operated but it does help. You can set the probe resolution on it and probe as often or as little as you want. It requires the True Basic program language to run though. I havn't tried it on round-overs yet but it works with datos. And you need to re-run the program for each new piece if your worried about dust making a differance.

[artisan]

I may be missing something here... but couldn't you just do this on a regular router table so much faster...first cutting the shapes with the Bot and then edging on a standard table ?

[gerald_d]

Exactly, Darrell. Matt complained about using a hand router in his opening post at the start of this thread. Maybe he hasn't tried a table router yet?

[Matt Barinholtz, Covenant House Washington D.C.]

Thanks for the feedback - and warnings about the pitfalls! We've been rounding over edges on a pair of router tables, and the difficult part is teaching our students to start and stop inside and outside of marks on a template or the workpiece. We are always wondering how other folks have approached these situations - before we take the time to make mistakes that may have been made before.

Excellent suggestion, Bill - we'll go that direction first.

I can imagine the buckling/warping problems that uneven edges would pose - we rely on the vacuum of the table to solve the majority of that problem, but still battle warped / twisted stock in the humidity that has smothered the mid atlantic over the past month.

We're still interested in pods for cutting elevated pieces - what pitfalls do we face with stock falling away from the piece? is this managed with bridges? The huge cnc center that I was watching was able to zip it's way around so fast, it seemed that the waste stock hardly had a chance to sag before it was snipped away... Harold - did you elevate your stock when slotting the sides? This may be a solution for installing edging on some of our furnishings.

Also, anybody cutting linoleum or vinyl floor tiles? We're specifically interested in recommendations for cutters and speeds, before we light our table on fire or melt too much tile. I suppose I could always call Onsrud...

We appreciate your feedback - I look forward to hearing more!

Matt Barinholtz
Covenant House Washington Artisans Program
artisans(at)chdc(dot)org

[davidallen]

I've used vacuum pods to elevate workpieces. with about 10 sq.in. of vacuum area, it holds fairly well. the main problem I had was supporting the work to prevent flex between pods. I used wood planned to the same thickness as the pods, worked well.

one advantage, you only need to re-flatten the pods, not the entire surface.

[pjweber@insightbb.com]

Matt, yes I did elevate the stock when slotting the edges, but this was because I needed clearance for the nut holding the slot cutter on its arbor.

To deal with the scrap falling away when supporting the work on pods, I program in extra cuts so the scrap falls away in managable sections.

[Pete Meacham]

Hi, has anyone tried the Vac-U-Clamp system recently introduced by Rockler? Could be an inexpensive vacuum pod system for ShopBotters.

http://www.rockler.com/ecom7/showdetl.cfm?offerings_id=10571&objectgroup_id=332 &catid=54&DID=6

thanks, Pete

[toys]

I Think those clamps are quite expensive. Then only thing that is really worth the money on it is the valve that blocks vacuum loss if you loose a pod. You can build a system lot less out of MDF. You can get some round 1/4 diameter EDPM sponge rubber cord from MSC http://www.mscdirect.com/ (item #31944630 its about 15$ for a 100' coil) use a round nose bit and cut a track 3/16 deep for the cord. This tucks in real nice and stays put. You can also use crazy glue to weld this rubber together forming an "O" ring. Hollow out a chamber under in your MDF PUCK. If you want it like the Rockler system then do the same to booth sides of the pod and seal your table top so the vacuum holds from both sides. Add some inexpensive tubing from a home improvement or hardware store. Add some plastic nipples. The most expensive part would be the venturi vacuum which is $99.00 from http://www.qualityvak.com/venturi.html. Or save your money for a dedicated vacuum pump. To seal the mdf I've thinned out 100% silicone with white gas. (This is an easy one coat step that seals the mdf very well.) Yes its a little more work to make your own, but they work just as well and if you run over it by accident its cheap and easy to replace. Plus you can make the puck any shape that you want so that it perfectly supports the work piece with just a little over hang. This keeps the work very flat/uniform. I've made vacuum pods like this for my puzzle backing boards. One day I'm going to try making a valve with a spring and ball. I was thinking of flipping my pod over and plunging the bit in until just the tip penitrates the other side. Then put in a ball and spring and maybe a glued on washer to retain the spring and valve. It will take some experimenting to get the right spring for the right preasure so the workpiece would push down on the ball (which I guess would have to be smaller in diameter then the hole diamer to allow air to pass) opening the vacuum for air to flow out of the pod. When released the spring would push the ball up blocking the flow of air.

I too would like to do the round over with the shopbot, but for my puzzle application is just easier to roundover with my table router.
So. . . what about making a floating head system to glide over the work. One that locks when you want to use it in the standard way. You would need to be able to quickly remove the foot. What kind of slide could you use? I tried to build one of these, but it caused the router to stick out too far and introduced a lot of flex.

[davidallen]

Pete,

that's the system I used. there are cheaper ways to do it.

a good introduction to vacuum holding is to work through the stepped miter, box project from ShopBot. it includes a custom sized vacuum table, which building and using, will show you the basic principles.

if you want it quick and generic though, the pod concept is a better fit.

da

[gerald_d]

David Fisk, you asked "What kind of slide could you use?" Well, your z-axis already has a great slide, if you mechanically disconnect the motor/gear drive . . . . . . .

[benchmark@tesco.net]

David F, you would not like woodworking the UK as four vacumm pucks "without" the venturi vacuum and tubing is $263 inc tax, UK munufactured.

Paul

[toys]

Here is a revised drawing of the pod idea

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[gerald_d]

You guys are taking us back (http://www.talkshopbot.com/forum/messages/27/735.html?#POST3980) about 2 years.

[rgbrown@itexas.net]

I bought a vanturi vacuum "pump" at Harbor Freight for ~$10 on sale a while back. Square bottom bits work well for "O-Ring" seals and, they give the ring somewhere to go when under pressure.

For parts over about 25 square inches, it makes more sense to me to use a "ShopVac" and a "low pressure system". I buy my vacuum motors for low-pressure systems for about $15 from Surplus Center. Damn they are make some racket.

[toys]

Gerald, it must be a good topic to come back like this. I thought you didn't use a vacuum system or was that someone else?

On the floating head: So what is needed is an easy/quick way to disconnect the motor drive. It seems to me you still need it though to do Zups and move to the next piece. Any ideas? ... thinking out loud. . . Maybe, some sort of pin that is pulled in and out by activating an output switch hooked to a air cylinder? I guess it would be much different for rack and pinnion z's and ball screw z's. I quess a bpin wouldn't work since it might not line up properly when your finished with the edging. Hmmm, ... maybe some sort of device that grabs or clamps the z carriage to the drive motor mechanism. Then if it wasn't lined up it wouldn't matter.

Maybe we can all pound our heads together and come up with a solid (non-virtual) solution for floating head idea? Sure would be nice for putting profiles on boards.

[gerald_d]

We still don't use a vacuum system as the primary method of holding down. We use clamps, screws, etc, In addition to that, we use a shopvac to suck boards down flat, but we don't trust this to stop parts from sliding around.

You sound as if you are talking about a "clutch" between the motor and the pinion gear. Now, where is the catalog that I had on small electro clutches . . . . *rummages in dusty drawers*

[toys]

Gerald that sounds like it would work on the PRT (Rack&pinnion) but what about he PR(Ball Screw)? Any Ideas for it? On my set up there is a worm drive clamp around the mechanism with the balls in it and a piece of aluminium.

[sheldon@dingwallguitars.com]

Two ideas come to mind:

1 - a delrin ring surrounding the bit, set a bit lower than the lowest sag point to force the work down to a common level.

2 - build a set of microswitches into the ring to send feedback to the SW to raise or lower the Z. Somewhat similar to the Zzero system.

[gerald_d]

A table router is still the most appealing at this point

[artisan]

To ....possibly....save time, you could make your intial edge run with the Shopbot after you've made your cutting run. You could leave "tabs" in place with no problem to hold the work. Then, you would cut loose the work and move it to the standard router table and use a bit that "laps" over your initial edge run slightly. This would remove the tab marks at the same time. This might save you a little time. All the other stuff sounds neat....but unless you get a government contract (laughing).... too hard to make money with. It would be fun to watch however....D

[artisan]

OR....you could put each piece on a pod.... run the PROBE over the entire lot...and use the bullnose bit that Bill suggested in a 3D file to TOTALLY automate everything...(yeah I know)....D

[rgbrown@itexas.net]

2690

Here is the part I was cutting

[rgbrown@itexas.net]

2691

Here is my vacuum table and the "mask" I used. I can configure the gasket as I see fit. On this part I set it to leave .010" on the bottom. The actual "tab" remaining measured from ~.012" to .019". The reason for the great variation is I haven't flattened my top in several months.

One should be able to see the "port", a $15 vacuum motor is below, and the gasket grid. I used 3/8" "Caulk saver poly-foam" on this table.

I would think the ~.010" deviation would not be noticed using a "bull-nose" bit like Bill Young suggested.

Your mileage may vary.

[kerrazy]

ROn I am very intrigued, how big of a piece can you hold down with this?

Dale

[kerrazy]

Hey could you also post a picture of your vaccuum mount as well?
Dale

[rgbrown@itexas.net]

I think the question should be how SMALL of a piece on can hold down. I put the small end at ~25 square inches - about a 4" X 6" piece. Larger pieces are easier to hold except for the initial "pull down".

The "Grid" allows the "Vacuum" to get to all of the part until one reaches the gasket. On my "next" table, I plan a large plenum 8nder the table that will actually make the table a large box beam type structure. It will have as many as 4 vacuum motors and I am thinking 16 or so ports on a 4' X 8' area. These multiple vacuum motors will be all on for parts that need the volume for "pull down" and through a series of micro switches sense when they can be shut down and check valves will keep the air from back-flowing through the motors.

I think all the parts can be made on the ShopBot or in a "normal" wood working shop. I plan on spending a stunning $150 dollars on my "new" table when I build it. I think it will be superior to many of the tables I have used and seen in other shops where the vacuum pumps cost $5000.


2692

[gerald_d]

Ron, I wonder where (http://www.talkshopbot.com/forum/messages/28/466.html?#POST2177) you get some of your crazy ideas from?


I really like your practical approach. Have you included for ear protection in the $150, because that is the only single downside that I see.

[toys]

Sheldon, What is a delrin ring? How does it work?

[rgbrown@itexas.net]

Gerald,

Although I don't remember that thread, there are some good ideas there.

As far as getting "Ideas" from other sources, yes, I steal any idea I think worthwhile and apply it as I need it. I have been vacuum laminating large panels since the mid 1980's as well as using vacuum jigs for parts holding on plastic parts on table routers from the same time period.

My table design is getting near complete in my mind. And yes, there will be "Muffler boxes" over the vacuum motors and other impovements including down-draft dust control built in the system. The built in "T-Tracks" you failed to copywrite will be there too.

One could also overlay a vacuum table like the one I propose to build with specialty "plattens" and "pods" for doing the work Matt started this thread with.

David Fisk - Delrin is a very stable plastic. Pod supports made of Delrin would be nice, but are not necessary. Almost any industrial plastic that is non-porus would work.

[gerald_d]

Ron, if you know the rules (http://www.talkshopbot.com/forum/messages/373/374.html?1005250081) of this Forum, "All...postings become the property of ShopBot Tools ", you will understand why I never post anything important here.

[rgbrown@itexas.net]

Well Gerald,

Most patent law states if a project is revealed in a public way befroe the patent is applied for it is considered "public domain". Most, if not all, of the things discussed here would come under the classification of "prior art" if sited in a patent application or law suit.

Anyone working in "intellectual property" or those who have worked in development for companies who own "intellectual property" know who they can talk to and what they can talk about and to what level. I have had "my tail reamed" for handing project notes and discussions to a project head's secretary rather than the project head or placing it in a sealed envelope.

The "All...postings become the property of" statement would protect ShopBot if something mentioned here ended up in a ShopBot tool and a lawsuit too. It will also be a defense for anyone who uses a process described here if it ended up in a law suit.

When I finnish my new table, most the information and details will be offered in an open format. As my designs are built for my machine on my "home-built table" at a size that is not normal, I don't plan on publishing plans and cutting files. The image is the plenum rendering and base plate of the system.

Ron Brown

Diplomacy is the art of saying 'Nice doggie' until you can find a rock. - Will Rogers


2693

[gerald_d]

Have I caused a serious thread drift again? This (http://www.talkshopbot.com/forum/messages/2/611.html?) is the right thread for copyright issues.

But, if I recommend something dangerous here on this forum, and someone loses a limb, then ShopBot takes the can? Okay, okay, I'll stop the mischief now.


Your pic looks like one of those wafer things that stick out of ice-cream, or the waffle under the ice-cream.

[Ron Brown]

"Have I caused a serious thread drift again?"

Yep, and you will get demerits and bad Ju-Ju when the moderator gets back.....

[gerald_d]

oops

[toys]

Back to the original issue of rounding over on a shopbot... Sheldon this delring "plastic" would be a sort of probe that would send feed back to automatically adjust the depth? Am I missing something? Sounds like you would need more than a micro switch something more like an encoder, because of the constantly changing surface. The probe works because it comes up and then plunges down triggering the switch in a one time event.

[rgbrown@itexas.net]

David,

My opinion is a properly surfaced table takes care of most, if not all, of the "problem". Bill Young has worked on something similar to what Sheldon proposed.

A "pot" - the variable resistor, could be used to adjust bit height. Radio-control model airplanes and such use a feed-back system for this sort of control. I don't know how it could be interfaced into the ShopBot but a seperate control and "rack" or "cam" might be used for the "fine control".

Of course, each solution will create a minimum of two more problems to solve....

[toys]

So if the probe had a pot connected to it, it would give a variable resistance feed back that could be used on . . . maybe a small circuit board that would send pulses back to the ShopBot on two input switch's one for plunging, and one for climbing. Then you could write a small sub routine that would lift the router on. . . lets say input from switch 1 and plunge from input on switch two. Boy I wished I would have paid better attention when I was learning about basic circuits. It sure would come in handy. This gadget has the potential for helping out a lot toward Brians trouble and others. Anybody out there that could design a circuit to do this?
Ted Hall, you could do this couldn't you?

[rgbrown@itexas.net]

David,

It would not be your standard "ShopBot Probe" but a variable resister follower, in my version and mind. The curcuit I imagine would be a "Pulse matching" curcuit as used in R/C servos.

I think "turn-off" and "turn-on" commands would need to be written into the files to keep the bit from hunting for a point that didn't exist.