[dberndt]

Hi,

The following is just sort of an semi-serious exercise in design brainstorming.

I've been thinking about making on ofthese but scaled up to be on some grander scale, like 6 feet by 4.5 feet.
Now I havent really mapped it out yet or anything but I was thinking about having 10 pins per square inch or so. That'd probably be something like a .25" diameter rod, 9 per square inch or some such thing. That'd be like ~35000 rods/pins.

So the drilling part doesnt seem to hard, make the back board in smallish pieces and then attach it all together or get a large router table to do it. One of the questions would be what to use for a backing material, how thick etc.
Secondly the pins, well thats alot of pins, and each one needs to have one end crushed/mushroomed out so that it is retained. Some sort of an automated gadget for this would be good, or prebought because if each rod was 1" long that'd be ~2916 feet of .25"dia rod. Which isnt a small amount.

So, how would you go about doing this, what changes would you make, what insights do you have

[HuFlungDung]

Doesn't the back have to be left open to allow somewhere to place the object to form the relief?

One problem you'd have is the substantial weight of the whole thing: 800 pounds or so. 1" pin length may not give you all that much travel to form a significant relief, since the pins must be nested for some length. Depending on what you wanted to do, maybe a 2" long pin would be more practical.

Perhaps headless pins would be better, a spiral roll pin would be a tiny bit less heavy. Just let them nest against one another. Perhaps if you magnetized the whole lot of them (roll pins are hardened and probably will acquire and hold some residual magnetism), they would kind of stick together well enough to stay put (or maybe not). Perhaps placing a real magetic "booster rod" every so often would accomplish the same thing.

You might want to fashion some kind of a vise type frame for it, so you could tighten the whole thing up to lock in a shape in the relief.

[Bloy2004]

I've seen several versions of this "toy". The older one was heavy despite its small size because of metal rods/pins. The newer one used composite or plastic pins which made it considerably lighter and also "glowed" neon when under certain lighting conditions.
The big model could use these same plastic rods(larger diameter) to decrease its weight.
Using this material would allow using heat and jigs to create the needed "mushroom" ends on the pins.

[ViperTX]

Well....I'm not sure what the purpose is...but if it does not have to remain vertical you might use some of that memory foam / gel to get the same result.

[Kmed]

Well if I was going to do that I would probably use 1/4" polycarbonates for the flat areas and add a few standoffs to replace a few of the pins to keep everything flat. Then you could actually use off the shelf hollow plastic rod, and mushroom the end by heating it up and pressing it into a mold. You could also use a heated mold and just press each pin in. Another option for 35,000 pins would be to injection mold them. I would also have a custom bit made to dril and ream the hole at the same time that way you have good sliding action and only have to drill the holes once. Cut down on the cycle time.

[dberndt]

Hmmm, plastic pins. That seems like an excellent idea. Except I was playing around at one point with the idea of magnetizing them or using a magnet to move the pins around, neither would obviously be possible with the plastic pins. It's a tradeoff.

As far as pin length goes, yes, maybe something like 1.5" or 2" length makes sense because I had hoped to have most of the 1" available to play with.

The unit will be permanently installed in a vertical position, thanks for bringing up the weight issue. That will potentially be a problem. Mainly in terms of what backing material do I use to hold the pins. Some sort of uhmw or something like that in a sheet form might be a good choice? One of those self lubricating plastics should be easy to drill and provide smooth pin action. I was hoping to make the large panel out of many smaller panels joined together somehow in a nearly seamless way. Welll it doesnt matter if there is a seam the important thing is that it be strong and that it not interrupt pin flow so that its not obvious there.

[ViperTX]

You haven't mentioned a purpose for this.

Another thought which I would consider more exciting is creating a hologram...any thoughts....

[dberndt]

The purpose is ofcourse top secret. Errr, ummm, actually its more or less an attempt at an art piece. It will render shapes by using a stepper motor setup in the rear. Sort of a piece of continuous moving art. I had thoughts about letting it render fractals, that should keep it busy, give it a few patterns to switch between and it'd always be making nice new designs.

[lerman]

Have you considered using nails. 60d nails should be around the right diameter -- and they already have heads.

Ken

[dberndt]

Lerman gets a gold star.


Yes, some sort of nail with the right finish and shape would be excellent and I'm sure thats where the project will end up heading. I am inclined however to think that this is the easy part of the project and getting the 10000's of holes in the backboard might be the harder part.

[nervis1]

I can't think of anything to add to the above...but when you are finished I want to be the first one to get a running start and jump into it.

[HuFlungDung]

I thought about the headed pin, but thought maybe it would add the unnecessary complexity of making the "tube sheet", which is a formidable job.

What if you were to simply use plastic soda straws? These have a good length, low mass and would pack together nicely (with good compressibility). All you might have to do is devise a method to close off the ends, with a suitable material which might have more aesthetic properties than hacked off steel pins.

Are you going to program the stepper system to push the pins a certain distance outwards?

[garagefela]

Hi,
At our museum there is a kids area set up and they have a toy exactly like the one you want to make, although it seems you are not making it as a toy rather a moving wall.

From memory its around 5 feet high and 6 feet wide and uses plastic pins in a plastic board, I think the pins had around an inch of movement, I use plastic as a broad term not sure what it was. The kids (and a few fully grown "kids" as well) lean into it, press faces, hands, arms etc and have a good old time against it.

One really good thing it has is a reset button this must move a full size board from the rear to push all the pins out at once to make the "canvas" new again.

The main thing I remember about it was the sheer amount of holes in the board and as a machinist I could imagine the drill cycle time

Cheers all M

[sendkeys]

i was at target today playing around looking at the sales. saw one of the toys there. reminded me of your post. It was the metal stainless steel type. And the sucker was heavy and hard to push. Think i would go with plastic and or maybe aluminum welding rods/wire. As if you go with nails/iron it will be Way to heavy and you will not be able to push it.

[dberndt]

Yes, incase I hadnt made it clear I am going to have a stepper or similar motion system behind the unit to create the drawings on the "wall". So forces required to move each pin or whatever arent really significant to me I suspect. I was planning on using something like a circular bit or maybe a slightly modified V-bit from a router at like 45 degrees. It would be used to push the pins in as it travels creating the design. So smooth motion on the pins is a plus, and I certainly can't have them jamming, but the forces that the steppers will easily put out will surely overcome the resistance of the pins. I plan on treating the surface as though it were a solid, and not individual rods, so the pins will almost always be pushed down from the sides by the 45 degree or spherical profile (some profile experimentation needed) of the bit. This does mean that the more resolution i want in the final output the smaller the cutter and thus the smaller the Z depth achieved by each pass due to the smaller cutter. So because the cutter will only be in contact with a few rods at once the forces required are quite small in comparison to those that you might see when trying to imprint an entire face at once or something like that. Because as I have said the pins will more or less be plowed into from the side by what is in effect a wedge it is important that the piece be fairly rigid so it does translate the motion into travel in the depth dimension instead of just bending and mucking things up. This is why things like straws might be a bit too weak.

The default position of the pins will be pushed in with respect to the viewing surface, so that the stepper system can come along and push them out the appropriate amount. I will devise some sort of a blade type thing to traverse the front of the plate in order to wipe the board and put all the pins back at 0.

I've used the words, tool, cutter, bit, etc in a fairly interchangable sense in this post please just take it all to me some sort of a sloping profile that allows the "tool" to plow into the side of the pin and create motion in the perpendicular axis.

Garagefela, you know thats pretty close to garageflea right? Anyways, I was hoping you could estimate for me what the diameter of the pins they use in the museum installation is and what sort of spacing they use, ie how tightly packed they are.

[HuFlungDung]

Any chance that a wooden dowel could be found that was a close enough fit inside of a plastic straw? If so, then you could assemble the tubesheet out of the straws (bound together maybe with some kind of casting material). The dowels would be a slide fit inside the straw, and perhaps could be reset with a vacuum nozzle from behind the unit.

You could use a standard gcode program to create the toolpath in several levels (like Z level roughing in OneCNC), so that your roller tool did not have to make too deep of an impression in one go.

[garagefela]

Hello dberndt and everyone,
Unfortunately I wanted the user name garagefella ( double L )which is what I use elsewhere but it seems we are limited to 10 characters and could only have garagefela which my wife calls garage feeler (sounds sort of perverted). Although garageflea would have done, both in 10 characters as well as character

Somehow I knew you would ask something about the wall I was mentioning (damm it) only because I don't recall much of the actual dimensions of the pins or spacings. I am actually on holidays over the Xmas break and coincentally my nearly 4 year old daughter has been pestering me to take her back to the museum, if I go soon I will take in a digital cam and take some happy snaps of the wall. (and sneak in a plastic vernier caliper!!!)

[dberndt]

Ok, so it seems to me that something like McMaster Carr #9412K15 might due the trick. I wish I had more info, is it really honecomb in that the cells are 6 sides or 8 sided or whatever, and not round? and if it isnt round what is the maximum diameter of a round peg that can be fit in the holes.

Edit, fixed link and also looked around at perforated sheet. Seems more ideal, I really wish that there was some 1/2" or bigger stuff because i'm concered about a large piece of the stuff having too much flex. Heres anothe McMaster Carr part number 92985T28

[HuFlungDung]

Perhaps you can make a sandwich of two pieces of the perforated sheet, bonded to a layer of the honeycomb panel. Hopefully the spacing would work out so that you could offset one relative to the other, without obscuring any of the holes in the top or bottom. I suspect that the honeycomb material is too delicate to be used directly as a guide for your pins. The hole dimensions are nominal, you might have to allow .01" to .03" leeway for actually fitting the pins.

[lerman]

Since you've said that the exact spacing doesn't matter, consider this:

Get some lengths of tinned brass tubing (you might have to tin it yourself) of a suitable inside diameter. Chop them into two inch lengths and put them in a form, standing on end. Jog the form and get them all aligned and jammed together. Apply flux and run them through an oven to reflow solder them. (You did want to build a four foot wide reflow converyor oven didn't you?) You might need a little paste solder between the tubes. Brass tubing is readily available in a large number of nesting sizes.

You might even consider using lengths of tubing for the "plungers". Find someone with a screw machine to make you thirty thousand sets of plugs of the right shape. A slight taper and a shoulder on the shaft end would let you insert them in the tube and then press to seat them.

Ken