Mini Vacuum Table

[big_teee]

No need to make this stuff, just Hire John, and Jonson to do it!
Good job Guys!

[Jason Rodgers]

Go for it! I spent too many years "planning" for something that is so simple. Most of the questions that you have will answer themselves once you take action. It's not a big gamble. I had less than $25 invested into this entire experiment, and was making usable covers on my first hits. JFDI

I have everything I would need, save for the plastic, in the shop. "Planning" for me is doing the research, like you see here, to get grounded in the concept before jumping in. I really appreciate this thread.

I tried working with a smaller format. I don't recommend it. The covers weren't as nice, and I had more attrition due to working with smaller pieces. jonson was spot-on. 6X6 is too small for me to get the best results. It's not worth trying to save a few pennies on material. My final cost on 9X9 ABS blanks is below fifty cents ea. It's not worth it.

Ok, noted. I might try 8x8, then, as that divides into big sheets evenly.

It's ALL about getting the plastic to the right temperature. The best way to learn is to do it. Once you know what is too hot, you'll know when to stop heating.

I'll probably start with the kitchen oven, but I have an idea for a method using a heat gun. Gonna hafta grab one of those, too, I guess. Dang, my cost just went up!

I've got a new oven for heating plastic that I haven't had a chance to try yet. At $6 it was a great deal from the Goodwill store. It's a small convection oven with digital control. Cuisinart Exact Heat Convection Toaster Oven/Broiler - Contemporary - Toasters - by HPP Enterprises Stay Tuned.

Hey, that's fancy! A Cuisinart for $6?! Sweet!

In the Acrylite data sheet I referenced, there is some info about stretching the heated plastic when using a positive mold "drape method," as we're talking about here. The heated sheet is suspended over the mold, compressed air is shot in to slightly lift and billow the sagging plastic, and then it is introduced to the mold and vacuum. I wonder if it would be worth it to try to incorporate this step?

Also, for the perforated vacuum platen, there are some good suggestions about counter-boring the backside of the holes, or using slits, to increase velocity. This allows for faster evacuation in order to pull down the plastic before it can cool, thus achieving better detail and avoiding splits/cracks.

One of the things I'd like to eventually try is molding a logo in the top of the pickup cover. I read elsewhere that this requires drilling very fine vacuum holes in the bottom of small details: essentially, your mold must have additional vacuum paths within it, so that the plastic can be drawn down into all surfaces.

Building a vacuum table is a couple steps down the line for me in my current line-up of projects - finishing a uke, a 3/4 size guitar, an OM size guitar, and an electric that will get the first set of pickups in thermoformed covers - but I'll post when I do. Until then, I shall follow this thread and any new developments.

[David King]

Jason if you dig around a bit I bet you'll be able to score someone's stash of thermo-forming plastic on ebay or Craigslist.

[Jason Rodgers]

Jason if you dig around a bit I bet you'll be able to score someone's stash of thermo-forming plastic on ebay or Craigslist.

Good idea! For every person who decides to pursue a new path, there are probably 10 who have decided to abandon it!

Turns out I had a couple spare hours yesterday (and no, that's not Daylight Savings joke), so I went ahead and built the box. Looks like this project just got bumped up the line!

[David King]

Sign shops use a lot of this plastic to make raised letter signs in big vacuum tables. It's possible they would sell you some cut offs or pieces that got screwed up.

[John_H]

In the Acrylite data sheet I referenced, there is some info about stretching the heated plastic when using a positive mold "drape method," as we're talking about here. The heated sheet is suspended over the mold, compressed air is shot in to slightly lift and billow the sagging plastic, and then it is introduced to the mold and vacuum. I wonder if it would be worth it to try to incorporate this step?

It's a small piece of plastic that we're dealing with here. I can see how what you describe would be a benefit on a large scale where the hot material might sag excessively.

Also, for the perforated vacuum platen, there are some good suggestions about counter-boring the backside of the holes, or using slits, to increase velocity. This allows for faster evacuation in order to pull down the plastic before it can cool, thus achieving better detail and avoiding splits/cracks.

Again, this looks like something that would work better on a large scale, but on a small surface with a powerful vacuum there couldn't be much difference. What size vacuum hose are you using?

One of the things I'd like to eventually try is molding a logo in the top of the pickup cover. I read elsewhere that this requires drilling very fine vacuum holes in the bottom of small details: essentially, your mold must have additional vacuum paths within it, so that the plastic can be drawn down into all surfaces.

I haven't tried it, but one idea I had was to make a little stamp with a logo and mash it into the plastic while it's still hot. It's a simple approach, but might work pretty well.

...so I went ahead and built the box. Looks like this project just got bumped up the line!

Cool, I'm assuming that you went with 8x8. That should work fine. I'm sure that the cost per sheet at your local supplier is much less than with the cutting fee tacked on. They roll it up just as they would with a piece of plastic laminate, so it's easy to carry. I cut it into blanks on my table saw. I buy the HIPS online in 18x18 pieces. That's how I ended up with 9x9 modules.

[Jason Rodgers]

What size vacuum hose are you using?

It'll be the standard 2.5" shop vac hose. I have one of the bigger RIDGID vacs pulling through an Oneida mini-cyclone. It sucks real good.

I haven't tried it, but one idea I had was to make a little stamp with a logo and mash it into the plastic while it's still hot. It's a simple approach, but might work pretty well.

I considered that, too, even using a female mold over the top of the whole thing, but I think that is a more advanced thermoforming trick. A stamp of some sort should work fine, though you might have to experiment with how much pressure you use.

Cool, I'm assuming that you went with 8x8. That should work fine. I'm sure that the cost per sheet at your local supplier is much less than with the cutting fee tacked on. They roll it up just as they would with a piece of plastic laminate, so it's easy to carry. I cut it into blanks on my table saw. I buy the HIPS online in 18x18 pieces. That's how I ended up with 9x9 modules.

Yep, an 8x8 table. And yes, my closest TAP Plastics is down the street from my Home Depot, so it'll be convenient and inexpensive. From looking at their ordering page, I can't make out if they even charge for cutting sheets down. They just ask for a day or two notice to build your order.

[jonson]

I've tried most of the getting a name tricks in the covers and very difficult. You are pulling on the inside so anything you engrave in the buck needs to be a lot bigger than what you want to see one the outside and it still comes out as a rounded mess and never sharp as required. the best success I had was to pull a cover down into a depression as one would do a drawn metal cover and I glued brass letters into the bottom of the mold but backwards reading. Not bad but no cigar either. I did a set of 7 string pickup specials a short while ago and the young guy wanted a name in them and routing them in with an engraving bit follwing a pattern was the ideal way and filling them with paint after similar to tone and volume on knobs. A stamp may work but the plastic will try and return to it's former shape and branding them is probably a fire hazzarding nono. Good luck with all you do and keep everybody up to date with your winings and the failures so we know where not to tread.

[Jason Rodgers]

I've tried most of the getting a name tricks in the covers and very difficult.

Ooo, you know what would work and look cool? Masked and sand-blasted lettering. Of course, you'd need access to a sand-blaster, but you could get a single custom template cut in stainless shim stock or some decals, give it a quick shot of sand, and it would etch the unmasked areas.

EDIT: This would work, and not be too aggressive http://www.garagenight.tv/diy-soda-b...own-rig-cheap/

[jonson]

Got to admit Jason to a been there done it with the blasting and that works. Spence bought out his Area 51 buckers a few years ago and I lasered some .5 mm stainless masks for him and then he blasted them in the metal covers with an airbrush sand blaster normaly sold as an air eraser. Takes a bit to do it in plastic but I have tried it and changed to a bigger system and glass bead medium. It works well.

[Jason Rodgers]

Ha! Sweet! Yeah, nothing new under the sun.

[Bruce Johnson]

Ha! Sweet! Yeah, nothing new under the sun.

My recommendation for putting a crisp logo onto a thin vacuum-formed shell is to mechanically emboss it. Have an EDM shop make up a steel block with your logo on it (backwards, of course). Sort of like a branding iron. It doesn't have to be strong. Mount that to the quill of a little tabletop arbor press. Make up a wooden block that fits inside the shell to support the backside. Lightly press the logo into the surface of the plastic, cold. It should give you a nice crisp logo, fast and repeatable. That plastic is very soft, and will form out with very low pressure. Fine lines will look about like engraving. You can also have the EDM shop put a textured surface inside the fill of the letters, if you like.

Once the logo is embossed in the plastic, you can also paint fill it. Dab on some thin paint, let it dry, and lightly drag a scraper over the surface.

[Jason Rodgers]

My table and sheet clamping frames are built. I might not have a chance to do any tests until winter break, but I'll update.

[Jason Rodgers]

So I did some test runs of my setup this weekend. Should I post pics here, to maintain the topic, or start another?

[jonson]

Post it here Bro and keep all the info under one roof rather than spread it about. Good learning curves should become stickies rather than secrets or having newbies spending time hunting threads. This isn't winding information this is do the overpriced parts guys no favours.