Cutting foam sheets... with a needle!

jhitesma

Some guy in the desert
Mentor
Okay... all's good :)

In the simplest case, the stack (probably best if glued up with some of repositionable spray glue) is placed on the work surface (if smooth enough) and the piece to be cut is placed on top of the stack, over the holes layer. Lightly pressed down flat, the vacuum should take hold and the entire stack, along with the workpiece, is sucked down onto the work surface... hopefully under the tool head of your CNC :eek:

Few notes on this.

I did glue mine with spray glue. One thing to watch for is warping. Weight it down with a large board while it drys and will want to warp otherwise. Also once it's built store it flat (and best with weight on it) as I've found it wants to warp if stored upright or even just sitting.

I want to make a new one with a wooden frame that it glues into so it will stay flat and I can position it easier. In fact I may just make the two lower layers out of wood to make sure it stays flat.

I don't really even have to press mine down except in the corners when it starts to warp. Even with a tiny $20 super cheap shop vac it makes enough vacuum to hold the pad to the table with nothing on top - it's not a super strong grip so you can still reposition it but it's strong enough that the weight of the vacuum hose won't pull it out of position.

And once you put your workpiece on top - it's not going anywhere. If you want/need to reposition anything you either have to pull the plenum out or lift the workpiece and let some vacuum out. (which is the other reason I want to add a wooden frame - so it can act as a "stop" to hold the workpiece aligned with the left and bottom edges more accurately.)

The top layer of the stack, the "holes" sheet, becomes the sacrificial layer and will eventually have to be replaced... but that should be many sheets down the road. A sheet of DTFB from the local dollar store, 15-20 minutes cutting the holes in the sheet, and you should be back in business :)

I've cut more foam than I can track (probably 2-3 cases of it at this point) since building my vac table and my top sheet is still going. It's getting pretty worn in some areas (for some reason the lower left corner seems to get more use than the rest even though I usually cut full sheets...I guess I just tend to put more small parts down there when I lay out sheets!) and I'm starting to think about replacing it....but not in any rush. And due to the warping I'm experiencing with the whole thing I'll probably just remake all of it rather than replace just the top sheet. (I did use reposition-able spray glue for the top sheet so it can be removed...but I kind of suspect it won't come off cleanly enough to be worth replacing.)
 

dkj4linux

Elite member
Hey, Jason! I hope all is as good as it can be -- and getting better -- with you and your daughter. I'm still thinking and praying for you all.

The wooden frame thing would work, of course... we're thinking along the same lines. Back when I was doing the Phlatprinter-style foam cutter and was playing with the window screen frame materials, I came up with a little vacuum pad that I think could be made to work. I stopped short of trying to figure out how best to stick a plenum through the side wall... maybe just common aquarium airline and printed(?) tees and fittings could work without collapsing? Or, maybe Mark's plenum modded with round finger-tips -- or adapters made -- that could simply poke through holes drilled through the frame piece? [Aren't 3d printers great? :)]

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This particular little frame has the aluminum oriented 90* from how it's used with screen material... and a glass fitted into the groove. I printed custom corner pieces which fit nicely into the cut end of the frame aluminum and it was stupid easy to build an custom sized, surprising sturdy, flat, and accurate frame.

I have a larger one already for DTFB... I think I drag it out and start playing with it. Maybe it doesn't need any glue at all... just a lightweight frame around it to keep the stack in alignment? :)

-- David
 
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Hai-Lee

Old and Bold RC PILOT
Just your thoughts on the possible use of thin MDF with a sheet of FB adhered to it as a cutting board or bed for this machine. I understand that MDF, (properly sealed), is warp resistant even though a little heavy. I intend to build my machine to be stored hanging on a wall because floor space is at a premium.

Eventually I will try the vacuum bed design but it will definitely be a much later part of the build.

have fun!
 

jhitesma

Some guy in the desert
Mentor
Hey, Jason! I hope all is as good as it can be -- and getting better -- with you and your daughter. I'm still thinking and praying for you all.

We're surviving. There are ups and downs but we're trying to stay positive.

I have a larger one already for DTFB... I think I drag it out and start playing with it. Maybe it doesn't need any glue at all... just a lightweight frame around it to keep the stack in alignment? :)

I think the glue will still be needed due to the tendency of foam board to warp. The vacuum isn't really strong enough to overcome the warping by itself...at least not with my quick and dirty groove design - there just isn't enough vacuum on the corners to hold them down once it starts to warp. I think I may have also removed the paper from my foam thinking it would just delaminate if I left it on and peeling it off would make it more likely to hold up longer term...but the paper really does help prevent it from warping as well and peeling it off makes it warp almost instantly.

A bigger vac helps too - using my big vac it sticks a lot stronger. But...I don't want to risk my big vac. I'm using the super cheap $20 vac because I'm worried about it possibly burning out like my old vac did on the table. The cheap $20 Stanley vac I'm using has a separate fan for the motor so it should be ok as it doesn't seem to rely on airflow through the vacuum to cool it...but then again neither did the old vac that burned up on me as it also had a separate external fan over the motor. I figure a $20 vac is almost disposable and worth risking. But I don't want to risk my nice big vac.

Hai-Lee said:
Just your thoughts on the possible use of thin MDF with a sheet of FB adhered to it as a cutting board or bed for this machine. I understand that MDF, (properly sealed), is warp resistant even though a little heavy. I intend to build my machine to be stored hanging on a wall because floor space is at a premium.

Yes, MDF does need to be sealed since it's porus - but for the lower layers I'd probably skip sealing it (other than the edges) since that may just help it suck itself down to the table. I think I've linked it before but CNCNutz on youtube has a great 2 part series on his vacuum table:

He does a couple of things I found interesting. He not only demonstrates just how porus MDF is he also designed his plenum in an interesting way.

Specifically he has big holes facing the work - but the bottoms of those holes only have very small passages through to the plenum. He explains the benefits of this better than I can but it has me wanting to try and create a new version of my table with 4 layers - two with the long slots, one with VERY small holes (say 1mm instead of the 3mm I used previously) , and a top layer with larger 1" holes center over the tiny holes.

My quick and dirty vac table has been great - don't get me wrong. The warping is frustrating and is the #1 reason I want to build a frame for it, adding the ability to align my work quicker and more repeatedly is a tempting side benefit though for sure! Makes me wish I had time to get out there and work on it right now...but it's too hot to use my outside wood shop so even if I had time I'd be finding excuses to put it off for another month or two :D
 

Hai-Lee

Old and Bold RC PILOT
@jhitesma I thank you for the info. I understand the large surface hole approach to the vacuum table. I also am contemplating either a raised bead, (<0.5mm), around the bed to seal the outer edges of the sheets I use or a tape to the bed approach around the sheet.

Once the air can no longer under the edges of the sheet the bed vacuum can really nail the sheet in place though the cutter itself will introduce some airflow and loss of vacuum as it cuts out the required shapes. Luckily not a great amount of negative pressure is required to flatten the worksheet.

Have you thought of a vacuum relief valve to allow for some airflow to the vac when the bed with sheet has a perfect seal?

Have fun!
 

jhitesma

Some guy in the desert
Mentor
@jhitesma
Once the air can no longer under the edges of the sheet the bed vacuum can really nail the sheet in place though the cutter itself will introduce some airflow and loss of vacuum as it cuts out the required shapes. Luckily not a great amount of negative pressure is required to flatten the worksheet.

Have you thought of a vacuum relief valve to allow for some airflow to the vac when the bed with sheet has a perfect seal?

The cuts don't really cause that much leaking. There is some I'm sure but the work is still held very well even on sheets that have a lot of little parts cut (hence a lot of cut area) when it's done.

I have tried allowing some relief - in fact at the time my old vac died I had some relief - basically I removed the foam on the middle sheet of the 3 sheet stack between the arms of the plenum. This noticeably reduced the grip (though it was still enough grip) and the tone of the vacuum so I figured I had a good bit of additional air flow. Even so that vac died.

To be fair though - that vac was about 14 years old and been abused heavily before being used for the vac table.

With the new little $20 vac it doesn't really make enough vacuum to deal with any relief. But since the vac is only $20 I don't really care if I burn it up. It's almost a year old now (and I'd estimate more sheets cut in that year than the time before I built the vac table) and still works fine. In fact I even use that little vac for cleaning the car as well since it's a lot easier to carry around compared to my big vac :D
 

RAGII

Member
Finally success after many trials and tribulations. I just added a small shim between Marks needle holder and the cutter wheel and it has been working well so far. (5 sheets of foam and counting). Might still try out David's new method, but I have planes to cut right now so I am more focused on getting that done right now.

Next "big" project is to update the rollers on the MPCNC, one of mine is cracked and I can tell it does not roll real well. I am loving the new middle assembly though.

Thanks for all the help guys.

Rob
 

dkj4linux

Elite member
Okay...

Finally started messing with the vacuum pad again. Didn't have any of the repositionable glue so decided Elmer's school stick glue (goes on purple!) from the dollar store would probably work fine for what we're doing here.

Glued the two slotted layers together and weighted them down while they dried... at Jason's suggestion and while I watched the golf tournament. They seemed reasonably flat, after golf, so cut the 5 ports to receive the 5 ends of Mark's plenum. I really wasn't sure I needed to glue the hole grid sheet and decided to try without glue... it's also the spoilboard, remember, so it'll eventually be replaced with a new sheet at some point down the road. Also decided to forego a frame of any sort at this point... I'd like this to be the minimalist version.

So, here it is in action. Spotted the hairy gorilla in the yard and called him in to help out... he did better, with supervision, but he's still a crappy actor. Go Navy! ;)


$3 worth of foam board and a printed vacuum fitting... and it sucks! Hopefully the shop vac -- a small 2.5 gallon unit -- will not overheat with the restricted air flow in the time it takes to cut a sheet. I guess that's the next on the agenda for testing... actually cut a plane and see how it does. Since Jason is fond of the FT MIni-Scout... maybe that would be a good one to try :)

-- David
 
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jhitesma

Some guy in the desert
Mentor
$3 worth of foam board and a printed vacuum fitting... and it sucks! Hopefully the shop vac -- a small 2.5 gallon unit -- will not overheat with the restricted air flow in the time it takes to cut a sheet. I guess that's the next on the agenda for testing... actually cut a plane and see how it does. Since Jason is fond of the FT MIni-Scout... maybe that would be a good one to try

This is the vac I'm currently using:

https://www.walmart.com/ip/Stanley-...-Wet-Dry-Vac-with-Wall-Mount-Bracket/34770967

I picked it because it was the cheapest one I could find in town. I've run it for 2 hours straight on the vac table in a cutting frenzy cutting a full set of FT Alpha/Bravo/Charlie jets for a friend and it's still doing fine. That's after almost a year of semi-regular use for 2-3 sheets at a time.

And last weekend I used it just fine to vacuum the carpet in our new car. So far it's the best $20 I've spent on a vacuum :D
 

RAGII

Member
This is the vac I'm currently using:

https://www.walmart.com/ip/Stanley-...-Wet-Dry-Vac-with-Wall-Mount-Bracket/34770967

I picked it because it was the cheapest one I could find in town. I've run it for 2 hours straight on the vac table in a cutting frenzy cutting a full set of FT Alpha/Bravo/Charlie jets for a friend and it's still doing fine. That's after almost a year of semi-regular use for 2-3 sheets at a time.

And last weekend I used it just fine to vacuum the carpet in our new car. So far it's the best $20 I've spent on a vacuum :D

Looks like due to the popularity you have started with this vacuum it is no longer $20.00 :D.

I might need to make a vacuum table my next project. Right now I use a "picture frame" to hold my foam flat. Works great but I lose 1/2" on the sides with it. Makes a few plans challenging to cut out.
 

jhitesma

Some guy in the desert
Mentor
Looks like due to the popularity you have started with this vacuum it is no longer $20.00 :D.

I might need to make a vacuum table my next project. Right now I use a "picture frame" to hold my foam flat. Works great but I lose 1/2" on the sides with it. Makes a few plans challenging to cut out.

Woah, that's crazy. When I posted it it was showing as $17 online and I almost commented on how I paid more because I didn't want to wait for shipping. It also showed 6 available and now it only shows 2. Either I'm a bigger "influencer" than I gave myself credit for or that's a weird coincidence!
 

dkj4linux

Elite member
Woah, that's crazy. When I posted it it was showing as $17 online and I almost commented on how I paid more because I didn't want to wait for shipping. It also showed 6 available and now it only shows 2. Either I'm a bigger "influencer" than I gave myself credit for or that's a weird coincidence!

I was sure I saw the same as you as soon as I saw your post... less than $20. Weird!
 

Michael9865

Elite member
Yes it was $17. I saw it was available locally so I figured I would go check it out tomorrow. Guess I should have went yesterday. 😕
 

dkj4linux

Elite member
While responding to a thread on the MPCNC forum on laser cutting cardboard, I've been a little side-tracked from the FoamRipper and vacuum pad but it's all been good. I've revisited the laser air-assist stuff and have printed a great design using a squirrel cage fan from "Pawpawpaw85" out on Thingiverse (https://www.thingiverse.com/thing:2832127). Check out the thread here. A couple of photos of the air-assist for my Banggood 3.5 watt laser and a logo I cut from 3mm cardboard... very clean cuts with little/no burning/charring, engraving at 800 mm/min (13.3 mm/s), and through-cuts in a single pass at 200 mm/min (3.33 mm/s)

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I’m calling it good for now and gonna get back on the FoamRipper and vacuum pad. Daughter and family coming in a couple of days and I need to clear out of the dining area 😉

— David
 

Hai-Lee

Old and Bold RC PILOT
I have got my printer sorted and will soon be expanding the bed to enable printing to at least 200mm in the dimensions required for the parts posted. It turned out that my bed was warped, (out of the box!).

Anyway the question I wish to raise in this post is having drawn up or imported the plans into my cad software How do you specify the depths of each cut. Varying the Z axis.

Do you 3D model and make each slice 5mm thick or is there a simpler method?

Have fun!
 
There exist plugins for Inkscape that generate gcode (including depth changes I think) from a 2D vector+ depth annotation (color coded IIRC) , but the other way is to use a CAM (slicer equivalent for CNCs) to do that.

Fusion360 has a CAM package, but i's quite "heavy" to use.

Ryan "Allted" Zellars (v1engineering.com) promotes the use of an easier sogftware called ESTLCAM (cf. https://www.v1engineering.com/estlcam-basics/ ). You import the vector files in it, select the profiles and depth of cut, and it generates gcode. (ESTLCam is not free (not costly though), but can be tested for free. (The "depth" is parametered for each tool path)
 

jhitesma

Some guy in the desert
Mentor
Shorter version of what TheSFReader is saying:

Cut depth is defined as part of the CAM operation not the CAD.

You use 2D vector artwork which you load into your CAM software to generate gcode. When defining the operations you choose how deep each operation should be.
 

ironkane

Member
For cutting foam with a needle cutter:
Use Inkscape and Estlcam. It doesn't get any simpler.
Use Inkscape to convert .pdf page to .svg. Set your document properties to the size of a sheet of DTFB and then use the Import function to import a page from the .pdf. Ungroup everything and delete anything that isn't going to be a cut. Remove all the bevel marks by selecting one and right-clicking and selecting Same Stroke and Fill and then delete.

Big Pro Tip: Break line intersections of non-related cuts. For example the red score cuts intersecting with the through cuts. When you're in Estlcam and you try to select the outline that does not form a continuous loop, it will throw an error when you mouse over it to click. Removing intersections by just nudging them over a pixel will fix that. This will save you tons of time in Estlcam.

Estlcam: Open the .svg you made in Inkscape. Use the Move and Rotate commands to position your drawing to inside the work area. The two tools I use the the most are the Part and Engraving tools. Part will only create a tool path that loops back on itself. Engrave allows you to create a tool path that you can terminate at any node by pressing the Enter key. Part tool you'll use Automatic Detection most of the time and Engraving will ususally be Manual Detection (Connect the dots).

Set your max depth per cut to something larger that what you use for a through cut or Estlcam will make multiple passes.
I use basically 3 Z depths of cut: Full, half (score) and a just barely marking the paper for reference marking.
Create all your tool paths/cuts first. Once you're done, go back and change the machining order. Select what you want to cut first (interior cuts) and in the properties box, click "Automatic" and it will change to 10. The next one you click will be 20. They do it in steps of 10 so that you can go back and fix what you got wrong or forgot.

When you're done, save the Project and the CNC program. The latter will pop-up a virtual preview of the machining action. You can speed up the simulation with the fast forward button. This is where you'll usually catch your mistakes/omissions. After you've done one, it goes pretty quickly. I did the FT LongEZ (single sheet) last night from download to cutting foam in about an hour.

Tip: When doing arcs in the node by node selection process, you can get Estlcam to do the heavy lifting by tracing along the nodes and you'll notice a green line as well as blue line. The blue just goes in a straight line from point to point when you left-click. But when you right-click, Estlcam will connect the dots for you and connect all the nodes your green line intersects. Also, BackSpace will undo your last node selection. It's chainable.

You can run the gcode in Estlcam (if controller compatible) or in Universal GCode Sender (UGS).

Trying to think of anything else that's helpful. Ctrl-Mousewheel roll = Zoom In/Out. Set your tool diameter to something like .1 so that it remains a thin line and not some end mill swath.
 

Hai-Lee

Old and Bold RC PILOT
For cutting foam with a needle cutter:
Use Inkscape and Estlcam. It doesn't get any simpler.
Use Inkscape to convert .pdf page to .svg. Set your document properties to the size of a sheet of DTFB and then use the Import function to import a page from the .pdf. Ungroup everything and delete anything that isn't going to be a cut. Remove all the bevel marks by selecting one and right-clicking and selecting Same Stroke and Fill and then delete.

Big Pro Tip: Break line intersections of non-related cuts. For example the red score cuts intersecting with the through cuts. When you're in Estlcam and you try to select the outline that does not form a continuous loop, it will throw an error when you mouse over it to click. Removing intersections by just nudging them over a pixel will fix that. This will save you tons of time in Estlcam.

Estlcam: Open the .svg you made in Inkscape. Use the Move and Rotate commands to position your drawing to inside the work area. The two tools I use the the most are the Part and Engraving tools. Part will only create a tool path that loops back on itself. Engrave allows you to create a tool path that you can terminate at any node by pressing the Enter key. Part tool you'll use Automatic Detection most of the time and Engraving will ususally be Manual Detection (Connect the dots).

Set your max depth per cut to something larger that what you use for a through cut or Estlcam will make multiple passes.
I use basically 3 Z depths of cut: Full, half (score) and a just barely marking the paper for reference marking.
Create all your tool paths/cuts first. Once you're done, go back and change the machining order. Select what you want to cut first (interior cuts) and in the properties box, click "Automatic" and it will change to 10. The next one you click will be 20. They do it in steps of 10 so that you can go back and fix what you got wrong or forgot.

When you're done, save the Project and the CNC program. The latter will pop-up a virtual preview of the machining action. You can speed up the simulation with the fast forward button. This is where you'll usually catch your mistakes/omissions. After you've done one, it goes pretty quickly. I did the FT LongEZ (single sheet) last night from download to cutting foam in about an hour.

Tip: When doing arcs in the node by node selection process, you can get Estlcam to do the heavy lifting by tracing along the nodes and you'll notice a green line as well as blue line. The blue just goes in a straight line from point to point when you left-click. But when you right-click, Estlcam will connect the dots for you and connect all the nodes your green line intersects. Also, BackSpace will undo your last node selection. It's chainable.

You can run the gcode in Estlcam (if controller compatible) or in Universal GCode Sender (UGS).

Trying to think of anything else that's helpful. Ctrl-Mousewheel roll = Zoom In/Out. Set your tool diameter to something like .1 so that it remains a thin line and not some end mill swath.
Great advice and I will install inkscape ASAP. As for the Esticam the licencing structure is a bit of a put-off. Personally I am getting a little distraught at all of the trial software that does not give you sufficient time to learn enough about it to make an educated decision. Sadly I am old and some things take longer to learn than they used to PLUS I have a head full of useless information from years in the workforce and there is no method of doing a memory dump or a biological "FDisk and reload operating system"

Anyway thanks for the info and it at least gives me a path forward!

Have fun!