Cutting foam sheets... with a needle!
- Thread starter dkj4linux
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David, Nice idea on the pointy trivit. I was actually looking at it thinking, I could scale this up and use as a sort of pigeon hole storage unit in my workshop!
Anyway something interesting just happened. I was cutting some 4mm ply for control horns and a firewall. I though it about time I make some more planes so I needle cut the parts for a new FT sparrow.
Anyway I made a mistake while setting up the gcode. Instead of power 100% I set the feed speed to 100mm/min instead. I set up for 4 passes. I refocused and turned on the air assist. My jaw almost dropped when one of the horns fell through after just 1 pass! All fell through after the second pass.
So I did a few more experiments.
At 100mm/min and 1 pass, it almost cuts through 100% The part marked 1x100%: I could later push through with my finger. I slowed to 75mm/Min and the part just fell out by itself. Without air assist I could not release the part by hand. A 3.5W laser cutting 4mm ply in one pass! I think thats remarkable!
Anyway something interesting just happened. I was cutting some 4mm ply for control horns and a firewall. I though it about time I make some more planes so I needle cut the parts for a new FT sparrow.
Anyway I made a mistake while setting up the gcode. Instead of power 100% I set the feed speed to 100mm/min instead. I set up for 4 passes. I refocused and turned on the air assist. My jaw almost dropped when one of the horns fell through after just 1 pass! All fell through after the second pass.
So I did a few more experiments.
At 100mm/min and 1 pass, it almost cuts through 100% The part marked 1x100%: I could later push through with my finger. I slowed to 75mm/Min and the part just fell out by itself. Without air assist I could not release the part by hand. A 3.5W laser cutting 4mm ply in one pass! I think thats remarkable!
dkj4linux
Elite member
Welcome, Glenn. I'm not sure if your interest is in lasering, needle-cutting foam, building an MPCNC, or all of the above, but...
This thread has grown a bit "eclectic" but is primarily geared to CNC machines and using them to cut/score/engrave various materials of interest to most RC'ers. It began featuring the MPCNC and the needle cutter I developed to do exactly what you're looking for... cutting DTFB and various other sheet foams for RC aircraft. But the needle cutter is a simple-to-build device that is easily adapted to virtually any CNC out there so all CNC's being used to cut foam and related materials are welcome to the discussion. Various other tools of interest to CNC'ers have also been discussed... lasers, drag-knives, extruders, vacuum hold-down, etc. Everybody here seems to be enjoying themselves and the lively discussion and exchange of information gives us all a chance to both share and learn... and broaden our knowledge/skillsets.
That said, most of us are hobbyists and DIY'ers and are primarily using these devices in a home/hobby environment. Numerous folks have tried to "harden" these tools for a production environment but those who insist on "maintenance-free", "must-run-forever-between-tuneups", and/or who feel they must push feeds/speeds to the absolute max... are going to be quickly frustrated. These are basic machines and simple devices that require a little care and occasional repair/maintenance... but bring much enjoyment and satisfaction to their builders. So, if you are "handy", like DIY, and don't mind taking a few minutes every now and then to fab/install a new needle, apply a drop of oil or a dab of grease, etc... then this is the place for you.
Nobody knows whether you'll be able to cut 300 sheets of DTFB a week. Numerous folks who've taken the time to get "in tune" with their machines and their capabilities and have been willing to stay conservative with the feeds/speeds have reported running for amazingly long periods of time and cutting numerous sheets of material between needle changes or repairs.
The MPCNC itself is an amazingly well-engineered machine and perfectly suited to needle-cutting foam and carrying around a laser head... the tool forces involved are extremely light. If it can be put in place, left alone, and not pushed beyond its limits, there's no reason in the world the MPCNC can't last for many years.
To handle the sheet foams in common use you'll probably be looking at 24" x 48" working area... I've not personally built a MPCNC that large; i.e. the footprint for that size would be about 36" x 60". For DTFB, however, a 20" x 30" working area is adequate... and I have built several in 36" x 48" and 48" x 48" footprint. I've never used mid-span supports... needle-cutters and laser heads are so light extra support isn't really needed IMHO. Heavier tools... maybe.
Sorry for the long winded introduction but I really want you to know what you are up against. As I say, nobody can tell you how many sheets you can cut or how long between machine repairs but if you want to be a part of trying to find out... welcome to the party. We're having lots of fun here. -- David
Adding to David's comments on the MPCNC, I would be a little concerned on rail wear also. If you went with the 3/4" EMT design I am not sure how long the conduit rails would last. You can keep rotating them to even out the wear, but I am seeing some mild flat spots and I know I haven't come close to cutting 300 sheets of foam yet.
If you went with the 1" design and used stainless conduit for the rails you might get longer life out of them.
Having said that, conduit is cheap and it is easy to swap out the rails as needed.
dkj4linux
Elite member
Glenn,
Adding to Rob's comments (Thanks, Rob!) about rail wear, another caveat is regarding the plastic parts - usually PLA - that comprise the bulk of the MPCNC. IF this machine will be in a temperature-controlled environment, you'll probably be okay. But if it is exposed to temperature extremes it's possible that you may have plastic parts crack or deform.
I think your best source of information will be Ryan ("allted") Zellars, himself... http://www.vicious1.com/. He's the talented young engineer responsible for design and development of the MPCNC, the MP3DP (3d-printer), and the LowRider (a full-sheet 4' x 8' CNC router). He uses these very machines in as close to a "production environment" as you'll find... 3d-printing the plastic parts bundles and producing the machine-cut frame parts that he sells in his store-front and uses to design/develop new machines.
-- David
Adding to Rob's comments (Thanks, Rob!) about rail wear, another caveat is regarding the plastic parts - usually PLA - that comprise the bulk of the MPCNC. IF this machine will be in a temperature-controlled environment, you'll probably be okay. But if it is exposed to temperature extremes it's possible that you may have plastic parts crack or deform.
I think your best source of information will be Ryan ("allted") Zellars, himself... http://www.vicious1.com/. He's the talented young engineer responsible for design and development of the MPCNC, the MP3DP (3d-printer), and the LowRider (a full-sheet 4' x 8' CNC router). He uses these very machines in as close to a "production environment" as you'll find... 3d-printing the plastic parts bundles and producing the machine-cut frame parts that he sells in his store-front and uses to design/develop new machines.
-- David
Hi David,
you are absolutly right with the max speed....the very limit is by heating up the needle in the foam (not in the guide)....
I played many hours with this kind of cutting (since I send my first post) to find out the limits...and now, I'm let this little thing run in a very "safe" area...the reliability and the precision is more important (for me.)...and far below these limits, the construction may be "nearly" maintenace-free.
High numbers of "production" ??? - I do not know/believe....not with such a DIY tool!
Just for information
--> the Dino was cutted with very low feed speed (many curves) in ca, 40min!
--> the parts for the plane took some 25min
Could be, that I can crank up the speed a little, but the router/mill is a real heavy machine, which can reach very high speed on straight lines...but I don't like the hard accelerating and slowing down with this tricky small parts not so much.
This system is for higher speed...it's not a needle...they using an oscillating knife. This is a heavy head..so you need a big maschine and an additional axis (the direction of the knife)
https://youtu.be/6eXPA1z5nG8
https://youtu.be/kYBW9iWeWec
----> but I do not believe that they can cut the small part for my Dino
dkj4linux
Elite member
That is impressive, Dave. I'm really beginning to believe these little lasers are far more capable than we've been led to believe...
That said, all plywoods are, of course, NOT created equal. Is that 4mm stuff some of that "special" plywood... designed for laser cutting? I've heard that there is a line of plywood with special glues that make it easier to cut with a laser.
The stuff I have on hand is just plain old plywood paneling... 3mm and 4.75mm. The 3mm is actually harder to cut than the 4.75mm. It was factory-painted... maybe an epoxy paint. It seems harder/denser for some reason... maybe some of the epoxy has impregnated the plywood itself?
Anyway... good work, Dave! You RC guys are going to lose me when this thread becomes focused on building and flying actual airplanes. I'm resigned to never flying worth a flip... old, spastic/twitchy thumbs and a propensity for playing on the edge of the sky closest to the ground
-- David
dkj4linux
Elite member
I'm sorry... I remembered earlier today that you'd asked the Inkscape question earlier and I intended to reply but got side-tracked...
I think you need to specify a valid directory into which the output file is placed. -- David
That's odd. I always output to e:\FILENAME.gco since that's where my sd card is. Wonder why it chokes on that on your computer but not mine...
dkj4linux
Elite member
I may be all wet but I'm sure that for C:\ it's a permissions thing... root/admin rights and systems-level directories only IIRC? You have to have write access to where you want the output file to go... you have that if/when you are able to mount the sd card. -- David
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It's absolutely what David said. root c:\ is set with read only permission by default in windows. Other root folders are fine. You can just change the permission on root c:\ if you must.
dkj4linux
Elite member
c:\ is the absolute top of the Windows file system tree... g:\ and any other "drive" letters (other than a:\ or b:\) are symbolic and are simply aliases assigned to a location somewhere in the tree under c:\ . I really can't think on any good reason, that as a normal user, you should put any files you produce in that reserved primarily for system use. But that's just me...
I'm primarily a Linux user by choice... though the logic above holds true for any OS IMHO
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dkj4linux
Elite member
And now... back to our regular programming
I downloaded the dxf file for the dino that Joachim displayed a few posts back. I decided to use the cardboard box my new coffee pot came in... the cardboard is about 1.5mm thick, which makes for an awfully small dino. Anyway, I scaled it down about right but the pieces and fit are a bit loose and the model is pretty unbalanced... so my dino has a "broken-back" look to him. That, plus the slick printed side of the cardboard detracts from the overall look IMHO. Oh, well...
A funny story... I engraved the "solution" lettering for the dino before cutting out the parts and while my CNC machine rapidly engraved each letter, the stepper motors made a distinctive "warbling" sound... I could barely hear it and don't pay much attention anyway. But a mockingbird in the tree outside heard it and started doing a perfect imitation. It was so cool listening to the machine and the bird "talking" to each other!
That's all I've got... I pretty much wasted a bunch of time with that ill-fated dino project... -- David
I downloaded the dxf file for the dino that Joachim displayed a few posts back. I decided to use the cardboard box my new coffee pot came in... the cardboard is about 1.5mm thick, which makes for an awfully small dino. Anyway, I scaled it down about right but the pieces and fit are a bit loose and the model is pretty unbalanced... so my dino has a "broken-back" look to him. That, plus the slick printed side of the cardboard detracts from the overall look IMHO. Oh, well...
A funny story... I engraved the "solution" lettering for the dino before cutting out the parts and while my CNC machine rapidly engraved each letter, the stepper motors made a distinctive "warbling" sound... I could barely hear it and don't pay much attention anyway. But a mockingbird in the tree outside heard it and started doing a perfect imitation. It was so cool listening to the machine and the bird "talking" to each other!
That's all I've got... I pretty much wasted a bunch of time with that ill-fated dino project...
-- DavidRC Sea Foam Guy
Member
Thanks for the feed back everyone.
Seems to me that the MPCNC would be a great start platform, and see how things go from there.
It looks like adding mid span supports is simple and could be accomplished after the fact if needed.
I will contact Vicious1 and get his thoughts.
3/4 inch rigid conduit is available? Thoughts vs EMT?
What is the source of SS tubing?
Thanks all
Glenn
Think big
Hi David...what's about this size?
https://cdn.instructables.com/FGR/T2C5/ILV8CSQY/FGRT2C5ILV8CSQY.LARGE.jpg
With this little monster in my garden, my neighbours will call the police!
A "glow-in-the-dark" paint would be nice!
But being more serious ---> did you ever try to make (needle) such a small Dino from this "take-away-boxes"?
This foam is similar to Depron, but only 1mm thick...should be perfekt?
...not nice!!I pretty much wasted a bunch of time with that ill-fated dino project...
Hi David...what's about this size?
https://cdn.instructables.com/FGR/T2C5/ILV8CSQY/FGRT2C5ILV8CSQY.LARGE.jpg
With this little monster in my garden, my neighbours will call the police!
A "glow-in-the-dark" paint would be nice!
But being more serious ---> did you ever try to make (needle) such a small Dino from this "take-away-boxes"?
This foam is similar to Depron, but only 1mm thick...should be perfekt?
dkj4linux
Elite member
You're welcome. The MPCNC would indeed be a great start platform and it would be wise to get set up, cut some foam, and see how it all goes. Mid-span supports can be added after the fact if deemed necessary. The conduit used most commonly in the US is inexpensive, zinc-coated, steel 3/4" EMT sold at most any big-box hardware store... and it has a 23.5mm OD that the MPCNC525-"C" parts will fit. The zinc coating will fairly quickly wear (cold-flow?) where the bearings ride but it's not a big deal IMHO... the rails will remain smooth for many sheets of material. I've never used the SS so can't help you there. -- David
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The needle and I ... some secrets reveiled...
...and talking about SPEED again....
................................................
By trying to make the needle cutter as smart as such a simple "tool" can be, I made up my mind about the "real" function.
We were discussing (a few times) the sense (or nonsense) of trying to shorten the time for a project by making the process faster...but the limit for that is not too far away.
So I tried out to find the reason for this limit in looking a little more closely......
What will we see, when the needle is working? --> we see a fast punching needle and an advancing router/mill....so it seems to be easy to say: " if I'm going to increase the feed speed...I only have to crank up the motor revs for the needle the same percentage" ...but as said before: this is not true...it's not "linear"...but why?
Let's have a look how a sewing machine is working...
...the machine is advancing the fabric while the needle is up...then it makes a stop and the needle is going down and up...and the fabric will be moved one step further ----> there is No sideforce on the needle!!!!
Our system works a little differend ---> the needle is going up and down and the router is advancing continiously
This will create a sideforce, because the CNC is traveling, even when the needle is way down in the material....so we have friction in the guide and friction in the material...
The effect will encrease if the material is thicker...then the needle will nearly beeing forced to bend in the "hole"
OK...but one can say" if I crank up the needle, the time in the hole will be shorter....and can travel with more speed!
Sounds realistic at first...but is not!
---> the cutting/punching of the needle is generating heat within the material - even without any sideforce (I got smelling/melting Depron)
---> the movement of the needle in the guide is generating heat too (and some early weareouts of the guide and the needle)
---> sometimes you will run into resonances and vibrations (on/in the parts to be cut)
My suggestion to SPEED is:
---> find out the optimum for your system and a certain material (depron is much differnd to cardboard)....
---> and then go SLOWER by ~30%!!!!
---> this will produce nice results and a real long lifetime of the cutter (with a little mainternace/oil)
So stay cool and slow down...
Joachim
BTW
who knows this machine?
https://www.inventables.com/technologies/x-carve/customize#750mm
I need some infos on the rails
...and talking about SPEED again....
................................................
By trying to make the needle cutter as smart as such a simple "tool" can be, I made up my mind about the "real" function.
We were discussing (a few times) the sense (or nonsense) of trying to shorten the time for a project by making the process faster...but the limit for that is not too far away.
So I tried out to find the reason for this limit in looking a little more closely......
What will we see, when the needle is working? --> we see a fast punching needle and an advancing router/mill....so it seems to be easy to say: " if I'm going to increase the feed speed...I only have to crank up the motor revs for the needle the same percentage" ...but as said before: this is not true...it's not "linear"...but why?
Let's have a look how a sewing machine is working...
...the machine is advancing the fabric while the needle is up...then it makes a stop and the needle is going down and up...and the fabric will be moved one step further ----> there is No sideforce on the needle!!!!
Our system works a little differend ---> the needle is going up and down and the router is advancing continiously
This will create a sideforce, because the CNC is traveling, even when the needle is way down in the material....so we have friction in the guide and friction in the material...
The effect will encrease if the material is thicker...then the needle will nearly beeing forced to bend in the "hole"
OK...but one can say" if I crank up the needle, the time in the hole will be shorter....and can travel with more speed!
Sounds realistic at first...but is not!
---> the cutting/punching of the needle is generating heat within the material - even without any sideforce (I got smelling/melting Depron
) ---> the movement of the needle in the guide is generating heat too (and some early weareouts of the guide and the needle)
---> sometimes you will run into resonances and vibrations (on/in the parts to be cut)
My suggestion to SPEED is:
---> find out the optimum for your system and a certain material (depron is much differnd to cardboard
)....---> and then go SLOWER by ~30%!!!!
---> this will produce nice results and a real long lifetime of the cutter (with a little mainternace/oil)
So stay cool and slow down...
Joachim
BTW
who knows this machine?
https://www.inventables.com/technologies/x-carve/customize#750mm
I need some infos on the rails
Its a lot like the "Ox". http://www.openbuilds.com/builds/openbuilds-ox-cnc-machine.341/
Some of the same linear v groove rail is used but on the other axis it looks like the v groove rail is extruded. Anyway that type of rail is known as "v groove" rail. I use it on one of my machines. It's excellent.
Cheers
Dave.
PS I think I found the rail they use on this machine;
https://www.inventables.com/technologies/makerslide
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