Cutting foam sheets... with a needle!

[dkj4linux]

By now you may have realized I love to take machined parts made for different purposes and put them together in ways other than intended by the manufacturer

Thurmond

Here's my latest attempt to use the copper welding tip with my PLA plastic guide holder. Small insulator/bushing/spacer cut from broken carbon arrow shaft and a 3-point "floating" screw/nut arrangement on a redesigned guide holder (still need to adjust for the screw head interference yet... ). It's to keep the hot tip from direct contact with the plastic... seems to work for the couple of sheets I've cut so far -- David

 

[RAM]

Could you design a 3D printed version with little air ducts to cool the copper tip? It's already spinning so it might work pretty well.

 

[RAM]

Something else that might work is part of a fly tying bobbin. They make them with ceramic tips or all ceramic. The metal ones are cheaper.

 

[dkj4linux]

Could you design a 3D printed version with little air ducts to cool the copper tip? It's already spinning so it might work pretty well.

I'm sorry, RAM, I wasn't clear. This is the needle guide tip... nothing's moving here. The friction-heat from the needle in the hole through the guide tip is the bad guy I'm trying to keep away from all the yellow PLA plastic. The arrangement I've shown seems to be working for me so far. -- David

PS: It seems I need to dress my needle point... labors a bit heading "north" and "west"...

 

[dkj4linux]

Getting ready to deliver this last MPCNC to my buddy, I've gone back to the hard-mounted MPCNC foam cutter for a little more rigidity and mounted a 2822 1200kv brushless motor. The lower kv rating of the motor better utilizes the servo tester's potentiometer range. I've used the 0.035" copper welding-tip in my latest 3-point floating needle guide holder. Feed rate is 609 mm/min and cutter is running a more relaxed 6000-7000 rpm. This is a successful attempt to stay below the point where the guide tip heats excessively and the needle begins melting the foam. All in all, this seems a good combination... good quality cuts in DTFB (paper on) and everything running pretty stress-free. -- David

 

[dkj4linux]

Here's the MPCNC hard-mount foam cutter from before but now outfitted with the "floating" guide tip holder with 0.035" copper welding-tip. The "floating" tip holder uses a short section of carbon arrow shaft for a spacer/insulator and a 3-point set-screw arrangement to effectively isolate the hot (in use) copper tip from the yellow PLA plastic. -- David

 

[Shurakair]

My attempt at this (first post also)

Inspired by what you guys have done here and encouraged and assisted by friends (quimney and a great machinist I work with) I took a stab at making one of these myself. Here is the result.

Thanks dkj4linux for posting this. I have tried other cutting methods with variable degrees of success. I have a drag knife/tangent knife setup that I've used but sharp corners don't turn out very well. I have a router head/spindle and some 0.8mm end mills but they break very easily and can gum up with foam. This design I think is the best of both worlds. Its simple, tough, doesn't require strong work piece holding, the cuts are nice and it can do very intricate cuts. Thanks again.

Shur

 

[dkj4linux]

Inspired by what you guys have done here and encouraged and assisted by friends (quimney and a great machinist I work with) I took a stab at making one of these myself. Here is the result.

Thanks dkj4linux for posting this. I have tried other cutting methods with variable degrees of success. I have a drag knife/tangent knife setup that I've used but sharp corners don't turn out very well. I have a router head/spindle and some 0.8mm end mills but they break very easily and can gum up with foam. This design I think is the best of both worlds. Its simple, tough, doesn't require strong work piece holding, the cuts are nice and it can do very intricate cuts. Thanks again.

Shur

Absolutely fabulous, Shur! I love the rigidity of your design. At 0.032" diameter you're using a slightly heavier needle and there appears to be very little "slop" between needle and guide... it looks very precise. Are you using any sort of lube in the needle guide? Is that a custom-made needle guide? What is the diameter of the bore? Any info on the flywheel material and configuration? What cutter rpm and feed rate are you using here? Again, it looks great. Thanks for posting this and please join in the conversation... it's great encouragement for all. -- David

 

[ttprigg]

+1 on looks fabulous-

 

[jhitesma]

The lower kv rating of the motor better utilizes the servo tester's potentiometer range.

Have you looked at using one of the servo outputs on the RAMPS to control the motor? Seems silly to tie up a servo tester when the RAMPS board has several servo outputs.

I'm getting ready to start printing a set of MPCNC parts (was hoping to do ABS but I can't take the smell of printing that big of a project in ABS.) I'll have to order more PETG though. I need it to be usable outside and PLA melts in the shade here in summer While I'm working on that I may have to look into if it's possible to use a bit of G code to trigger a Servo output...can't be too hard.

Oh wait...quick google: http://3digitalcooks.com/2013/12/setup-servo-with-marlin/

Yeah. Just enable the servo pins and then use M280 PX SX (P=which servo S=angle or miliseconds)

Should be able to control the speed for different types of cuts if necessary then too...but that would take some manual g-code tweaking or a smarter slicer or some kind of g-code post-processor.

Or is there something I'm missing that makes this not a usable method?

 

[Shurakair]

I am not using any lube in the guide perse. However, it is a custom made needle guide. The material the guide is made out of is called Oilite. Its an oil empregnated bronze. A friend of mine built it for me yesterday as a replacement for the copper MIG tips I used initially. It has the same threads and length as the MIG tips so my cutter will work with either.

The diameter of the bore is .038 for the bottom 0.5" with a linear taper from there up to the top.

The flywheel is made out of nylon. As you can see in the pictures its two separate pieces of nylon because I used scraps and none of them were big enough as is so I joined two pieces to make the flywheel. The design doesn't exactly match my drawing because I don't have a lathe and I just built it at home. Going forward I may beg my machinist friend to make me a new flywheel out of aluminum. My flywheel design differs slightly from others but so far it seems to be holding up well. I use a bolt opposite the bearing to balance the wheel.

As far as feed rates and rpms. I haven't settled on a combination yet, I've probably not run the same set twice. I'm going to estimate my RPMs to be somewhere in the 6000 to 10000 range and my feed rate has been around 15 ipm.

 

[RAM]

Here's something for the engineers. The page shows a copywright of 2011 but is doesn't state the design was made in 2011.
http://mwdes.com/index.php?/design/foam-core-cutting/

Apparently they did a lot of testing (but they don't show any of it) on methods used to cut foam board. They ended up with the needle idea combined with razor blades to score the paper.

 

[dkj4linux]

I am not using any lube in the guide perse. However, it is a custom made needle guide. The material the guide is made out of is called Oilite. Its an oil empregnated bronze. A friend of mine built it for me yesterday as a replacement for the copper MIG tips I used initially. It has the same threads and length as the MIG tips so my cutter will work with either.

The diameter of the bore is .038 for the bottom 0.5" with a linear taper from there up to the top.

The flywheel is made out of nylon. As you can see in the pictures its two separate pieces of nylon because I used scraps and none of them were big enough as is so I joined two pieces to make the flywheel. The design doesn't exactly match my drawing because I don't have a lathe and I just built it at home. Going forward I may beg my machinist friend to make me a new flywheel out of aluminum. My flywheel design differs slightly from others but so far it seems to be holding up well. I use a bolt opposite the bearing to balance the wheel.

As far as feed rates and rpms. I haven't settled on a combination yet, I've probably not run the same set twice. I'm going to estimate my RPMs to be somewhere in the 6000 to 10000 range and my feed rate has been around 15 ipm.

I really like your needle cutter, Shur... especially the needle guide. And of course being non-plastic it is far sturdier than the 3d printed ones I've been making... my original ones were not printed of course but I also didn't know at the time that my cuts could be much cleaner and crisper than they were then. I've kicked around the idea of using an aluminum platform plate bolted onto my plastic foam cutter motor and cnc mount but I'm trying to keep it as reproducible, with garden-variety parts, as possible for those that may not have a well-equipped workshop and/or machinist friend but do have a 3d printer.

I have a suggestion that you may want to consider... speed up your feedrate and/or lower you cutter rpms. The fuzzy cuts on the top and bottom paper I think indicate that you are melting foam that adheres to the needle and grabs/pulls the paper upward as the needle is extracted from the foam board. The little black speckles are little bits of melted foam and also indicate you need to speed up. You may even detect the faint smell of melting plastic at times. I've found that about 10 perforations per millimeter of cut works for me and is about the right combination for clean cuts in DTFB so I use a "rule of ten"... 6000 rpm on the cutter and 600 mm/min (24 in/min) on feed rate, etc. You needle appears very sharp and free of burrs so I think the melting foam thing is all you need to deal with if you want slightly cleaner cuts.

Again, I love it. You've got a very nice foam cutting system and it is cutting and performing very well... even if you don't change a thing. Good work! -- David

 

[dkj4linux]

Here's something for the engineers. The page shows a copywright of 2011 but is doesn't state the design was made in 2011.
http://mwdes.com/index.php?/design/foam-core-cutting/

Apparently they did a lot of testing (but they don't show any of it) on methods used to cut foam board. They ended up with the needle idea combined with razor blades to score the paper.

Interesting, RAM. I'd never seen that page, though I've Google'd for several years to find anyone else using this method to cut foam. I found only one and he was my inspiration for the foam cutter... Tom McGuire, a very talented artist/engineer, who made several versions of a foam cutting machine and to whom I'm very grateful for starting me down this slippery slope

I simply adapted his cutter head to a conventional 3-axis CNC machine. Interestingly, it was him who also inspired me to build my very first CNC machine...

A dozen or so machines later, it's been a very fun and satisfying trip! -- David

 

[RAM]

Thanks for the links. I bookmarked his youtube channel. Just when I think I've surfed the whole internet something else turns up

 

[wire10ga]

Just got my MPCNC built last night and 1st movement. Now onto leveling and printing out the needle mount and hub.

 

[RAM]

Just got my MPCNC built last night and 1st movement. Now onto leveling and printing out the needle mount and hub.

Do a build article if you can!

 

[jhitesma]

Just got a fresh roll of PLA to start printing my MPCNC

Really worried about doing it in PLA...here in the desert PLA isn't a very good material since it deforms at such low temps. But I'm not convinced PETG is stiff enough and ABS I just can't get good enough bridging to have confidence that the parts will be acceptable.

One of my long term plans with my 3dprinter has been to print parts to use as patterns for metal casting. Either by simply using them as patterns for sand casting on simple pieces or for more complex shapes trying "lost PLA" casting.

So I'm thinking I'll print everything in PLA and get the machine built (hopefully before summer!) but will have to use and store it inside due to the heat issues and PLA. Which means I'll have to take it apart and put it back together each time I want to use it. Not ideal. But it's the only way I'll be able to store it inside where the PLA won't melt in the summer. (I'm actually thinking about ordered a few rolls of extra PLA now while the weather is nice - I'm concerned that just shipping PLA here in the summer would be enough for the filament to fuse to itself on the roll. (Even this time of year when we have nice 80f weather we can't ship stuff like chocolate. Two years ago my mom sent us some chocolate in March, it shipped from CA with cold packs and arrived in two days...but was still melted.)

But long term...I'm thinking about combining these projects and trying to cast aluminum parts from the PLA originals. Then the machine would be able to live outside, or out in my office (which has AC, but we only run it when we need to to save money.)

Either way it's looking like the first bits should come off the printer today

 

[dkj4linux]

Just got a fresh roll of PLA to start printing my MPCNC

Really worried about doing it in PLA...here in the desert PLA isn't a very good material since it deforms at such low temps. But I'm not convinced PETG is stiff enough and ABS I just can't get good enough bridging to have confidence that the parts will be acceptable.

One of my long term plans with my 3dprinter has been to print parts to use as patterns for metal casting. Either by simply using them as patterns for sand casting on simple pieces or for more complex shapes trying "lost PLA" casting.

So I'm thinking I'll print everything in PLA and get the machine built (hopefully before summer!) but will have to use and store it inside due to the heat issues and PLA. Which means I'll have to take it apart and put it back together each time I want to use it. Not ideal. But it's the only way I'll be able to store it inside where the PLA won't melt in the summer. (I'm actually thinking about ordered a few rolls of extra PLA now while the weather is nice - I'm concerned that just shipping PLA here in the summer would be enough for the filament to fuse to itself on the roll. (Even this time of year when we have nice 80f weather we can't ship stuff like chocolate. Two years ago my mom sent us some chocolate in March, it shipped from CA with cold packs and arrived in two days...but was still melted.)

But long term...I'm thinking about combining these projects and trying to cast aluminum parts from the PLA originals. Then the machine would be able to live outside, or out in my office (which has AC, but we only run it when we need to to save money.)

Either way it's looking like the first bits should come off the printer today

I like your plan to go ahead and build with PLA. I live in East Texas, am currently building my 4th MPCNC, and in our balmy low-100's summer-time heat my machines have shown no ill-effects in a non-a/c environment, but out of direct sunlight. I did however have a heat-related problem with one of my 3d printers caused by an over-driven motor. I understand your reservations about the heat where you live but I also believe there's great value to building the MPCNC as designed and then observing for yourself where things may, or may not, prove lacking. The MPCNC design, with its plastic parts and small motors has, time and time again, proven incredibly strong and capable and has been a pleasant surprise in almost every way... it's quite a nice piece of engineering.

I like your "fall-back" plan even better. I too have been looking at lots of "lost-foam/PLA" metal-casting videos and been thinking how much nicer an all-metal MPCNC would be... how PLA's lack of heat-resistance might actually be a virtue. I've finally gotten a simple foundry build underway and hope soon to start looking more seriously at making foam patterns and playing with simple "lost-foam" casting. A logical next step would then be extending it to "lost-PLA"...

Anyway, keep us posted as to how your build progresses. I like the way you think. -- David

 

[dkj4linux]

Do a build article if you can!

wire10ga: Congratulations! Please do provide pictures/videos... they are a real encouragement to all!

RAM: Hear, hear! -- David