Cutting foam sheets... with a needle!

[ironkane]

No, I don't use the cotton wad and oil. But thanks for the suggestion.
I got my 25 pack of WPFB Saturday, which shocked the hell out of me because I ordered it 9AM Friday! Is FliteTest using Amazon Fulfillment?
So I got to cut some of the good stuff. I had forgotten what a night and day difference there is between DTFB and WPFB. Sticking problem went away. Top of the cut is clean, but the bottom is still a little fuzzy. I also received some more 3mm ID bearings that also ordered on Friday. The shipping gods were smiling on me I guess. I think after I make a new needle, I'll be back to to clean cuts top and bottom.

For those who haven't tried it, FliteTest's WPFB is worth the money. DTFB is better suited to testing and prototyping. WPFB is crisper, the paper is stronger and better adhered to the foam.

 

[CMS_1961]

Please reference red circle on photo attached>>

I just saw this actual representation on the workings of a sewing machine mechanism. It gave me an idea about trying to build a needle cutter the same way because it may help guide the needle better, maybe smoother? I just finished building my MPCNC machine and I am building one of David's 3D printed needle cutter designs now. David or Jason, I know you guys have a lot of experience with the needle cutters, do you think this type of double joint could work better?

 

[dkj4linux]

I think you should try it. There have been numerous attempts to try something like this but so far, to my knowledge, nothing "better" has been presented. I'm sure the needle cutter can be improved -- and it has been -- though the basic configuration has largely stayed the same. The biggest issue has been additional moving parts/joints are difficult to make light, yet robust, and added mass only adds to the vibration and resonances. This thread is littered with our attempts...

 

[CMS_1961]

Thanks for the feedback David!! If I have any luck I will post it for everyone. I think you are correct though with additional moving parts being an issue and possibly causing added/more vibration. The video made the up and down movement look straighter/smoother and that was what I thought could be improved with a double joint. Well, for now I am going to get one of your (proven) cutter designs working so I can start cutting foam and I will let this idea sit for a while.

BTW--That sewing machine mechanism was on a youtube video--that is where I saw the movement. The picture was just to show the double joint.

 

[billr]

After building a foam vacuum table I was having trouble with too shallow of cuts in some areas and too deep in others. There is a valley in the middle of the foam board. I decided to try the automatic bed leveling feature of Marlin and I am happy to say it works very well. I enabled AUTO_BED_LEVELING_BILINEAR in configuration.h and set it up to probe a 5 x 7 grid. I have the BED_SIZE set to the foam size of 762 x 508 mm. I also set LEVEL_CORNERS_INSET to 30. The software automatically figures out the probe points from those definitions. I used a clip to ground the mig tip and used a rubber band on the flywheel to keep the needle fully extended. For a touch plate, I used a scrap of 1/8" aluminum with a wire connected to the Z-min endstop input. I set the Z_PROBE_OFFSET_FROM_EXTRUDER setting to -1.58. While probing, move the plate as the needle moves so it will touch down on it. You can control the XY speed of probing by setting XY_PROBE_SPEED. After probing, the grid is displayed. M500 will save the grid, so you don't have to probe again until something changes. Turning on LCD_BED_LEVELING adds a bed leveling section to the menu where you can start the bed leveling function and also turn it on and off.

Now I am getting consistent depth cuts and light markings, which were hit or miss before, all come out. I just finished cutting the Edge 540, which has a lot of small parts with numbers to match up with where they go, and they came out great.

--Bill

 

[TEAJR66]

Brilliant!

 

[jhitesma]

Very nice. I've been meaning to try that, but need to upgrade my firmware and have been putting it off since I got the machine running about 2 years ago I got better results once I added my vac table - but it's still not as flat as I'd like. Makes sense that auto level would work as well. I also wanted to get "too fancy" and setup a more permanent machine mounted z probe instead of using a touch plate....but the touch plate would be a lot quicker. For foamboard though I'd like to probe each sheet to catch if it's my table or the foamboard that's more inconsistent And if I'm doing each sheet then I'm back to wanting to mount the probe and not worry about it. I should try the IR sensor I have on my printer right now. I'm not 100% happy with it against glass on the printer, but it would probably work great on foamboard.

 

[TEAJR66]

I am going back to a sheet of nicely finished plywood for my machine.

I made the new table with MDF for the bed. It is not as flat as it should be. I am not making the vacuum mod till I get the bed sorted.

Short of a nice flat bed, this auto level seems to be an excellent way to ensure consistent cutting depths.

 

[billr]

Very nice. I've been meaning to try that, but need to upgrade my firmware and have been putting it off since I got the machine running about 2 years ago I got better results once I added my vac table - but it's still not as flat as I'd like. Makes sense that auto level would work as well. I also wanted to get "too fancy" and setup a more permanent machine mounted z probe instead of using a touch plate....but the touch plate would be a lot quicker. For foamboard though I'd like to probe each sheet to catch if it's my table or the foamboard that's more inconsistent And if I'm doing each sheet then I'm back to wanting to mount the probe and not worry about it. I should try the IR sensor I have on my printer right now. I'm not 100% happy with it against glass on the printer, but it would probably work great on foamboard.

I use a BLTouch on my 3D printer. I have a spare one I might try on the foam cutter in the future.

 

[jhitesma]

I put a lot of effort into making my bed as flat as I could. It's 1/2" particle board only a 2x4 frame but I added quite a bit of bracing to help make sure it wouldn't sag - at the time I built it I was afraid I was going overboard with the bracing...but I'm glad I did since it's stayed very flat. If I ever do it over again I'd probably do more of a proper torsion box with a top and bottom skin - but I'd keep a lot of the internal bracing as well.

I had planned on using the machine to level itself after it was built. But man would that take a long time to do the workarea I use. And it seems like it would complicate placing work having it set down into a pocket instead of sitting on top of the table. Not to mention I change the machine so much so often that I'd have to keep redoing it. So I never actually did it.

Ryan (designer of the MPCNC) isn't a fan of auto level...but I love it on my printer so have been wanting to try it on the CNC.

 

[TEAJR66]

My first table was a finely finished 3/4" plywood top, 2"x4" framed and the bottom skinned with some trash board. There was no internal structure and when I made it a vacuum table it stayed flat and true.

The second table has an MDF/particle board top, 2"x4" framed and the bottom closed with another piece of MDF. Particle board isn't very flat to begin with, so there is the starting behind the power curve part of it. Using the machine to mill out a flat bed was my idea also. I was not worried about the pocket because the waste board would bring things back above the table top. But,,,,,, the machine is in my garage now and I don't trust the MDF against the climate changes.

Gonna go back to a finished piece of 3/4" plywood. Then make the new table a vacuum table like the last one.

 

[bperc]

After building a foam vacuum table I was having trouble with too shallow of cuts in some areas and too deep in others. There is a valley in the middle of the foam board. I decided to try the automatic bed leveling feature of Marlin and I am happy to say it works very well. I enabled AUTO_BED_LEVELING_BILINEAR in configuration.h and set it up to probe a 5 x 7 grid. I have the BED_SIZE set to the foam size of 762 x 508 mm. I also set LEVEL_CORNERS_INSET to 30. The software automatically figures out the probe points from those definitions. I used a clip to ground the mig tip and used a rubber band on the flywheel to keep the needle fully extended. For a touch plate, I used a scrap of 1/8" aluminum with a wire connected to the Z-min endstop input. I set the Z_PROBE_OFFSET_FROM_EXTRUDER setting to -1.58. While probing, move the plate as the needle moves so it will touch down on it. You can control the XY speed of probing by setting XY_PROBE_SPEED. After probing, the grid is displayed. M500 will save the grid, so you don't have to probe again until something changes. Turning on LCD_BED_LEVELING adds a bed leveling section to the menu where you can start the bed leveling function and also turn it on and off.

Now I am getting consistent depth cuts and light markings, which were hit or miss before, all come out. I just finished cutting the Edge 540, which has a lot of small parts with numbers to match up with where they go, and they came out great.

--Bill

Bill,
Would it be possible for you to post some screen shots of the changes you made in configuration.h? I would like to try this, but have not tried moding any Marlin files. I am using Marlin 1.1.0-1. I just want to make sure that I change the correct settings.
Thank you,
Britt

 

[billr]

Hi Britt,

The attached file has the sections of configuration.h that I changed. Note that I am using dual endstops on my X axis and I home Z to the max endstop.

--Bill

 

[bperc]

Hi Britt,

The attached file has the sections of configuration.h that I changed. Note that I am using dual endstops on my X axis and I home Z to the max endstop.

--Bill

Thank you Bill,

So do I copy and paste your changes to replace the corresponding parts of my configuration.h?

 

[billr]

Thank you Bill,

So do I copy and paste your changes to replace the corresponding parts of my configuration.h?

You should look for the similar sections in your configuration.h and compare, then change the settings as required.

Here is a link to the Marlin documentation on bed leveling that will explain how to use it:
http://marlinfw.org/docs/features/auto_bed_leveling.html

--Bill

 

[ironkane]

Here's my setup. Plywood benchtop with MDF vacuum table glued and screwed down. I made it with a dado blade on my table saw. I just a video yesterday of a guy cutting T-Slots into a MDF Waste Board using a router and a really simple jig. I think I might try this method next time.

After laying down the vacuum table, I added more MDF to bring it all up to just past flush. I added a shim layer so that after taping down my paper-stripped DTFB as a waste board, it is all flush.

 

[ironkane]

Adventures in Needle Making. Here's my latest/greatest foray into crafting the perfect needle. I bought a couple of larger bearings (3x10x4mm) thinking they would be more robust and increase the amount of throw a little. I didn't have anything to accommodate this larger diameter bearing, I decided to make a better system that past efforts.

I needed a post to wrap the wire around. A drill bit was perfect. I just needed a chunk of 4x4 so I had something deep enough that I could bury it to the end of the flutes. I needed something to clamp one end of the wire. Found a decorative Simpson Strong Tie angle piece for $1.68. It's a heavier guage than the construction stuff.

I've had problems in the past when winding where my winder bolt would catch on the wire on the first pass. So I cut a slot in my 4x4 right up to post hole. Then in order to use a steel washer that I added so that the winder bolt head wouldn't gouge into the wood, I drilled a 3mm hole off to the side and then used my Dremel to open it to a slot so that the wire could pass through to the post.

Next up was making the winding bar. Which is just a 3D printer bar with a hole to pivot around the post and a 3mm hole for a M3 socket head screw that will force the wire to bend around the post. The 2 holes are distanced by 1/2 dia of post hole + 1/2 dia M3 head + 1mm for wire.

So you clamp one end of the wire to the angle piece. Run the wire up the slot and through the slot in the washer. Slide the winder bar down over the post and start winding. For this bearing, you want 3 tight winds from the needle side. So you'll want to add a few extra winds to be cut off when done. Invest in some wire end cutters. It's the only good way to cut off the excess without undoing all those nice tight coils.

Anneal your finished needles! 500 degrees in the oven for a hour, then turn off the heat and let cool. This will de-stress your coils as well as the rest of your needle. Needles tend to break wherever there is stress or any other weak points like nicks. Another good reason for the end cutters.

Mounting the needle to the bearing has been problematic. Best way is to counter-rotate the coils which causes the diameter of the coil to expand. Then you press the bearing in and let the coil contract again around the bearing. This is easy when you have two long ends to grab. But after you trim it, it becomes a lot harder. I found a cool trick. I had some syringes laying around. Not sharp. The barrel of the "needle" was large enough to slide over the wire at the coil end and provided the leverage to expand the coil.

Then it's cut to length and sharpen... then it's ready to mount.

The larger diameter bearing was a good decision. My cuts on the WPFB is like a laser. DTFB shows more of a series of overlapping holes when viewed really up close. DTFB paper isn't as crisp, but it's acceptable.

Fyi for those who aren't familiar with my setup, I have my needle mounted directly to a large diameter motor. the needle is mounted to one of the threaded prop mount holes. The pic of the cutter is of previous bearing and not the new 10mm bearing.

 

[billr]

I've been planning to try this spring winder https://www.thingiverse.com/thing:88569 to form the coils. It seems similar to what you are doing.

 

[TEAJR66]

I like the process. Pretty in depth explanation.

Since the needle is offset to the side of the bearing, moving your hole and MiG tip to the right 1/2 the bearing diameter will reduce friction in the MiG tip. Not sure if that would be an appreciable difference or not.

 

[ironkane]

I like the process. Pretty in depth explanation.

Since the needle is offset to the side of the bearing, moving your hole and MiG tip to the right 1/2 the bearing diameter will reduce friction in the MiG tip. Not sure if that would be an appreciable difference or not.

Interesting notion. Have you tried this out? Sounds like it would tighten the orbit by 10mm (plus wire coil). That's what? 50% reduction? Looking at the specs for the motor, the prop holes are 12.5mm from center. It's something to consider.