Pattnmaker
Stainless
- Joined
- Nov 2, 2007
- Location
- Hamilton, Ontario
Instead of using babbitt I would give body filler a try. Use it to fixture prevent chatter etc. Then clamp in a place or two...
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Wire-EDM for part of my production process... Feedback, machine suggestions please!
- Thread starter aarongough
- Start date
- Replies 34
- Views 5,433
Does the alloy have to grab onto the flat surface? Almost all of the material removal is done while it's in the picture frame. All you need the alloy to do is support the material during the final profile cut, by which point you have lots of pockets in the handle for the alloy to grab onto.
This actually reminded me of an article I saw a while ago on an adhesive fixturing setup: Shop Finds Fixturing Solution for Flexing Parts |
Modern Machine Shop
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again Aaron:
There is, of course, another path forward, and that is to hardmill the shape complete, staging the final profiling and the cut direction so the knife stays attached to the blank for as long as possible and is cut free strategically so it never gats a chance to vibrate and scream and trash cutters and generally make a nuisance of itself.
Here's what I envision:
The blank is drilled for mounting hardware along its periphery and in the rivet bore locations for the handle and then hardened.
It's made flat with a press and surface grinder, and then bolted to a plate.
One side is milled making no attempt to profile the outside.
The second side is milled and the back is profiled leaving tabs on the back.
The edge is not profiled yet.
The handle is rough profiled too.
The last operation, beginning at the tip of the blade, is to cut the edge side up to the first tab on the back, then cut that back tab, then go back to the edge side and profile to the next back tab, then cut that tab, then walk the whole length of the blade that way.
Once you get to the the handle, you can finish profile it conventionally because you have bolts going through the rivet bores and the blank is fully supported at that point.
If you need to keep the blade from singing, hot melt glue or even a blob of Plasticene under the tip will work wonders.
The biggest nuisance is to avoid divot marks on the back of the blade where the tabs were cut...lead in and lead out moves will prevent those, as will never letting the cutter dwell in the corners when the tabs were first made, so "lead in" and "lead out" those too.
You could even rough profile the back and handle with tabs while it's still soft, so you only have to finish mill the back and handle in the hard state.
I'll betcha it'll work slicker than snot and it will avoid all of what it takes to mount the parts on a separate machine for the separation from the blanks.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
There is, of course, another path forward, and that is to hardmill the shape complete, staging the final profiling and the cut direction so the knife stays attached to the blank for as long as possible and is cut free strategically so it never gats a chance to vibrate and scream and trash cutters and generally make a nuisance of itself.
Here's what I envision:
The blank is drilled for mounting hardware along its periphery and in the rivet bore locations for the handle and then hardened.
It's made flat with a press and surface grinder, and then bolted to a plate.
One side is milled making no attempt to profile the outside.
The second side is milled and the back is profiled leaving tabs on the back.
The edge is not profiled yet.
The handle is rough profiled too.
The last operation, beginning at the tip of the blade, is to cut the edge side up to the first tab on the back, then cut that back tab, then go back to the edge side and profile to the next back tab, then cut that tab, then walk the whole length of the blade that way.
Once you get to the the handle, you can finish profile it conventionally because you have bolts going through the rivet bores and the blank is fully supported at that point.
If you need to keep the blade from singing, hot melt glue or even a blob of Plasticene under the tip will work wonders.
The biggest nuisance is to avoid divot marks on the back of the blade where the tabs were cut...lead in and lead out moves will prevent those, as will never letting the cutter dwell in the corners when the tabs were first made, so "lead in" and "lead out" those too.
You could even rough profile the back and handle with tabs while it's still soft, so you only have to finish mill the back and handle in the hard state.
I'll betcha it'll work slicker than snot and it will avoid all of what it takes to mount the parts on a separate machine for the separation from the blanks.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
aarongough
Stainless
- Joined
- Oct 27, 2014
- Location
- Toronto, Canada
Having used body filler quite a bit in the past: no way!!
I hate the smell of that stuff, and most chemical smells don't bother me much at all!
aarongough
Stainless
- Joined
- Oct 27, 2014
- Location
- Toronto, Canada
Quickly revisiting the idea of babbitt/bodyfiller/hot glue for second op fixturing to supplement tabs:
I have previously tried some fancy hot glue as a quick/temporary fixture measure. From memory I thought it was a urethane thermo-set but it is actually a polyamide thermo-plastic, this stuff: Ad Tech 700 Polyamide Hot Melt – Hotmelt.com
Applying this to cold metal parts gets you a bond that isn't that strong, it peels away cleanly and fairly easily. Two 9" lengths of steel joined with a 3" long lap joint of the adhesive can be broken by hand easily...
However: I just tried pre-heating the two bits of steel before applying the glue, and holy shit!
No way is that bond being broken by hand. I had to get a steel wedge (scrap blade) and hammer it in between the two pieces with a mallet to break the bond, and even then it took more than a dozen strikes with the rubber mallet to get the wedge in far enough for the bond to fail! Very surprised at how strong it was.
Seems like by controlling the pre-heat I might be able to tune the strength of the bond. I didn't measure the exact temp of the pieces before trying, likely around 100ºC or so...
Using that method with a controlled pre-heat and filling the gap in between the blade and a pocket underneath it, like suggested with the babbitt metal, might well give enough structure to be able to clean up the profile with a gentle operation. Seems like it would certainly be worth a shot!
I'll have to work out if there's some not-too-nasty solvent that will dissolve this stuff though because if I overdo it with the pre-heat accidentally the bond looks like it would be permanent in that situation lol
I have previously tried some fancy hot glue as a quick/temporary fixture measure. From memory I thought it was a urethane thermo-set but it is actually a polyamide thermo-plastic, this stuff: Ad Tech 700 Polyamide Hot Melt – Hotmelt.com
Applying this to cold metal parts gets you a bond that isn't that strong, it peels away cleanly and fairly easily. Two 9" lengths of steel joined with a 3" long lap joint of the adhesive can be broken by hand easily...
However: I just tried pre-heating the two bits of steel before applying the glue, and holy shit!
No way is that bond being broken by hand. I had to get a steel wedge (scrap blade) and hammer it in between the two pieces with a mallet to break the bond, and even then it took more than a dozen strikes with the rubber mallet to get the wedge in far enough for the bond to fail! Very surprised at how strong it was.Seems like by controlling the pre-heat I might be able to tune the strength of the bond. I didn't measure the exact temp of the pieces before trying, likely around 100ºC or so...
Using that method with a controlled pre-heat and filling the gap in between the blade and a pocket underneath it, like suggested with the babbitt metal, might well give enough structure to be able to clean up the profile with a gentle operation. Seems like it would certainly be worth a shot!
I'll have to work out if there's some not-too-nasty solvent that will dissolve this stuff though because if I overdo it with the pre-heat accidentally the bond looks like it would be permanent in that situation lol
aarongough
Stainless
- Joined
- Oct 27, 2014
- Location
- Toronto, Canada
The main issue if it can't hang onto a flat surface is going to be the area around the blade... Because the blade is a fairly large smooth flat surface if the fixturing alloy can't hang onto it then cutting the profile in that area would be very dicey!
Seems like adhesive fixturing of some kind might be worth a shot though! This hot glue that I just tried certainly hangs onto flat areas without any issues, maybe too well which brings its own problems!
newtonsapple
Hot Rolled
- Joined
- May 16, 2017
One thing that might make this easier is that the blade edge area does not really need to be finish machined as I sharpen that area away anyway, so perhaps I could mount toggle clamps overhead in that area to hold the blade down. That would potentially be fairly simple and only require a single customized fixture per blade shape... I was mucking around with this concept a little last week:
The idea being that I would machine the blade in the 'picture frame' similar to what I show in my first post, but I would cut out the outline oversize and leave tabs, then finish the outline in this fixture. The red marker indicates the areas where I would take a finish cut. The biggest issue I see is that the toggle clamps are fairly tall which would get in the way of having nice stubby tooling, but perhaps a different kind of clamp or something could be used.
Check out pneumatic or hydraulic swing clamps for this application
https://www.ebay.com/sch/i.html?_fr...0&LH_TitleDesc=0&_osacat=0&_odkw=swing+clamps
You could mount them below your fixture plate. It wouldn't be too bad to even program them to swing out of the way as needed.
I don't think we see a picture of your fixtures without a knife, but make sure to relieve the middle to guarantee clamping ends up near the perimeter being milled.
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again Aaron:
If you place the tabs strategically and cut the tabs strategically you don't need to hold the part securely with the potting, whatever it is.
Plasticene will work just as well as some super sticky adhesive...you neither need nor want something that may be a nightmare to remove.
All you need from the potting is to suppress the vibrations from the tip of the blade as the tabs are cut and the edge side is profiled in stages from tip to base.
The material adjacent to the cut will stabilize the cut zone, which is all you need to keep the cut from screaming and beating up the cutter...the biggest trick as I alluded to before, is to keep from making divots in the profile as you start and stop it in little increments.
It's a bit like turning a long skinny part in the lathe in stages...if you turn the first quarter inch to 0.100" diameter and then the next 1/4" to diameter and etc etc, you can walk down the whole length of the part in these little steps leaving a very nice part, so long as you don't let the cutter dwell at the end of the cut, and so long as you enter the cut with a radiused lead in rather than just ramming the cutter into the already finished bit and then driving it forward.
It would be a technique I would certainly try...it takes almost nothing to give it a go.
You don't even need to harden the blank before trying it...you will learn plenty about what works the first time you cut one.
I've made hundreds of "impossible" parts using this technique; some of them so floppy they needed to be stabilized bit by bit with successive dollops of hot melt glue as the part was developing.
I don't have any photos I can find of those, but I can show you a tiny slide ejection system for a mold that shows the result of the "nibble it in stages" technique.
The smallest pins are 0.0468" diameter and if I remember correctly, they are about 3/4" long.
They were cut in a Haas Minimill with a necked down cutter, so only the first 0.050" would actually cut.
If I remember right they are S-7 at 58 RC cut in the fully hard state from the solid.
Here you go:
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
If you place the tabs strategically and cut the tabs strategically you don't need to hold the part securely with the potting, whatever it is.
Plasticene will work just as well as some super sticky adhesive...you neither need nor want something that may be a nightmare to remove.
All you need from the potting is to suppress the vibrations from the tip of the blade as the tabs are cut and the edge side is profiled in stages from tip to base.
The material adjacent to the cut will stabilize the cut zone, which is all you need to keep the cut from screaming and beating up the cutter...the biggest trick as I alluded to before, is to keep from making divots in the profile as you start and stop it in little increments.
It's a bit like turning a long skinny part in the lathe in stages...if you turn the first quarter inch to 0.100" diameter and then the next 1/4" to diameter and etc etc, you can walk down the whole length of the part in these little steps leaving a very nice part, so long as you don't let the cutter dwell at the end of the cut, and so long as you enter the cut with a radiused lead in rather than just ramming the cutter into the already finished bit and then driving it forward.
It would be a technique I would certainly try...it takes almost nothing to give it a go.
You don't even need to harden the blank before trying it...you will learn plenty about what works the first time you cut one.
I've made hundreds of "impossible" parts using this technique; some of them so floppy they needed to be stabilized bit by bit with successive dollops of hot melt glue as the part was developing.
I don't have any photos I can find of those, but I can show you a tiny slide ejection system for a mold that shows the result of the "nibble it in stages" technique.
The smallest pins are 0.0468" diameter and if I remember correctly, they are about 3/4" long.
They were cut in a Haas Minimill with a necked down cutter, so only the first 0.050" would actually cut.
If I remember right they are S-7 at 58 RC cut in the fully hard state from the solid.
Here you go:
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again Aaron:
I just read your last posts; you don't need to fear hardmilling the second side of the blade if you haven't profiled it yet.
So long as it's fully supported all along its edges it'll be strong as houses.
You need to use sharp cutters; it's beneficial not to have much material to remove, and the amount to remove should be very consistent when you do the finishing.
This argues for roughing it while it's still soft if you can.
But it's not going anywhere if you surface mill it before you cut tabs along the spine.
It's when you profile the edge and spine that it's going to start to sing.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
I just read your last posts; you don't need to fear hardmilling the second side of the blade if you haven't profiled it yet.
So long as it's fully supported all along its edges it'll be strong as houses.
You need to use sharp cutters; it's beneficial not to have much material to remove, and the amount to remove should be very consistent when you do the finishing.
This argues for roughing it while it's still soft if you can.
But it's not going anywhere if you surface mill it before you cut tabs along the spine.
It's when you profile the edge and spine that it's going to start to sing.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
plastikdreams
Diamond
- Joined
- May 31, 2011
- Location
- upstate nj
You could always try left hand cutters so it forces the piece down.
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi BSCustoms:
You wrote:
"have you thought about wiring your bevels?"
It's an attractive thought: sadly though it is fraught with problems that are not trivial to ovecome.
The first is material movement through stress release.
I first knocked up hard against this when I naively took on a part for a film winding machine with a similar thickness to length ratio as a knife and just couldn't keep it from crawling all over the place during cutting.
I tried damn near everything: annealing. stress relieving, shot peening, staged roughing etc etc etc.
The warpage need only be very little to forever make wire shorts and stall the cut continuously...it can drive you absolutely bonkers.
If you can eventually make a cut, it looks like a pig's breakfast with lines all over it and you only get one shot at it...you simply cannot run a skim pass because you have no idea where the surface is in space anymore...it could be anywhere.
The second is how long it's all gonna take...if the blade is 2" wide at the handle and 10" long, it's 20 square inches per side and at 20 square inches per hour that sounds not too bad.
The reality though is that the bevel angle changes continuously and the flushing is imperfect so if you can get 10 square inches per hour, you're doing pretty good.
So now it's not a 2 hour cut, it's a 4 hour cut.
The third of course, is the complexity of programming a shape like this.
The way to do it is to map the upper contour onto a flat plane above the widest part of the blade; map the lower contour onto another flat plane below the lowest part of the blade and connect the two in CAM with a programming technique called "complex upper and lower" where you take each portion of each contour and connect it to its counterpart on the other contour; linking them together segment by segment.
The wire EDM will use the U and V axes to intersect both edge contours making a flat connection between them.
If you've mapped the contours properly you will get the edge profile and the bevels at the same time...only the back will need to be profiled as a separate operation.
So supposing you want to do it this way.
Making them out of thin plates is hopeless as I described above...they'll crawl all over the place as you cut them.
But you can profile a thick block and then flip it 90 degrees and slice knives out of it like Bologna slices.
On the first side you can rough and skim it as many times as you want.
The thickness of your blank will keep it straight although your waste stock will curl like a potato chip as you cut it free.
On the second side you get a single shot so it will be roughing pass precision and finish.
That might be good enough.
You will also pray a lot that the knife blade you're cutting free doesn't also curl like a potato chip.
So you could give it a try, and you may well prove me wrong, but I'm not betting on it.
I've thrown away enough experiments like this over the years that I've become a sceptical old fart.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
You wrote:
"have you thought about wiring your bevels?"
It's an attractive thought: sadly though it is fraught with problems that are not trivial to ovecome.
The first is material movement through stress release.
I first knocked up hard against this when I naively took on a part for a film winding machine with a similar thickness to length ratio as a knife and just couldn't keep it from crawling all over the place during cutting.
I tried damn near everything: annealing. stress relieving, shot peening, staged roughing etc etc etc.
The warpage need only be very little to forever make wire shorts and stall the cut continuously...it can drive you absolutely bonkers.
If you can eventually make a cut, it looks like a pig's breakfast with lines all over it and you only get one shot at it...you simply cannot run a skim pass because you have no idea where the surface is in space anymore...it could be anywhere.
The second is how long it's all gonna take...if the blade is 2" wide at the handle and 10" long, it's 20 square inches per side and at 20 square inches per hour that sounds not too bad.
The reality though is that the bevel angle changes continuously and the flushing is imperfect so if you can get 10 square inches per hour, you're doing pretty good.
So now it's not a 2 hour cut, it's a 4 hour cut.
The third of course, is the complexity of programming a shape like this.
The way to do it is to map the upper contour onto a flat plane above the widest part of the blade; map the lower contour onto another flat plane below the lowest part of the blade and connect the two in CAM with a programming technique called "complex upper and lower" where you take each portion of each contour and connect it to its counterpart on the other contour; linking them together segment by segment.
The wire EDM will use the U and V axes to intersect both edge contours making a flat connection between them.
If you've mapped the contours properly you will get the edge profile and the bevels at the same time...only the back will need to be profiled as a separate operation.
So supposing you want to do it this way.
Making them out of thin plates is hopeless as I described above...they'll crawl all over the place as you cut them.
But you can profile a thick block and then flip it 90 degrees and slice knives out of it like Bologna slices.
On the first side you can rough and skim it as many times as you want.
The thickness of your blank will keep it straight although your waste stock will curl like a potato chip as you cut it free.
On the second side you get a single shot so it will be roughing pass precision and finish.
That might be good enough.
You will also pray a lot that the knife blade you're cutting free doesn't also curl like a potato chip.
So you could give it a try, and you may well prove me wrong, but I'm not betting on it.
I've thrown away enough experiments like this over the years that I've become a sceptical old fart.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
aarongough
Stainless
- Joined
- Oct 27, 2014
- Location
- Toronto, Canada
I have a friend who made knife bevels for quite a while with WEDM, and while it did work he did end up with striations across the blade bevel, and his hand finishing times were significantly longer than mine are with hard-milling.
He has since switched to hard milling his bevels and from what I've heard he has zero regrets!
Marcus: one small thing worth noting is that, for my knives at least, the bevel is a simple 2D contour with a vertical wire when viewed from a specific angle... To illustrate here is a view from CAD of my knife at an angle 90º relative to the blade bevel:
Most hunting/folding/kitchen knife blades should be the same way unless they are hollow ground or convex ground. Hollow being impossible with wire anyway.... I imagine a convex bevel would be possible with WEDM, but only after many cuts!
It's worth noting that it's also a compound angle because you have to lay it over in one direction for the bevel, and then drop the tip downward to get the angle correct in the area where the bevel transitions into the handle (the 'plunge line'). I would not want to be responsible for setting a part up like that, seems like it would be pretty fussy to get right!
He has since switched to hard milling his bevels and from what I've heard he has zero regrets!
Marcus: one small thing worth noting is that, for my knives at least, the bevel is a simple 2D contour with a vertical wire when viewed from a specific angle... To illustrate here is a view from CAD of my knife at an angle 90º relative to the blade bevel:
Most hunting/folding/kitchen knife blades should be the same way unless they are hollow ground or convex ground. Hollow being impossible with wire anyway.... I imagine a convex bevel would be possible with WEDM, but only after many cuts!
It's worth noting that it's also a compound angle because you have to lay it over in one direction for the bevel, and then drop the tip downward to get the angle correct in the area where the bevel transitions into the handle (the 'plunge line'). I would not want to be responsible for setting a part up like that, seems like it would be pretty fussy to get right!
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi Aaron:
Thanks for that, it makes perfect sense that the bevel could be a surface curved only in one direction and not twisted as I envisioned.
So one part of the puzzle need not be as complex as I pretended.
However, there's another point I want to make about wiring the bevels even though we're no longer seriously contemplating doing it that way.
You remarked on tilting the blade to get the bevels and the transitions...it's actually far more common and ultimately much simpler to tilt the wire as you need to and set up the blade only one time to get both bevels and to get the transition from blade to handle correct in one shot.
This "complex upper and lower" programming strategy is a good way to do it.
It doesn't seem to be that popular a programming technique, and I don't know why that it, but many wire guys seem never to have heard of it before.
But then most guys do most programming in some kind of CAM system and most of the high end ones have a similar way to make these kinds of shapes but they break each contour into a gazillion little line segments first.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
Thanks for that, it makes perfect sense that the bevel could be a surface curved only in one direction and not twisted as I envisioned.
So one part of the puzzle need not be as complex as I pretended.
However, there's another point I want to make about wiring the bevels even though we're no longer seriously contemplating doing it that way.
You remarked on tilting the blade to get the bevels and the transitions...it's actually far more common and ultimately much simpler to tilt the wire as you need to and set up the blade only one time to get both bevels and to get the transition from blade to handle correct in one shot.
This "complex upper and lower" programming strategy is a good way to do it.
It doesn't seem to be that popular a programming technique, and I don't know why that it, but many wire guys seem never to have heard of it before.
But then most guys do most programming in some kind of CAM system and most of the high end ones have a similar way to make these kinds of shapes but they break each contour into a gazillion little line segments first.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining