Machining glass, borofloat, b270- w/Haas vert mill

For 6 months I've been lead programmer and operator for a glass company. We have 2 haas vf4ss and 2 mini mills. Since I took over I have revamped the department with machine able vises, using their opm40 probes to their fullest rather than just an edgefinder like they have been. And I've reduced cycle times to the best of my ability by researching new tooling and program methods. I am in need of advice from someone with knowledge of the glass industry. I utilize "stepover methods" only .010 at a time at most. with 120 – 600 grit bits ranging from .020 dia to 1.5 inch diameter, some solid abrasive tools, core drills for plunging, ramping in, and helical entries either to get another tool to finish the profile with side cutting since I have not found bits for glass that will cut downward as well as side or stepover movements besides core drills but those are limited to their small cutting depths and their need for cleaning and dressing too often. For milling and edge grinding borofloat, fused silica, flashed opal, b270 and Uv filters I've been using these diamond grit end mills called CeraX endmills. I am in dire need of someone with experience with these materials as there isnt much on the web as far as advice on toolpaths, feeds and speeds (hands on learning) workholding is typically pine wax and ground aluminum bases, or vacuum which we are in need of reliable and modular vacuum fixtures , all we have are what weve made in shop. Which only work 50% of the time and being only one person with 4 machines I'd rather convince them to invest in products rather have me fashion them all. Does anyone have any recommendations regarding abrasive tooling with plunging and edging capabilities, workholding, and toolpath/ programming advice. any articles, Websites, forum posts. any and all info helps. Thanks for listening to my convoluted cry for help.

Nickysticks,

How does it feel to be one of the leading world experts in machining borofloat, fused silica, flashed opal, b270 and Uv filters?


One company to ask about their help would be Union Tool. They have end mills that have been used to mill carbide.


Good luck!

Whoa! You ask a lot! ;-)

Glass is tough! It seems you have direct experience in just how tough. It also sounds like you are asked to do some complex and interesting things with glass! Good for you! I've been mostly concerned with plano elements. (no LENSES! ;-)

There is no possibility for plunge cuts in glass, as the surface speed goes to zero in the center, and glass will not flow like metal will.
orbiting plunge cuts are possible, but tool life is always a problem. The cutting facets dull, then pressure goes up and the glass fractures.
That sucks when the parts have $2K worth of work into a $3k substrate.

The big picture is always how to rough off the waste with large diameter wheels or saws.
Abrasive charged wire saws are an option. Think of a multi axis Wire EDM

Wax works well to mount to sacrificial plates (glass) that are standardized to suit your vacuum table. (6.5 inch rounds were "standard "
for me).

Universal Photonics were always a help, but not always a solution. Same goes for all the "diamond tool" vendors.

It sounds to me like you are in an enjoyable position!

ETA

Question:

Are you machining with Water? Soluble oils? mineral oil? or synthetics?

And.. by the way, I have machined glass elements on both the Hubble Space Telescope and the "first" two Mars Rovers.
Spirit and Opportunity!

ps

your "typical" work piece geometry will be most informative. The exception always requires exceptional consideration.

Could you elaborate on what sort of applications? I know people who have done microfludics in glass, such as drilling small holes and cutting channels (long time ago so can't find them to ask easily) but that was on the millimeter or sub millimeter scale. So with that in mind, the VF4ss is a very big machine for anything I could imagine in glass!

You fundamentally cant plunge grind with more than about 40% of the cutters diameter with a solid faced tool or pin, just does not work at all well, its not just a case of cutting in the middle, the cutting surface just becomes bound up with swarf and it all goes to shit. Contact length is everything in all grinding operations, its the key thing about how abrasives work. helical in with a wider faced core drill is to my knowledge the only way to go and you need through spindle coolant. The narrow cutting band of the core drill means you can keep it flushed well so long as you have through spindle coolant. If your suffering issues with dulling or build up and haveing to dress loads it points to you either feeding too hard or inadequate flushing, diamonds do really well cutting most glasses and stones, key thing is the flushing, because the swarf tends to errorde the binder and that then lets the diamonds fall out.

Very few people on the planet do this kinda stuff, i had a friend who was a Crystal cutter and he use to make all sorts of wacky stuff out of quartz, synthetic ruby etc. Nothing about what he did could be compared to metal cutting on a similar time scale and accuracy requirements were through the roof.

CalG said:

Whoa! You ask a lot! ;-)

Glass is tough! It seems you have direct experience in just how tough. It also sounds like you are asked to do some complex and interesting things with glass! Good for you! I've been mostly concerned with plano elements. (no LENSES! ;-)

There is no possibility for plunge cuts in glass, as the surface speed goes to zero in the center, and glass will not flow like metal will.
orbiting plunge cuts are possible, but tool life is always a problem. The cutting facets dull, then pressure goes up and the glass fractures.
That sucks when the parts have $2K worth of work into a $3k substrate.

The big picture is always how to rough off the waste with large diameter wheels or saws.
Abrasive charged wire saws are an option. Think of a multi axis Wire EDM

Wax works well to mount to sacrificial plates (glass) that are standardized to suit your vacuum table. (6.5 inch rounds were "standard "
for me).

Universal Photonics were always a help, but not always a solution. Same goes for all the "diamond tool" vendors.

It sounds to me like you are in an enjoyable position!

ETA

Question:

Are you machining with Water? Soluble oils? mineral oil? or synthetics?

And.. by the way, I have machined glass elements on both the Hubble Space Telescope and the "first" two Mars Rovers.
Spirit and Opportunity!

ps

your "typical" work piece geometry will be most informative. The exception always requires exceptional consideration.

Click to expand...

... i know totally loaded post... we use mandrel wheels with varying grits to ground our geometric shapes.. typically diameters with thru holes or inner diameters, "donut" shapes... from .500 to 12 13 inches. Alot of odd jobs that standard bases and fixturing requiring customized setups. I'm learning core drills are my best friend when it comes to ramping in to acquire inside shapes and holes.. we use water soluble coolant, and we have had thru spindle coolant in the past ( before I arrived) but apparently it causes problems so the prior operator/programmer removed it. I dont why they would just do away with something that's proven to be beneficial and some even say makes this type of work impossible on these machines to do without. Glass is a whole different animal alot of trial and error and process of elimination. Unfortunately this company has been behind in their jobs and has a problem getting orders out the door. And me being new to this material. And having noone here to guide me besides their "engineer"/ mechanic whom doesnt know much about programming cant help as much as I need. And theres next to nothing online for reference. Alot of things have come natural but I'm recently experimenting with conventional and climbing, as well as playing with speeds and feeds. The last programmer would just jack it up to 10k every time every tool and adjust the feedrate.. I can share some pictures if that will help with understanding my applications and tooling

With core drills used to produce a hole (or slug) from a solid, there is no real option to through spindle coolant supply.
There are useful add on fluid couplings sold for this purpose. Additional flood coolant is always welcome I don't feel there can be too much.

How are you pulling out the swarf from the coolant? Recirculating glass grit is not a good thing.
Filter paper as the coolant drains into to coolant tank, baffled tank, Long settling times in the tank and regular waste removal from the tank are all necessary. Keep that coolant CLEAN!
My experience is with mineral oil, but I have run water base in an edger.

Just a note regarding machinery. To produce rounds, the method of sawing squares, wax stacking the blanks between centers on a cylindrical grinder is a very reliable technique. Maybe not as fast as a core drill the correct size, but the finish results will be superior,
A stack of roughed out core drilled blanks could be treated in the same way.

Getting familiar with your tooling is a big learning curve. Diamond grit size concentration and depth all matter when it comes to how hard you can push the cut and what one might expect for finish results. I never saw useful performance from electro-plate bonded diamond.
Perhaps others have.

Depending on the geometry of the parts you make, either investigating laser cutting of glass: Mound Laser Myth Busting: Laser Machining Glass Snowflakes - YouTube or advanced methods of sawing with diamond edge tooling may be of use.

Yeah you badly want thru spindle coolant, pretty much every diamond sawing, grinding etc operation out there uses it, from industrial concrete cutting on through to even stone work, grit - cuttings naturally get slung out, add a coolant flush and it works even better, try and blow coolant in and your going to get no were fast. You have to clear the swarf, if you don't you eat tooling fast and make heat.

Milland said:

Depending on the geometry of the parts you make, either investigating laser cutting of glass: Mound Laser Myth Busting: Laser Machining Glass Snowflakes - YouTube or advanced methods of sawing with diamond edge tooling may be of use.

Click to expand...

Laser cutting of glass is possible, But working out the parameters for each TYPE of glass is an exercise. Even thickness matters!.

The big downside for technical applications is the presence of micro cracks in the heat effected zone. Invariably those defects grow!. I've been through the misadventure trying to laser mark glass items.
Great for commercial novelties, but disappointing for items that carry large price tags. (Things that go "klink" in the night.

Marking glass with laser activated transfer inks worked well.

There's new ultra-high speed pulse laser systems that cut using an ablation process rather than "heat", and should produce less edge damage.

Laser Ablation Processing (LAP)

Probably has issues with "tuning", as you suggest, but I'd expect these will become more commonplace in high-end specialty machining in the coming years.

How are you filtering your coolant!!!! I use a settling tank, then anther much bigger settling tank, then 20 micron pleated filters, then a 1 micron pleated filter. It takes a few hours of use to load up the 1 micron filter before the coolant is clean, 1 micron is too coarse. Done right you only need to clean your filters once a year and you won't have any problems with pump or TSC seals. I have only machined fused glass once, the wear on my diamond tools was such that I will not do it again without charging enough to cover the tools, which is too much for my product. Glass is fun, nice and brittle, but I would hope yours is tempered so you don't get any residual stress surprises.

Make sure your coolant is getting properly filtered and then get your through spindle coolant operational again, it will save a whole lot of pecking with your drills and premature wear on your mills.

Not much info on the web about this and I have not found an expert that really knows either. Sorry but trial and error is the only way, what works will be dependant on what your are machining, the shapes you cut, and ALL the things used to cut it. I have heard it take 10 years of doing it before you are ready to learn and I have to agree.

Just looked up your tools, you lucky dog! They look real nice. Not what I would make myself but pretty good. If you get your TSC going I am sure tool life will increase DRAMATICALLY! I ended up making my own bodies and getting the diamond done by a company that specializes in this, and I have tried quite a few over the years. The many radially aligned coolant holes look good, but drop the flutes and make the holes .015" with 200+ psi coolant pressure. Just what my experience has taught me works best. What matters is not volume of coolant but quality of delivery, your grinding not milling. I will say the grit size looks much too small for roughing, much too small.

Diamond crystal size makes a massive difference in tool life. When I made a single size jump for my roughing tools, against the experts advice, my tool life went up 10-60 fold and I could feed faster. Diamond quality also has a big effect on tool life. Trial and error, there is no other option here.

Looks like you have a really fun job, this is exactly what I wanted to do. Here is a link to my website showing the product I make with diamond tools. This is the front of a glass switchplate view with the pockets on the backside. The radiused edges would be polished if I had finished it, which I do on my machine. I design and make all but 2 of the tools I use, the polishing tools I do all inhouse.


Question time. Please answer the ones you can as it will help us answer yours, including the ones you are not asking.

Probably my most important question. Do you have a good microscope to inspect your tools to see how they wear and how they fail? This is critical to figure out how to improve your process, critical!!!! You need to be able to inspect the crystals cutting edges and bond. You need to be able to see the cutting edges and how they wear and how the bond is eroding.

Do you keep tools separate and only use them on similar materials? I have found mixing too broad a range of materials on one tool dramatically decreases that tools life and quality of cut.

What size tools are you using, what size diamond crystal, and what bond including percentage of bond line if plated. If you really know what you are doing then you can't answer the last two.

Curious what a Cera-X 1/4" mill costs?
Are they carbide bodies?

Also curious how your way cover wipers are holding up?

Now I get to go clean out my first holding tank.