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Question about milling on BT-30 machines (DT-1, Speedio,etc)

DanASM

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Mar 11, 2019
I have been recently looking more into cnc machines as my cash situation has been improving.

I was always thinking that a bigger machine running smaller parts would offset any weaknesses that a smaller machine may have. Example - 5c collet system on an A2-5 spindle (lathe) keeping diameters to 1.00" or under to make sure the machine has enough power to do its job.

Now I am looking into mills and 4th axis stuff instead of looking at live tooled lathes. With a 4th axis setup I could essentially run parts that a live tooled lathe would do but still have the ability to mill other parts that a live tooled lathe cannot do. I could even get a 5th axis unit and do 3+2 setups quickly.

My question is more related to the Haas DT machines. I have seen videos of them milling somewhat impressively. Looks like more high speed machining techniques but seemed to not have problems.

So the more I look into these machines the more I like them for my current situation. I am sure they will have their limitations too. I hear great things about the Brother Speedio line and have been told it has little power milling anything hard or anything with heavy cuts (understandable), but they do say great things about aluminum and steels and no one can touch the speeds they have.

Share your thoughts on the good/bad/ugly about the BT-30 spindles. I dont know if one would be a good investment for me or not. Any cnc milling will allow me to take on additional work that would bring in additional cash to the company. A 2 axis cnc lathe will not really bring in too much additional work but will make my current workload easier to handle.
 
30 tapers have been my choice for the last 25 years. How capable they are depends on how you use them. Keep your projections to a minimum and tailor your tools, speeds, and feeds to their strengths and you will do fine. Treat them like 50 taper box way machines and you will be disappointed. Keep in mind that like other machines the taper size is a tiny indicator as to the machine's capability. In many videos of 30 taper machines cutting you hear a lot of ringing indicating it is being pushed hard, on my 8000 lb box way 30 taper I don't ever hear noises like that, ever. I have cut steel in the 55-60 HRC ranges with no problems with far lighter built 30 tapers so they can cut hard just fine.

What tools do you use most and how do you use them? Often I rough with a 1/4" or even up to a 3/8" mill so a 40 taper would be a waste of energy, size, and speed for my parts.

And the acce/ decel of everything and tool changes will be addictive.
 
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In the 80's and 90's all BT30 machines had 5 or 7.5hp spindles. Now 15 and 20hp is the norm. One thing has remained the same though, the retention knob. That is the weak point of all BT30 spindles. Make sure you get good quality retention knobs, ours for example are made from H-13 tool steel.

Nice short gage length tool holders really help a lot and will allow your machine to take decent depths of cut. Situations like long flute lengths or finishing tall side walls are better left for 40 taper machines.
 
This all does make sense.

I am a brown and sharpe screw machine shop with no cnc's so I am looking into my first one. I am not looking to buy what I want. I am looking to buy what will make me the most money.

I was thinking of the smaller parts that I wouldnt need a cmm or any other expensive measuring equipment. Gas Blocks are an easy example.

I see a couple of DT-1's on ebay but no DM's (40 Taper).

If I were to run round slugs in a 4 axis rotary, it would be as if I had a live tooled lathe. I like that idea very much and can see it being easier to recoup my money.

I can imagine tooling would be less expensive as they are all mostly smaller.

I guess anyone can run a good machine the wrong way and some people can run a bad machine just right. So I shouldnt be too concerned.
 
Check into the tooling question a little bit - yes 30 taper is smaller, but 40 taper is ultra common and very high volume. For example Franks's site (maritool) lists BT30 ER16x50mm at $104.30 while cat40 er16x2" is $103.65. So BT30 tooling isn't necessarily any cheaper than CAT40 - this is surely solely a function of the huge volumes of CAT40 tooling.

As DanASM surely knows, screw machines go pretty fast for the things they're suited too. I'd say the same is true of 30 taper machines - quite productive for the right sorts of parts.
 
In the 80's and 90's all BT30 machines had 5 or 7.5hp spindles. Now 15 and 20hp is the norm. One thing has remained the same though, the retention knob. That is the weak point of all BT30 spindles. Make sure you get good quality retention knobs, ours for example are made from H-13 tool steel.

Nice short gage length tool holders really help a lot and will allow your machine to take decent depths of cut. Situations like long flute lengths or finishing tall side walls are better left for 40 taper machines.
Frank, what do you think is it that breaks the 30 taper pull studs? The tensile strength on a through coolant type is around 11,000 lbs so it's not drawbar tension. And if you pull the tool holder out of the spindle in a cut that would pretty much kill any pull stud, I would think.

Dan, keep in mind drawbar tensions on 30 taper mills are around 500-1000 lbs so 15 hp could get you into trouble with the wrong cut.
 
Situations like long flute lengths or finishing tall side walls are better left for 40 taper machines.
That is a relative statement. 1/4" may be a huge sidewall for someone doing tiny medical parts with .010" endmills, but practically microscopic to someone running large parts that require a crane to load and unload. To be more specific, on a Brother BT30, I feel comfortable with a 2-3" sidewall in 6061 or a 1-2" inch sidewall in steels etc.. depending if the machine has Big Plus/Dual Contact Spindle.
DanASM, many Brown and Sharp and Davenport shops out here love the R450 pallet change machine to make them the most money. Easy to add 4th axis. First time I ran a Brother was at a Davenport-Miyano shop. They had 3 of the R450 style machines, used to be called the TC-324. I was impressed with the quality, reliability, accuracy and efficiency of the Brother machines.

R450 video with 4th on pallet 2:
YouTube
 
I guess anyone can run a good machine the wrong way and some people can run a bad machine just right. So I shouldn't be too concerned.
They are not so fragile you can't use them, but you do have to listen to them and gently push their limits as you learn them, same as any machine. I think the biggest drawback of a 30 taper is you REALLY have to keep your tool projections to an absolute minimum!!! This can't be overstated.
 
They are not so fragile you can't use them, but you do have to listen to them and gently push their limits as you learn them, same as any machine. I think the biggest drawback of a 30 taper is you REALLY have to keep your tool projections to an absolute minimum!!! This can't be overstated.

I was just going over a thread about tool length stickout and noticed that 1/2" endmill had an LOC of 1.25" This didnt seem like much at all. I then looked over a print of a gas block that I have and it appears to be 1" x 1.25" after machined.

It does kind of limit the work it could do. I dont see much aluminum in my world. I see mostly steels and Stainless. I do have about 30-40 customers on my list and I would say half of them I dont do work for because I dont have the machinery needed. They would gladly send me work to quote and I am sure my current customers would have mill work as well.

I tend to cut harder metals without going into the super alloys. I dont see much aluminum in my future and there is always someone else low balling brass jobs just for the scrap.

A BT-30 machine wouldnt take up much space and I could use it for teaching new workers in the future. I feel like I may be better off with a mini mill with a 40 taper. I could run it at a cheaper hourly rate to make up for the slower speed and maybe find enough work to keep it running.

Lots too think about boys. Thanks for the insight. Everything spoken about makes perfect sense to me.

My worst fear is spending the money and then 2 months later wishing I had the cash to put towards a different machine that would do what I really wanted it to do.
 
You're fine with a 1/2"x1-1/4" or 1-1/2" endmill, as long as you don't stick it in a 4" projection holder. Frank makes some wonderful stubby sidelock holders.
 
Dan, before you set your mind against it, wait for BROTHERFRANK to tell you about the high torque spindle variant. If my memory serves, it's his favorite, and may be well suited to the work you're doing.
 
Are you familiar with PM member SRTMike? He is in the Mass. area also. He speaks very highly of his local Yamazen rep.. Mike has a S700 and recently was involved in the purchase of a R650 pallet machine. Yamazen currently has some inventory clearance opportunities on S500 and S700 size High Torque (17 hp) Big Plus machines. You may be pleasantly surprised with what you can get. Some large tools going into steel on this High Torque:

YouTube

This is typical HSM type technique in steel:

YouTube
 
Don't buy a mini mill unless it has a riser in it.
Spindle nose to table,4 inches is not going to allow much Z travel.
Cat 40 taper sticks out 2 inches from spindle any 6 inch vice is 2.875 thick.
Add it up and you need at least 7 inches from spindle nose to table.
With only 10 inches of Z travel to work with.
I was looking into a mini mill and bought a used tc-227 and found out that a Z deprived machine needs at least 7 inches spindle nose to table. On one job I only have 1 inch of clearance above vise.
 
so what it the amp draw on a S500 or S700 putting out 17HP?

there is a "TON" of info about how well BT30 spindles do or do not hold up on here, I looked at going to a bt30 machine but for my parts it was just to small and I ended up getting a DT2 and well I don`t like the machine as well as my VF2ss mills mostly do the long reach in a super small door and that I do like the 31 tools on the newer VF2SS mills. If I was going to run "ONLY" 3/8" and under cutters or small drills I would look at a 30 taper machine but I do a lot of 4th axis parts and have found long reach holders and longer tools are needed a lot to reach the sides of the parts on the 4th and a 30 taper would just be to limiting.

I like how someone points there finger at 99.99% of the busted studs as "Operator error" lets face it we all have "operator error" but its kind of nice to know with a 40 taper your not going to snap a pull stud from just cutting to heavy or using a tool that is a little to long.
 
IME, the breaking 30 taper pullstud "issue" is overblown with regards to heavy cutting or long tools.

Shop I retired from had at one time, four 30 taper machines. Never had a pullstud break.

My home CNC is a 30 taper. I've had it for about 8 years now. All my pullstuds are from 1995-1998 and came with the toolholders I got with the machine (company name and date vibro etched into the toolholders and studs). Never had one break despite using a 3/4" endmill in a sidelock holder as my primary rougher/finisher. Mine is only 5HP continuous and 7.5HP intermittent so not stressing a stud as much as a higher HP spindle. A couple times in a pinch, I've run a 5/8" tool with 3" LOC for finishing the ends of parts.

I think the real damage occurs mainly because the 30 taper machines are so fast. Both speed and acceleration. If a 30 taper or 40 taper machine smacks the tool into a part at ~2000IPM things will be damaged regardless of taper size.
 
so what it the amp draw on a S500 or S700 putting out 17HP?

ID Plate on the machine and the power spec in the brochure both state 10.4 KVA power requirement for the High Torque Brother machines. At 220V 3 phase that works out to 27.3 Amps. If your not pushing it with a 2" drill in steel or a 1"-8 cut tap in steel, they average about 15 amps. Coolant pump(s) is one of the biggest loads!
 
Frank, what do you think is it that breaks the 30 taper pull studs? The tensile strength on a through coolant type is around 11,000 lbs so it's not drawbar tension. And if you pull the tool holder out of the spindle in a cut that would pretty much kill any pull stud, I would think.

Franks are the only studs that have broke from my research. I have not broke a pull stud and I push my Speedio hard, but I have Nodicor and JMR high strengths for roughing.
 
Franks are the only studs that have broke from my research. I have not broke a pull stud and I push my Speedio hard, but I have Nodicor and JMR high strengths for roughing.


If you're not pushing it hard enough to pull the tool holder out of the spindle you're not pushing it hard enough to break a pull stud. From my understanding that is what they break from during use, crashes are an exception.
 
Share your thoughts on the good/bad/ugly about the BT-30 spindles.

Good:

- Speed. BT30 machines are fast because the tool holder is half the size, so the spindle is half the size. The Z axis can accelerate faster, the spindle can accelerate faster. There is a reason the Speedio X1 machines were the fastest mills in the world until the Speedio X2s came out. Even with the same G-code, BT30 machines ability to transition from cut to cut eliminate inefficiencies and show relatively dramatic cycle time improvements.

- Tool Changes. Half the tool size allows for turret tool changers that you could never do in a 40 Taper. Sub-second tool changes, 1.3 seconds chip-to-chip... and those are real-world numbers. Programing a fast BT30 machine means never using the wrong tool for the job to save 6 seconds off of a program because fetching a tool will take longer than the total cut time.

- Repeatability. Fanuc and Brother both sandbag the overall accuracy and repeatability of these machines. In production environments, if you do your part on the workholding, tooling, and fundamentally good programming? These machines can't help but run hot, straight and normal. They consistently deliver fantastic results on tight Cpk values in punishing environments. Part of that is Fanuc and Brother being finicky as fuck Japanese engineers, part of it is the nature of BT30's size advantages throwing around way less inertia into the overall activities.

Bad:

- Depth. BT30 wants short projection holders and just isn't very comfortable going beyond 4x DOC on a 8mm/.375 end mill or bigger. You can absolutely baby it for prototyping, or in production scenarios where the rest of the cycle will make up for it, but that edge of the envelope is definitely a limit.

- Hogging. These machines can provide impressive MRRs, provided you are using modern techniques and tools. The speed makes them adaptive roughing rock stars, but they punish users who throw CAT40 circa 1995 style roughing tool paths at them. For younger guys, this isn't a problem as most of us have never roughed a part without adaptive strategies, but the old-school "Speed up the cut till the carbide snaps, then back it off 85% and call it good" strategy is a solid way to buy spindles.

Ugly:

- "Your game shows reward knowledge, ours punish ignorance." One of the best episodes of the Simpsons has a Japanese game show host say this, and it is the same in BT30 land. Shit happens *fast* in these machines. On a CAT40, you can get away proving out your programs at 75% rapids and your finger on Feed Hold... that does not happen in BT30 land, because unless you are a cat, you'll never react fast enough to do sweet fuck all. No, you double check a fresh program 3 times, and you run at 25% rapids, and you constantly hit Feed Hold before the tricky bits. I would say I am very comfortable running a Speedio, and if you ever watch me do it? It is the only time in my life I become a slow, careful, methodical son of a bitch.

- Spindles. Yes, the pull-stud on a BT30 machine is the de-facto failure fuse, and busting one is preventable with basic good programming practice. Don't be a fool with your cutter engagements/feeds/speeds. Verify your tool paths with simulation, making sure your sector-to-sector transitions and clearance planes are set up properly. Dial in your post processor to prevent funky operation-to-operation transitions, especially in multi-axis setups. Have Yamazen turn off Dog Leg Rapids. This is all basic Programmer 101 level stuff, but people get forgetful and/or cocky - in a CAT40 machine, your sins will give you a broken tool and a ruined workpiece. In BT30, there is a higher chance that those mishaps will cost you a $6k spindle.

Beyond that?

Brother: I'm obviously a Speedio fan boy. The positive reputation on here and in industry speaks for itself. Yamazen also has as sterling a reputation as can be had in this industry, and for good reason.

Robodrill: Good machines, but insulting that the Japanese ones are nicer than the US ones. Slower than a Speedio in prismatic parts production by a significant margin, but Fanuc has better motion control on really complex surfacing applications. If I was 3D surfacing medical/aero parts all day, I would get Yamazen and Methods to go head to head with my code on my part to pick the winner, but in every other application I would just get the Speedio. Methods sucks.

Haas: Tool changer demos well but sucks in reality; there is a reason the two market leaders use turrets with 25 years of development behind them. Not good in the Cpk. Poor surfacing ability. I would never buy a BT30 machine that wasn't Big+, unless I'm buying it to make one part for it's entire lifecycle that doesn't require it, so the DT1 is a non-starter. When Apple, Samsung, Toyota, Honda, Denso, etc need to place a PO for 100+ mills? They don't call Haas, they have Brother and Fanuc battle it out.

DMG Mori: Make sure your lawyer goes over the PO contract. Good for people who also buy new Range Rovers as they have proven a taste for extremely expensive, extremely beautiful hardware tha performs well on paper, but will leave you stranded in the middle of nowhere.
 








 
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