[DaQue]

Do the toolroom mills and lathes have scales to know where the are (closed loop) or do the just assume x .xxx turns equals y.yyyy inches (open loop). I'm pretty sure the higher end Haas models all use scales but can't tell for sure on the toolroom (cheap) line . The scales if present compensate for thermal expansion on the screws?

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[underthetire]

No, they have encoders on the motors, and scales are typically an option on the higher models. If your looking at a T series, thermal expansion is not going to be an issue. Others Haas just use software to compensate. Good quality machine builders stretch the screws when cold so there is no change, and run refrigerated chillers for spindles to keep everything at ambient temp. High accuracy machines may chill the screws as well, but not all. Scales on a Haas is like putting a band aid on a chopped off limb, the rest of the machine isn't accurate enough to justify the added cost. Nothing wrong with Haas, don't get me wrong, but they are simply a inexpensive production machine.

[DaQue]

Thanks. Even the toolroom line is more than I need or can afford really. At least with Haas you can use their build a quote on the website and get an idea of cost. Anyone else have a comparable price range to the TM line?

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[underthetire]

There are dozens in that price range, however Haas gives a lot of bang for your buck in that range. I've had no issues with the few TM's that we have, and a couple are seriously modified to use with lasers. I will say, Haas support has been good, parts are cheap and always available.

[DaQue]

Thanks. I will look around some more.

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[mtlhe]

FYI- I bought a TM-1 1-1/2 years ago and it holds parts -.001 all day long. I would prefer to have scales but truth is their system thus far has been extremely accurate.

[WallyL7]

Most of the time on a tool room lathe the tool post is the biggest cause of repeatability errors. Holding .001" on a TL1 is normally quite common.

Glass scales on a 20k machine...? I'd have to agree with underthetire on that one. One thing to add though to his post is that Haas does not use anything for (actual) thermal expansion. They use an algorithm that is based off "distance travelled"...and I may be wrong but I don't even think they use it on the lathes.

[mtlhe]

The TM series are a $30K machine so I can't imagine it costing that much more if they used glass scales. We have a Sharp LMV knee mill with 3 axis Acurite control that uses glass scales. Of coarse no match for the TM in performance. However, we"ve never ever had accuracy issues with the Haas machines. So apparently they have it figured out.

[underthetire]

Only 2 reasons IMO to use scales. Bad machine construction, so scales make it hold size, or, extreme accuracy machines to hold sub micron. Other than that, scales are a huge PIA.

[Machineit]

I have not owned a machine with "scales" but I can imagine it might be difficult to keep them clean and dry etc. With newer rotary encoders I would think that linear scales would become less popular. A quick check on line found an encoder for sale with a resolution of 30,000 per revolution. That would be pretty accurate. They are much easier to keep clean.

Mike

[Hirudin]

Haas has a PDF that answers this question and many others. I've been to their site many times in the last few weeks but I only noticed it for the first time yesterday. The link is a blue "EBOOK" icon on the header of every machine description page. I've pasted the direct link below for convenience...

http://www.haascnc.com/DOCLIB/brochu...nloads/VMC.pdf

According to the chart on pg. 33, the scales are an option on the VF-6 - VF-12, VM, and VR machines. On the VF-6 the option is nearly $16k.

[Machineit]

Making continuous glass scales in those long lengths is very costly and they would be fragile. The rotary encoder uses glass scales too, they are just made in a circle, a glass disc that can be turned continuously for any length.

Scale costs are coming down all the time, but still fragile and difficult to keep free of moisture and debris on the linear type.

I bought a DRO for my lathe a while back. What used to be many thousands of dollars a few years ago, was now about $500.00. When I got it installed, I could not believe that it went to 5 decimal places. Not 5 or 0 either, 1/100,000 of an inch. Totally unusable on an old Jet lathe, but interesting!

Mike

[Machineit]

Site still quite messed up. Double posting today as the first time said site was down.

Mike

[mactec54]

I have not owned a machine with "scales" but I can imagine it might be difficult to keep them clean and dry etc. With newer rotary encoders I would think that linear scales would become less popular. A quick check on line found an encoder for sale with a resolution of 30,000 per revolution. That would be pretty accurate. They are much easier to keep clean.

Mike

30,000 per revolution is a good number, Dmm are selling 16 Bit= 65,536 that you can use on a hobby machine, The new Haas machines have improved a lot as far as Encoder count goes, the Sigma 5 motors they are using now have a 20Bit Encoder which is 1,048.576 counts per revolution that is over 1 million counts per revolution, I don't think the Haas machine is using the full 20 Bit but they have improved a lot with there HSM

The Fanuc 35i Nano series uses a 32 million count per revolution Encoder

I have found that 16 Bit to 17 Bit is about as low as you can go for a smooth running CNC machine milling

Scales fitted to most CNC machines are only used to correct for thermal expansion, Don't have any other purpose, when you have high count Encoders

[Machineit]

Cool huh!

[underthetire]

Actually, the new Fanuc Ai encoders are 10 MILLION count standard ! Fanuc used 10K count back in the 90's, at least on the higher end machines.

[mactec54]

Actually, the new Fanuc Ai encoders are 10 MILLION count standard ! Fanuc used 10K count back in the 90's, at least on the higher end machines.

There older Ai series may have been 10 million

The latest Ai 3 series has 16 Million counts per revolution, this is half of what the 35i series has 32 Million counts per revolution

[underthetire]

No, just got the info from Fanuc last week. 10 million is standard, the others are options.

[DaQue]

The only possible use for that high resolution that I can think of is it allows you to get an accurate velocity over a very small movement so you use that information to help plan other moves.

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[mactec54]

The only possible use for that high resolution that I can think of is it allows you to get an accurate velocity over a very small movement so you use that information to help plan other moves.

That is correct but you missed one very important part, smoothness at which the machine can move,while moving at high cutting speeds & still maintaining high accuracy

This can not be achieved on low count Encoder machines, The lowest count you can have for smoothness, velocity & accuracy is 16 Bit, 65,536 counts per rev, below this number which most machines are, you can not get the fast acceleration/deceleration needed for smooth & accurate machine movement