Lagun FT1 as a CNC Beginning?

[JimDawson]

I see you are on the west coast. Look for a shizouka with a dead control. This is NOT a good deal but it is an example

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I watched for one of these for years, they were always in CA.

If you ever get out this way, bring you trailer and I'll load one up for you. I have a spare taking up floor space in my shop, even has a fresh retrofit on it. It really needs a new home.

 

[Karl_T]

Why do you say that is not a good deal? I think that machine looks like it is in awesome shape, plus it already has industrial ball screws and an ATC on it. Rip the control off of it and install a Centroid Allin1 on it, and you would (maybe) have an awesome machine. Of course, an in-person look at it and determining servo motor compatibility with the Centroid system would be warranted. There would be a possibility of being into that machine with a new CNC system for $7k or so. Not bad at all.

OK, fair deal. BUT I have seen them go for a song. I agree; put a new control on this and you got one NICE machine.

The OP should talk to Jim about his shizouka.

 

[pontiac428]

Accuracy and repeatability is a result of the sum of the components.

I don't disagree, but I think components are about 40% of the accuracy and repeatability formula. The balance is the machinist, not the engineer, who sets up the paths and G-code. There are many tricks and techniques in setting up movement that your schoolhouse engineer can't grasp, that a talented machinist with many years of experience can implement to tighten tolerances, improve finishes, speed up cycle times, and reduce waste. It makes me sad when people think if they buy a machine and call up a .DXF of a part that they can just push a button and get perfection. The machine is part of the equation, but the knowledge and skills are the key. The machine is just a dumb tool with enough rigidity, power, and tolerance to execute the movement. Whether it has linear scales or servos with rotary encoders or a bed or a knee is irrelevant to the output.

 

[pontiac428]

The OP should talk to Jim about his shizouka.

Before I do... You got 48 hours to decide.

 

[Firebrick43]

I would respectfully disagree. Linear scales take ball screws, couplers, reduction gearing, and other sources of backlash out of the equation.

No they don’t. A machine with backlash/lost motion in an x or y axis will not make true circle such as helical boring or circular interpolation in radius. As you change one of the axis from a positive moment to a negative the back lash will rear its head and show up as oblong circles or tool marks.

A ball bar test will show this. Even before the scales are turned off for the test.

It’s not going to be overcome entirely with “skill” from the machinist either.

Only if you were just drilling holes and such were positions were made in x/y before plunging in z will scale compensate within reason. Even then machines with lost motion can develop bad feed back loops trying to hold position due to back lash causing motors to sing/overheat and the small but huh frequency moment on the ball screw cause localized wear in spot as the balls vibrate. Seen it multiple times in the past 16 years I have been repairing CNC machines

And it doesn’t help at all the rocking in the knee of most knee mills without the knee locked if CNC’d causing perpendicularity issues.

Why would machine builder use high dollar precision ground ball screws, abec 7/9 support bearings, zero back lash couplers and even harmonic gearbox reductions costing an additional 10’s of thousands of dollars to a machine if the scales that many have already have installed could compensate for lost motion due using much cheaper components?

 

[pontiac428]

It’s not going to be overcome entirely with “skill” from the machinist either.

Case in point, the skilled machinist knows how to code backlash compensation. There are several G code routines to accomplish that depending on your controller. And what knee mills rock? In standard operation, the spindle is always dead center of the knee. How much error does that generate from "rocking", six zeros past the decimal maybe? I get confused over the insistence that good work isn't possible with reasonably good equipment and attention to detail in the process. I'm not intending to be snippy, I just don't know how an ABEC 9 bearings and $2000 a pop ballscrews are going to make the difference between perfection and scrap in a one-man home shop, dig?

 

[pontiac428]

Hey, man, I just had to think about it while I was out walking the dog. I get pushy sometimes when I post, and it's not my intent to belittle or naysay. I think the point I am trying to put out is when planning a big step up, focus on the process instead of the equipment. The equipment is part of the conversation on this board, of course, but so much is about technique, knowledge, and process. Learning how to work within the limits of the machine and still produce good parts is a better investment than shopping for hour upon hour finding the tightest machine components and dismissing the reality that it is indeed skill that exceeds equipment. That's why the guy with the vette gets smoked at the drag strip by the guy with the rusty '76 Nova all the time and wonders why. It's because the guy with the fast Nova invested in knowledge and skill, while the vette guy shook bills out of his wallet instead. It's worth a thought.

 

[7milesup]

If you ever get out this way, bring you trailer and I'll load one up for you. I have a spare taking up floor space in my shop, even has a fresh retrofit on it. It really needs a new home.

I can't get this dang thing out of my head, even though I have a Sharp mill sitting in my shop. If I were close to this, I would be going over there and taking a look.

 

[JimDawson]

There is no substitute for a tight machine. I'll concede that you are not going to convert a <$10K knee mill in the average home shop to the accuracy of a multi-million $$ DMG-Mori by adding linear scales. Will my machine interpolate perfect circles? No. I have about 0.004'' backlash in the Y axis and it will hold 0.001'' on roundness. It's just a matter of the system being able to compensate for the backlash as best it can. Linear move deviations are normally better than I am able to measure. My knee mill is actually just a little better than my Haas.

Really the most important parameter is repeatability. If the machine will repeat, then you can compensate for the accuracy. If you need perfectly round holes, then use the boring head or a reamer.

 

[pontiac428]

Somehow I'm convinced that there is no substitute for a rigid machine. But when the computer is calling the shots a thousand times a second, and it's equipped control system is "smart" enough to enable compensation, the tiny contributions of premium tight components (read: exorbitant capital cost) are less significant than intelligent setup and movement paths (the machinist's input in precision). We're probably working toward the same point here, a BP conversion ≠30 million dollar machine, just going about the argument differently. I am strictly speaking in the context of the practicing home shop. We make our lives from getting the most out of what we can attain as a hobbyist or Lilliputian home business. It's synergistic when skill meets "good enough for $10k," you can really do good work in that range. There is no reason to give up on ever having precision over compromising to use Chinese ballscrews and ABEC 5 bearigns in a home build.