CNC conversion

[Zap]

I recently purchased one of these.

http://www.grizzly.com/products/item...emNumber=G0517

I'm almost ready to start buying parts to convert it to CNC. I'm interested in the FET3/Cruiser system at stepperworld.com. This is my first CNC project and I have a few questions.

1. Are 150 oz. steppers using a direct drive strong enough or should I multiply torque with a cog at 2:1 ratio? I will only be machining plastics and aluminum. Or should I just buy larger motors?

2. There seems to be a fair amount of backlash on the lead screws. Will I see much improvement if I convert to ball screws? I guess I'm trying to find out if it is worth the extra cost and time to do so.

3. I'm stuck on the Z axis. what would be the best way to set this up? I'm kind of leaning towards something like this.

http://www.homecnc.info/Pics/400z-axis-installed.jpg

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[HomeCNC]

The 150 size stepper motors will not be strong enough for a Drill/Mill CNC conversion. You should look into at least 300-400 oz/in.

Glad you liked my Z axis design!

[cncmojo]

Hand wheels

I will caution you that if you use a Z design with out a hand wheel to use for small movements during setup, you may regret it. I have found that conversions without hand wheels are much more time consuming to use. Good luck with your conversion.

[ballendo]

Hello,

I guess I disagree with the previous replies...

150 0z. in, though a bit small, WILL work with this drill/mill. Set em up 2:1. (and do that even if you use bigger motors)

You didn't say if you were using the original leadscrews or not?
Using the smaller motor will limit your machining speed, but you WILL be CNC machining... And you can increase motor size later, if you wish.

Also, there is no inherent advantage to having handwheels on a CNC machine. The jog buttons on the control will do ANYTHING you might have used a handwheel for...

Perhaps the poorly implemented Jog functions of some of the PC-based controls are responsible for this continuing myth. I'd like to hear just why a computerised handwheel is "slower" than a manual one?

Against this, the handwheels can present a real danger as they spin, and if the handle is left on, can also increase vibration and chatter in the cut.

Finally a point of agreement, sort-of. Since this machine has no fine feed, a Z drive like Jeff uses would be a decent choice. BUT, it will be more work than necessary. You don't need to use a spinning nut...

Hope this helps,

Ballendo

[cncmojo]

Torque multiplication through belts and gears is a wonderful thing. Being able to use a smaller motor to perform a job that is way beyond practicality, is definitely possible. This process is nothing new, this guy was on to it …
“Give me a place to stand and a lever long enough and I will move the world”
Archimedes, 220 BC


The problem is after expending lots of money, and even more time you probably will not be satisfied with the end results. By spending a few more dollars, and purchasing adequate size motors, the machine has much more potential regardless of what you intend to do with it once finished.

Now as far as the handwheel issue is concerned.

” handwheels can present a real danger as they spin”

So does the cutter, the spindle, pinch points, high voltage, and just about every thing about these types of machines.
I suppose I could correctly say that even plugging the machine is a greater danger than three rotating handwheels.

” The jog buttons on the control will do ANYTHING you might have used a handwheel for... “

How about a fast manual cut?

Most home, or shop made CNC machines have poor, or no jog controls at all. With handwheels you can easily move the machine manually, just think about having to do this electrically ALL OF THE TIME, while building, servicing, setting up, and ANY time the machine has to move for any reason.

Have you ever need to do any thing manually on a machine with no hand wheels? Yes there are times when manually is the only practical way, do you really want to eliminate this option. When setting up nothing replaces the Feel you get with a hand wheel. You can feel the cutter making contact, and you know how much tension is on the cutter. If you do not understand this then you have not done much machine work, on these types of machines.
I would throw away a lot more metal with out handwheels.


Bottom line is do you want a slow machine that has to be jogged any time it is moved, I don’t think so. I have used them and they are a real PAIN.

[HomeCNC]

cncmojo: I must disagree with you. I have helped a few people make the addition of hand wheels on my CNC plans. After about 6 months of use I asked for feedback on the conversion. Every one of them said that they felt the extra work adding the hand wheels was a WASTE OF TIME! They now don't use them.

I too have found that I can use my controller software very easy. I get much better finishes on quick cuts because it's like having a power feed on the table.

I figured that professional CNC milling machines don't have hand wheels on the machine, there must be a reason for it.

[cncmojo]

Jeff

Well I will have to disagree with you , based on thousands of hours of experience operating CNC machines.

“I figured that professional CNC milling machines don't have hand wheels on the machine, there must be a reason for it.”

There is a reason for it, an automated machine center does not, use, need, or have handwheels. The same goes for most production CNC mills. The reason is they are intended to be placed into production . This includes ten of thousands of dollars in jigs and supporting equipment for production. The machine will normally be set up to replicate part after part with some type of precision alignment fixture. After performing an automated function, the machine returns to home X 0, Y 0, Z 0, and the cycle repeats. Over and over again. On the same type and size of material, precisely aligned in the same manner every time. In this situation there is no great need for hand wheels, although the service personnel would love to see them, as well as who ever sets up the fixtures initially.


I cant even imagine a home cnc machine without hand wheels, these are not production machines. They rarely make the same two parts. Also why rob their ability to be operated manually? There is no need to remove this function from a home CNC machine unless you just like to play with controls. The wheels are irreplaceable in function for non production machines, you would only know this if you were an experienced machinist. I just stepped out in my shop and asked the 5 machinist that I have working for me, what would you say if I told you I was going to remove the hand wheels from your all of your CNC machines, because you do not need them. They thought I was nuts.


Have you ever seen a non CNC Bridgeport mill with a power feed on the X ,Y, & Z with no handwheels. NO, and do you know why? It would be a pig. Believe me if the “No Handwheel” with power feed was a good thing you would have seen it on a Bridgeport, they knew what they were doing.

[HomeCNC]

Well it's done without hand wheels in my Garage.

[buscht]

Zap,

1. I'd look at bigger motors. If you multiply the torque x2, you are also slowing down the speed x2.

2. I'd try tightening up the leadscrew nuts to remove the backlash before going to the expense of ballscrews. There are several threads on this site that discuss methods for this.

3. I think HOMECNC's Z axis if fine. I wouldn't have the handles on my machine either. I agree with Ballendo on this one.

I've run a Bridgeport with power feed and you do need the handles for fine adjustments, but with a CNC control its as simple as jogging .007", very easy for almost anyone to do correctly.

Maybe there is a way to make removable handles and everyone is happy.

[IndHobby]

I do this size mill for a living. here is a snip from my site:

Where are the hand wheels?
They had to go for a couple of reasons:
The increased diameter and mass of the hand wheels degrades CNC performance.
The side where the encoder is mounted, the shaft it thinned quite a bit, adding a hand wheel is a bad idea.
Ballscrew speed can be as high as 900 RPM, handles are attached the the table which moves. Put that all together you have a 900 RPM wheel traveling at 180 IPM which means - accident waiting to happen. Although it's listed last, safety was the number one concern when the hand wheel was left off. Too many times you'll find yourself leaning up close to take a peak, or put something on the bench within the "reach" of the handle. Now some folks might be saying I'm a little overly cautious, but I'll bet that a spinner-handle on an hand wheel can snap your wrist or a bone in your fore arm like a twig. (NO BULL)


If you want to move the table, just run MACH 2 and get a $5 joystick, or use the keyboard.

Next point, if you reduce the drive ratio and you use a handle it will work against you when your doing it manually. Make it easy for the stepper, make it hard for you.

If this is your first CNC project you might want to put some sort of small knob or thumb wheel on the screw, this way if you hit a limit it's easier to back off. Once you get the hang of it you'll never use them.

If you tighten up the "anti-backlash" brass nut tight enough to prevent lash you'll do one of two things:

The increased drag and friction will cause you to loose steps or move so slow as to make CNC a joke.

The brass nut will wear faster than normal and you will always find a lash issue when you need it the least.

For a mill of that size look at 400+ in/oz steppers. Bank for buck ratio I would go with 640's and a 65VDC 20 Amp PS with G201's and ballscrew.

It's one thing to ask the little woman for money to do the project right, and another to ask her the second time for money to fix the mistakes you made in the first place.

Do it right and never look back.

Just my two cents.

Thanks
Aaron Moss
www.IndustrialHobbies.com

[lsfoils]

Cha ya Aaron,

The Mach series controller software make it easy to jog any where your machine can go. Ta hell with the hand wheels. Can't control 'em as well as the software, myself. Just figure, you can control your feed rate, the amount of movement and direction. A good machinist will find out the proper feed rates for the material he's removing and plug it in.

Ball screws, man! Roton! Spent a whole $30 an axis. No contest. Get an extra nut if you don't want to have the software deal with the back lash.

Good luck with your Grizzly. I'm not sure you need all that power for such a short stroke. By the time you accelerate to your max speed you've shot the table onto the floor. If yer cuttin' steel you won't need that much speed, anyway. By the by. is there enough room in the head stock for Jeff's marvelous Z trick? Roton does sell 1/2" ball screws. Post pictures when you get there, ok?

Doug

proly to much suds to make much sense tonite, folks

[lsfoils]

Oh yeah, the wiff. Don't tell her nothin and have all the bills sent to a freinds house...(dark)

[cncmojo]

It seems like it keeps coming up again and again that hand wheels are dangerous, that is crazy. With pinch points, crush zones, rotating cutters, hot sharp flying chips, sharp tools, sharp edges on stock, and rapidly moving axis’s, the hand wheels do not even rate on the danger scale.

I use these machines, and based on thousands of hours of experience operating CNC machines hand wheels speed up all types of operations. Handwheels also offer the ability to use the machine manually, Manually is the only way to make some cuts, every experienced machinist knows this. Manually lets you use the sense feel of when your cutter touches the material, and this is paramount. You do need the handles for fine adjustments.

“The increased diameter and mass of the hand wheels degrades CNC performance.” Any ultra small difference in performance would with laboratory equipment be virtually impossible to measure. What maybe .05%? if even that much. How often does the handwheel move at a high speed while the machine is operating, not very often. The handwheels actually increase the torque available through inertia.

The actual truth is hand wheels are necessary for a PRACTICLE machine. If you are using Jeff’s Z drive and you hit your limit switch on the Z what do you do? Start unplugging limit wires, and try to jog it ? this drive is totally enclosed, if it had a handwheel, two seconds later the problem would be solved. Practical is what it is about, and that is all I am talking about. I am not trying to step on any toes. Jeff’s Z drive is a very complex and interesting design that took lots of skill to conceive, and make; but it doesn’t have a wheel, and you can’t jog it when you are on the limit switch.

Now the X & Y axis without a hand wheel are just as bad because they are difficult to set up, no manual function, and what if you hit your limit switch on the axis what do you do? Start unplugging limit wires, ant try to jog it ? Or try to grab your screw with pliers?

If you want a machine that is easy to use, and is practical use handwheels, if you were an experienced machinist you would know this. If you just want build a CNC machine, and do not care if it is easy to use, or if you do not have the skill to design handwheels in, leave them off. You can always try to turn the screws with pliers, or jog it if you are not on the limit switch, or maybe unplug the limit wires if you hit the limit switch. You could even disassemble the machine to move the axis when it will not move under power.

Motors….. lightweights are just asking for trouble. Undersized motors are overworked, and will have a much shorter life than the proper size motor. Under powered motors have many negative effects, steer clear of the temptation, and you will be much more pleased with the end result of your labor.

[Chagrin]

The increased diameter and mass of the hand wheels degrades CNC performance.

From experience I'll agree with this one. At higher movement rates my CNC would miss a lot of steps until I removed the handwheels. My wheels were 4" diameter and made of wood; I wouldn't have expected degraded performance from something that light if I hadn't experienced it.

I still like the wheels though! If I ever find the right springs I hope to re-use them with a "push to engage" type of mechanism; hopefully something that would appease the performance and safety critics alike

[Stevenpats]

There are easy work-arounds for hitting limits and not having handwheels. I use NC limits in series to pick a 24v MCR(master control) relay, normally closed contacts on the MCR give me shutdown inputs for each amplifier. A simple 2 position selector switch labeled Manual/Automatic allows me to power the amplifiers even when I have a limit switch open, so I can jog off my limit. The software E-stop is momentary and is run through a N/O MCR contact, so jogging off limit will not cause machine to restart. No pliers necessary.
Steven

[ballendo]

I agSnips, inserts below...

>Mojo wrote:It seems like it keeps coming up again and again >that hand wheels are dangerous, that is crazy. With pinch >points, crush zones, rotating cutters, hot sharp flying chips, >sharp tools, sharp edges on stock, and rapidly moving axis’s, >the hand wheels do not even rate on the danger scale.

Mojo, Ask the guys I know who've got it "in the shorts- " from the Y axis of a mill/drill or BP. Or the ones who've been "slapped" HARD by an x or y wheel handle... I ALSO have "thousands of hours" with BOTH commerical AND homemade CNC machines, and I just don't get that you don't see the difference between a handle spinning at the ENDS, or FRONT of a machine (sticking out, so to speak) , and the other "safety" items you compare to... I'd MUCH rather get hit by a hot chip than hammered by a handwheel. And the pinch points and sharp tools are red herrings...

> I use these machines, and based on thousands of hours of >experience operating CNC machines hand wheels speed up all >types of operations. Handwheels also offer the ability to use >the machine manually, Manually is the only way to make some >cuts, every experienced machinist knows this. Manually lets you >use the sense feel of when your cutter touches the material, >and this is paramount. You do need the handles for fine >adjustments.

First let me say that if you've got thousands of hours in CNC and you're still making fine adjustments with the drives off... I'd hate to be paying for your productivity; even with one-off parts...

I guess none of your machines has an MPG? The idea that you MUST have a "manual" handwheel for "certain" machining is pure BS. There are thousands of parts made COMPLETELY WITH CNC nowadays that oldtimer machinists would have argued similarly...
A MPG (electronic handwheel for those who don't know; it's part of nearly EVERY commercial control, and performs the handwheel functions that a machinist needs, but with NO "manual feel"...) is very useful, but it is still only a jog device, and the pc based jog devices work just as well, (and exactly the same)

Additionally, I find (with my thousands of hours of experience) that my EARS and EYES are much better indicators of when a cutter touches material. I mean, give me a break; any converted manual machine has the drag of the motor and perhaps belt, with the attendant cogging to disrupt this "sense of feel" you say we can't live without... IMO, you're just fooling yourself to say otherwise. I'm not disagreeing that when MANUAL machining the handwheel "feel" is important. But we're not manual machining, or we wouldn't be here!

>“The increased diameter and mass of the hand wheels >degrades CNC performance.” Any ultra small difference in >performance would with laboratory equipment be virtually >impossible to measure. What maybe .05%? if even that much.

This depends COMPLETELY on the SPECIFICS of a given machine! As one reply has already stated, it DOES make a difference. So empirical evidence would have to be ignored to support your statement... (Just to be fair, I myself have posted on CCED that retaining the handwheels on a sherline mill cnc retrofit using steppers is a GOOD idea. This is because the relatively small diameter of the scrw--and therefore its inertia and mass-- is not matched well to the rotor inertia and mass of the typical motors used with sherline retrofits. As I said, depends ENTIRELY on the machine in question)

>How often does the handwheel move at a high speed while the >machine is operating, not very often. The handwheels actually >increase the torque available through inertia.

How about During EVERY SINGLE RAPID move... If we believe your 2nd sentence, we must also remember that that added inertia is evident at the END of any move, when we're trying to stop the axis/axes... With steppers, this can lead to missed steps. With servos, to increased following error, which will require either additional settling time, or "exercise" of the servo amps to compensate. (again to be fair, I don't really think these last two are much of an issue with servo machines, but the stepper example is VERY true; as the added inertia is most during rapids, which is when the steppers are at their weakest...)

>The actual truth is hand wheels are necessary for a PRACTICAL >machine.

No, they're not. Unless you're trying to say that the thousands of commercial CNC machines without 'em AREN'T PRACTICAL?!?!?

I already saw your assertion that commercial cnc machines are used for production. Sure they are. They are ALSO used for one-offs, short runs, and every other possible use that a machining device can be put to. To say that al those guys and gals who are setting up one-of, or short run parts with a "typical" CNC mill (which means it DOES NOT have manual handwhels with "feel") are lusting after manual control is just plain nuts, IMO.

What IS true, is that they've "graduated" to using CNC the way it is intended to be used; possibly by RE-learning what they "had to do" with manual machines. I have both manual and CNC machines in my shop(s). I do NOT treat them the same. Each type requires its OWN mindset... Kinda like the guy who knows how to drive a model T, when he gets into a car without a spark advance lever. Does he say, where is it? ALL cars need a spark advance lever?!??

(To be fair, I DO appreciate how my manual machining abilities help me with my CNC machining. There's no disagreement there!)

>If you are using Jeff’s Z drive and you hit your limit switch on >the Z what do you do? Start unplugging limit wires, and try to >jog it ? <snipped rest of paragraph>

Nope. I enable limit override (evey commercial machine I've ever seen has at least one mathod to do this. The older ones might have been buried in the parameters, but the newer ones are easy enough to activate), and jog off the switch... Maybe five seconds.

But in your "2 second" example, you forgot to power down the drives so you COULD turn the handwheel. And then you've got to power them back up again. And then you've got to home the machine because when you powered down, you lost position...
2 seconds? Hmmm...

Additionally, I don't hit my hard limits, because my soft limits stop me before I do. And my soft limits (or stored stroke params) are recoverable without a re-home. What was the advantage of the handwheel?

>Now the X & Y axis without a hand wheel are just as bad >because they are difficult to set up, no manual function, and >what if you hit your limit switch on the axis what do you do? >Start unplugging limit wires, and try to jog it ? Or try to grab >your screw with pliers?

I'm really trying to think of when or why or how setting up with an electronic jog is inferior to the handwheel. In fact, I've found the opposite to be true. Let's say we're doing a one-off, 2nd setup; and using an edge finder to be SURE we don't scrap what we've already machined...

You mean to tell me you can turn that (manual)handwheel (with the drives off) by .0001? And that you think it's going to stay there when you turn the drives back on!?!? I'll just cough like the guy at the beginning of TopGun<G>

On the other hand, I can EASILY do this .0001 move using either jog increment, or an MPG. Repeatedly. So I can SEE EXACTLY when the indicator bumps (or lights, if its the newer electronic type.)

>If you want a machine that is easy to use, and is practical use >handwheels, if you were an experienced machinist you would >know this.

As an experienced machinist myself, let me re-phrase this:

If you want to be hamstrung by your experience with manual machining, and not enjoy the FULL benefit of having CNC, by not having to learn the new (and better, IMO--and I'm NOT alone in this thinking )techniques which replace the old ones you're "comfortable" with, then keep the handwheels.

>If you just want build a CNC machine, and do not care if it is >easy to use, or if you do not have the skill to design >handwheels in, leave them off. You can always try to turn the >screws with pliers, or jog it if you are not on the limit switch, or >maybe unplug the limit wires if you hit the limit switch. You could >even disassemble the machine to move the axis when it will not >move under power.

More red herrings. Every machine I've ever designed has an easy-to-use method for manually moving an axis without power. In many cases, its a bolt head. the key factor is that it is there for EMERGENCIES, and not for casual use. As mentioned above, if you are an experienced CNC machinist and you're needing to dial things in manually-without power- I'd suggest you take a fresh look at your approach. Because you just don't need to, if you're using CNC the way it's meant to be used. If I need to move an axis witout power, something terrible has gone wrong. Perhaps a drive runaway (cable or connector failure, most often) these things DO happen. In thousands of hours of machining. But they are FAR from an every day occurance in my shop(s).

Had to break this into two parts<G> See nextmessage for the conclusion...

[ballendo]

Finally this:
>Motors….. lightweights are just asking for trouble. Undersized >motors are overworked, and will have a much shorter life than >the proper size motor. Under powered motors have many >negative effects, steer clear of the temptation, and you will be >much more pleased with the end result of your labor.

I agree. The only consideration is that this is a hobby oriented forum, mostly. And from what I've seen in tens of thousands of
posts by newbie hobby CNC'ers; some just don't have a lotta cash. telling them to wait until they have the "right" motors, might mean thay never get their first CNC machine. But its a fairt bet that if they DO get as far as movement- and if the movement gotten is not "good enough"-- they WILL likely go buy the motors they need. I've seen it happen many times since I've been posting on public DIY CNC forums...

This is a pretty strongly worded post. Please take it as strongly worded, and not in any other way. There are always more than a few viewpoints that work...

Ballendo

[cncmojo]

Ballendo

I wont even attempt to reply to every thing you posted, it is to disorganized. Your post is filled with excuses, irrelevant thoughts, and just plain distortion.

You had to really jump all over the spectrum to try to justify the EVIL of the ominous flesh, and bone destroying handwheels. Really to the point where you made no sense. Bottom line is if you don’t have enough sense to steer clear of the hand wheels while the machine is in operation, you do not have any business being any where near a CNC milling machine. I have never been exposed to a situation where someone was trying to make so many excuses to try to make something sound dangerous. My god it is just a simple rotating disk, some of mine are solid with no handle. You could throw your body on them and they could do you no harm. GET REAL

After writing the epic you did, I cant help but assume that you have designed or purchased a no wheels cnc drive. If you did then you designed a much harder to use machine than a machine with death wheels, I mean hand wheels.

I could spend lots of extra time at a keyboard or other interface trying to make the machine do what I want to do, I could even tie my hands behind my back and use other body parts to operate the controls and still cut metal. But some things are just stupid, and you will always see me avoiding them like a plague. Not having hand wheels on a converted mill is simply poor engineering. A machine without handwheels is much harder to use, and set up. Who wants to play with buttons when there is a better faster way to do it. The electronic CNC controls are wonderful as long as you use them for their strengths, and not their weaknesses.

If you have a button and keyboard fetish that is just fine, but me I have long strived to perform every task in the best way possible, and that is what my posts are about. Don’t muddy the waters to prove a point, you can have a negative effect on lots of CNC newbies.

You also seem to be confused about what I said about motors, or were you just trying to discredit every thing I commented on? The importance of adequately sized motors is very critical. That being said undersized motors can be used if one is scraping up parts, just be aware of the disadvantages of using them.

QUOTE FROM Ballendo
“I guess none of your machines has an MPG? The idea that you MUST have a "manual" handwheel for "certain" machining is pure BS. There are thousands of parts made COMPLETELY WITH CNC “ There is lots of BS here and you are dishing it out. We were discussing home CNC conversions, not machine centers. You are reaching really far away from the subject here, come back to reality.

Oh and by the way I make parts for 7,000 horsepower top fuel dragsters, Bell Helicopter, and many other high tolerance parts. I also perform machine engineering consulting for over $300 an hour, with many clients including NASA Langley Research Center, I was recommended to NASA my the director of the facility Roy D. Bridges, Jr.
What do you do?

[cncmojo]

Stevenpats

Setting up electronic limits is a great idea, yes it can be done, but what do you use to set them up? Manual motions, hand wheels would help here. Most newbies, or average home CNC enthusiast would not know about this, or even how to do this, but this is good stuff. Do you still need wheels, for tool changes, material changes, setting up, unexpected occurrences, and emergencies? I think so, not having hand wheels is like taking your mouse off of your computer because you can do every thing with the keyboard. Good stuff though, electronic limits.....

[cncmojo]

Chagrin

If simple wood wheels degraded your performance then you may have serious problems. What happens to the performance of your system when the cutter encounters the material you are cutting, this is much more resistance.

Can you drill, and tap the end of your screw, then screw in a short bolt very tightly. Take an old socket and attach it to the center of your wood wheel. Grind the OD of the socket to roughen it up, and use epoxy to attach it, if you are using a wood wheel. Any time you need to manually move the screws you could use the wheel as a tool. The user friendly round shape of the wheel is easy to use while making fine adjustments, much more so than a wrench or ratchet. Good luck…