Topics

21

Show"N"Tell ( What you have made with your CNC machine.) / First cut on new router..

« on: July 06, 2007, 09:46:38 PM »

Hi Guys. Thought Id show you this "coin" from insulation foam. Its about 400mm square, and in case you cant read the lettering, at the top it says "Incompetance is an Art"
and on the bottom it says "ArtSoft - Mastering incompetance"

:-)

 Art

22

LazyCam (Beta) / LazyCam Pro Turn profiles..

« on: April 18, 2007, 04:29:10 PM »

Hi Guys:

  Till the video is done, not many know exactly how to do a turning profile.
The rules are that the line, after cleaning must be one chain. And it has a line on the right going up to stock diameter showing its an outside profile, or a line going down to bore size to show
its an inside profile. Here are a couple so you can see what I mean..

Art

23

Show"N"Tell ( Your Machines) / My workplace..

« on: March 15, 2007, 01:49:35 PM »

Hi:

  Thought you might like to see my workplace..

Art

24

Mach3 under Vista / Getting up and running in Vista

« on: February 04, 2007, 04:55:22 PM »

In order to run under Vista takes a couple of steps..

1) First, run the install as per normal.

2) Now you need to run the file enclosed as the attachment to this topic. Save it , unzip it to memoryoverride.reg , and just double click it, it modifies
the registry to allow MAch3's driver to run.

3) Now you need to go to the C:\Mach3 folder, (or wherever you installed Mach3) and right click drivertest.exe , select
"Run as Adminstrator.". It should tell you to reboot. Do so, or you will crash. No question about it..

4) Now you shoudl be able to run Mach3, try the drivertest.exe again, and it shoudl run.

 Note:
   You may get errors reported when running DriverTest, in fact it may not run at all first time, then
Vista will ask you if you wish to run it in compatability mode. DO so, and it will run..

25

Building or Buying a Wood routing table.. Beginnners guide.. / Photos of the old table..

« on: October 24, 2006, 08:26:12 PM »

Well, lets see what our old table looked like. (No flames.. , it was our second attempt..

 Lets see how we did it all..

...

26

Building or Buying a Wood routing table.. Beginnners guide.. / More On Motors...

« on: October 17, 2006, 10:31:00 PM »

Well, I guess theres allot to be said about motors. Stepper or servo. I dont htink we'll ever cut throguh everything one woudl want to know, but let me blog a few points,
usually more information is better than less.

 I get alot of questions about analogue servos. Theres quite a few of them out there, and its common for an owner to have no idea what they are.

An analogue servo, takes a voltage from +10 to -10 volts to make it work. Basically, the control unit or computer sets a refernece count for position internally, it then
looks at how far out the encoder count from the servo is from the ref point, if the motors encoder is way behind, the computer puts out a voltage which is about +10 volts,
this drives the motors amplifier to put out a high current to the motor to make it spin fast forward. As the distance in counts of the encoder gets closer to the computers set point,
the voltage drops, making the motor go slower and slower until the count of the encoder is the same as the computer. If the encoder was far ahead, the voltage goes negative making it go
the other direction. Thats an analogue servo in a nutshell. Since the computer is calculating how much voltage to apply to the motor based on the actual encoder position, this is refered to as
closed loop. Mach3 is open loop, so to use an analogue servo, the loop must be closed somewhere else. All servos are closed loop of sorts, just a question of where the loop is closed at.
In a Gecko 320 driver, for example, the servo loop is closed between the motor, and the driver.
  For some applications where you have an analogue amplifer and motor, you could use a step/dir convertor, such as those at http://www.skyko.com/products/ , they basically close the loop
at the convertor. But often, if your motor specs will match a Gecko driver, Id install a G320 and be done with it, much more reliable i think..
  Then there the question of using a non-servo motor as a servo. Im asked that allot. I personally prefer someone ask Mariss about such things, he's the guru, but Im of the "If it works, its a good solution" school,
so if you have an encoder on a DC motor, Id hook it up and go, (but then...thats just me..).

    In the end , with either motor, you worry about speed. Speed in servos (as in all motors) is tied to resolution. If a servo has a 500 line encoder on it, thats 2000 counts in quadrature for every rotation. So if one
rotation is one inch, then at 25Khz maximum Mach3 output, you'd get 25000 / 2000 = 12.5 rotations or 12.5 inches per second output speed, at 1/2000 of an inch resolution. Its a pretty easy calculation. (at least it is when I word it that way. )
 The general rule is you try to keep the servo going almost full out when your table is going full out, so you should pay attention to the details of the max speed of the servo vs the max speed of the table. Take note many servo driver
packs allow such options as gearing and ratios so the max speed of MAch3 may not matter in your calculations. Many , however, siimply go with the greatest oomph they can, and rework it if it doesnt work. All depends on how much you like to tinker and how picky you are with the end result.  It important to understand people build things much as they drive a car, some do it right , (me) some do it wrong. (everyone else..). CNC is like that. In the end, if it works, its right, maybe not as good as it could have been, but you learn form your mistakes. This will be my third table, so Ill try to learn from some of my mistakes previously.. I have th eluxery of not needing this for commercial use, just personal, so keep in mind that if your building this for the boss, think
three times about everything, and check your facts with others to make sure you get as much agreement as possisble.  I intend to spend less than 2000.00 or so, its likely to cost you much more as I already have alot of parts laying about..
so the more important your tabel is to your particular enterprise, the more planning  you should put into it..


  Well, thats it..another long day.. Time to put this blog to bed for the night..

to be continued....
Art


 





             

27

Building or Buying a Wood routing table.. Beginnners guide.. / Servo ratios and drives..

« on: October 12, 2006, 11:13:36 PM »

Hi all.. continuing on with this very rambling topic..

 Today we discussed motors. We're going servo as I said earlier, but the question comes up , how to connect the..ballscrews.. belts..ect..

 The idea is to have as low a mass as possible to move, but with the rigidity required to get a good cut. Ive seen many designs, and we're not
close yet to deciding. Brian mentioned an interesting design where a timing belt is flipped inside out on a pulley and the pulley runs on a track with
a series of tapered slots on it. This woudl kill backlash problems as the rubber of the belt compresses into the track slots.. interesting.. might have to try something
like that. Ball screws are great and tight, but they do have a rotational inertia and that adds some acceleration time to the movement. Hi acceleration is the
ultimate target. Like all things in life, tradeoff's abound in the design of a router table. The stiffer the heavier, but the lighter the higher the acceleration,
the trick woudl appear to be getting just the right balance. Since we'll be using Servos that at fast speed are about 3000RPM, the perfect design is about 3000
rpm ratioed to give the highest speed we would want at the drive.  The required acceleration then would simply be a function of the mass of the gantry. Y on the router tabel is
the long axis, so it will push the whoel gantry, its the worst one, the X is usually a cakewalk as it has less than 1/2 of the mass of the Y, and the Z is in a class of its own
 as it has to lift or drop the weight of a carriage. Even with counterweighting, there is the mass to consider on that one. (Just because somethign weighs nothing, doesnt mean
you dont have to take its mass into consideration.. )

  Id like about 12,700mm's per minute. Or about 500 inches per minute as my rapid. It may be overreaching, but we'll crunch some numbers and see. That means on a 4" pulley, Id need about
2*3.14*2 or about 1 foot per rotation on a 4" pulley with  reversed belt, so an end speed of about 500/12 = 41rpm , so a reduction of about 75:1 woudl seem great under that scheme.
Gonna have to look around to see what I can find and make a compromise I suspect. More thought required. Just thought Id mention all this so you get an idea of what to consider in
some of the planning of driving the gantry about to get a better result.  Ill keep you informed on the progress...

Art




   

28

Building or Buying a Wood routing table.. Beginnners guide.. / Lets talk about motors..

« on: October 11, 2006, 09:52:03 AM »

Motors---

   Well, motors and drivers are something that are frequently asked about. Allot of people have tried to go too small on a system,
and surprisingly, allot of them try to go too big. Yes, you can go too large. At least in steppers. You can make errors here, a stepper
can be switched to a servo at any time with a new driver and a bit of rewiring, or a smaller stepper can be swapped for a larger one if your
power supply will handle it. Lets talk steppers first. Theres allot to be said for Servos, I like them myself, but many getting into CNC will
be using steppers.

   Steppers come rated at a voltage and current. Its typical to see 4.5Volts at 1Amp and such written on the motors faceplate. The rule is:
NEVER go over the rated current, if it calls for 1 amp, don't go over that 1 amp, it will overheat the motor. But voltage is a different matter. You can go
up to 25 times the voltage on a motor. Typically, most steppers like about 48Volts or so. Ive used from 24Volts to 65 volts quite successfully. The
Higher the voltage, the more power you ll have and the higher acceleration you'll be able to get. (Remember..acceleration is good.. )

   I used AC steppers rewired to DC for my first table. Big Honking 72RPM steppers. They used to be easy to get and a simple rewiring of the
coils in the back made them work fine. In fact, their still in use. But you'll want to use normal steppers, 4 wire, 8 wire..doesn't matter really. I
wont get into all the arguments on Bi-Polar ..etc.. Usually most will use what they have. Nema 32 are pretty good for a router table, if the gantry
is heavy you'll want about a 4 amp motor running at 48 volts at least. Don't be too tempted to get Nema42's with 1200oz inch power, as steppers
get larger, the detent torque (that clicking you feel as you turn a stepper) increases, and it can be a devil to tune them or get great acceleration.
I recommend (just me..) that you don't go higher than 800oz in for a stepper. If you need more, think about servo's.

  Servos' are great. Harder to hook up, but they work very well, and once you've used them, your unlikely to go back. Out table will be using Technique
SST-1500 servos for the X and Y. Still not sure for the Z yet. But we'll probably use a servo there as well. (Though a stepper is tempting on the Z as its easier..).

  For either stepper or Servo, I usually use a Gecko stepper (201) or Servo( G320) driver. Ive had very good experiences with Gecko drivers, great support,
and they work very well. But I happen to have some SST's here, so we'll use them. Ebay is great for getting motors , you can often get a servo and matching driver
at a fraction of the cost of a new one. They can all be the same or different, doesn't matter as long as they do the job. If you ask around, people will tell you
how much power you may need, Ive never had Anything that a 200watt servo wouldn't drive. But with servo's , you can go as large as you can handle.

   Steppers, (or servos) are pretty easy to hook up. If using Servos, make sure the driver is a step/direction interface. Otherwise, you'll need a step/dir converter to make
the step/dir signal from Mach3 an analogue output for the driver. Your power supply should have enough oomph for the motor. If you have 3 steppers at 4 amps, you
don't need a 12 amp supply. (many just add them up, but it doesn't work that way..), you'll need about 60% to be safe, so 8Amps at speced voltage would drive 3
4 amp steppers. For servos you'll need lots of power. They can draw 20-30 amps when they need to kick in current, so check with the driver maker as to specs of that.
The servos Ill be using come with a power supply, so we wont have to worry about that one.  We'll go into tuning when the motors are all attached, and Ill show you
 what trouble we hit. Servos can be a real pain to tune in depending on the system, some are easy, some are hard. Persevere, in the end it'll work great usually.

    The only other thing you need to get movement is a breakout board. Check the web links on the artofcnc website. Many makers there and their all pretty good. A
breakout boards job is to give you a wiring platform AND to isolate signals, and condition them from your computer. IF your computer is 3.5 volts only on its printer port
(use a meter and measure a few pins from pin 25 , if you see 5 volts on any, you have a 5 volt motherboard, if you see 3.5 volts on one, then you have a 3.5 volt port.)
then you need a breakout board that will accept 3.5 volts and condition it to 5. Many are available. You CAN just cut off a printer cable and wire it direct, but I don't recommend it,
you'll be confused enough at times, the breakout board really helps calm the confusion and is easier to wire up, it also allows for future additions, so trust me, don't cheap out here,
their only about 125.00 or so typically, and well worth it..

 More on motors and breakout boards soon, specially as we begin to hook them up. Ive asked Bob to take pictures of the old table as examples so Ill post them soon, and as we go, we can draw
comparisons between old and new to show various differences between a Servo and a Stepper operated table. As well as wiring and performance.. In the end, we'll have 2 tables that can cut our
jobs and you'll have seen our mistakes. (allot of them to show you. ), hopefully we'll all learn something..

  Bobs great at the mechanical work, I'm more the theory guy and the software guy these days. But I wont code anything special for this table, Ill show you how it works out of the box, and
we'll solve any troubles we get along the way showing you everything we hit, in hopes you'll be better prepared for what you may hit..

to be continued...
Art


 
   

29

Building or Buying a Wood routing table.. Beginnners guide.. / Size of a table..

« on: October 10, 2006, 03:11:58 PM »

Table - Continued..

   Well, Size is something to be considered. Not alot to say on it other than it must be large enough to hold what you need held.
Dont forget to consider though how to connect your gantry to the table. Some youll see overhang the table anf literally hang from
bearings under or on the side of the table. Those are nice, keeps the material away for the bearings. I didnt do that , of course,
I went for the more obvious method of bolting the bearings to the table and having the gantry ride on top of them. Works well,
and I dont really regret the decision, but it is somethign to consider.

Plan the size to hold the gantry. Personally, I think making the gantryand then making a table to fit it is the easier way to go. Our gantry was a 3/4 aluminum
side wall with an Aluminum beam riding between them.  The sides were gussetted for strength, and had flat bottoms put on that would just sit on the bearing
carriages when done. That part worked very well, we may even keep it that way.  Still hasnt been decided to start again from scratch or resuse the old table,
but I lean toward reuse.

   That made a very tight gantry and the X axis was a dream, the Y axis was tougher. We quickly found that keeping it square was difficult. Luckily, we had lots of linear rails
hanging about, so we just doubled them up, so with two sets of rails on each side, everyhting became much more rigid.  We bolted a 1/4 steel plate about a foot wide on each
side of the table to hold all this, and that too worked pretty good. Its easy to level a steel plate bolted to a wooden top, and the thing IS quiet when moving. Originally we
put rack and pinion on the Y axis, but found it noisy and abit too slow to accelerate. A belt drive fixed that, and we found the belt tended to dampen vibration to the extent
that higher acceleration was available without having a resonance problem. (Resonance will lose you steps if the coupling between motor and carriage is too tight.. and belts flex enough
to greatly aid in that. ).

   We used about 16" centers on the wooden joists, and it has incredible strength. The total cost for the table was about 200.00-300.00 I think with an extra 50.00 for the steel plates.
We have found it very nice to work with... Id match its performance to a steel table any day, and I suspect no difference would be seen. So if your building a table for yourself, I do suggest
a wooden one. Might defy convention, but hey, its relatively cheap, works well, and youll have lots of other places to put your money.. might as well spend high when needed , and keep it low otherwise..

More later, I need to get some photos of this tabel Im describing so you can see what I mean on construction..

Art

30

Building or Buying a Wood routing table.. Beginnners guide.. / Planning Strength, speed, stability..

« on: October 10, 2006, 12:45:13 PM »

PSSS....

  I got a secret!!.

  PSSS- Planning, strength , speed and stability..

  Well, Ive planned this before. So have a few thousand others. A router table. How much easier can it get, all you need
is a table, a router , some motors, drivers, wires, and a breakout board. Sounds pretty simple, after all they all plug together
work out of the box, right? Wrong!. Well, OK,..sometimes..

  There are many ways to start. Some of you will just want to buy a table on the internet, and get running. No problem there, right?
WRONG!. The internet IS a great place to buy a table, and many of the builders out there are fantastic at supporting their products,
and they sell great products. From motors, to drivers, to frames, skeletons, bearings, gantries and full "turnkey" systems. But that doesn't
make it plug and play, nor does it mean they match your needs. You need to PLAN!!, I didn't on my first, planned quite a bit on my second,
and intend to plan all to hell on my third. (Does this tell you something. ). Planning is very important even if you intend on buying a finished
routing system complete. Planning takes into account all the rest.. Speed, strength , stability and a whole lot of other things not listed in above.
Planning lets you hit the snags in the rebuild stage, which can save you lots of time and money..

 Remember the ramplings  I talked about earlier in the topics.. this is one of them..

Money: How cheap can I go. ?

  This is a pretty typical question. With no absolute answer. My own philosophy is cheap is good, but you have to tie that into my other
philosophy  "If it works, its a good solution.". The test of any system is , in the end, does it work well. "Well" is a relative term. Some want
very fast, others will take what they can get..  Ive done this to much to "take what I can get.". Cheap usually means bad, inexpensive is a better
term.

  I wont be purposely picking on any vendors here, and Ill ask no one else to do so as well. Being that quality is relative to what you need, one mans junk is another's
treasure. That being said, cost is a factor to consider and the term "You get what you pay for" is something you need to trust to be true. For example,
a Gecko 201 ( A motor controller) , last I checked, was about 120 bucks a pop. Thats roughly 300.00 for a 3 axis system. Check on Ebay and you'll find many at
about 39.95 for three axis. Which one do you think works better? If you said the 39.95 one, please slap yourself for me, as my keyboard doesn't have that function.

  You know, as well as I , that a 39.95 3-axis whizzbang is not going to function as well as a 330.00 set of motor drivers. Is the 39.995 junk? No, not necessarily, but it
may be designed to do something lighter than what you want.  Thats not to say either that the $600.00 per diver motor drivers are better than the 300.00 ones.
They may be, depends on the system, the use and the reason your using them. (Nothing is simple, eh?  -- we Canadians say -eh? allot..).

   My general rule is to check any driver , power supply, bearing...whatever, carefully with other users. The Mach3 group , for example has about 6000 of them.
All great people that are happy yo tell you of their mistakes, and experiences. (Hopefully mistakes not being using Mach3., eh? ).

   So when contemplatling any component, check around, a single saved mistake can save you time and money. OR you can be like me with shelves filled with
stuff you replaced and really wouldn't use again, but too good to throw away..  So .. to stop rambling.. CHECK OUT YOUR PLANS..Don't cheap out unless others tell you
its OK to. I'm sure many will shudder at some of the things I do, but on the other hand, I need only live with myself and my friend Bob, and we'll undoubtedly curse
each other frequently. (We always have..).

   When planning a table, consider everything you want to use it for. Size increases cost. More importantly, it increases space. I once had half my basement filled with table,
till Bob was kind enough to take it to his place, now HE has a garage full of table. (And adding his third..this one we'll be building as we go on this forum.. )
Of course for some space is available, so if likewise, money is as well, then 4x8 foot is awfully nice to have. For many though, 4 x 4 is a good compromise.. With a stand
and turning things around even a 4x4 can cut 4x8..just a bit more work is all.

  Speed is a function of the motors and the mechanics. As well as the software. We'll go into that in another topic, but just so you know that end resultant speed is
tied to many things other than just motors and dirvers.

 Stability is very important. My first table was built with some Thompson linear bearing, good, but not great ones, and flimsy gantry strenth. I regretted it quickly.
Being Strong usually means heavy. Heavy is good. Flimsy is bad. I know, youve seen tose wooden gantrys out ehre using drawer slides as bearing. Yes, they will
work, but I havent met the person yet who didnt rip it all apart and rebuild. So its a great learnign experience, but you probably wont like the end result. You
want strength and power, in equal measures to make a good router table. Not a bad idea to ask others what they think of your design as well. (I wont do that as I
have a sensitive nature and hate to be laughed at, but then I probably have more spare parts than you, so Im not really wasting much by trying., and besides,
you may gain from watching my mistakes and my redesigns to fix our troubles..

to be continued...

Art