Hello Guest it is November 15, 2019, 01:40:39 PM

Author Topic: Planning Strength, speed, stability..  (Read 22038 times)

0 Members and 1 Guest are viewing this topic.

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
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



Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Planning Strength, speed, stability..
« Reply #1 on: October 10, 2006, 12:59:06 PM »
The table..


  Well, theres alot of ways to build a table. Ive used an aluminum table from an old table saw, still works pretty good, but wasnt ideal for what I wanted,
then we build a wooded one. Just like youd build a deck on your house. 4x4 legs, 2x8 joists, and a plywood top. (We'll only be discussing thetable itself here, not the gantry..)

  The table itself is basically a platform to set your gantry on. We're talking wood routing in this forum, so generally, anythign will work. You could bolt linear rails to a floor and it would
work great, but Im assuming your like me and dont want to crawl on the floow when putting material on your table, so we need something to hold thematerial at least at waist level,
thus we need to build a table. I was pretty impressed with the wooden one we buiild, pretty stable, no real warpage over time, and pretty easy to build if you can use a saw.
Metal tables are great too, if you can weld and have steel or dont mind the excessive cost of steel these days. My second table was about 4x8 and completely made of wood. To hold the
gantry, two plates of 1/4" steep were bolted to the side about 8" wide or so to bolt the gantry bearing to. Ill post photos of that one shortly. While Bob wants to build a completely new table,
Ill be lobbying for tearing down the wooden one and just rebuilding from there. In any event, theres only a few things to worry about in the table area. It must be strongly built. This is because you want
to dampedn vibrations , and keep things from warping. Good thing about a wooden table structure is it can be told to plane itself down to a flat top when your done. That worked very well for us on the last table.
 Id liek to go that route again. But if Bobs heart is set on it, what the heck, we can do steel as well. The end product probably weighs in about the same, I just like wood because its easily modified, and
relatively cheap. I HAVE see systems overengineered in the table, and then lightly engineered int he gantry..bad mistake.. If your going to overengineer, do it in the gantry (which we'll get to
soon. The table should be strong enough to so the job, overkill is good, and made of whatever makes you happy, take it form me though, wooden ones DO work well, sufficiently designed for strength.

to be continued...

Art

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Planning Strength, speed, stability..
« Reply #2 on: October 10, 2006, 02:23:34 PM »
The Table.. continued..

  OK, so I haven't badgered Bob yet to keep the old faithfuls wooden table, but Ill go on the
assumption he's willing to go along with that. Most of this little followup will pertain to either
a wooden or a metal table. I cant really say this is the best , or the worst way to go, Ill leave that to you
to decide. Of course, you may have decided to purchase one outright. SO before we discuss building a table,
lets talk a bit about buying one.
  It disturbs me when I get support letters from people who have purchased a system and feel let down. While
I'm in no way responsible for that, I'm empathetic enough that I truly feel bad for them, typically it can be
allot of money, or even if not allot, it can be all they had for their new hobby or business. And I hear it all.

  From the people that send a check for $25,000.00 for a system which never arrived, and will likely never arrive, to those that spend $5000.00
on a system that performs very badly, I ve seen many bad purchases.  I don't judge others systems, unless I'm buying them, and Id ask you not to send me ad's asking me
if I agree or disagree with the design of someones system they are selling, I CAN tell you what I look for, (and again, what the hell do I know?)..

  When I look at a possible purchase of a table, and Ive considered and drooled over a few, I look at several thing. How well is it build, and weight tells you something there.
Not everything, but weight is a good guide. Its typically heavy to build strong. Does it have bearings on the table where the gantry hooks up to the table? How good are they?
 Linear bearing, like Thompson linear rails cannot be beat. Two pipes with roller bearing on them is probably not what you'd want. The thing here is the gantry you WANT doesn't
easily swivel out of square. Some have two motors to keep it square, others just rely on the bearing to do it. Having two pipes with roller bearings are unlikely to do that.
Linear bearings have car's, or carriages that do not easily swivel out of position, they stay parallel to the rails they are on, that means stability and less vibration.
  This is an important thing to look for, there are three weak links in any table, the connection from table to gantry( Y axis) , the gantry's side to side carriage (X axis),
and the Z axis which resides on the X axis carriage. They should be pretty beefy. The best Ive used or seen is either a single beam being the X axis or a dual beam one on top of the other.
  Having a beam in front of a beam with a router carriage mounted between the two beams should be avoided. Not that it cant be done properly, but it interferes with tool changing
and can be a bit of a pain. Again, Ill post photos soon of what I mean , showing what we've done on ours, (trying to keep expenses down), and we've been very happy with it over time.
  Dive systems on a purchase table are important as well. The ultimate of course is good Ball screws. Take not a Ball screw is not just a screw. Ball screws can be recognised typically
by a barrel looking nut with tubes on it. The tubes allow ball bearing to race around the screw very tightly allowing no backlash and very tight coupling. Thats the ultimate.
 Prices on those have fallen a bit over the years and where you can use one, I more than highly recommend it. 

 Second to that is an ACME screw. AntiBacklash nuts can be made or added , and they can work very well, and are very inexpensive. They do wear out faster than ball screws,
but depending on the performance you want, even an Acme screw can work.

 Often, the X axis ( since it runs 4 foot or less across a table) can easily use a ballscrew, but the long axis (Y) of many tables would require a 8 foot ball screw,
 thats hard to come by, so I use a belt. Some use rack and pinion. I actually used belts on both X and Y axis, I like belts, very quiet, not any backlash to worry about,
 can be hard to find though with timing gears to match. We stole ours from XRay machines so I didn't have to search hard, but personally, Id like to have ball screws this time, so I'll
be lobbying for those or at least one of them with a belt for the long axis perhaps. (Anyway, this is about purchasing at the moment.. :) )

  Plywood tops are nice, they can be replaced or used sacrificially, but many of the units out there have aluminum tops, even a user with an aluminium top will often bold plywood to it
to use as a protector as it can easily be replaced after a couple years of mistakes and cutting. I guess my point here is that almost anything else can be modified or fixed pretty easily,
but basic construction can not. Look for well built tables that show the engineering skill used in its design, usually, if it looks tough, it is. An dont discount used tables, they often
are the greatest deals in the world, as long as they were good to begin with. Show a picture to a friend in engineering, ask him where he suspects any weakness, Even 1/4" steel
can flex, and you don't want flex, so its always good to ask, unless you know enough to judge. Its your money, but Id use caution.  Ive seen pretty bad designs that end up
being just about impossible to get running. Take specs as a general guide, they are often inaccurate as to maximum speeds, and they dont mention accelerations which is more
important than speed. Ill take a slow table with fast acceleration anyday over a fast table with slow acceleration, we'll deal with accel and speed when building later one, but if buying,
check it out well, its usually a big purchase.

 What should I pay? ---

    Good question. Only you know the answer. Ive seen tables from 1000.00 to 100,000 dollars, and the quality range is usually not linear with price, so again, check carefully with
your requirments in mind. I can tell you building one isnt cheap unless you root out the bargains. Our large table cost about 2000.00 to build and does great work, but Ive seen
systems costing $20,000 that I wouldnt trade for my 2000.00 table. (On the other hand I sometimes drool over a $3000.00 one..)

  EBay is great for parts, for almost anything on a router table, but like a flea market, junk abounds, be sure of what your buying, unless its a good risk. Good risks are there.
I got 3 yaskawa servos for soemthing like 600.00 , AC brushless with drivers.. thats a good deal for all the servo motors and drivers a router table will need, and the seller was great to talk to,
so I called it a good risk. They worked great.  Linear slides also go for great prices some days, and are very nice to have. (I swear by linear bearings).  Never discount Ebay just because
the parts may be old or used,many of them come from factories with tolerance much higher than youll ever have, and a set of linear bearings for a hundred or two is a great start to a
system that is extremenly tight and accurate.  And even if you dont think your going to want "Extremely tight and accurate, trust me,..you will..)

  Ill keep this forum to Wood routing, but those reading it and wanting to build plasma systems can consider the differences that they need. For example, for plasma work, rack and pinion (R&P) is great
, R&P can also be used for wood, but its not my preferance, been there, found it just abit crappy, belt is much better in my experience. There are different types of R&P though, and Im told the better
ones eliminate backlash as well as wearing very nicely, probably great for wood, I just havent used them.

 (Boy the people disagreeing with me are starting to build up now., Again, this is all jusy my personal experience..   :) )

 Anyway, when buying a system consider some of the above points, at worst youll be better informed, at best youll save time and money..

(to be continued..)

Art







Re: Planning Strength, speed, stability..
« Reply #3 on: October 13, 2006, 11:26:43 PM »
Art:

In the second section of this topic you say your X axis will be 4' and your Y axis 8' and of course Z up and down. I have always been lead to believe that X is the long axis left to right Y is short axis at 90 deg to X away from you when facing the machine and Z up and down. Do you folk do it different in Canada. Just asking so that as the build goes on I am on the same page you are.

Thanks

Dave

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Planning Strength, speed, stability..
« Reply #4 on: October 14, 2006, 09:23:27 AM »
Hi Dave:

  Good point. Someone else mentioned that to me. The position of X and Y are a bit arbitray and depend on the way you look at things. But unlike a mill,
I consider the short axis to be X for a reason. Consider a photograph you wish to engrave on a door. The door's long axis, woudl lay on the long axis on the table, the X woudl be the short 4' side.  Consider the X on a photograph or drawing, (the bottom of the photo.right? ), and you wish to engrave this on the door, well, if you dont want to rotate the photo's X,Y, then youd consider the router tabe's X to be the short axis. As to which side of the router you face when using it, many of us face the short 4' side. Not the long 8' side. This makes the 4' side the X in our case and really helps when putting any designs on a door as the X is the side to side axis of the door.

  Its the reverse on a mill , where the long axis is the X. All a matter of perspective, but since when doing wood work, you typically lay the X on the short side of the router table, it save alot of headaches to simple consider the short side to be the x. But as in all things, people differ, but when using a wood routing table, you save a lot of headaches if you consider the 4' side of a 4x8 table to be the X, not they Y.. (My opinion only..but thats pretty typical. :) )

Art
Re: Planning Strength, speed, stability..
« Reply #5 on: October 14, 2006, 11:59:16 AM »
Art

That does seem logicail in this case. I would like to design a machine that can be both router and mill so would go the traditional XYZ route.
I also need the 4th axis A to X and a 2nd spindle so I will not need to do a tool change for a very receptive job that the machine will be doing. Thinking fixed gantry moving table 18" X 36" Main spindle would eather be changeable from high speed router to low speed mill operations or have enough belt steps to change from high speed to low speed. Thinking R8 taper with Thormach tool holders. 2nd spindle would be high speed only. All total I'm looking at 5 axis machine.
What are your thoughts on the use of Polymer concrete in machine construction?

Dave

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Planning Strength, speed, stability..
« Reply #6 on: October 14, 2006, 01:20:20 PM »
Hi Dave:

   I have heard great things about tables from Concrete. (As long as you never have to move it. :)
It woudl be handy to have two heads.. or some tool change mechanism, Ill have to give that some thought as
well..

Art

Offline ger21

*
  • *
  •  6,288 6,288
    • View Profile
    • The CNC Woodworker
Re: Planning Strength, speed, stability..
« Reply #7 on: October 15, 2006, 09:52:38 AM »
But as in all things, people differ, but when using a wood routing table, you save a lot of headaches if you consider the 4' side of a 4x8 table to be the X, not they Y.. (My opinion only..but thats pretty typical. :) )

Art


I'll disagree here. On large machines I don't believe it's typical at all. I run and program a large commercial router (which happens to use X as the long axis). Other than your door example, Imo most other examples would be the opposite. Especialy when cutting parts out of large sheets. Typically, when drawing your parts in a CAD program, you'll draw them with the longer side on the X axis, left to right. This makes more sense since it fits on the screen much better. And this translates much better when the machine is setup the same way. Imo, it's a very simple task to rotate the door in the CAD program.

As you stated, it's always the users choice, but I see confusion amongst beginners with this topic all the time. Imo (and most large woodworking machinery manufacturers), the axis on the gantry should be Y. I think making that a "standard" would be a benefit with support issues, if everyone was always talking about the same thing. Or at least let people know that making the gantry axis X is deviating from industry standard, so they know what to expect.

Just trying to minimize confusion. ;)
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline ART

*
  • *
  •  1,698 1,698
  • Tough as soggy paper.
    • View Profile
Re: Planning Strength, speed, stability..
« Reply #8 on: October 15, 2006, 10:04:01 AM »
Hi Gerry:

  Thanks, its nice to hear alternate opinions. The word "Typical" in relation to cnc is a bad one. Each person uses it based on personal experience.
In my experience, 90% of the tables Ive seen use the short axis as X, but in yours it sounds reversed. SO I guess we each have our own typical. :)
 Since out table tends to be placed in a location that gives us access best from the end of the table, X still makes sense as the short axis, but of course,
the argument is moot as using it either way requires some jobs to be reversed. In fact, it may be worthwhile to even add two buttons to a screen set
to automatically swap the axis configuration so the table may be considered to be either. That way there is no typical, and the orientations are then
dependent on the job. In Mach3 , its quite simple to do that unlike most software, so having buttons makes sense, I think Ill do that, I have to admit
having a button that tells thetable which axis is which on the fly could be very handy and eliminate having to worry about it. The argument of
which side of a wood router is X or Y, will in the end devolve to what the user does with it, if all a person does is doors, then he'd want to consider
X shortest, where another who does landscape signs only would want the inverse. A person who does half of one and half of the other woudl like both..
so I'll shoot for both, that way no CAD work or CAM work would be required to change any job around. Makes alot of sense..

  See, its these types of discussions that will make a router project conform to its use, rather than a dogmatic approach of who's right and who's wrong. :-) ,
in CNC, no-one is ever really wrong..just looking at things from his or her perspective. I like this because it allows for the software to create a conformance..

Regards,
Art


Art

 

Offline ger21

*
  • *
  •  6,288 6,288
    • View Profile
    • The CNC Woodworker
Re: Planning Strength, speed, stability..
« Reply #9 on: October 15, 2006, 04:43:15 PM »
Art, try loading 4x10 sheets from the end of a router by yourself. ;) I would never build a large machine and plan on loading it from the end. Thanks for listening.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html