Machsupport Forum
General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: toomanyhobbies on April 20, 2010, 10:58:50 PM
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Several years ago I built my first cnc router. It started as a plasma machine and evolved into a plasma/router/light duty mill. It never really was built to mill metals.
So, I decided it was time to build a new machine. This one will be much heavier then the first one. Hopefully it will mill aluminium and steel without too many problems.
The drive system will be AC servos run through a 1856 Galil card and Mach3. As far as speed goes, the goal is 600+ IPM on rapids.
Pictured is the gantry. 6x8" steel tubing, 1/2" thick wall, 70" long. Weighs about 300# with the flat bars welded on. Add the z axis and a spindle and the "mass in motion" will be over 500#!!
more to come...
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Very interesting project.
I think the most challenging part will be choosing the right guides and transmission.
I have a router with casting aluminum gantry I reinforced both gantry sides by making them 1" thick and added two UPN profiles to each.
Still the problem is at the linear guides.
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elpablito, please elaborate.
I have Rexroth Star linear guides for this project. 25's for the y axis and 20's for the x axis. They should be large enough. The one thing I did not do that I will be doing with this build is having a machine shop surface all the areas the guides will be mounted to. One of the problems I have with my first build is the gantry binds because the linear rails are not perfectly aligned.
Some more specs:
travels: x 59", y 33", z about 15"
3/4" precision acme screw 2 turns per inch direct driven 1:1 by 1100w ac servos
Full flood coolant system
BT30 spindle rated 15000rpm (I know it will be grossly underpowered, but I want to try driving the spindle with a 1kw Automation direct servo through Machs spindle control)
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Some pics of the first router I built several years ago.
Gantry style with about 38" x 38" travels and 12" z travel. I should have made the x axis 48"+ so a sheet of material would fit into it. I used THK RSR 15 W rails brand new off ebay. They work very well. However, one problem with the rails on this machine is the y rails are too low and are always covered in swarf. it would have been better to raise them up to the level of the gantry. The other shortcovering of this machine is the spindle. I never had a proper spindle on the machine for metal work. These issues are addressed in the design of the new machine. After I get the new machine up and running I plan to use the rails, motors, leadscrews etc. from the old machine and make a cnc lathe :)
Rob
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My router has a gantry made from cast aluminum. On each side of the gantry, there are 20mm amt linear guides, with two blocks each, 300mm from block to block.
Check at the figure (by the way I took it from http://www.superiorbearing.com/images/amtbrochure.pdf (http://www.superiorbearing.com/images/amtbrochure.pdf), very useful doccument)
(http://www.gausstek.com/guideways.jpg)
For what I know, the bigger the guides, the bigger the force they can sustain.
But also by sepparating the blocks along Y you reduce the gantry twist in the MY and MP direction but loose some Y travel.
If I had to mill steel I would think of making the gantry sides as rigid as possible and putting two guides on each side at different heights to reduce twist in the MR direction. And maybe the screw or rack between both guides
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Picture of the gantry sitting on top of the base. So far the machine weights about 1200lbs. Gantry is 8"x6"x1/2" thick wall steel with 1" x 3" flats welded to the face. Base is made of 3/8" plate and 1"x2.5" flat bar.
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Here's a pic of the drives and some other items i'll have in the enclosure.
Anyone have any pointers on laying out the electronics in a enclosure to keep it neat and help prevent emf noise?
Looks so neat without the wiring :)
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Danaher servo motors i'll be using. On the left is the nema 34, 990 watt for the z axis. On the right is the larger 1100 watt motor I'll use on the x and y axis. Should have enough torque to move that heavy gantry. Planning on running them direct drive hooked to 2 turn per inch acme screws. I'll drive the gantry (y axis) with a similar belt setup as the old router with dual screws. This time I'll use GT2 timing belts because the htd belts I have on the old machine introduce a small amount of backlash. The GT2 belts seem to lock into the pulley better and eliminate the backlash - and they are quieter.
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Anyone have any pointers on laying out the electronics in a enclosure to keep it neat and help prevent emf noise?
I've done a bit of wiring in my time, but haven't really had to be concerned with EMF. The box itself should do the trick, I would think, as long as it's grounded. Generally, when I wired up enclosures, we tried to maintain 20% free space for upgrades/additional components. Personally, If I were to do one for myself, I would leave even more than that.There's always something you will find a need for. Relays, PLC, more inputs, more outputs, switches, indicators.... the list goes on. Space becomes a premium real quick. It looks a bit cramped already, so you may find yourself with an additional box in the future, or rewiring the whole thing in a bigger box if you do many additions. Small zip ties can help keep bundles of wire tight and neat. It looks like your moving right along though. Keep posting pics as you go, and thanks for sharing.
Here's a pic of the last enclosure I done. With the type of terminal blocks we used, we were far from 20% free. As the project progressed, I had to cram in a Danfoss VFD, an electrical outlet, more relays, and TONS more wire that came in and went out to all the components. The box is about 5 feet tall. As you stated.... Looks so neat without the wiring.
How true indeed!!
Remember, too much space is always better than to little.
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Sam, do I spot a PLC there with 12 IO moules? What brand is it?
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Allen Bradley
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Here's a pic of the drives and some other items i'll have in the enclosure.
Anyone have any pointers on laying out the electronics in a enclosure to keep it neat and help prevent emf noise?
Looks so neat without the wiring :)
Cooling fan?
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I picked up the gantry today from the machine shop. They cut the surfaces for the linear rails and squared up the mounting feet. I dropped off the base and they think it may be done next week :)
I put a heavy coat of primer on the gantry. Not sure if I should paint the surfaced areas??? Anyone think a light coat of paint on the surfaced areas would interfere with the linear bearings?
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I would put some grease or oil at the machined surface which is covered by the rails. If some of the machined surface is not covered by the rails I would have carefully covered the "under rails area" with masking tape and painted the remainder of the machined area.
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I would put some grease or oil at the machined surface which is covered by the rails. If some of the machined surface is not covered by the rails I would have carefully covered the "under rails area" with masking tape and painted the remainder of the machined area.
Sounds like good advise, I'll do it that way. Thanks
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Try using BOE SHEILD , It acts just like cosmolene and in a spray can, I get it at the marine supply. It sprays on thin and even like paint but drys kind of waxy like cosmolene for rust and corrosion protection.I dont have a can around but I think I have seen it even at home depot as well..Also there is a brand sold by mercury and evenrude if your near a marine store..
Gary
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Try using BOE SHEILD , It acts just like cosmolene and in a spray can, I get it at the marine supply. It sprays on thin and even like paint but drys kind of waxy like cosmolene for rust and corrosion protection.I dont have a can around but I think I have seen it even at home depot as well..Also there is a brand sold by mercury and evenrude if your near a marine store..
Gary
Thanks Gary, there is a marine supply store on my way to work, i'll see if they have that.
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You can keep the RFI to a minimum by building the electronics in a metal enclosure. Use shielded cables for all the drive motors, and make sure everything is well grounded together. Using a couple of 'feed thru" capacitors where the line cord exits the box will keep the whole system very quiet.
George
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George, i'm not good with electronics. When you say feed thru capacitor what size would I need and how would that be wired?
Thanks for your help.
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What I am talking about is a device used to remove electrical interference that is being conducted by a wire.
A feed thru capacitor is about 1/2 and inch in diameter, about 2 inches long, and has mounting tabs on one end. There is a threaded screw opening on each end. These were originally made for aircraft and military use during WWII. They can still be purchased at places like Aircraft Spruce, Allied Electronics, DigiKey, and other electronic suppliers.
A good value for your application is a .1mfd at 600 working volts rating. And yes, they will work with 110 or 220 VAC.
The attached picture will be worth a lot more than words.
Click on the picture to see it at just about actual size.
George
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Thanks George, I never saw one of those. Thanks for the clarification.
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Just a bit of further information regarding feed-through capacitors.
As George has said these are ideal for use in series with the AC line cord but they are not suitable for any DC signals, they are purely AC related devices.
Tweakie.
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Just a bit of clarification on the post about DC.
The feed through capacitor is exactly that, a feed through!
If you put an ohm meter to both ends of the feed through capacitor you will find zero resistance. The center post is a solid piece of metal, the capacitance if formed between the outer, grounded shell, and the center conductor. They are wrapped internally with two layers of foil, with an insulator, dialectic, between the foil layers. In aircraft design they are used primarily to feed 12 or 28 VDC through a firewall, leaving any spiking noise pulses being shunted to ground through the "Capacitance" of the device. The AC impedance of the capacitance is very low to the low level AC signals that are the noises pulses that you want to remove due to their high repetition rate. when the 60 Hertz (Cycle) AC comes along the small value of capacitance does not shunt the line voltage to ground, but any "High Frequency" noise riding along on the AC Power will be removed because it is so much higher a frequency rate.
Kind of hard to explain and understand if you are not into electronics. Hope it makes sense to all who read it.
George
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George, thanks again about the clarification on the caps.
I made some progress this past weekend..
I got the rest of the parts back from the machine shop last week. I'm really pleased with the work they did. If anyone needs quality machine work done give Bill Hall at Able Machine in Delaware a call. www.ablemachine.net (no affiliation, just a satified customer)
So, all the machine work (hired out work) is done on the x and y axis. I wish I could have taken a picture of my "little mill" sitting on the table of his VF7. It looked so small sitting on that machine.
I fabricated a stand out of 3"sq tubing, and got everything primed. Now I need to decide what color to paint it.
Next I'll start mounting the rails and getting the screws setup.
Then the dreaded electronics...
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Got a coat of silver gray on the base and mounted it to the stand. I chose that color because it was leftover from another project so it was a freebie.
Hope to get some time tomorrow to set the y axis.
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pic
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Looks like it's coming along nicely. Thanks for posting your progress, we love pics!
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Some more progress....
tonight I finished drilling and tapping some misc. holes in the 46" long carriers that support the y axis. Then I sprayed Boesheid T9 on all the bare metal machined surfaces and mounted the carriers to the towers. There are four 3/8" bolts that are accessible from inside the towers that hold the y axis carriers to the top of the towers.
Also got the the Rexroth 25 linear bearings for the y axis cut to length and mounted them to the carriers.
I intentionally had the slot cut into the carriers so I could use these toe clamps to wedge the rail against the reference edge as I tightened the mounting bolts.
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i guess the next thing will be mounting the gantry and making end blocks for the lead screws. That will most likely take some time to get done.
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Very impressive work you have done so far!
Can't wait to see the machine completed.
Keep posting pics :)
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Looking good!
JH
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Got a little more done :)
In an earlier post I showed the 16x24" electrical box as it was when I bought it. Since then I cut out the back and left side and mounted a 1/4" thick aluminium plate to the back of the box. This allowed me to drill and tap the mounting holes for the drives and other electrical gadgets. Mounted some large heat sinks (3) to the back of the aluminium plate for cooling. Plan to make a operator panel for the left side.
From left to right, there are 3 Danaher drives for x, y, z. Then a 1kw A/D servo drive for the spindle. Then another Danaher drive for 4th axis. Galil ICM2900 mounted to far right. There is a opening for the 100 pin cable connection at the right side of the box. Power will come into the box from the bottom and I have distribution blocks I can mount to the din rail under the drives. I am going to take an approach similar to how the machines at work are laid out to help fight EMF. Basically, the high voltage ac devices are mounted in a separate chassis and include ac circuit breakers, transformers, high voltage relays etc. Another chassis will house the servo drives, I/O and other noise susceptible devices.
Also started mounting the y axis limit switches and trips.
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I am at a juncture in this build where i have to decide if I want to spend the extra money and get ball screws or continue on the path I was originally going and stay with acme screws and Delrin nuts. I am guessing the ball screws will last longer and have no backlash. Also the ball screw I was looking at are accurate to +/- .001 (Nook XPR) whereas the Acme screw is only good to +/- .009 per foot.
I used the acme screws and Delrin nut concept on the first build and it has been ok. I noticed recently that the Delrin nuts are starting to get some backlash on them. They had been tight without backlash until recently.
Anyone want to chime in on this????
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well.....I mean....considering the investment (time and money) that you have already put forth in this project, I would go for the ball screws. If it were me, the delrin and acme screws wouldn't have even entered my mind. Great job so far, by the way. Keep the pics coming!
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Regarding Ball Screws...
If I do go with ball screws, what would be a good lead to choose? Nook has .200, .250 or .500 leads
I used .500 lead on the last router, and I was planning to use .500 lead acme screws on this. Judging from recent experience, maybe a finer resolution would be better though. I have more then enough RPM from the servos for the finer pitch screws, the limiting factor is whip from the x axis screw.
just thinking... If I went with .200 lead or 5 turns per inch I could possibly see 400IPM If I can get the longest (67") screw up to 2000 rpm????
According to Nooks critical speed calculator, I can get about 1900 RPM from a 1.15" screw, however, the ends need to be supported with angular contact bearings spread apart a minimum of 1.5x dia of the screw and at both ends. With regular ball bearings at both ends the RPM limit drops to 1266 or 253IPM.
So, are the calculations Nook uses conservative? Can I massage the numbers a little and still be OK?
My original goal was 600IPM, but 400IPM would be OK. Less then 400 may be a problem though.
What are your experiences?
Thanks
www.nookindustries.com/engineering/calculators/CriticalSpeed.cfm
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Attached is Nooks formula for determining critical speed. Didn't try the calculator......
You can also take a look at other manufactures guidelines. Are they being conservative, well, sometimes companies have deternined
what is good engineering practice based on time tested information. If you want to ignore the info, then sound engineering experience
or analysis would enter into the judgement. What you want is to operate away from the critical speed
and other possible harmonics. Naturaly this is not limited to just the simple calculation as other things can come into play.
RICH
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Can anyone help me with ID'ing this spindle and it's components?
I bought this spindle cartridge off ebay a while ago. Plan is to use it on this router when it's done. It was expensive and I don't want to destroy it. So, not knowing anything about it can anyone help me by pointing out anything I should know?
I was told it is from a Kitamura Mycenter 0. Supposed to be a 15000 rpm unit, and has a bt30 taper. This seems to check out looking at the specs on the Kity site. A Mycenter 0 has a BT30 taper and can come with an optional 15000 rpm spindle. OK, so maybe this is true.
The questions I have about it:
I think it is it an air/oil feed lube type spindle? Is that what the hole in the mounting flange is for (with the red plug)? If it is an air/oil feed lube type, how much air pressure, how much oil, how ofter and what oil do I use? What is the hole in the side, near the center, that has a hex plug in it for? What is the notch in the aluminum part at the top where the draw bar pokes out used for if anything, maybe alignment during a tool change? Can I apply force to the draw bar and have that force held back by the bearings or is the flange under the aluminum part used for squeezing the draw bar between the part that sticks out and the flange therefore not putting excessive force on the bearings?
Lot of questions... Any help would be appreciated. Thanks
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Well, after hearing the price for the ball screws I decided to use the acme screws for now, at least on the y axis. Maybe in the future I'll upgrade the screws if the need arises. Would have been really sweet with zero backlash ball screws on this machine.
Got the y axis screws mounted. Used the inexpensive stamped steel flanged bearings. They actually work very well. There is less then .001 backlash in the whole system.
Also got the gantry set onto the y axis platforms and mounted the x axis linear bearings. Used the same toe clamps to hold the rail against the reference edge, same as on the y axis bearings.
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Couple more pics...
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Worked on finishing the Y axis drive. After running the axis a few times, I think it needs larger belts. Sdpi didn't have the 25mm belts in stock, so I got the 15mm wide belts. I made the pulleys wide enough for a 1" belt. I machined the pulleys from pulley stock. The gadget you see holding the pulley on the shaft is a tapered hub. Fener Drives supplied those, very nice.
I do need to change that upper idler pulley so it has grooves in it for the teeth on the belt. I can't believe how much noise the belt makes going over that flat idler.
Quick video of me testing the Y axis drive.
http://www.youtube.com/watch?v=OORg43YlVoE
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Couple pics of the Y axis drive.
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Been making some good progress on this build. Although, I suspect progress will slow considerably from here on considering how cold it's been here and I have no heat in the shop :(
Anyway, some of the work I got done:
Got wider belts for the y axis, the narrow ones were stretching a little.
Finished the X and Z axis. The X was easy after I figured out how I was going to do it :) The Z turned out to be a long project that involved purchasing a Bridgeport Series II mill to make the 3 plates that make up the Z axis. Then after I finally got the Z axis done, I had to change out the Acme screw/delrin nut combination to a ball screw due to a bad vibration from the acme screw.
Quick Z axis demo:
http://www.youtube.com/watch?v=dt9paSCZvhs
Pen plotting a part file with feed rates of 30 to 250 IPM and rapids at 600 IPM
http://www.youtube.com/watch?v=dbIUzRVaNq8
I guess the next project will be getting a spindle on this beast.
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Couple pics of the Z axis getting a ball screw transplant and a few pics of the X axis.
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Its progressing nicely, great work !
JH
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Its progressing nicely, great work !
JH
Thanks JH. I was checking out your Bridgeport retrofit. That is an awesome build!!! I really like vintage iron, I wish I had thought to retrofit an old machine instead of building this machine.
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Well, it's starting to get warmer outside and so I have been working on the cnc machine a bit more. Sure wish I had heat in the barn this past winter. could have got a lot more stuff done!
Anyway, I finished the Z axis. Mounted the cable chains for X, Y and Z. All I need to do now is finish the home and limit switches for X and Y and wire up a output to turn the spindle on/off. Also I would like to setup a mist coolant system, I am very impressed with the mist coolant I put on the old machine! It works great and it was free (made it from a soda bottle, an old air soleniod, a regulator, and some clear tubing). I'll try to get a few pics posted in a day or two.
Here is a video of a test cut run on the new machine. Cutting 6061 aluminum at 50 IPM and then 120IPM ;D Keep in mind the majority of the chatter comes from the Porter Cable router and a dull end mill.
http://www.youtube.com/watch?v=a974jExoLak
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Pic of the cut, showing surface finish.
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Managed to get some work done on the spindle. Fabbed up a housing for the BT30 Kitamura spindle cartridge. Was concerned about the weight of the assembly, maybe around 80-90lbs for the spindle & housing plus 20lbs for the motor. Z axis seemed to lift it ok though. May add a gas spring to the Z axis just to alleviate some of the weight.
So, the plan is to use 1:1 on the belt drive. Figuring the motor running on a vfd is good for about 1000-7000rpm. What do you guys think? Sound like a good rpm range? My expected use will be milling, boring and tapping aluminum and occasionally milling some steel. Cutter sizes typically from .125" to 1.00" and ,if the rigidity allows, a small (2.5"?) face mill. Maybe someone could chime in on my plan.
Next on the list is mounting the motor, fabbing a mount for the hydraulic cylinder and making a air over hyd booster. Also have to setup a spindle oiler. What is the correct oil to use for a air lubricated spindle? Mobil Velocite ???
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Sorry I don't have any input on the spindle, but I do have to ask....what's the story with the Firebird?
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Sorry I don't have any input on the spindle, but I do have to ask....what's the story with the Firebird?
The Firebird is a 1969 convertible, originally had a 350HO however the motor was missing when I purchased it. It now has a worked 455 with KRE heads, roller cam, etc. It's mostly done but still needs a little work on the interior. I've owned it for about 17 yrs. Done 2 restorations on it! You may see it at a car show this summer if you live near me.