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  1. #1
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    A Different Machine - Downdraft/water table

    I finally got started on my table replacement. I've been using an old rolling cabinet with a blower installed in the botton and exhausting out the side. It's been really beat up plus it's only for freehand work. However, it does run pretty clean so I thought the addition of a water tray would really clean it up.

    I've been collecting parts for several months, motors, controller (g540), power supplies, switches, rails, etc. I am using V rails for the x axis, linear rails for the y and z, The drive will be 3/4" belt on the x and y and acme screw on the z. I am using 2 motors on the x.

    The table is relatively small compared to most on these forums, 4 x 2 ft. This is for 2 reasons. One is I don't need a large table and second it would be extremelly difficult to do the downdraft with a large table. the exhaust can either be filtered or ducted outside.

    The table will be built from 2x2 square tubing, 2x2 angle, 1x1 angle, and various strip stock. Panels will be 18ga sheet. I built the top and bottom rails and posted the pics. Getting them square and level was a lot tougher than I thought it would be.

    I'll keep posting my progress. Any suggestions would be welcome.

    Willy
    Attached Thumbnails Attached Thumbnails Top Frame.JPG   Bottom Frame-squared & welded.JPG  

  2. #2
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    It's got legs

    Been a busy day. Got the legs cut and installed. Also added the top frame to the assembly. Learned a good lesson today - you can't have enough clamps and they can't be big enough.

    Used a borrowed laser level to square and level the legs and top. Worked great - lots easier than a bubble or water level.

    Added 2 pics of the work.

    More to follow.

    Willy
    Attached Thumbnails Attached Thumbnails Legs Attached.JPG   top frame installed.JPG  

  3. #3
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    Water Table supports installed

    Got a little bit done today. I installed the water tray supports. I decided to make it removable since it's not that heavy without water. It should simplify cleaning sludge. I plan to put 3 baskets (each 1/3 of water tray) in the bottom of tray - just remove slats and lift out.

    Just need to figure out where to put drain so tray will slide out.

    The build is going very well so far. Hope it continues.

    Willy
    Attached Thumbnails Attached Thumbnails water table supports installed.JPG  

  4. #4
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    Looks like a good start! A 4X2 is a handy size. A high percentage of the work we do is modifying existing parts, all of them are under 2X2. Our next machine will be a small one.

    Look forward to your progress, good luck.

    WSS

  5. #5
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    A little more progress

    Had a little time today so I installed the blower supports. Since the bottom of the machine will be covered, I welded nuts on the bottom of the supports for the blower mounting bolts. There are rubber buttons on the bottom to isolate the blower.

    The blower is a belt drive Lau rated at 950 CFM. I chose a belt drive to keep the motor outside of the machine. My previous table used a direct drive blower and I had lots of trouble with dust getting in the motor so this should solve that problem.

    Pics attached.

    Any suggestions welcome.

    Willy
    Attached Thumbnails Attached Thumbnails DSC01352.JPG   Blower supports installed.JPG  

  6. #6
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    More progress

    Added the blower shield supports and the slag filter. These are the inclined angles in the middle of the frame (sloped from right to left in the pic) and the small opening at the left of the incline. This should catch any bits that escapes the water table and is sucked down to the blower. The filter will be a fairly fine stainless screen. I had a rudimentary version of this in the original table and it worked very well. My real hope is that the water tray catches most of the debris. A piece of sheet steel will seal off the blower from the upper part of the machine except for the filter opening.

    The vertical pieces opposite the blower on either side will be the door frames to allow access to the blower. At the lower left side of the frame is the beginning of the exhaust tunnel. I plan to have 12x12 furnace filter on the outside of the machine for a final air filter.

    That's it for now.

    Willy
    Attached Thumbnails Attached Thumbnails Side View Blower Mounted.JPG  

  7. #7
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    Quote Originally Posted by flyinwilly View Post
    Had a little time today so I installed the blower supports. Since the bottom of the machine will be covered, I welded nuts on the bottom of the supports for the blower mounting bolts. There are rubber buttons on the bottom to isolate the blower.

    The blower is a belt drive Lau rated at 950 CFM. I chose a belt drive to keep the motor outside of the machine. My previous table used a direct drive blower and I had lots of trouble with dust getting in the motor so this should solve that problem.

    Pics attached.

    Any suggestions welcome.

    Willy
    How are you planning to keep the dust/grit out of that sleeve bearing on the end of the blower shaft?
    If it works.....Don't fix it!

  8. #8
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    Millman:

    I had those same thoughts so I have some caps with wipers that I am planning to use. I don't know how long they will last or how effective they will be.

    The original design was to use a blower with sealed bearings but I picked this one up on Ebay for $35.00. It might prove to be a mistake but at least it won't have cost too much.

    I originally was planning on having filters on the outside of the blower intakes thus the 2 maintenance doors on each side of the blower. I hope the water tray will reduce the dust and grit to a level that won't require them but if necessary, I can add them later. It's also possible to add dust filter material under the slag screen since it just drops into the opening.

    Only time will tell.

    Willy

  9. #9
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    Exhaust tunnel frame

    Finished off the exhaust tunnel frame today. I extended it back so the neck of the blower slides right in. Might be a problem if the blower has to be replaced and a different size is used.

    Build is going really smooth. Hope it continues.

    Any suggestions welcome.

    Willy
    Attached Thumbnails Attached Thumbnails Exhaust Duct Framework.JPG   exhaust tunnel - side view.JPG  

  10. #10
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    X axis rails

    Got quite a bit accomplished the last few days. Installed the upper and lower X axis supports and the V-rails. I originally planned to use 4x2 channel for the rail support but it was really expensive so I used 2x2 angle instead. It was quite a bit more work to get them straight and true but large clamps and careful welding did the trick. I added extra supports in the rear of the angles to make sure they stay straight. If I had to do it again, I'd buy the channel.

    The v rails are from PBC and are very nice. I used the #4 rails but could have used the #3 with no problem. It's a lot of work to drill and tap all the holes for the rails. I made all of my own spacers to mount the rails and had to trim the screws since there was a support behind the screw holes. The laser level shows the rails are mounted perfectly true.

    Also installed the sheet metal on the exhaust tunnel and painted part of the machine. Starting to rust in the humidity.

    Next comes the gantry and x axis plates and belt drive.

    Willy
    Attached Thumbnails Attached Thumbnails v-rail installed.JPG  

  11. #11
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    More parts done

    Completed the gantry and some miscellaneous parts for the drive system.

    The gantry is made from 2x2 steel tubing with 1/4" base plates for attaching to x axis plates. I drilled and tapped both gantry rails for the linear rails before welding. I used machinists angle blocks and lots of clamps to keep everything square while welding. Worked out really well.

    Also made some drive bushings and the bearing mounts for the main drive shafts for the belt drive. I had planned to buy the mounts until I started pricing them out. Decided that I could make them for a lot less. Made the cup a slight press fit and welded to a piece of 1/8" steel. Froze the bearing and then just pressed it in. Fit beautifully and the bearings run smooth. Also no set screws to tilt the bearing.

    Still working on the x axis plates. Had to make some changes because of the larger x axis v rails. Change one thing and screw up 5 others. Live and learn.

    Pics attached.

    Willy
    Attached Thumbnails Attached Thumbnails gantry.JPG   belt idlers with bushings.JPG   drive bearing mount.JPG   V bearing with spacer.JPG  


  12. #12
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    More misc stuff

    Started planning on how to close in the sides of the beast. Decided to tack weld all the sheets except the bottom. That will be screwed so I can access the bottom under the blower shield.

    One thought popped into my mind as I was moving the frame on the dolly is that it is getting quite heavy. Must be pushing 200+ lbs. I've added leveling legs so I will need some way to move this beast around the shop – can’t slide it.

    I added inclined casters on one end and pipe sections on the other end so I can stick pipes in to gain leverage. It works pretty good.

    Still working on the x axis plates, rails, and drive system.

    Pics attached.

    Willy
    Attached Thumbnails Attached Thumbnails caster  inclined mount.JPG   lifting sleeve.JPG  

  13. #13
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    Adding the skin

    Added some of the outside sheet metal this weekend. It's a pretty easy job except for moving the 4x8 sheets of 18ga steel around. The plasma cutter really makes it easy to cut out the pieces and they are fairly clean even doing it freehand.

    I did both ends and then made the motor mount. The motor I was planning to use for the blower was an old 1/2 HP I had laying around. I tried it on the blower mounted in the machine and the air coming out the tunnel was unbelievable. However, the motor ran for a few minutes and then the overload tripped. After several more runs, it became clear I need a bigger motor. I put on a 1HP and it ran fine but the mount was too small to support this motor. Back to the drawing board. Pics of new mount attached.

    Almost have the x axis plates done. Just waiting for some belts from Econobelt. Ordered them over a week ago and they promised 3 days. Called today, guess they lost the order. Supposed to get them tomorrow.

    It's coming together quite nicely. Can't wait to get something moving on this beast.

    Willy
    Attached Thumbnails Attached Thumbnails belt drive motor mount.JPG   exhaust end with filter door opening.JPG   motor end - belt opening.JPG  

  14. #14
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    More stuff

    Closed up the right side and installed the blower shield. Hopefully I can get the left side closed and the whole unit primed and painted over the holiday weekend.

    The belts finally came in so I finished machining the x axis plates. Everything fit just right although the clearances were a little tight due to using the oversized rails. They should work just fine. The V pulleys are on the outside of the plate, the belt idlers are next, and the final drive pulley is in the middle. The two bearings on the bottom ride under the lower angle to keep the plate from lifting up. With the weight of the gantry, I don't expect that they'll be required but better safe than sorry. The whole unit rides really smoothly on the rails and requires very little force to move. Stopping it may be another matter but that's a subject for later.

    I need to make the motor mounts which will hang below the axis plates. I also need to finish the belt clamps. I've been trying to see how to adjust the tension on the main drive belts. This is the belt that rides over the idlers and around the small pully to drive the plates bach and forth. It's difficult to get them tight. I'm thinking of bolting one end to the underside of the x axis channel and using a good size spring on the other end. If anyone has any ideas on this, I'd appreciate hearing about them.

    Pics of latest work attached.
    Attached Thumbnails Attached Thumbnails blower shield installed.JPG   X axis drive.JPG  

  15. #15
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    Quote Originally Posted by flyinwilly View Post

    I need to make the motor mounts which will hang below the axis plates. I also need to finish the belt clamps. I've been trying to see how to adjust the tension on the main drive belts. This is the belt that rides over the idlers and around the small pully to drive the plates bach and forth. It's difficult to get them tight. I'm thinking of bolting one end to the underside of the x axis channel and using a good size spring on the other end. If anyone has any ideas on this, I'd appreciate hearing about them.

    Pics of latest work attached.
    If I understand this right, it is the long belt running the length of the table you are tensioning.

    I don't think you will want a spring on that. You will need something positive to hold that belt in tension. Any place the drive motors can find slack (spring stretching) will translate to error at the cutting head.
    If it works.....Don't fix it!

  16. #16
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    Millman:

    Thanks for the reply.It is indeed the long x axis belt. My question is what would be worse, the regular stretching of the belt under normal use which would probably go unnoticed or maybe an occasional skip due to spring stretch.

    I did a very scientific measurement on the machine. I hung a weight on a string from the gantry over the edge of the machine to see what force is required to move it. With all of the motors, rails, and a extra 10 lbs of steel hanging from the gantry, it took less than 1 lb to move it. I would think a spring of 20-30 lbs (just a guess) should be sufficient to keep the belt tight and minimize or eliminate chance of skips. I need to give this some more thought. Maybe some of those math majors out there can give me the scoop on the numbers.

    No more progress on the build. Took the day off and cleaned up the shop. Got to the point where I was spending most of my time looking for tools.

    Willy

  17. #17
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    Quote Originally Posted by flyinwilly View Post
    Millman:

    Thanks for the reply.It is indeed the long x axis belt. My question is what would be worse, the regular stretching of the belt under normal use which would probably go unnoticed or maybe an occasional skip due to spring stretch.

    I did a very scientific measurement on the machine. I hung a weight on a string from the gantry over the edge of the machine to see what force is required to move it. With all of the motors, rails, and a extra 10 lbs of steel hanging from the gantry, it took less than 1 lb to move it. I would think a spring of 20-30 lbs (just a guess) should be sufficient to keep the belt tight and minimize or eliminate chance of skips. I need to give this some more thought. Maybe some of those math majors out there can give me the scoop on the numbers.

    No more progress on the build. Took the day off and cleaned up the shop. Got to the point where I was spending most of my time looking for tools.

    Willy
    I'll try to explain a bit better the problem I see with a spring tensioned belt.

    First off you are correct that it will not take much to just hold the gantry static.

    Once that 50-75 # gantry is running @ 150-200IPM & needs to break rapidly to a stop & return in the opposite direction, it's going to stretch the springs while stopping thus overshooting & you will see very ragged cuts on those sudden direction changes. I really don't think spring tension even at a very strong pull will work.

    I really think you are going to have to tension the belts very much like a guitar string is set up. Mounted solid on 1 end & a bolt tensioner to literally stretch the belt tight.

    If your belts stretch a bit over time you will begin to see rounded corners where they should be square & most surely wiggle in the kerf. But most likely still usable parts. & the warning signs are there to tell you to re-tension the belts.

    On the other hand if the spring allows the notched pulley to skip a tooth you just trashed a part(s)
    If it works.....Don't fix it!

  18. #18
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    Machine is painted

    Didn't do too much the last few days but managed to get the machine sandblasted, bottom installed, and painted. Also installed the motor mount . However, the new motor has a different frame than the one the mount was made for so I have to build a small adapter plate to extend the mounting holes.

    Started several new items - electronics enclosure and wiring power supplies, drivers, etc. More things to do than time to do them but I think there is a light at the end of the tunnel (although it's very small).

    Pics attached.

    Willy
    Attached Thumbnails Attached Thumbnails front - painted.JPG   left side-painted.JPG   Motor end - Painted.JPG   right side - painted.JPG  


  19. #19
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    flexible cable track - where do you get them ?

    Looking ahead, I am going to need a cable mangement system. I like those flexible tracks that follow the gantry back and forth. What is the best place to get them ??

    If there are any other systems, I'd like to look at them.

    Thanks,

    Willy

    P.S. Finished the x axis plates and motor mounts. Camera needs to be recharged so pics to follow later.

  20. #20
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    Motor mounts done

    Finished and installed the motor mounts on the x axis plates. The mounts hang down from the bottom of the axis plate. I used 2 aluminum plates, one is attached to the axis plate while the second mounts the motor. The motor slides up and down in .75" slots to account for belt adjustment. The plates are separated by 4 nylon standoffs. The main 10 tooth drive pulley is between the 2 plates.

    I used a 4:1 reduction. The smaller pulleys are made of aluminum while the larger, 40 tooth pulley is steel. It is really heavy so I drilled a few holes in it to try and lighten it up. Helped a little (I think) but it was a lot of work. Good thing the Bridgeport has auto feed.

    Pics attached.

    Willy
    Attached Thumbnails Attached Thumbnails motor mount & standoffs.JPG   motor mount with pulley reduction.JPG  

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