New member, sweet find at the auction, and a massive gantry

[SolarImages]

Also your drawing looks like the cncrouterparts pro 3:1 rack and pinion make sure you factor in the Pro model having a bearing that puts the assembly out board another 8th inch. I am using there pro 3:1 for my rebuild.

[Simko]

I would in your case look at extending the verticle extrusion down to the Linear bearing plate to reduce movement from quick corners 1" x X of gantry depth verticle support in my opinion will serve you way better here. As well you will lose some long travel but the higher the gantry needs to be the wider the distance between the linear bearings need to be i would suggest using some more 8020 and mounting them 1o" apart teeing up to the gantry from that.

Thanks for the insight! I like the idea of extending the vertical extrusion down to the bearing plate. That will help stiffen up the assembly. I am also working on gussets for the inside.

The gantry riser plate is 11" wide which puts the bearings 11" outside-outside. When I check the usable area of the table with this arrangement, I end up with 8'-8" usable of the 10' table.

I agree that my gantry is pretty high off of the bearings (10" tray + 9" clearance under beam) But I have scaled everything up that I think it will be stiff enough. I could probably shrink the tray some and go with a downdraft only table. I have the extra height there to put some water at the bottom of the tray in addition to the exhaust. From what I read, you need to be around 8" below the bottom of the cutting surface to keep water from splashing everywhere.

Yes, I am using CNC router parts NEMA 34 Pro belt reduction units. Thanks for the heads up on the clearance.

[SolarImages]

Just a thought. I would maybe look closer at closing the sides of the table off adding a fan to one end or side. Then use the tables cutter and cut a bunch of .5 diameter holes in it about 4 inches from the sides for the down draft table option. Just a thought.

[Simko]

Just a thought. I would maybe look closer at closing the sides of the table off adding a fan to one end or side. Then use the tables cutter and cut a bunch of .5 diameter holes in it about 4 inches from the sides for the down draft table option. Just a thought.

You are probably right... I am way overthinking it and trying to engineer solutions that allow me to not have to cut that 3/4" table top. If I take the tray down to just slat height (2 or 3 inches), I may be able to use the standard CRP riser plates instead of having to machine custom ones.

Why holes only around the edges instead of over the whole table? Is that how some companies design their downdraft?

Looks like I'm going to have to get a Hyperthem that can pierce 3/4" plate

Thanks again for responding, it's nice to have other people to bounce ideas off of.

[SolarImages]

I meant to say, start holes about 4" from the sides just to leave you room for the slats to be supported etc adjust as needed. The holes will cover the entire table other than strips down the sides.

[muzza]

Just a thought. I would maybe look closer at closing the sides of the table off adding a fan to one end or side. Then use the tables cutter and cut a bunch of .5 diameter holes in it about 4 inches from the sides for the down draft table option. Just a thought.

You are probably right... I am way overthinking it and trying to engineer solutions that allow me to not have to cut that 3/4" table top. If I take the tray down to just slat height (2 or 3 inches), I may be able to use the standard CRP riser plates instead of having to machine custom ones.

Why holes only around the edges instead of over the whole table? Is that how some companies design their downdraft?

Looks like I'm going to have to get a Hyperthem that can pierce 3/4" plate

Thanks again for responding, it's nice to have other people to bounce ideas off of.

Just a thought but have you done the exercise of working out the cost and end result of basically building what you really want by keeping and using the racks, linear bearings etc. and any other parts suitable and building a new table which is purpose built for what you need and want and maybe keeping the existing purchase as a heavy duty welding/ fabrication bench or selling it off as such and use the funds towards the table you really want.

Having built three tables it appears to me that you really aren't saving much work if any by modifying this one and you will always have a compromise. I think you will find it will also work far more efficiently and have a better resale value also.

Sometimes we go backwards to move forward.
Murray

P.S. many years experience in the industrial ventilation industry also tells me your planned ventilation system wont work without huge amounts of baffling and zoning on a table that size.

[Nacs Fab]

Why are you making your tray so deep? Believe me when you go to fish out small parts, that would make it near impossible to find them. Mine is only 3" deep and I wouldn't ever want it any deeper. Just thought I might save you some heartache.

[Simko]

I was going to make a tall tray / fume extractor so that I didn't have to cut through the 3/4" plate on the table, but I have since decided to make a shorter tray (around 3" high ) and cut through the plate and put a standard trapezoidal exhaust box under the table.

The original fear was that if I cut out the middle of the table that the resulting structure may warp due to releasing some stresses in the weldment. I decided I'm going to take that chance and deal with the issue if the table warps any.

I spoke with Corry at CNC Router Parts today regarding some pieces that I need for my build. He was super helpful and spend quite a while on the phone with me discussing options and getting me weights for components so I can estimate my gantry weight. He also mentioned that they are going to be coming out with a plasma specific electronics package with their own torch height controller sometime late this year.

I also spoke with ??? at Velox and he was very helpful as well. We spoke at length regarding z-axis travel, the weight of their different z-axis, and electronics packages. He recommended Tom and CandCNC very highly. Also, Velox is supposed to be coming out with a magnetic break-away plasma mount sometime around the end of the year.

So far since getting into this hobby, I am 2/2 for vendors with good customer service.

Oh yeah... My estimated gantry weight at this time is around 170lbs... NEMA 34, here I come....

[Simko]

Quick update...

I had the riser plates machined out of aluminum. Did a test fit on the table and they are perfect The gear rack and belt-reduction units should be delivered today so I have my work cut out for me this weekend.

I just set the extrusion on top of the risers to see what the clearance would be (12.75"). If you subtract 3" for a tray, I will have 9.75" clear under the gantry. I could always go to 2" tray for an extra inch of clearance (10.75").

I made some changes to the gantry design that should bring my total weight down to about 140#, still heavy, but not as bad as my original 175# gantry.

Once I get the gantry installed along with all of parts needed for motion, I will start working on the x-axis carriage.

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[Simko]

Well... I spent nearly my whole weekend drilling and tapping 46 holes. Burnt through three 6.8mm high speed steel drill bits and two 8mmx1.25 taps.

At the end of the day, I have both sides of gear rack within 0.004" of being parallel to the linear bearing over a distance of 10'

If you ever decide to do anything like this, I completely recommend doing whatever you can to buy/rent/borrow/steal a magnetic drill press. There is no way that I would have been able to pull this off without it.

I have not had a chance to run an indicator down the outside of the gear rack to see how bad it is in that direction, but I am going to assume that I need to do some shimming since the gear rack is mounted to a non-machined surface (structural steel). How critical is it that the pinion rides on the entire width of the rack? If the rack tracks a 1/16" to 3/32" from one end of the table to the other, is it worth shimming it out or just let go?

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[Simko]

I ran the indicator down the outside of the gear rack last night and it is within 0.025" of being parallel which I though was pretty impressive considering that the table frame being parallel to the linear rail was not critical to it's original function. There is a 2' long section at the far end that gradually runs out to 0.060" on the one side which is less than a 1/16". Rather than shim the whole rail out 0.060" to match the 'high end', I think the plan is going to be to shim the majority of the rail so that it is within a couple thousandths. If I do that, the last 2' of rail will only run out about 0.045" which is only 3/64" of lateral movement of the pinion on the gear rack in that short section

Once I have the mechanics for the Y and A axis dialed in, I need to start working on the X-axis. The gear rack is going to be a lot easier for the x-axis because I am going to bolt it to the extrusion using t-nuts... No more drilling and tapping!

I have been using CNCRouterParts design for inspiration so far, but I think that I am going to have to do something different for my X-axis. Does anyone have any pictures of an X-axis that has a linear rail on the face of the gantry and a gear rack either on the top or back of the gantry?

[acourtjester]

I think this what you are asking for. Some use 3M tape to attached the rack.

[Brand X]

I have been using CNCRouterParts design for inspiration so far, but I think that I am going to have to do something different for my X-axis. Does anyone have any pictures of an X-axis that has a linear rail on the face of the gantry and a gear rack either on the top or back of the gantry?


I would like to see some too.. I believe Arclight tables use the design you are looking for.. I am upgrading my Y axis with CNCRouterParts pro stuff.. My rails are all 30/30 from the Y to the X I think the pro gear racks with the raised away from the 80/20 pl is the easiest to use mount..(IMO) I have V ways on the X now, and might want to keep that setup . I believe using just a the Y axis pro motor mount on the X will get me there.. Otherwise 4 inch cold roll, and two extended carriages with a connector plate will get me there..

My old table frame is really pretty nice, but I have always wanted a better Y rail setup. It also had one motor running the Y axis (driveshaft) and gear rack on top of the 30/30 Just rode on top.. Sucked but worked fairly well for ten years..

PS- I have a nice auto feed Nitto mag drill, but the metal muncher has a place too..

[Simko]

Acourtjester and Brand X... These pictures are great.

Acourtjester
Have you had any issues with your fixed pinion? How critical is the pinion to rack engagement in this type of arrangement?

BrandX
I see that you are currently set up to ride on bearings and CRS rail, but those 8 through holes in your carriage plate look curiously close to the spacing on most linear bearings. I have been trying to decide on using one linear bearing truck or two trucks on the same rail for my x-axis carriage. I already have one linear bearing for the X and could buy a second one on Ebay for $75.



I also like the 'top plate' and how the belt reduction pivot is mounted. Have you had a chance to run this yet? I considered a set-up similar to this, but I was concerned that the pinion would try to climb out of the rack in one direction. After doing a little research on rack and pinion design, it appears that the best place to put the pivot is right over the pitch line of the gear rack. I believe the benefit to this is that it will require the same amount of spring tension to keep the pinion in the rack in both directions. As the angle gets greater, it requires more force in one direction to keep the pinion from climbing out of the rack. I am not sure how important it is though because CNCRouterParts seems to do it 'correctly' on their x-axis and does it 'incorrectly' on their Y and A axis.

I would love to have a MetalMuncher/Ironworker in my home shop!

[acourtjester]

No sir I have not I have built 3 table using that same setup and sold 2 for shop use.
I also sold many sets of plans with no feed back from the builder's about their having any problems either.
I do not believe there is a great amount of pressure at the point of contact between the gear and rack that would cause any separation.

[acourtjester]

No sir I have not I have built 3 table using that same setup and sold 2 for shop use and I still use the 3rd.
I also sold many sets of plans with no feed back from the builder's about their having any problems either.
I do not believe there is a great amount of pressure at the point of contact between the gear and rack that would cause any separation.

[Brand X]

I understand the concerns on the layout of the pivot, and spring setup.. but I think full contact gear rack, that the pro allows is more important.. Remember this is plasma, and these parts are designed for using as routers. Should not even be a issue ever. 2.71? gearing on the 3/8 shaft 22 tooth motor gear..I have the 620 oz steppers..

I have not ran it yet. Waiting for some thermal paste for installing my 203V driver in my Box.. Bought the box from Tom, (Cancnc) in 2006, and it supports the extra drive.. Nice plug, and play.. New ones have a extra spot (five) I sent my box in last year, and had them upgrade to the 3100 I think Tom here has the same system. Works fine with one cat 5, and one parallel port. It can be upgraded to the full cat 5 setup at any time.. Love the way I can keep a lot of my parts when doing upgrades..

I would like to use the shorter carriage they sell for the standard cnc parts, but then I can't use the pro parts I used on the Y axis, My Z is setup well enough, and could be made to work either way.. Once I get my gear rack here, I will know what will work.. I am using two carriages on the X if I upgrade. no real reason, but it will really lock thing down. Arclight uses one carriage per side on the Y, and the gantry locks it in..

One thing, I had a new style Esab 1600, and it cut as fast or faster then most Hypertherm specs on the 85. Although it had many more options on Nozzles to slow it down on sheet metal, and even thicker stuff too. I now just have my backup A-120. ( Sold the Esab to help pay for my upgrade) It cuts slower then either of the other two machines in general, so I really will never need above 200 IPM. Never needed over that with the Esab.. Mostly cut below 100 ipm.. I have had Thermal/victor's one torch for many years, and it took about all of it to get it cutting right.. I would like to see how it does on a smooth machine, because I do now get quality cuts on my old one. Tom told me a long time ago to just sell my table, and buy- make something else.. I am so happy that I keep plugging away at it.. Mine was one of the original Practical CNC tables, and all the problems with them. I have added lots of bracing, and it really is one tough 80/20 frame now.. Way better then any other 80/20 table out now,, It has some interesting layout options with the tall side rails, low gantry.. Ton of room on the Z, adjustable level on the table slats,easy to put a water table, and raised Gantry setup with the CNC router parts.. One huge advantage of 80/20 frame..Things that you would think would be deal killers turned out to have some nice features all on their own.. I can bolt my gantry right to the carriages and use as is for now.. I bought that table in about 2004, because I needed one to unbolt to go into my basement.. No longer a issue.. It came with Wincnc, bobcad, and that's it.. Les at Sheetcam wrote me a plasma program to get my table to move. Then Tom made a connector to run one of his stand alone THC, and Mach 2..(my factory PCNC $1000.00 THC upgrade was totally garbage) Been a long time coming to get something I like.. It so much easier now,and still confusing, but nothing like it was..

I love your table, and just how heavy/well built it is.. It's going to be one great table when you are done!!

PS- my X gear rail is .250 #24 gear rack.. Small pinion, and no tension setup on the Gear to the rack. I never had a real issue with it. Not the best, but it does work for Plasma. I am probably going to revamp the stock setup with bigger shafts, and bearings short term. It always ran much smoother then the Y axis.. It's getting the CNC router parts down the road, but not sure how much of it I will use.. If I can keep at least 60 inches of travel in the X, then I will use the wide carriages, and Pro rack, motor mounts. Same 4 inch cold roll will also work with the 30/30 on the X axis..

Added my driver, and looks like it needs a trip back to CandCnc to get the box figured out.. (Can't get movement to the A axis slave motor)Few more tests,and it's off to Texas.. The CandCnc guys are good about keeping the older stuff running.. Luke has been really helpful there.Nothing is ever as simple as you think it's is going to be..

[Brand X]

One last post on some of the CNCRouter guys.. They get the order right, and fast too. At my door in less then two days. Rest of the stuff is showing up today.. I never called them yet, but I emailed them to add one thing to my order. It was handled as fast as it could be.. Like 5 minute.. I am impressed! They are in Wa. State, and I am in Oregon. (Close to Arclight) I guess it makes sense for Arclight to use their parts..

[hsolve]

apologies for interjecting. I have NO spring tension or pivots for my drive pinions to the gear rack, just a good interference fit resulting in no play and a repetability of .01mm which I believe is sufficient for me. I have built my frame out of 80mm by 80mm Rexroth extrustion and all function well. If anyone is interested I have just published on youtube two videos of my machine marking, cutting 6mm and 20mm alli plate.

[BTA Plasma]

Keep in mind a spring loaded gear mesh will give up under hard acceleration so your stuck with variables like gantry weight, motor/gear dynamics or you will have to live with loosing occasional positioning. When you get your spring too tight you give up pinion life. Then most accurate longest lasting systems use the rigid mount with a gear rack that is true to the center of a linear rail. You can get results but you should be able to really dial that rack in unless it is a cheap rack that was never strait to begin with and was made with the intention of running a spring loaded pinion to take it up.

[Simko]

. If anyone is interested I have just published on youtube two videos of my machine marking, cutting 6mm and 20mm alli plate.

Post them up... I'm interested!

You can get results but you should be able to really dial that rack in unless it is a cheap rack that was never strait to begin with and was made with the intention of running a spring loaded pinion to take it up.

I just spent last night shimming the gear rack so that it is parallel to the linear rail. If I run an indicator down the outside of the rack, the worst that it runs out is 0.030" (about 1/32"). If I run the indicator down the top of the rack, I have it +/- 0.003" which is probably straight enough to run a rigid pinion. Since I already have all the pieces for a pivot style, would running a turnbuckle instead of a spring work?

[Brand X]

I got one axis moving using the pro spring setup.. Tom seems to have no issue using the lower end CNC router parts.. I had the fixed gear rack before I started, and now have the spring Totally. fine if you are not running a 200 pound gantry at a acceleration of 50 accel in mach, cutting at 1000 IPM.. These parts will put a lot of small table makers out of business. Since many of the successful ones use them anyway..

https://youtu.be/aH4rVFOKmvM

[SeanP]

I would not hesitate at having a spring loaded gear, I thought long and hard about which way to go when building mine, after 2yrs running it hasn't skipped once, I tell a lie I don't use limit switches on the table extents and have run into those on occasion
I did read somewhere having the pivot as close as you can in line with the rack helps for jumping the teeth.
Its fine all its all new but what happens when the rack wears a bit in the most used area? that's how I looked at it, there is not a bit of backlash using very little tension and I'm not using any fancy rack.
I would go for 2 carriages on the X really.

[hsolve]

Good morning all. My table operating, cutting alli plate 6mm and 20mm ( for Americans about 1/4" and 3/4").
The scribe stopped pulsing due to too much oil, I have resolved this. Am in the process to mount the scriber differently, closer to the plasma torch to keep the table envelope smaller. I will be enlarging my table to mark and cut 5' wide and 13' long.
https://youtu.be/7a6uxnKdIC4
https://youtu.be/r5lalVLlyXg

[Brand X]

Sean,
I said this before, but you got a great looking table there.. Simple/clean, and a well thought out design. Good parts too..