[JFL4066]

One big advantage of a moving table design is that you can have a central ball screw whereas the moving gantry even with a central ball screw under the table and on the crossmember can have the gantry slew if the cut is to one side of the job....that can never happen with the moving table due to the table lin bearing layout.

That is apart from the more rigid fixed gantry of the former one.

True you need more length to cover the table with a moving table but you can make the table wider than longer to compensate somewhat as the fixed gantry can be made quite massive.

Here's a pic of my favourite design type, a machine made in Hindustan......note the tool changer rack behind......this would be so good with ISO 30 etc.
Ian.

Very Nice! Good point on moving the short side on a movable table. I really like that design style, thanks for the photo.
Do you or anyone have a line on a good (reasonably priced) 5 or 7 HP spindle? How are the Chinese imports? Is there a good one?

[Goemon]

There are degrees of "diy" with these builds. Some of the Youtube "diy" cnc builds show guys starting with a full machine shop... Obviously it is easier to make an accurate machine if you have a VMC in your shed to make all your parts and drill holes precisely etc.

I wasn't so lucky and I started my build with nothing but a drill press and a hand drill. To achieve the accuracy I wanted, I decided to use NSK linear actuators. NSK can obviously machine a precise base and mount rails far better than any of us. I bought my spindle mounting plate from Damon CNC and I purchased a ready-made t-slot table that had already been face milled on both sides.

If you have high standards and insist on making every part from scratch, be prepared to buy a mill or milling services. You will never achieve precision eye-balling it with a hand drill....

[handlewanker]

With all things being equal, if you have the right design and the means to make it almost perfect, then yes, anything is possible...…….it would be like getting to the top of the ladder of your brain child only to find it's leaning against the wrong wall...…..I think that the design is the critical factor before you start sourcing metal etc.....you only want to build your perfect machine once.
Ian.

[JFL4066]

There are degrees of "diy" with these builds. Some of the Youtube "diy" cnc builds show guys starting with a full machine shop... Obviously it is easier to make an accurate machine if you have a VMC in your shed to make all your parts and drill holes precisely etc.

I wasn't so lucky and I started my build with nothing but a drill press and a hand drill. To achieve the accuracy I wanted, I decided to use NSK linear actuators. NSK can obviously machine a precise base and mount rails far better than any of us. I bought my spindle mounting plate from Damon CNC and I purchased a ready-made t-slot table that had already been face milled on both sides.

If you have high standards and insist on making every part from scratch, be prepared to buy a mill or milling services. You will never achieve precision eye-balling it with a hand drill....

Where did you buy the T-slot table?

[Goemon]

Where did you buy the T-slot table?

ebay initially but then I realized that I could do a better job cutting my own T-slots and doing my own facing on the machine I built.

For ease of set up, I wanted the t slots to line up perfectly with the X and Y axis. This was most easily achieved (for me) by cutting the slots on the machine where they would be used.

But, there is nothing wrong with starting with ebay t-slot plates like these:

https://www.ebay.com/itm/T-Slot-plat...0AAOSwAypZsf5H

it would not be too much trouble to bolt a few of these to an aluminum tooling plate and giving it a one over with a fly mill. They are already face milled on both sides. from my testing, they seemed accurate enough for most people.

If you need hyper precision, you can also use granite surface plates or optically flat breadboards. I suspect that most of use don't need that level of precision and could not measure it if they did though. I struggle to even get the same measurement twice with my calipers....

Also, search ebay for old cnc pallets, t slot mill tables, granite coordinate measuring machines, vibration isolation tables, aluminum breadboards, Haas fixture plates, granite surface plates, granite gantry, welding tables, machine bases, machine tables. ebay is a mass grave for old precision machine parts...

[JFL4066]

ebay initially but then I realized that I could do a better job cutting my own T-slots and doing my own facing on the machine I built.

For ease of set up, I wanted the t slots to line up perfectly with the X and Y axis. This was most easily achieved (for me) by cutting the slots on the machine where they would be used.

But, there is nothing wrong with starting with ebay t-slot plates like these:

https://www.ebay.com/itm/T-Slot-plat...0AAOSwAypZsf5H

it would not be too much trouble to bolt a few of these to an aluminum tooling plate and giving it a one over with a fly mill. They are already face milled on both sides. from my testing, they seemed accurate enough for most people.

If you need hyper precision, you can also use granite surface plates or optically flat breadboards. I suspect that most of use don't need that level of precision and could not measure it if they did though. I struggle to even get the same measurement twice with my calipers....

Also, search ebay for old cnc pallets, t slot mill tables, granite coordinate measuring machines, vibration isolation tables, aluminum breadboards, Haas fixture plates, granite surface plates, granite gantry, welding tables, machine bases, machine tables. ebay is a mass grave for old precision machine parts...

Thank you for the info. I'm inclined to purchase cast aluminum jig plate. Not sure if I want or need T slots. May go with a 6 x 6 grid of 3/8-16 threaded holes.

[JFL4066]

Hi JFL - I'm designing a router at present in this forum look up Maximus. It discusses many of these issues and goes through the calcs to achieve various accuracies (your a numbers man). I'm a mech eng and design machinery for my bread and butter. So have a look thru that, may give you an insight into where your going. Also note that I'm probably well over the 200 hours into so far so quite a slog and not at the finish yet. Peter

Hi Peter - I just finished binge reading your Maximus build thread over the weekend. I commend you on your time and skill! You certainly answered a lot of my concerns.

[ericks]

So exciting planning a machine build all the best!

[peteeng]

Hi JFL - How long did it take to read? I've scanned through it once, was surprised it was 3 months worth!! and still not there...Peter

[dixdance]

Thank you for the info. I'm inclined to purchase cast aluminum jig plate. Not sure if I want or need T slots. May go with a 6 x 6 grid of 3/8-16 threaded holes.

How thick?

I'm thinking to do the same for a small 2' x 3' router I want to build. Plus a grid of 1/4" or larger dowel hole for fixturing. Did that on my tiny Techno Davinci 10" x 12", worked great for tiling banjo fingerboards for inlay and fret slotting. My son-in-law did it for me on his Haas mill - 1/4" dowel hole with 1/4-20 thread beneath. I have a couple of 1" and 1-1/4" thick used jig plates I bought cheap locally, very flat even if not cosmetically perfect. A 2' x 3' plate wont fit his machine, thinking to do it on my Bridgeport. Also thinking to cut t slots as well, wondering if it would move around from t-slotting, that's a lot of material from one face? Could also have it ground as a final step, Nifty Bar is right here in Rochester. Working with a very modest budget, need to be resourceful and scrounge. I've collected a few Techno gantry slide units to use as actuators, want to have dual x drive to allow for a well in the middle of the table for a tilting rotary later down the line. Also keeping my eye open for a "decommissioned" 3 x 4 granite surface plate to use as a reference surface for the build, can't imagine one of those getting too far out for that purpose.

[JFL4066]

How thick?

I'm thinking to do the same for a small 2' x 3' router I want to build. Plus a grid of 1/4" or larger dowel hole for fixturing. Did that on my tiny Techno Davinci 10" x 12", worked great for tiling banjo fingerboards for inlay and fret slotting. My son-in-law did it for me on his Haas mill - 1/4" dowel hole with 1/4-20 thread beneath. I have a couple of 1" and 1-1/4" thick used jig plates I bought cheap locally, very flat even if not cosmetically perfect. A 2' x 3' plate wont fit his machine, thinking to do it on my Bridgeport. Also thinking to cut t slots as well, wondering if it would move around from t-slotting, that's a lot of material from one face? Could also have it ground as a final step, Nifty Bar is right here in Rochester. Working with a very modest budget, need to be resourceful and scrounge. I've collected a few Techno gantry slide units to use as actuators, want to have dual x drive to allow for a well in the middle of the table for a tilting rotary later down the line. Also keeping my eye open for a "decommissioned" 3 x 4 granite surface plate to use as a reference surface for the build, can't imagine one of those getting too far out for that purpose.

Peter may give you better insight on the thickness.

Craigslist will usually have used granite surface plates a couple times a year. A 3 x 4 is usually the moving cost. You might want to call the nearest recertification service in your area for the surface plates. They may know who has one to get rid of. The farther out of date the certification is the more possible wear on the plate.

[JFL4066]

Hi JFL - How long did it take to read? I've scanned through it once, was surprised it was 3 months worth!! and still not there...Peter

LOL. About 5 hours with studying each picture and pdf file. I like the concept of bent metal plate gantry. The use of timing belts is interesting as well. Is there an effective controller that will keep the two X drives in sync? In your experience, how much will the gantry skew?

[ger21]

Is there an effective controller that will keep the two X drives in sync?

Just about every controller can do this.

[peteeng]

Hi JFL - Controllers send out perfect in sync signals so if the gantry is walking its mechanical. The machine controller has a slave function which makes two outputs identical eg X with A. The gantry can skew due to various things going on when the power is off. But once on it stays wherever it is does not change unless crashed. Usually you have a home on each side and these are adjusted square. When the machine is homed it automatically squares if not quite square mechanically. Scoot my half sheet machine has springy columns and they need squaring occasionally. Best columns are SHS or RHS welded/brazed into the top and bottom bits. Make the columns as big, big as possible and the gantry as big, big (stiff as) as possible and the bearings as far apart as possible. Cheers Peter

[dixdance]

Craigslist will usually have used granite surface plates a couple times a year. A 3 x 4 is usually the moving cost. You might want to call the nearest recertification service in your area for the surface plates. They may know who has one to get rid of. The farther out of date the certification is the more possible wear on the plate.

Thanks for the suggestions JFL. Something will show up, always does. Transport will be the real cost, will prob need to rent a dock ht truck rather than try to wrestle out of my van.

[dixdance]

"Is there an effective controller that will keep the two X drives in sync?"

Just about every controller can do this.

I'm planing to have an additional c axis, can a 4 axis controller handle y, z and twin x drives? Thinking maybe Acorn...

[ger21]

That would be 5 axis. I believe that Centroid is coming out with an expansion board to support additional motors, but you'll need to ask them if the software/hardware will support what you want to do.

[109jb]

I'm planing to have an additional c axis, can a 4 axis controller handle y, z and twin x drives? Thinking maybe Acorn...

What you could do is run the 2 X motor drivers from the same step/dir signals.

[Goemon]

Thank you for the info. I'm inclined to purchase cast aluminum jig plate. Not sure if I want or need T slots. May go with a 6 x 6 grid of 3/8-16 threaded holes.

Check out these Haas aluminum Sub plates. They are all over ebay and likely to be sufficiently flat and stiff out the box:

https://www.ebay.com/itm/Sub-Plate-H...cAAOSw5QlbLQcz

[Goemon]

Thanks for the suggestions JFL. Something will show up, always does. Transport will be the real cost, will prob need to rent a dock ht truck rather than try to wrestle out of my van.

The cheapest way I found to buy a granite surface plate was to get a new one from Grizzly. Their freight shipping costs are reasonable too. I couldn't find a used one on ebay or craigslist for any less.