CNC Gantry Build. The $1 mistake that started it all.

[mactec54]

Some material sources outside of Gotham. All will UPS ship.

https://www.onlinemetals.com/en/buy/...sort=price-asc

https://www.midweststeelsupply.com/s...eelsquaretube#

https://www.mcmaster.com/steel/shape...thickness~1-4/

They all will have a higher price than what he posted Midwest being close to the same

Online Metals 2x2x1/4=$408.12
Midwest 2x2x1/4=$284.34
MCM 2x2x1/4= $435.28

[LorenBMS]

My bad! I read 24' (ft) as inches....Looks I need a trip to the eye doc.

[mactec54]

My bad! I read 24' (ft) as inches....Looks I need a trip to the eye doc.

You don't see many people here that refer to Feet as in a 24-Foot length, so you eyes may be ok, two things come into play when seeing something like this Price and length

I brought 20 Ton of steel before the tariffs kicked in so still have a good supply, I hope they remove some of the tariffs so things can get back to normal, these high steel and aluminum prices are hurting everyone

[peteeng]

Hi CBF - Here's an article that discusses movement after stress relief. Peter

[ChipsBFlyin]

Thank you everyone for the replies. I know material prices are nuts. At this rate, with material cost. I may want to end up making the sand from concrete and casting in my own drains into the stand, but I don't want to get ahead of myself.

Pete, thanks for the article. After reading it, I updated my Y axis rail mount design. I think I am going to ditch trying to add side drains to the Y axis rail mounts for now, and accomplish pushing the chips control from them via auxiliary coolant nozzles spraining the rails constantly while the spindle is on. I see this method used on Mazaks, DMG over the axis covers to keep chips off them. Attached you will find my updated design, constructed from 1/4" plate. I still don't know how I will brace the rear of the Y axis mounts. Let me know what you think, I'll work on the stand after I get over this hump.

[peteeng]

Hi CBF - The foundation of the rail is very important so double the thickness of the rail foundation plates and include the machining allowance. But you can back the other thicknesses off. I'd also double the thickness of the plate that is on top of the cars. That's where the action is and these are little parts doing a big job so weight is not important. Looking really good. If you make the columns shorter and the "walls" higher it will be muck stiffer. High rail designs are very very stiff and they get the rails and screws up out of the muck. I would make the walls as high as poss and the columns nearly gone.... Peter

edit - by the way with TSR you cannot have closed out hollow parts. You must have good breathers everywhere. 1) the heat treater will not accept the part if closed out or 2) The part will blow up and distort due to the internal pressure...

[ChipsBFlyin]

Pete,

Thank you for the suggestions. Made a few updates per your recommendations. I got inspired by the DMU 200, although I really liked the gantry on the DMU 350. I think it came down to aesthetics, I liked the way the DMU 200 looked better and that's what I based my design after. I may try to see how it looks with higher walls and shorter columns and go from there.

You can see what I was originally aiming for with my chip control on both sides. After reviewing the DMU 200 base frame design, I can see my original design flaw.

[ChipsBFlyin]

So I raised the Y axis rail mounts 3.0" and lowered the columns by 3.0" and this is how it looks. I would have to offset the Y axis mounts at least by an in or two and extend the gantry length to allow for spindle housing to Y axis mount clearance or they would kiss as the spindle travels to the end of the X axis travel.

[peteeng]

Looking good but now you are at the point of adding drives and this will mess with your clean design!! I have always liked the Mori designs very classy I think... Peter

edit - is your saddle steel or aluminium? and what is its current thickness?

[ChipsBFlyin]

They do make beautiful machines and their promo videos are very nice. So onto the next hurdle, how do I design the stand, any recommendations? The only steel, in large sizes, that I can probably find affordably is probably I beam and C channel.

[ChipsBFlyin]

Pete,

My X axis saddle is aluminum and its 1.5" plate

[ardenum]

.
I'm thinking of bolting+glueing(with steel filled epoxy) my steel undertable joints. Wanna avoid warping/heat treating or buying welding equipment or having a company make it. Issue here is tubes are hollow so the joint would be only on the perimeter, unless I can get closed of tubes, that would solve all my issues with the table.

They design like this to have a chip tray under the table, which can be pulled out from the front, they work well the Datron is designed like this.

I think the problem with that design was that the table and the gantry were not 'connected' as in all the machining forces between the granite plate and the gantry were going to go through the table, which would be the weak point in this design. All current datron series have the gantry riding directly on the mineral plate. with M8 its suspended under the table and on m10 and mx cube its directly on the table.

So I raised the Y axis rail mounts 3.0" and lowered the columns by 3.0" and this is how it looks. I would have to offset the Y axis mounts at least by an in or two and extend the gantry length to allow for spindle housing to Y axis mount clearance or they would kiss as the spindle travels to the end of the X axis travel.

Although the thing looks sturdy, there's lots of optimizing you can do. Gantry legs look like they are fully closed off, you could remove the lower portion, open the top portion up on one side and put a grid inside, they look really complex now. Honestly at this point I wish you just got a wider plate instead and put the gantry directly on it. Do you need that much workspace? You'd be saving yourself some $$ and a few headaches if you make it smaller and mount it directly to the plate. Can mount it under it or on the sides too to preserve all the plate space.

Are you sending this to machining after you glue and screw in the side rails to the plate?

Are weldments cheap around your area? I found out that over here ordering the gantry legs from solid aluminum was cheaper then having a weldment done.

[mactec54]

Thank you everyone for the replies. I know material prices are nuts. At this rate, with material cost. I may want to end up making the sand from concrete and casting in my own drains into the stand, but I don't want to get ahead of myself.

Pete, thanks for the article. After reading it, I updated my Y axis rail mount design. I think I am going to ditch trying to add side drains to the Y axis rail mounts for now, and accomplish pushing the chips control from them via auxiliary coolant nozzles spraining the rails constantly while the spindle is on. I see this method used on Mazaks, DMG over the axis covers to keep chips off them. Attached you will find my updated design, constructed from 1/4" plate. I still don't know how I will brace the rear of the Y axis mounts. Let me know what you think, I'll work on the stand after I get over this hump.

You still will need a space between the Table and the sides, you have a step which may be enough, getting full table coverage will depend how much you step the sides out from the table, I have a similar design and use a 30° slop on the sides, I don't have any razed gantry like you have, and it seems to be working well, the Ballscrew mounting is where everything will change with this design, I have 2 different designs like this one with the linear rail on top like this and one with the linear rail and Ballscrew under to keep them protected

Parts like this could be cast with a concrete mix and have steel inserts to be machined after casting, which I'm considering my next build to have these parts cast

[ChipsBFlyin]

Ardenum,

Nothing is cheap around my area. Ice cream truck milkshakes are $9 and a breakfast sandwich and a coffee is $13 from a deli.

I thought about mounting directly to the table, but I would loose about 8" on the X travel. I ended up with this surface plate by accident and it only cost me $1. I rather pay up front now, then be wishing I had an extra 8" later. I thought about mounting under the table, but construction and service down the road would be a pain.

[peteeng]

Hi CBF soon - 1.5" is 38mm quite sturdy but the top of the saddle is a cantilever. If you can add some flanges to the sides this will help. The same rigidity thickness in steel is 22mm 7/8" so a 1" steel plate is considerably stiffer if you want to use that... its 8x stiffer and thinner so maybe steel is the go for the saddle. "thin" aluminium parts often aren't as stifff as steel.. Esteel 200GPa Eal=70GPa makes a diff...Peter

edit - as usual check the math

[ChipsBFlyin]

Pete,

Thank you for the recommendation, will work on it tonight. Here is my latest design of the stand. 1/4" construction, with 3" ribs.

[peteeng]

Hi CBF - 8x stiffer didn't sound right so I checked the math again. Its 1.36x stiffer. Sorry about that. Peter

[ChipsBFlyin]

Pete,

Thanks for looking it over, I started to design the updated version of the saddle before checking the math. I still have to dial in how the screw and the servo motor will mount. I am also trying to determine what pitch I should use, its lot of information to process. I also had to redesign the gantry itself after getting a $879 quote for the 6x12" tube. So I will be welding the gantry from 1/4" flat stock. What are your thoughts on the stand design I posted above?

[peteeng]

Hi CBF - comments
1) My current router has 5mm pitch on Z and 10mm pitch on the YX. I'm happy with the Z as this gives me lots of grunt for plunging & and Z speed is not too critical. They are 16mm diameter fyi. Next machine I'm changing to 1616 for the XY to gain a bit more speed from the steppers. They are direct drive to the screw. Your Z has a belt so you can adjust speeds via the ratio...
2) do not fully weld your gantry only stitch it to minimise distortion. maybe 50% welded or even 40% will be OK
3) The stand is probably a little overdone and the big flat plates may drum...Peter

[ChipsBFlyin]

Pete,

Thank you for the tips on the gantry. I will keep them in mind as I fabricate it.

How can improve the stand? Should I cut holes on the side panels? I looked at the Haas mini mill base, its constructed from steel sheets and it also serves as the coolant tank. Although I don't plan to integrate the coolant tank into the stand because the mimi mill coolant tanks are a pain to service.