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  1. #81
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    Default Re: Catahoula's router/mill build - welded steel with EG

    Machinist started today. This is the 34" gantry on the massive old Hydrotel milling machine. This will be one of the last jobs he does before closing the shop and moving the machine to his home shop, so I was glad to be able to sneak the work in.

    After much deliberation on whether to machine shoulders for rails or not, the machinist thought the base would still have a few thou of warpage with the extra material removal required for shoulders, despite the thorough welding sequence and thermal stress relief. He's an old salt, and I was inclined to listen to his experience, so going back to pippin88's advice, I deleted the shoulders and will have him face mill the rail mounts with as little material removal as possible, then machine the edge so I can indicate from that. This also opens the opportunity to surface grind the gantry, so he'll do that too. If I'd built the base without the integrated lateral column support areas, he could have surface ground that, too, but that's OK.

    I guess it's about time to order the controller!

    Attached Thumbnails Attached Thumbnails Catahoula's router/mill build - welded steel with EG-pxl_20210301_163014971-jpg  


  2. #82
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    Default Re: Catahoula's router/mill build - welded steel with EG

    Quote Originally Posted by catahoula View Post
    Machinist started today. This is the 34" gantry on the massive old Hydrotel milling machine. This will be one of the last jobs he does before closing the shop and moving the machine to his home shop, so I was glad to be able to sneak the work in.

    After much deliberation on whether to machine shoulders for rails or not, the machinist thought the base would still have a few thou of warpage with the extra material removal required for shoulders, despite the thorough welding sequence and thermal stress relief. He's an old salt, and I was inclined to listen to his experience, so going back to pippin88's advice, I deleted the shoulders and will have him face mill the rail mounts with as little material removal as possible, then machine the edge so I can indicate from that. This also opens the opportunity to surface grind the gantry, so he'll do that too. If I'd built the base without the integrated lateral column support areas, he could have surface ground that, too, but that's OK.

    I guess it's about time to order the controller!
    You Heat treated your parts, they are not going to move anywhere I heat treat frames all the time, and have never had or seen one move after stress relieving, they can still be ground even with a shoulder if the milling is not up to it, normally a milled surface is good enough for rail mounting grinding will give you a better surface, but can distort the surface also if to much heat is generated when grinding

    Machined edges are not just for alignment, they are there to maintain rail position the rails are locked against the edge, I mostly machine pockets that fit the rail so no clamping needed, the rails then have perfect alignment just bolt them in place and they are ready to go

    Mactec54


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    Default Re: Catahoula's router/mill build - welded steel with EG

    Hi mactec, thanks. I don't doubt that you're right about it, but the machinist seemed much more comfortable with facing when utmost flatness is desired on one particular part- the base. I'm aware about the advantages of shoulders and pockets, in fact I was originally going to use a granite surface plate as the base until I decided that shoulders/pockets would be best. But, the base of my machine is only 5"/125mm deep and 32.5"/825 mm long, which was a poor choice. If the base was thicker, say 7"-10" deep, as per an earlier revision of the design, I would've had the confidence to stick with the more aggressive machining. The gantry tube shown above isn't what I was worried about. But while adjusting rails isn't terrible, scraping the surfaces flat is not something I'm particularly interested in. So being a newbie to this, I want to err toward the largest guarantee of flatness, even if it means a bit more fuss.



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Quote Originally Posted by catahoula View Post
    Hi mactec, thanks. I don't doubt that you're right about it, but the machinist seemed much more comfortable with facing when utmost flatness is desired on one particular part- the base. I'm aware about the advantages of shoulders and pockets, in fact I was originally going to use a granite surface plate as the base until I decided that shoulders/pockets would be best. But, the base of my machine is only 5"/125mm deep and 32.5"/825 mm long, which was a poor choice. If the base was thicker, say 7"-10" deep, as per an earlier revision of the design, I would've had the confidence to stick with the more aggressive machining. The gantry tube shown above isn't what I was worried about. But while adjusting rails isn't terrible, scraping the surfaces flat is not something I'm particularly interested in. So being a newbie to this, I want to err toward the largest guarantee of flatness, even if it means a bit more fuss.
    I see where you are coming from when I want a flat surface like this on a thin frame I have it Blanchard Ground top and bottom faces no milling needed

    Mactec54


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    Default Re: Catahoula's router/mill build - welded steel with EG

    Slowly, slowly, slowly, but surely, coming together. Parts back from the machinist today. Not an inspiring experience, got charged double the estimate and some of the quality was so bad that I had to force him to do it over, after multiple arguments and an endless string of excuses. To other home builders: do it yourself on a friend's mill or just use a surface plate, unless you know a guy who's good.

    As mentioned earlier in the thread, opted to skip the shoulders for fear of warpage. The forum (mactec specifically) was right, machinist measured zero warpage with an indicator when unclamping after machining. But after the whole process, I'm glad I didn't ask for shoulders as the potential for error is higher. And the gantry is now surface ground, so it's gonna be pretty damn flat. Wish I could've had the base ground too. Next time.

    Forgot to take a pic of the base but here's the gantry.

    Attached Thumbnails Attached Thumbnails Catahoula's router/mill build - welded steel with EG-pxl_20210317_234132323web-jpg  


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    Default Re: Catahoula's router/mill build - welded steel with EG

    And here's another of the z-plate that I did on a friend's bridgeport knockoff.

    The big news is I've finally locked down a permanent workspace so should be able to assemble this in May-June!

    Attached Thumbnails Attached Thumbnails Catahoula's router/mill build - welded steel with EG-pxl_20210210_032840534-jpg  


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    Default Re: Catahoula's router/mill build - welded steel with EG

    fatherhood is a painful experience Peter



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Quote Originally Posted by catahoula View Post
    Slowly, slowly, slowly, but surely, coming together. Parts back from the machinist today. Not an inspiring experience, got charged double the estimate and some of the quality was so bad that I had to force him to do it over, after multiple arguments and an endless string of excuses. To other home builders: do it yourself on a friend's mill or just use a surface plate, unless you know a guy who's good.

    As mentioned earlier in the thread, opted to skip the shoulders for fear of warpage. The forum (mactec specifically) was right, machinist measured zero warpage with an indicator when unclamping after machining. But after the whole process, I'm glad I didn't ask for shoulders as the potential for error is higher. And the gantry is now surface ground, so it's gonna be pretty damn flat. Wish I could've had the base ground too. Next time.

    Forgot to take a pic of the base but here's the gantry.
    Looks good did not need to machine the whole surface in the center only where the bearing retainers are mounted and yes if the machinist is not competent to mill / Grind with shoulder then you did the right thing

    Can't say anything about the over cost everyone is different, I get a quote and that is all I pay

    Mactec54


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    Default Re: Catahoula's router/mill build - welded steel with EG

    Did you get a chance to measure the overall flatness of these ground surfaces?



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Mactec- good point. that's how i do contracts at work and should have applied that here. working with a shop that is closing is a red flag in general.

    Jack- not yet, but will before assembly.



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    Hey guys - I'm back from the dead!

    Took about 2 years there to buy a house with garages as well as remodel basically all of it. A good thing for my life in general but bad for CNC building, haha.

    I can now see some light at the end of the tunnel, so I'm starting to think about this machine again (now that there's a good place to put it!) which means of course I also have questions to ask, haha.

    As I left the project, the fabrication and machining work is basically finished, and I ordered and received all the linear motion components including ballscrews and linear guides, but not motors or control system.

    For fairly obvious reasons, my budget is significantly reduced compared to before I had a mortgage, haha. Unfortunately, I designed the machine around DMM 400watt servos, so I went with big, fat, long 5mm lead ballscrews that can spin up to 3000 rpm without whipping. But the controller I was planning on ordering from CNC4PC would have been close to 4 grand. Now I'm looking at going with some StepperOnline closed loop Nema 34s, and fully DIYing the controller box, thinking I can drop the budget to ~$1500, and keep the wiring and tuning relatively simple with the steppers.

    I guess I'm just looking for some general advice. I'm aware that ballscrew inertia is the major force that a motor fights. Obviously I'm now willing to accept some loss of cutting speed just to actually finish this thing before a decade goes by. It also uses HTD belts to drive the ballscrews so I can easily change the ratio, although given a stepper's torque curve that's not necessarily helpful with a heavy, slow lead ballscrews.

    I've been deep in motor specs the last couple evenings so I'm just looking for a reality check. 4.5 Nm Nema 34 steppers at 60v with modern drivers will probably get me to 100 IPM, right?



  12. #92

    Default Re: Catahoula's router/mill build - welded steel with EG

    uccnc sells ready made controls for steppers: Complete machine control electronics - CNCdrive - webshop

    personally I'm thinking to pay someone to do the electrics part while I do electronics myself, I'd never dare touch the mains, I'd probably electrocute myself or someone else and I don't fancy dying prematurely or having to wear a pacemaker for the rest of my days.



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Good point. I kinda decided to go with Centroid Acorn for the S-curve acceleration, though. Will be doing a lot of 3d contouring with this machine.

    I'm comfortable with the wiring in general, I've done a lot of electrical work including designing/building a PID oven control circuit, it's more just an interest in not getting bogged down with servo tuning, and cutting a couple thousand dollars out.



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Ok I might've answered my own question. back to the numbers.

    I weighed the giant 880mm 2005 ballscrew to verify - 2.4kg with the double nut! Then I re-ran the load/inertia calculation with a spreadsheet formula originally from MyCNCUK.com, going back to a 1:1 belt drive instead of 1:2, and came up with a max required torque of 0.774 Nm, given a 50kg load, 100N cutting force, and 3200 mm/min (125 IPM) feedrate. That allows the motor to run at 640 rpm, comfortably in the stepper torque band, with 1000 motor rpm / 200 IPM rapids coming in around 0.33 Nm. Machine work area is only 24"x18", so I think 200 IPM rapids are adequate.

    So really, even a 4.0 Nm/566 oz-in closed-loop NEMA 24 from OMCStepperOnline provides a decent margin for error, with ~1.3 Nm at 640 rpm and 0.9 Nm at 1000 rpm. Any thoughts on small NEMA 34 vs large NEMA 24? Overkill or just healthy margin? The 34's aren't much more expensive. I could see taking this control system over to a standard Avid-type 5'x10' router in a few years, and building a linear scale-driven super accurate control for this machine, so maybe that's the way to look at it.

    The downside of 1:1 motor:ballscrew gearing is that I don't love the idea of having the resolution of 1 step at 0.001", but that seems to be the only viable way to get decent speeds with steppers. I guess that's what microstepping is for?



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Hi Cat - Check the calc with a N23 and a N34. The 34 being bigger has more inertia and as the wiring is fatter it has more inductance so check that as well. Generally a N23 will accelerate and achieve higher speeds then a N34... Good to have you back in the game. Peter

    Attached is the motor spreadsheet I built if you want to cross check the cals...

    Attached Files Attached Files


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    Default Re: Catahoula's router/mill build - welded steel with EG

    Thanks a bunch, pete. I'm working through your spreadsheet calc. Can you speak to typical acceleration values and or what I should shoot for?

    From some googling, there seems to be a generally cited figure of 0.2G for run-of-the-mill VMCs. Per your calc sheet, 0.2G acceleration would demand 4.2 Nm torque available, which is fully in servo motor territory. 0.05G means the output roughly matches the MyCNCUK calc sheet. I guess 0.1G would be a decent target? (for a DIY machine, mine is probably on the upper end of rigidity for the frame and linear motion)



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Hi Cat - Yes 0.1g is the realm of fast hobby machines. Torque requirements start to leap over that. What to shot for? Hmmm just pick a motor and work backwards see where you get to... But if you get 0.1 you'll be happy. You mention s-curve controllers these are helpful at "high" g's. I'm looking at 3D printer controllers because they have gone past s-curve and have a thing called input shaping which is smoother motion again.... I finish a machine soon then I'm onto a high g machine after that. Peter



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Hi Cat,
    This is the controller I'm going to use. Its a BOB, velocity planner and computer all in one. 8 axes, 60V drivers with 3A max. Uses 3D printing machine controller (free) Marlin or Clipper. New territory but offers much more speed/smoother then the usual trapezoidal planner. Uses input shaping and accelerometer on head to control vibration. Long story but this is the future for CNC today.... Peter plus its half the price of the usual separate components always a bonus... and no need for all those wires!!

    https://store.dremc.com.au/products/...v1-0-f429-chip

    are you using a grade C7 ballscrew? if so thats the limiting component on accuracy. 0.001" is 0.0254mm and the C7 will only give you +/-0.025mm per 300mm



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    Default Re: Catahoula's router/mill build - welded steel with EG

    Yeah I think I'll go with the small NEMA 34s, the curve doesn't drop off nearly so fast as the long-for-diameter 8nm+ steppers. And I might just run them at 80v! Should clear up inductance issues, and at 3.5 mH these aren't terrible. I'm aware of the Gecko rule of thumb that voltage should be SqRt(inductance) * 32, but StepperOnline responded to my query and said 80v is fine. Maybe that'll get me to .1g, and if not the machine will definitely still function well.

    I got C5 ballscrews with double nut and preload. 2005 for X/Y and 1605 for Z. Zero backlash for now, that won't last forever but is a good start! They're TBI brand, OFU/OFUR style from BST Motion.

    The Octopus Pro is interesting. So you'll run the gcode through OctoPrint or something like that? Or just load to an SD card and straight to the board?

    Last edited by catahoula; 03-03-2023 at 03:18 PM.


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    Default Re: Catahoula's router/mill build - welded steel with EG

    Hi Cat - I'm learning about the toolchain at the moment. The hardware side looks easy. Klipper or Marlin is usually used then a SD card to transfer gcode to the motherboard. There are wifi and ethernet versions as well. Totally new game for me... I'm lost at the moment hope to see some daylight soon...Peter



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Catahoula's router/mill build - welded steel with EG

Catahoula's router/mill build - welded steel with EG