open source cast iron box way benchtop milling machine

[ihavenofish]

this topic has sprouted from another thread. i figured it woul dbe best in its own. to catch up on the details, you can look here:
NORTH AMERICAN MADE MACHINES

this is where we are at:


the principle of this thread is to create 2 different sized completely public domain machine designs. the result if all goes well is a set of castings for each machine, which one will be able to buy raw, squared, or finish machined from one or more companies. alternatively, enterprising individuals could make their own patterns and have them cast on their own.

potential buyers are diy hobbiests, and machine retrofitters and retailer who can supply turnkey machines or hardware kits and accessories.

the specifications have been derived mostly from my personal needs, but basically the 2 machines cover 2 distinct markets.

machine 1 is 14" x 6" travel and under 200lbs, and covers the range from the SX1 up to the SX3 and similar machines.

machine 2 is 24" x 8" travel, 500+ lbs, and covers the market from the KX3 up to the tormach Pcnc.

in both cases, the specification calls for no single piece to weigh more than 100lbs - movable by 1 person, so right off the bat we are ruling out completely very heavy machine design and likely epoxy granite as a solution. the intent is to compensate for lack of mass with smart design. the design is also meant to be viable as one off casting efforts. design elements that require mass production for price breaks are not going to be considered. likewise, "ebay deal" pricing strategies are not to be taken into account estimating turnkey and kit costs.

anyone who is interested in this idea, please speak up with comments, criticisms, suggestion, and honest opinions on pricing. its one thing to say "yes id buy it for $X" and actually writing the queque. anyone with expertise in casting iron, stress relieving, and milling would be most welcome in this thread.

i am not intent on selling the castings myself, or running the company that sells them or turnkey systems. what i personally want is a machine that works for me. if i can get a few sets of finished castings of each design, in exchange for my design effort and pattern building, i will consider the project a success. a bigger success would be several other companies jumping on a standardized cnc dedicated benchtop frame - much like the market is with the sieg manual machines.

and the disclaimer:

please do NOT lose sight of the intended goal of thse machines. they are NOT going to be 1000+ lbs linear railed do all cat40 spindle 10hp beasts. please do NOT bring up politics in this thread. if you have a vested interest in another mill maker and feel threatened by this thread, dont spam it with BS, go read something else instead.

thats all for now, ill post detailed specifictions as they are now in a bit.

[ihavenofish]

the sound of silence...



made the base taller to increase overlap on the column mount. the images show a "short table" version, with 16" x travel. this decreases the working width by 16", which might be useful for people who dont need the travel. makes enclosure possibilities smaller. also lighter by nearly 25lbs.

our total mass for finished castings (not counting the spindle head cover plate) is 353lbs for the short travel, and 377lbs for the long travel.

travels are 24"/16" in the X, 8" in the Y, and 14" in the Z. the head swivels 120 degees in either direction. there is 8" clearance between the spindle centre and the face of the Z saddle.

working width with a motor will be 64" on the long travel, and 48" for the short. working depth with motor and way cover is 28". working height to the top of the drawbar is 37"

im adding all the mount points for motors, ball screws, way covers, and general acessory points now.

[Enraged]

looking good!

I am considering an SX3 conversion, a KX3, or a Syil X4. This seems like a better alternative. I would likely want the 16" version, but would it be possible to upgrade to the 24" by simply replacing the table and associated ballscrew, etc?

if finished machined castings were available, do you have an idea of what the price would be?

[The Blight]

Beautiful!

[wildwestpat]

Congratulations only wished I was your side of the pond!

Suggest you might like to look at Kempe's Engineering Year Book for basic information on what is involved with cast iron from casting to finnished machine. In the 1994 edition the reference is C5/9 and C5/10 covering heat treatment and relief of internal stresses etc.

From the 'look' of the 3D drawings I would think the base of the Z axis mast could do with some further changes to improve stiffness further with respect to the base for X&Y. Suggest through bolts with the ability to fit dowels when the 'Z' mast is trammed correctly to the finished table. The build up of tolerances will almost ceretainly require some hand fitting to achieve acceptable accuracy. Think scrape mating face or use shims then drill and ream dowel pins to locate parts with some decent size high tensile bolts.

Not sure of the webs under the base. Thinish sections in a casting are to be avoided - try to keep all cross sections similar where possible. This is so the cast iron flowing into the cavity in the mold does not chilling befor the pour is complete. Chilling in the mould early in the pouring results in stresses or blow holes neither of which you want! Might be better to add a single thick web at the root of the mast mounting to fill in the bottom of the 'Y' screw cavity for say 2 inches leaving a generous curve onto the sides of the base. It is a good idea to avoid any sharp edges and to try and radius all corners. This helps avoid stresses in the casting and also helps strengthen the casting at points where there is a change in direction.

Hope someone with current casting experience will help you out. It might be a good idea to talk to your local iron foundry or factor that you have in mind for making the castings.

Wishing you every sucess

Pat

[ihavenofish]

looking good!

I am considering an SX3 conversion, a KX3, or a Syil X4. This seems like a better alternative. I would likely want the 16" version, but would it be possible to upgrade to the 24" by simply replacing the table and associated ballscrew, etc?

if finished machined castings were available, do you have an idea of what the price would be?

the machine keeps evolving, but the "reasonable" target price is $3500 for finished machined USA made castings including all required bolts, nuts, and hopefully the spindle cartridge and belt drive assembly as well. once i have concrete quotes from foundries, i will attempt to make adjustments to bring the price down as far as possible.

at $3500, thats alot more than say the typical $1200 for a complete X3, but i am trying to integrate parts into the castings. for axample, the X and Y simply take a ball screw, 1 bearing support, a motor and a coupling. no other parts to be fabricated. this in addition of course to the machine being far superior in ever possible way to an X3.

the smaller mill (6x14 travel) will in theroy be significantly cheaper both for the casting kit and hardware.

as for upgrading the table after purchase, you would need a new table, a longer ball screw shaft, and thats it.


so, some updates to the machine now. the base had to be extended about an inch as i adapted way cover brackets. there will be fabric covers front and rear sealing the ways and screw, as well as the motor if you mount it up front.

ive added provision for the motor to be mounted in the rear. all the hardware remains identical, you simply get a different screw shaft and put the motor on the back. then you can remove about 5-6" of "stuff" in front of the table which some people might find more convenient.

flexibility is the key here.

[ihavenofish]

Congratulations only wished I was your side of the pond!

Suggest you might like to look at Kempe's Engineering Year Book for basic information on what is involved with cast iron from casting to finnished machine. In the 1994 edition the reference is C5/9 and C5/10 covering heat treatment and relief of internal stresses etc.

From the 'look' of the 3D drawings I would think the base of the Z axis mast could do with some further changes to improve stiffness further with respect to the base for X&Y. Suggest through bolts with the ability to fit dowels when the 'Z' mast is trammed correctly to the finished table. The build up of tolerances will almost ceretainly require some hand fitting to achieve acceptable accuracy. Think scrape mating face or use shims then drill and ream dowel pins to locate parts with some decent size high tensile bolts.

Not sure of the webs under the base. Thinish sections in a casting are to be avoided - try to keep all cross sections similar where possible. This is so the cast iron flowing into the cavity in the mold does not chilling befor the pour is complete. Chilling in the mould early in the pouring results in stresses or blow holes neither of which you want! Might be better to add a single thick web at the root of the mast mounting to fill in the bottom of the 'Y' screw cavity for say 2 inches leaving a generous curve onto the sides of the base. It is a good idea to avoid any sharp edges and to try and radius all corners. This helps avoid stresses in the casting and also helps strengthen the casting at points where there is a change in direction.

Hope someone with current casting experience will help you out. It might be a good idea to talk to your local iron foundry or factor that you have in mind for making the castings.

Wishing you every sucess

Pat

thanks, ive put emails into a few foundries, but no responses yet. ill be calling them next week after the design is more complete.

the column mounting is intended to be at this point on a pilot much like the head, which will allow easy tramming and provide a positive "lock" rather than just the friction fit of bolts. the pilot is large - about 3", because it sits around the ball screw support bearing. im just drawing this part in now.

as for the base webbings ive somewhat closely followed an existing design for that, just making mine a few inches bigger in each direction. im familiar enough with casting to know about trying to keep wall thicknesses consistent, but its not always possible. for example in the base, most walls (not accounting for draft) are 16mm thick inclusing the webs. the deviations are under the dovetails, and the column mounting area. this is why im very interested in trying to figure out stress relief methods, because the castings will most cetainly need it. i figure is wiess can make a similar base, i should be able.... maybe..

ill post some more images in a while, with some updates.

[Enraged]

the bearing supports could be integrated into the casting to be machined, couldn't they? or is it better to have them floating so they can be adjusted?

[ihavenofish]

the bearing supports could be integrated into the casting to be machined, couldn't they? or is it better to have them floating so they can be adjusted?

they should be floating. if they were off by even .001", you could get binding and abnormal wear in the screw, so i think its better to have the room to adjust. plus it allows a standard thk type "FK15" mount, which is readily available and inexpensive from alot of places. it would have been nice to use one the the BK type mounts which are very cheap, but they dont fit the design requirements.

[ataxy]

where would the motor be mounted in the head like the kx3/syilx4 or on top

[ihavenofish]

ive extended the Y to 9" travel which increased the mass a bit less than 20lbs. but didnt extend the length of the base.

someone has been asking if the y travel could go up, but is still in keeping with the inexpensive hobby format... so i thought of a possible accessory.

heres a trick. you make a 2.5" spacer for the head, and a 2" spacer for the column where it attaches to the base. this will give you shy of 11" of Y travel fully supported with clearance between the spindle and way covers, though you still only have an 8" wide table. if you have a light duty operation, you could as a last resort overextend the saddle off the base another inch safely getting a total of 12" of usable travel, with 12" of clearance from spindle to column.

this way we dont need to make the machine bigger for those who dont need/want it.

[ihavenofish]

where would the motor be mounted in the head like the kx3/syilx4 or on top

motors smaller then 92mm/nema34 frame and 6" long can fit inside the head. larger motors can be fitted on top with a modified cover plate.

for example, one could use a parker 5000rpm 1.1kw servo motor inside the head and a 1:2 pulley for 10000rpm at the spindle. a longer version of the same motor is available with 1.6kw, which could mount outside.