General CNC Chat > Show"N"Tell ( Your Machines)
DIY Epoxy Frame based CNC MILL
John Mac:
Hi all
Its been a while since I popped in here, been pretty busy work wise.... and not enough workshop time.
Anyway I have started building a new CNC Mill and have started a blog here: https://www.model-engineer.co.uk/forums/postings.asp?th=139042
As you can see the build uses Mineral Castings (Epoxy granite in the US) The molds and many of the parts are laser cut steel.
I decided to make it as small as possible due to my small workshop space is at a premium. As you can see it will fit into a 1 Metre (about 40") cube plus the stand. It will not be a light machine and will weigh several hundred kilograms a kilogram is equal to 2.2 pounds approx. the travels are 520 x 300 mm If I had more room I would have made the 300 mm 700 mm Z axis is 250mm clear under the gantry plus tool shank allowance. For the odd time I want more clearance I will use the manual V mill. Less Z travel should improve the stiffness.
I have a mach 3 license so will control it with that. Drives will be DC servos old from stock but in good condition.
Currently the cross-member and two columns are cast. the base is next maybe this week. Nearly all the components and the molds are laser cut steel already done. So far I am really pleased with the accuracy of the castings.
Anyway if you are interested keep an eye on the thread I will keep posting as the build progresses.
Regards
John
Tweakie.CNC:
Wow John that is going to be some build.
Thank you for sharing the info with us - I will certainly keep following your progress on the Model-Engineer page.
Tweakie.
DICKEYBIRD:
Hello John; a marvelously well done machine you are building. Thanks so much for sharing it with us! ;D
Would you please show a drawing of the Z-axis design? I am building a fixed gantry mill as well and am not happy with any of the design iterations that have come to mind.
John Mac:
Hi Bird
Hopefully the base will be poured soon, We have had 40c deg heat this week pretty warm! So the pour was put off.
As soon as that is done the Z axis and carriage will be next. I will document it soon.
Tip.
If you are using linear rails and ball screws, make a definite decision on those first. When choosing ball screw end bearings for a given ball screw there will likely be two different sizes that will fit, Choose the larger size for extra stiffness. If you are not making your own there are also various ballnut mounts available, some steel some aluminium, I choose steel.
I am guessing you are finding that when you add up all the heights of the x axis bearing rails and slider blocks, the ball screw end bearings and ball nut mounts and allow for fastenings you end up with a height problem. The setup does not work well with simple plates unless you stack in spacer plates. One option is to machine the plates from solid if you have the facilities. The design I am working on uses a hybrid of laser cut steel plates, turned pillars and is epoxy filled. Oh! and the carriage is heavy.
If you like post a screenshot of your current design. Everyone faces this problem and it would be interesting to see different approaches.
Regards
John
DICKEYBIRD:
--- Quote from: John Mac on January 24, 2019, 10:12:15 PM ---If you like post a screenshot of your current design. Everyone faces this problem and it would be interesting to see different approaches.
Regards
John
--- End quote ---
I'm looking forward to seeing what you've come up with. By the looks of your machine as it stands, I'm sure much cleverness & attention to detail has been invested in the Z-axis as well!
I will clean up my crude 2D CAD sketch of my machine & post it here this weekend. Thanks for the interest John & I greatly appreciate any tips (or criticism.)
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