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Nick
03-08-2018, 10:41 PM
Right so I've started on an large cast iron/EG mill build. Plan is to use several cast iron surface plates I have bought on ebay and embeded in epoxy granite, the hope is this will give me a flat surface to mount the linear rails to.

This is the current design in fusion

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Travel: X 400mm, Y 250mm, Z 400mm
Total weight 600-800kg
Rails: 20mm hiwin clone rails
Ball screws: Generic rolled Chinese ball screws, with a plan to upgrade in the future.
Spindle: Initially: 2.2kw water cooled spindle. The plan would be to upgrade to a BT30 and 1.8kw servo from AliExpress if I can get this made and then integrate ATC
Electronics: UC400 ETH, Initially steppers, with upgrade to 400W AC servos.

Epoxy granite: Silimix 282 + west systems epoxy 105/206 10% by weight, 0.25% black iron oxide


Cast iron:
Iíve got one 36 x 16 inch plate

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Along with four of these 18x12x2in plates

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The large surface plate is reasonably flat, however the smaller plates are out by about 0.05-0.15mm. I am planning on trying to hand scrape them flat.

Issues:
1. I have got to cut one of the cast iron plates into four for the column mounting blocks, Iím not sure how I will do this as they're 2 inch's thick, I think I will try with a cutting disc
2. The column and table will consist of more than one cast iron piece, Iím not quite sure what the best way to keep alignment is, I think I will have to use a flat surface, possibly the big surface plate to cast against and an angle plate.


I've got the epoxy and Silimix. I have made the mould for the base and I think I will cast this first to check that the epoxy granite doesn't warp the surface as it sets. I'll post back with the results!

mekanik
04-08-2018, 10:57 AM
Hi Nick
Thanks for posting, will be following with interest.
Mike

Nick
07-08-2018, 07:15 PM
Right so Iíve casted the base. I started by preparing the surface plate, I cleaned the underside with a wire wheel and then drilled and tapped several holes for M6 and M10 bolts, so the epoxy would anchor.

The surface plate had a hole drilled in the top when I got it, I thought this might be helpful to run wiring/pipes through, so I routed some PVC pipe to the back of the surface plate. Before I decided to cast the surface plate in epoxy, I did briefly try and cut it, I sealed this cut with silicone. I also drilled two pairs of holes in each side and passed pvc pipe through, this will let me pass some chains through to lift it.

The mould was made of melamine "furniture" board I got from wickes, sealed with silicone and then three applications of wax were applied (three was necessary in testing, it's a huge pain when it sticks). The surface plate was lowered with an engine crane face down into the mould.

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Mixing the epoxy granite was the hardest part, it took ages. We did it in 25kg batches, with one person packing the mould while the other used a hand held mixer. We also had a bench grinder attached to the mould, with an eccentric weight, but it quickly ripped itself free of its base. It took just under two hours in total and I managed to add some steel plate to act as mounting points later on and a small section of steel as a future motor mount.

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I let it cure for about 48 hours before removing the melamine mould.

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There are some areas that haven't fully combined and some air inclusion, this is worse on the side away from the bench grinder and I think related to poor vibration. But overall i'm fairly happy with how it turned out. As a very crude test, I've put a tenth indicator on a 30cm extension and jumped up and down over the base, I can't really get it to deflect. It weighs about 220kg now.

I was also concerned that the curing epoxy would warp the surface, so I tried to map out the base with a indicator, there is very little movement (apart from the end I cut which shows about 2 thou of deviation). I also used a 2 foot straight edge, I can't pass a 0.02 mm feeler gauge under it. I don't think its warped significantly.

Next step is to scrape all of the cast iron inserts for the column, I've started to do this, its slow work, but I think will be possible. I'm going to have to think of a way to level the end of the base, my surface plate isn't big enough so i'm not entirely sure how to do this?

Nick

Chaz
07-08-2018, 08:01 PM
Following.

How big is the area you need to get flat? I had similar challenges so had to be inventive with my own concrete build.

routercnc
07-08-2018, 09:49 PM
Interesting project. I was thinking about building a dedicated milling machine the other day but priced up the off the shelf bits (motor spindle rails screws etc ) and talked myself out of it for now.
You have a nice set of parts lined up so should make a great machine. Looking forward to watching your progress.

Nick
09-08-2018, 11:13 PM
The area to flatten is 900 x 400mm and my surface plate is 600x600.

Yeah I talked myself out of it a few times. I'm not sure its going to be very economical, the BT30 spindle itself is a substantial cost.

Chaz, I found your concrete build very interesting and I've thought about a moglice/DWH approach. I'm lacking a big enough reference surface though, any ideas on how I could overcome this?

I'm starting to wonder if I will have to leave the base as it is. If I could be confident in the way I was measuring it and I was sure it was flat to say 0.02-0.05mm I would probably be happy and just shim/scrape it later. Does anyone a good way to measure how flat a surface is that's bigger than your reference surface?

Chaz
10-08-2018, 11:23 AM
The area to flatten is 900 x 400mm and my surface plate is 600x600.

Yeah I talked myself out of it a few times. I'm not sure its going to be very economical, the BT30 spindle itself is a substantial cost.

Chaz, I found your concrete build very interesting and I've thought about a moglice/DWH approach. I'm lacking a big enough reference surface though, any ideas on how I could overcome this?

I'm starting to wonder if I will have to leave the base as it is. If I could be confident in the way I was measuring it and I was sure it was flat to say 0.02-0.05mm I would probably be happy and just shim/scrape it later. Does anyone a good way to measure how flat a surface is that's bigger than your reference surface?

I bought a hollowed out 'reference' block from someone. Its around 900 x 600 x 600 and might be good enough for what you need. It has slots in it and few holes / marks but its what I used to lay my Y rails, then later X and Z from that.

Where are you based? Might be worth a chat, PM your number if you think its worth discussion via phone.

AndyGuid
11-08-2018, 10:07 AM
Was just trawling through some older "subscriptions" and think this might be your "reference box" Chaz :

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From http://www.mycncuk.com/threads/10480-Workshop-growing-nicely

Chaz
11-08-2018, 10:26 AM
Was just trawling through some older "subscriptions" and think this might be your "reference box" Chaz :

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From http://www.mycncuk.com/threads/10480-Workshop-growing-nicely

Yep.

Nick
16-08-2018, 08:46 PM
Chaz, that might work, how much does it weigh? I am based in Yorkshire, where about are you based?

Just changed jobs, making very slow progress on the build at the moment.

Chaz
17-08-2018, 09:22 AM
Chaz, that might work, how much does it weigh? I am based in Yorkshire, where about are you based?

Just changed jobs, making very slow progress on the build at the moment.

Hi, its fairly heavy (estimated 300-400kg). Pity you arent closer, I'm in Uxbridge / Ickenham, West London, Near the M40 / M25.

Sure, happy to help if I can.

Nick
08-10-2018, 09:18 PM
This is a bit delayed but I owe a big thanks to Chaz who has let me borrow his reference surface. It has been really helpful and I am not sure how I would of progressed without it. I tried to pick it up in a Fiesta, which unsurprisingly didn't work, thankfully it came on a pallet.

I've been making slow progress, I settled for an angle grinder for the cutting of the cast iron blocks, it took forever... I have managed to rough scrape all the surfaces for the column.

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These blocks of cast iron are the ones highlighted below.

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I have also scraped the main cast iron block.

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They're not perfect but within 0.03 mm. I am making the mold and getting the inserts ready, I plan to cast the column next week. Just trying to work out how to drill 18mm holes through the 2 inch cast iron blocks, my drill press isn't up to it and I really don't want to have to buy a mag drill, I don't know if anyone has any other ideas?

Nick

Chaz
08-10-2018, 09:41 PM
This is a bit delayed but I owe a big thanks to Chaz who has let me borrow his reference surface. It has been really helpful and I am not sure how I would of progressed without it. I tried to pick it up in a Fiesta, which unsurprisingly didn't work, thankfully it came on a pallet.

I've been making slow progress, I settled for an angle grinder for the cutting of the cast iron blocks, it took forever... I have managed to rough scrape all the surfaces for the column.

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These blocks of cast iron are the ones highlighted below.

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I have also scraped the main cast iron block.

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They're not perfect but within 0.03 mm. I am making the mold and getting the inserts ready, I plan to cast the column next week. Just trying to work out how to drill 18mm holes through the 2 inch cast iron blocks, my drill press isn't up to it and I really don't want to have to buy a mag drill, I don't know if anyone has any other ideas?

Nick

Scrape Scrape Scrape ....

I was going to ask how you were getting on.

routercnc
10-10-2018, 10:07 PM
Would the blocks fit on a lathe cross slide to drill the holes using a bit or boring head in the chuck?
Or the other way around with the block rotating on a lathe face place and bit or boring head in the tailstock?

Nick
21-10-2018, 08:36 PM
Quick update

That was a great idea with the lathe cross slide although I couldn't quite get it to work, having issues with its size. I ended up getting a mag drill... Drilled 60 holes and tapped for the insert bolts.

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Mould made and epoxy poured, all 150kg of it. Got it done in about 90 minutes with two of us. Had some slight issues, no vibration, we ran out of pigment towards the end and the mould blew out on one side. But overall went ok, if anyone wants more details on how to go about this I could write a more detailed post / video.

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Will probably de-mould tomorrow.

Nick
23-10-2018, 11:50 PM
It looks bigger out the mold

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Chaz
25-10-2018, 08:24 AM
It looks bigger out the mold

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Lovely. Keep at it ....

Nick
23-11-2018, 10:37 PM
Small update

I've made a temporary stand and put the column on the base

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I don't have a square big enough to see how perpendicular it is. Has anyone bought a granite square ? the only one I can find is this one
https://www.zoro.co.uk/shop/measuring-and-test-equipment/granite-and-cast-iron/sc250x160mm-granite-squareuare/p/ZT1017535X?utm_campaign=pla-Measuring+%26+Test+Equipment+-+&utm_source=google&utm_medium=shopping-pla&utm_keyword=ZT1017535X&istCompanyId=6aa6787b-063e-4414-802d-129f235df603&istItemId=wtqixraxat&istBid=t&gclid=Cj0KCQiA597fBRCzARIsAHWby0G1E86q2EKwm5Y_CtKv CBDQ2Vn4PZ_CN72Tnip4TnW703CYWfOIOvMaAg9CEALw_wcB

I have been making slow progress with the table, I have reduced the table width to 240 mm and I've got two ground 25x50x1000 mm bars to use as the rail mounts.

The table "offcut" from reducing the table size width has been cut into four and scraped flat and parallel to act as spacers. I was starting to scrape the table flat but the carbide came off my scraper...

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I am slightly concerned that there isn't enough support under the steel bars and they will deflect. You can see this in the renders below, with the overhanging steel bars and the small amount supporting epoxy granite. I'm thinking about adding some threaded rod or increasing the thickness of the epoxy, i'm not sure if this is necessary though, thoughts on this?

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silopolis
01-12-2018, 12:41 PM
Hi Nick,

Very very nice project! I'm planning the exact same machine but first option is to use steel tubes filled with EG. Second is directly casting EG like you did. Anyway, will follow with great interest.

Would you mind sharing your model for study, or maybe just give us dimensions of base and column?

Thanks for sharing your experience, this surely prove helpful at some point...

Cheers

Envoyť de mon ONEPLUS A5010 en utilisant Tapatalk

Nick
02-12-2018, 12:06 AM
Sure, it's not quite finished and I have had some difficulties with exporting it. All the joints have gone, does the iges file below work?

https://www.dropbox.com/s/6w12be2b4wt1f2e/EG%20v19.iges?dl=0

The rails are from the Hiwin website and I've used these models off grabcad

https://grabcad.com/library/lichuan-servo-60st-m01...
https://grabcad.com/library/ac-servo-110sy-04030-1
https://grabcad.com/library/bt30-spindle-2

The design is based around the cast iron surface plate and blocks that I bought, I think this has resulted in the base being too narrow and long.

I think with hindsight starting with a welded steel filled epoxy structure would of been a good idea.

I look forward to your build, let me know if I can help