DIY Epoxy composite gantry frame milling machine

[Nick]

Nice build, following with interest, I am also doing an epoxy build. The laser cut moulds look very neat.

Have you decided on your epoxy % and aggregate mix? Will you be vibrating the molds?

Nick

[John McNamara]

Nice build, following with interest, I am also doing an epoxy build. The laser cut moulds look very neat.

Have you decided on your epoxy % and aggregate mix? Will you be vibrating the molds?

Nick

Hi Nick
I will not be vibrating the molds, some sit on a surface plate that is used to provide a flat plane. I will be tamping the mix down in 25-50mm layers.

The Mix will be nominally 12% epoxy by volume. When I do the pour I will do a test just before to make sure the stone and sand batch has not changed.

Page down this post of a previous pour.

https://www.model-engineer.co.uk/for...p?th=51617&p=3

The objective is to use the least amount of epoxy.

I plan to pour over the weekend if all goes well.

Regards
J

[John McNamara]

Hi All

At last the first casting has been poured
Link below.

I will be very interested to see how accurate the cast in position rail supports are.

I will strip the mold later this week.

Regards
John

https://www.model-engineer.co.uk/for...?th=139042&p=2

[pippin88]

John,

Can you give us an update on the results of the first pour?

In particular - how is the alignment / flatness of the bearing mounting plates?

I've been doing a lot of reading, and am pretty sold on epoxy granite due to the excellent damping characteristics.

If I can cast in a linear bearing mounts with acceptable accuracy at home, and avoiding the need for post-machining, I'll be out the door for 20-40kg of epoxy.

Also, can you share how much the Megapo

[John McNamara]

Hi Pippin

I will be posting the results soon, my workload has piled up so have not had much time for the machine.

I have managed to prepare and undercoat the casting, there were more blemishes than I would have liked, I filled them with body filler and the part is now undercoated. The part is very massive too heavy for me to lift. Tapping it with a hemmer yields a dull click only, even on the metal parts. the damping propertied of mineral cast epoxy is clearly evident

A prelim check with a straight edge indicates that the cast in position rail mounts are accurately located and co-planar . By eye I was unable to see a gap. However I will feel happier when I have tested them properly. Now that the part is clean I will set it up on jacks on surface plate to take some proper measurements.

Regards
John

[John McNamara]

Hi All

I have reviewed the accuracy of the casting and am very pleased. Link below.

https://www.model-engineer.co.uk/for...?th=139042&p=2

The maximum error is 0.0018" as cast, that will be reduced by lapping to high accuracy there is not a lot of metal to remove so the process will not take a lot of time.

Regards
John

[John McNamara]

Hi All

The Base casting is poured!

This is the largest and heaviest casting over 200KG. I cant wait to remove it from the mold, finish and undercoat it than assemble the columns and gantry castings so that I can take some measurements.

Regards
John

https://www.model-engineer.co.uk/for...?th=139042&p=3

[John McNamara]

Hi All

At last the base, columns and cross-member are one and I don't believe I could achieve the level of accuracy obtained without a laser cut mold.

https://www.model-engineer.co.uk/for...?th=139042&p=3

Regards
John

[John McNamara]

Hi All

Assembly of some of the laser cut parts, also some machining done.

Write up here:
https://www.model-engineer.co.uk/for...?th=139042&p=3



Regards
John

[Lee Roberts]

This is looking fantastic John well done,

Example of how the rails will be aligned by Laser cut Then countersunk by me later cams Held by 30mm x M8 CSK machine screws, screwed into the pre turned drilled and tapped inserts glued into the lapped mounting bars. (Prior to drilling and tapping the M6 holes to mount the liner rails). This will be done after the casting has been made, small errors in placement prior to casting is easily corrected here. The cams will also make a very rigid mount for the rails.

I like the idea you've used for rail positioning with the disks/cams, what are the smaller holes in each disk for?

Looking forward to seeing how the rollers come into play!