DIY Epoxy composite gantry frame milling machine

[John McNamara]

25102

Hi All

Its been a while since I popped in here, I am working on a new milling machine build. This not a light weight design. It has been designed to work with steel or Aluminium depending on the spindle fitted.

Alas the thread describing making i will be huge by the time it is finished so posting on multiple forums is difficult.

I have posted it at another place nearby. https://www.model-engineer.co.uk/forums/postings.asp?th=139042&p=1

You may find it interesting.

Regards
John

[mekanik]

Hi John
Thanks for the heads up, i have been thinking about this for some time and a couple of years ago composite guy promised some info on construction but this was never forthcoming, i will be following with interest.
Regards
Mike

[Greeny]

Thanks for the pointer.
Very interesting so far, looking forward to the rest.
Cheers

[pippin88]

John, looks like a great build.

If you don't mind sharing, where in Aus are you? I'm in Melbourne.

I'm in the early design stages of a DIY mill. Manual conversions are troublesome, and true CNC machines are either tiny or very large and not feasible in the home shop / garage.

I'm planning a steel weldment, stress relieved and machined +/- ground. This is partly because I've struggled to find clear recipes for epoxy granite and don't really want to spend months experimenting. I may use epoxy granite to fill voids and add mass.
I'm looking at doing a planer style mill - double columns, with the gantry moving up and down on the columns. This avoids the long lever arm Z axis, but is a bit more complex to align.

I have a couple of comments and questions about your build:

I really like the rail alignment cams - did you make these or buy them? They are going to be great for both alignment and increasing mounting strength of the rails.

The Z axis travel seems a bit short compared to your other travels. What sort of spindle / tool holder are you going to use?

What was the cost of the laser cut steel? Do they cost it per cm cutting length or similar? I'm interesting in getting a milling head and gantry beam laser cut. I'll probably use square hollow section for the base however.

[John McNamara]

John, looks like a great build.

If you don't mind sharing, where in Aus are you? I'm in Melbourne.

I'm in the early design stages of a DIY mill. Manual conversions are troublesome, and true CNC machines are either tiny or very large and not feasible in the home shop / garage.

I'm planning a steel weldment, stress relieved and machined +/- ground. This is partly because I've struggled to find clear recipes for epoxy granite and don't really want to spend months experimenting. I may use epoxy granite to fill voids and add mass.
I'm looking at doing a planer style mill - double columns, with the gantry moving up and down on the columns. This avoids the long lever arm Z axis, but is a bit more complex to align.

I have a couple of comments and questions about your build:

I really like the rail alignment cams - did you make these or buy them? They are going to be great for both alignment and increasing mounting strength of the rails.

The Z axis travel seems a bit short compared to your other travels. What sort of spindle / tool holder are you going to use?

What was the cost of the laser cut steel? Do they cost it per cm cutting length or similar? I'm interesting in getting a milling head and gantry beam laser cut. I'll probably use square hollow section for the base however.

Hi
I am in Melbourne 3122

John1147 at big pond .net.au

You will have to edit the address above I guess you know how.
If you email your phone number I will give you a call :)

[John McNamara]

Hi
Most laser cutters provide the mild steel and cutting at a quoted price. Many will also have Stainless and Aluminium Etc.
It is not possible to work out the cost on the basis of so much a millimeter.

The main thing is to provide properly drawn 2D files, usually DXF files. The part outline must not have any breaks or overlapping lines, All holes must also be closed. (And nothing else in the file) Each part should have its own file. Don't try to nest the parts yourself in a big file.

Laser cutters are pretty busy businesses, If you provide good files you will be charged as a professional. If you cant provide files some will draw the parts for you, be prepared for a shock when they quote to do this.

Just email your requirements and the file set in a Zip file and most will reply with a quote in a day or two. (A separate zip file should be used for each material type and thickness. this avoids confusion) It is OK to have a short discussion when starting with them asking if they have any special requirements.

I really like the rail alignment cams - did you make these or buy them? They are going to be great for both alignment and increasing mounting strength of the rails.
[
I had them laser cut from 4mm steel they cost about 50c each the laser cutter provided the material

The Z axis travel seems a bit short compared to your other travels. What sort of spindle / tool holder are you going to use?

I drew in an Asian high speed spindle fine for Aluminium Brass and plastics and fairly low cost. I also plan to build a 30 or 40 taper spindle, Possibly using the high speed 2000 rpm spindle with a 4 to one reduction belt drive. I also have a large Manual V Mill, It is easy to make the Z axis taller I decided not to as this machine will be used for smaller parts. Shorter = less deflection

What was the cost of the laser cut steel? Do they cost it per cm cutting length or similar? I'm interesting in getting a milling head and gantry beam laser cut. I'll probably use square hollow section for the base however.
Laser cutting cost of the machine parts was about $500 including material plus the molds that cost more I am sharing the cost of the molds. 160+ part files is a lot quite a few of the parts were in multiples. looking at it that way the cost per part is modest. FWIW the cost per kg of parts was AUD $3.85 All up inc GST/VAT. I would not try to use that figure it will depend on the mix of parts, OK I guess as a ballpark.

[pippin88]

John,

Thanks for the info.

I've sent you an email.

[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/forums/postings.asp?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/forums/postings.asp?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/forums/postings.asp?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

[pippin88]

Thanks for the update John. Nice results.

So, do you reckon it's best:

a) To get ground stock (can be bought ground, but suspect $$$), predrill (most) holes and cast against surface plate as you have done

or

b) Use mild steel bar stock, cast in standard mold, not requiring surface plate, and pay someone with a big cnc mill to quickly machine the steel and drill the holes?

[John McNamara]

Hi Pippin in answer to your questions A and B.

Question A. “To get ground stock (can be bought ground, but suspect $$$), predrill (most) holes and cast against surface plate as you have done”

I considered precision ground stock and phoned around to locate a source, it was available at a cost, quite a lot actually; however the supplier would not guarantee flatness on longer lengths. They would provide a tolerance for constant thickness but not flatness, however for this project only one side has to be flat the other side is buried in the casting.

Laser cutting precision ground stock which is normally a water or oil hardening carbon steel is likely to make any hole or laser cut edge very hard. Also my laser cutter charges extra for precise positioning small pieces of material, they prefer to work with large plates. This hardening also occurs to a small extent with mild steel, making it hard going for high speed steel tools however I did not have a problem with HSS on the steel supplied by the laser cutter.

If I was able to locate precision ground stock with a guaranteed flatness it would have to be machined to size and the 16mm holes for the cam pins would have to be drilled. These holes do not have to be located to high accuracy so marking out and centre punching in the normal way would be fine. The cams will compensate for any small errors.

The 16mm thick standard mild steel plate supplied by the laser cutter has a reasonable surface finish free of the normal flaky scale you get on black bar stock, there is a black oxide coating and some mill marks. After cutting it is not flat there was heat distortion, bowing of the 16mm axis in particular. I mechanically straightened the pieces and then sent them to a firm with a surface grinder. This was not a success as they did not completely flatten then pieces. I suspect their operator was not up to the job. The big enemy is the magnetic chuck. Grinding long pieces requires packing the work so the chuck does not pull any bowing down before grinding a side then, then turning it over and repeating the process for the other side. This process may have to be repeated several times until any stresses are relieved and the piece will lay flat on the surface table. Even better would be to have the part stress relieved professionally another cost.

In the end I hand lapped the errors left by the surface grinder. As the post above shows there were some residual errors.
I have been working on them with the lap and now the maximum error is .001” over 800mm testing the part on the surface plate with an indicator. I am confident I can get that down to a tenth or so, however just turning the part 90 degrees would probably change that, gravity is a universal force. I guess I could set the part up on its airy point’s that would possibly reduce the measurement error however temperature is also a variable. My workshop has a skylight. We happened to have a hot day yesterday a high of 33 today the high was 20. As expected my error measurements changed with the sun shining on the part; the top face was heated and the face bowed up. Digging the depths of high accuracy is an interesting challenge.

Question B. “Use mild steel bar stock, cast in standard mold, not requiring surface plate, and pay someone with a big cnc mill to quickly machine the steel and drill the holes?”

That will work no problem, apart from finding a contractor that has a CNC machine and equipment that can handle large heavy parts and cost.

It was tempting me to take that option, were it not for the desire to to find out what is possible using a surface plate, small lathe and basic tools. The laser cut mold is optional it could be made of MDF for one time use. The machine does use laser cut parts, they could also be made by hand a large time cost. If I manage to make a workable machine and demonstrate a method that worked I hope others will maybe create their own designs and contribute improvements to the methods I have used for this machine.

[John McNamara]

Hi All

I just completed the columns for the mill next is the base, an exciting step as for the first time the frame of the machine can be tested.

I have a full write up here.
https://www.model-engineer.co.uk/forums/postings.asp?th=139042&p=2

25326

Regards
John

[pippin88]

Fantastic work!!

My mill looks like it will have to wait a good 18 months unfortunately. I will have to live vicariously and get the benefit of the what you learn.

[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/forums/postings.asp?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/forums/postings.asp?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/forums/postings.asp?th=139042&p=3

http://www.mediafire.com/file/e381x86wuyw8i8b/12-02-2019_6-48-35_PM.jpg/file

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!

[mekanik]

Hi Lee
Would imagine for a peg spanner to align the cams prior to locking.
Regards
Mike

[hanermo2]

John ..
Your work is the best I have ever seen in small mills in 16 years from 5bears on up.

[John McNamara]

Hi All

Firstly I am remiss for not posting an update for a while. I am working on the gantry saddle and Z axis. I will post some photos soon.

The small holes are indeed for a pin spanner. very little pressure is needed as the friction on the CSK machine screw tends to push the cam against the rail base. If you study the photo you can see they are not in line although the bolt holes are.

The rollers are to allow the chip guard curtain, made from aluminium slat curtain or alternatively a piece of rubber, high temperature rubber to roll down at the front and back of he machine. You can see the curtain in place on the cad drawing on the first page of this post.

Regards
John

[John McNamara]

Hi All

Some good progress. The saddle and Z Axis has been cast and machined.

25555

More photos at my blog at the other place.

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

Regards
John

[cncchris]

Very nice build mate. Where abouts in Australia you located?



Sent from my MI 8 using Tapatalk

[AndyGuid]

Very nice build mate. Where abouts in Australia you located?

G'Day Chris,

If you hover your mouse pointer over a members national flag, the system shows what the member has given as their location.

So in your case cncchris you live in Inverell?

But some might question that Inverell is in Afghanistan?????:hysterical::hysterical:

Cheers, Andy

[cncchris]

Lol suppose to be Australia. I'll update it

Sent from my MI 8 using Tapatalk

[John McNamara]

Hi All

Its been a while since I posted on my machine build, alas not enough time.

At last I have mounted the rails.
I am extremely pleased with the results. the method I designed works as planned.

I was able to position and drill the rails to within +- 0.001mm parallelism and straightness compared to my straight edge. When the machine is finally set up maybe this can be improved upon.

Yes I know that temperature effects etc will mean the the final accuracy of the machine will not be as good as this. However today the dial indicator only moved +- one 0.001mm division.

You can see the blog here:

https://www.model-engineer.co.uk/forums/postings.asp?th=139042&p=4

Regards
John