The Best way to level surface and then install the rails

Hi there

I just assembled a 3 axis wood cutting cnc machine. But I have some problems with my X axis.

My question is, What would be the best way to level the surface in order to install my rails?

I have a 200 cm - 4" by 4" Square Tube for my each Rails.

I know I could weld a Flat Bar on each of my Tube and then sub it same level, But I just do not know how to do it?

Do I need a laser level ? please explain. and if you have a video on this issue of how to exactly level it and then sub it would be great.

Regards
Johnansaro

First let me say there are many ways to get to a flat surface for rail mounting.

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Originally Posted by johnansaro

Hi there

I just assembled a 3 axis wood cutting cnc machine. But I have some problems with my X axis.

My question is, What would be the best way to level the surface in order to install my rails?

I have a 200 cm - 4" by 4" Square Tube for my each Rails.

I know I could weld a Flat Bar on each of my Tube and then sub it same level, But I just do not know how to do it?

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I'm not following your use of the word "sub" here, probably a translation issue.

In any event once you consider welding anything you need to realize that welding distorts metal. How badly the distortion is depends on the materials being welded, the technique used to weld the metal and just how much welding actually takes place. In an ideal world the welded structure would be stepped relieved after welding which might be a problem if you don' have a local heat treat business.

If you do get the frame heat treated one of the best ways to flatten and set up the frame for rail mounting is to have the frame machined on a large mill. This can be expensive depending upon local conditions. However what you get is a flat surface with hopefully. registration edged and parallel and accurately placed mounting holes. This route is a good choice if you have a largish budget.

It should be noted here that you may not need to weld any mounting plates on your frame if you intend to use epoxy leveling. What you need to verify is that the frame members are thick enough to hold the the threaded holes that get drilled and tapped to hold the rails in place. Generally you want at least 1.25 to 1.5 times the screw diameter so material for a 5 mm screw would need to be about 6.25 to 7.5 mm thick. That might be a bit thicker than some might suggest but I'm including a bit of loss due to counter boring or chamfering the screw holes a bit to make sure deformed threads don't impact rail installation. Also structural steel is a bit soft so a little extra doesn't hurt.

Quick edit for something forgotten:

1. When considering material thicknesses for screw holding (in similar materials) one approach is to assure that you have 5 to 7 threads engaged. A screw with a 1mm pitch would need material 5 to 7 mm thick using this rule of thumb. I'd still add a little bit to allow for a counterbore or chamfering of the hole on the rail mounting side. I tend to prefer a little extra thickness myself to a material that is too thin.

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Do I need a laser level ? please explain. and if you have a video on this issue of how to exactly level it and then sub it would be great.

Regards
Johnansaro

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If you are going to do a epoxy leveling approach realize that if everything works correctly the Epoxy self levels. More exactly the epoxy lays down matching the curvature of the earth, that is very flat for most of us. So in theory you don't need a level if you use epoxy leveling to produce your flat surface.

However for machine setup and maintenance a good high precision level is a very important tool. So I would strongly suggest getting a high precision machinist level. This especially if you intend to move the machine at anytime after the epoxy leveling is done. The reality is if you move the machine you will induce twisting in the frame which can be corrected by leveling the machine as part fo setting it up in its new location.

Hi

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Originally Posted by wizard

First let me say there are many ways to get to a flat surface for rail mounting... .

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Thank you for these educative infos [emoji106]
Do you, by chance, have any valuable resource to share about epoxy levelling ?

Thanks

Envoyé de mon A0001 en utilisant Tapatalk

Use a low molecular weight epoxy with a slow cure time. Use of a pigment seems to help with bubbles. I've done 2 successful epoxy leveling operations. I used SC15P from www.precisionepoxy.com

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Originally Posted by 1Jumper10

Use a low molecular weight epoxy with a slow cure time. Use of a pigment seems to help with bubbles. I've done 2 successful epoxy leveling operations. I used SC15P from www.precisionepoxy.com

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Thanks a lot ! [emoji106]
Now, to find similar product in Europe/France...

Envoyé de mon A0001 en utilisant Tapatalk

Hi wizard

Thanks so much for your detailed reply.

Few questions on this issue:

1: the surface that i must apply the epoxy as I mentioned before is 10 cm * 10 cm Steel Tube, Is this going to be a problem? Otherwise can I apply the epoxy on steel surfaces?
2: I oil painted the Tube, Do I need to sanding the paint away from the tube surface before applying the epoxy?

regards
johnansaro

Hi, just my 2 pennoth worth......as you only want to cut wood and that means you can get away with less exacting tolerances for rail alignment..........that interprets as..... provided the two rails are mounted on flat bases and are fairly level to each other, you will win.

If you do not have access to the full compliment of an engineering work shop, then something of a compromise is in the air.

I would find, get, acquire.....whatever..... a slab of granite.....approx. 600mm X 600mm and not less than 25mm thick...... the type that is used for a kitchen bench top......offcuts are as cheap as you want.

This will be about as accurate as you can get under the circumstances, not good enough for scraping ways etc, but good enough for alignment.

You didn't actually say how big the machine is or what it is and it's assumed it's a CNC router not a mill..... but a 600mm square granite slab should do the trick for leveling and alignment.

What more can I say.....if you can't relate to the granite flat surface as the best you have then you won't do it any other way.

I would mount the granite slab in a wood framed box with a cover and look after it for future reference......it won't be perfect but it's better than a piece of particle board topped with Melamine.

This is for aligning and checking the base Y axis linear rails.....then the X and Z axes can be aligned from them.
Ian.

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Originally Posted by handlewanker

Hi, just my 2 pennoth worth......as you only want to cut wood and that means you can get away with less exacting tolerances for rail alignment..........that interprets as..... provided the two rails are mounted on flat bases and are fairly level to each other, you will win.

If you do not have access to the full compliment of an engineering work shop, then something of a compromise is in the air.

I would find, get, acquire.....whatever..... a slab of granite.....approx. 600mm X 600mm and not less than 25mm thick...... the type that is used for a kitchen bench top......offcuts are as cheap as you want.

This will be about as accurate as you can get under the circumstances, not good enough for scraping ways etc, but good enough for alignment.

You didn't actually say how big the machine is or what it is and it's assumed it's a CNC router not a mill..... but a 600mm square granite slab should do the trick for leveling and alignment.

What more can I say.....if you can't relate to the granite flat surface as the best you have then you won't do it any other way.

I would mount the granite slab in a wood framed box with a cover and look after it for future reference......it won't be perfect but it's better than a piece of particle board topped with Melamine.

This is for aligning and checking the base Y axis linear rails.....then the X and Z axes can be aligned from them.
Ian.

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That is good, practical advice. [emoji106]

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Originally Posted by johnansaro

Hi wizard

Thanks so much for your detailed reply.

Few questions on this issue:

1: the surface that i must apply the epoxy as I mentioned before is 10 cm * 10 cm Steel Tube, Is this going to be a problem?

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I have no way to know the answer to that question. The quality of structural steel tubing varies widely. The size of the tubing isn't a huge problem but its straitness might be an issue. If the tubing is extremely warped I'd would likely avoid epoxy leveling. There are of course lots of qualifications here, we for example don't know much about your machine, especially its size. A machine to handle 4 x 8 sheets by design is a more appealing place to used epoxy leveling as getting work done on a large milling machine is expensive. A small table top machine can be handled in far more machine shops with than a one piece frame for machine with a 4.5 x 10 foot working area.

In the end you have to evaluate what is right for you. You can use epoxy leveling on a machine with a 12 inch square work area if you want too. It is just that on a small machine you might be able to farm out machined surfaces cost effectively thus not needing epoxy leveling. For that matter you can hand scrape in a small frame without to much effort.

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Otherwise can I apply the epoxy on steel surfaces?

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Epoxy will stick to clean steel surfaces. Ideally a rough surface will be worked up to give the epoxy something to key into.

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2: I oil painted the Tube, Do I need to sanding the paint away from the tube surface before applying the epoxy?

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Most likely!

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regards
johnansaro

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Hi All
I am building an open source machine to machine a flat surface on a steel tube or an applied strip on that tube.

Below is a link to GrabCAD Below that is a link to MYCNCUK where there is a discussion on using stretched wire and a USB microscope as used in the machine.

Regards
John

https://grabcad.com/library/machine-...der_id=9681130

DIY Laser levelling using webcam and laser level - Page 30

Hi John - Epoxy levelling is a two edged sword. Many people find it easy many find it impossible to do. This is a combination of preparation and using the right epoxy. In thick layers (4mm plus) epoxy can definitely provide a flat and level surface, however it is soft as it is plastic and would you mount your rails on a piece of 5mm polypropylene or nylon? If you try to lay a thin layer it will crawl and distort due to surface tension and exotherm and the surface will not be flat. Since your machine is for timber and you are not chasing +/- 0.01mm I suggest you buy a good machinist level and suitable straight edge.

1) set up a master side. This side needs to be level and flat. You can lap the high spots off with coarse grit paper (eg wet and dry) and a good lap. Firstly you need to make the lap so look up videos of how to do this. If you have a good strait piece of steel or aluminium it can be a good lap. You lap two "laps" together to get them flat. 3 is better in rotation and this is how surface plates are ultimately done so its not a poor substitute method.

2) Once you establish a master side that is level and flattish you can use epoxy to fill in the low spots or you can lap until done if its not too bad. I've seen people remove high spots with grinders so you can be a bit gung hoo about it.
3) Once you have the master side done you can tackle the secondary side. With the straight edge and level you can establish high/low spots then lap the high spots until its acceptable. Again can use epoxy to fill low spots. Will take a little time but this way is tried and proven over a long period of time (many decades perhaps centuries) to get something correct. Peter

Hi Pete

I said "I am building an open source machine to machine a flat surface on a steel tube or an applied strip on that tube."

It is not always feasible to directly machine a steel tube, due to the loss of strength particularly if the tube is thin. there is also the possibility that internal stresses may be released by the machining cut causing the tube to bend. There also may not be enough material left for drilling and tapping

The applied strip:
I have observed that most of the commercial CNC machine builders weld a strip of steel along the tube before machining. typically around 12mm (0.5 inch) the welds are spaced not continuous no doubt to avoid distortion. This has the added advantage of providing a thicker material thickness for later drilling and tapping to attach the linear rails. If you study the CAD files I provided you will see this strip in Red.

As an alternative although I did not mention it:
Metal filled epoxy will also provide a surface the machine will have no trouble machining that.

Regards
John

Hi John Mc - This was directed at the thread originator Johnansaro not you :) no problem with your machine. I hope it works out for you. All of your comments I agree with. The issue of flat-parallel and level surfaces is a big one. I have spent quite a bit of time looking for a laser measurement solution but none so far under $25000 AUD :( keep us informed of the results of the machine. Peter

Thanks Pete

Maybe I should have created a new thread? I do not want to hijack this one, however The title suggested it was on topic. If requested i would be happy to move it.

The thread over at MYCNCUK link in my earlier post has also morphed away from using a laser pointer source to stretched music wire. (It can also be nylon or kevlar.) I like Piano wire because it has very little creep unlike polymers. the linear accelerator at Cern is mostly aligned with stretched wire! If you read through it... yes i know about 300 posts... You will see how the software and methods has evolved.

https://www.google.com/search?rlz=1C...4dUDCA0&uact=5

Stretched wire combined with a USB microscope and the open source software developed by Joe "Devmonky" has given outstanding results. So far all the testing by various people has been manual. The two machines me and a mate are building will create a platform for further refinement.

As far as costs go I guess the laser cutting will be the largest expense maybe 250 = 300 AUD including the 5mm steel plate. An AUD= about 0.72 USD I don't know the cost of laser cutting in the US. The rest of it is pretty common Asian motion stuff. I have used an Asian 2.2kw spindle. the tiny cuts will allow it to be throttled down to around 12000rpm the desigh calls for 2 to 3mm cutters to be used so for a change it will be able to cut steel at the correct speed (Using a carbide tool)

As one off use machine the cost is a bit high but not insurmountable however built and shared by a few builders It is quite reasonable. There is a minimum amount of machining nothing that could not be done on a small bench lathe.

Regards
John

Hi All

I uploaded version 35 to GrabCad.
This is a major update. Many of the joints are now added.

Attachment 457854

This design is a good example of working with laser cut material.. No welding!

Regards
John

PS should I move this post to a new thread?

.

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Originally Posted by peteeng

Firstly you need to make the lap so look up videos of how to do this. If you have a good strait piece of steel or aluminium it can be a good lap. You lap two "laps" together to get them flat. 3 is better in rotation and this is how surface plates are ultimately done so its not a poor substitute method.

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hi peter i didnt understand you ,do you have any video demonstrating how to make a good lap and thanks

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Originally Posted by peteeng

Firstly you need to make the lap so look up videos of how to do this. If you have a good strait piece of steel or aluminium it can be a good lap. You lap two "laps" together to get them flat. 3 is better in rotation and this is how surface plates are ultimately done so its not a poor substitute method.

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hi peter i didnt understand you ,do you have any video demonstrating how to make a good lap and thanks

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Originally Posted by peteeng

Firstly you need to make the lap so look up videos of how to do this. If you have a good strait piece of steel or aluminium it can be a good lap. You lap two "laps" together to get them flat. 3 is better in rotation and this is how surface plates are ultimately done so its not a poor substitute method.

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hi peter i didnt understand you ,do you have any video demonstrating how to make a good lap and thanks

Hi Ben - A lap is a long straight member that you make or buy. You use SiC grit or wet and dry paper on it to "lap" the surface flat. Here's an example. Peter

https://youtu.be/-CM3VWKXasY

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Hi Ben - A lap is a long straight member that you make or buy. You use SiC grit or wet and dry paper on it to "lap" the surface flat. Here's an example. Peter

https://youtu.be/-CM3VWKXasY