Many questions before I build my first milling machine

[iGyros]

Hi folks,
I am Marcus from Germany (Hamburg). I decided about 3 months ago that I need a milling machine. I am still quite new to the whole subject.
Since then I have been reading and collecting ideas, but I still lack a lot of knowledge and experience. I have built a small CNC laser for "practice" to get familiar with the topic. But of course this is not comparable to a milling machine.
After that worked out quite well, I would like to tackle my actual goal.


My goals:
-I would like to build a milling machine to mill aluminum/steel parts for other projects (steel is secondary and probably not possible at first).
-I would like to build a portal milling machine to mill large pieces of wood and to mill enclosure panels.
-I haven't thought much about the accuracy yet. It should already give useful results, because I want to "improve" myself sometime and want to build a new milling machine with this one.
-I would like a machining area of about 700 mm x 1000 mm +/- 100 mm.
-My main goal is to learn about CNC machining and not to get more than 1500€ and still do something useful with the milling machine.


These are my options:
1. i first build a MPCNC because i have most of the parts lying around anyway. The design and the performance of the milling machine keeps me from doing so. I don't think I would learn as much as I hope with the milling machine. I think I will not be happy with it. Because of the price the MPCNC is still not completely out of the game (for practice).


2. i found the PrintNC project online. This is also an Open Source portal milling machine. It looks much more robust (steel frame, linear guides and ball screws). This is of course reflected in the price, but also extremely in the performance. But the videos here look really promising. Nevertheless, there are many points that bother me about the construction, e.g. due to the construction, a maximum of square tubes with 4 mm wall thickness can be used, the linear guides are screwed directly onto the steel beams (are they not too crooked?) and only one linear carriage is used on each of the guides. Some of these can be safely fixed. But then maybe I can design directly myself.

Maybe someone who knows more about the construction can answer a few questions.
- Do you notice any major errors in the design?
- What do you think about the milling machine?
- I have often read that it is better to screw the linear guide to the side of the portal, because the forces are better absorbed. Is that correct?
- Will it be a big problem that the guides are screwed directly onto the unmachined square tube?
- Is it worthwhile to mill over the steel profiles or to cast them flat with epoxy resin (I can't think of the name "liquid metal"?) or should I then simply place them directly onto another material?

Link to the PrintNC website: https://threedesign.store/gallery/
GitHub: https://github.com/threedesigns/printNC


3. I construct my own milling machine. But I still have many questions. Maybe the professionals can help me a little.

- I would like to build the milling machine similar to the PrintNC (frame made of steel square tubes). I would then go to 6.3 or 8 mm wall thickness and fill it with sand.
- Does it make sense to use steel profiles or are they unsuitable?
- Does it make sense to weld the frame or can I get a sufficiently strong connection screwed?
- When welding I have doubts, because I read about distortion and tension again and again. Is there any way I can avoid this (I have never welded before, but have a good friend who has already promised me his help). I also see a disadvantage in welding, because the subsequent alignment is very difficult.
- Do I "gain" anything from the steel profiles? I hope that the milling machine will be cheaper and at the same time much more stable or is it smarter to use the typical aluminium profiles?
- I would also have a design in mind with a fixed portal. I hope that this will provide stability. Is it worthwhile to build such a structure? I know without a drawing this question is hard to answer, but a "rule of thumb" would be enough for me. Is a milling machine with a fixed portal usually more stable or not?
- I am simply not quite sure how I can face mill the components. I think I have an understanding problem here. If I face-mill the parts on one side first, they will all lie on an uneven side, which is different for all parts. If I now turn the parts over and face-mill them from the other side, both sides are flat, but not all parts are the same, because all parts were previously on a differently inclined side. Or do I have to proceed in such a way that I do not place the components on the crooked side, but clamp them perfectly aligned?

I hope my questions don't seem too amateurish, but unfortunately I can't find much information about building with steel square tubes and if they are often old or not exactly what I want to know. Please keep in mind that I do not know that much about this topic yet. If I have written something wrong, please correct me.

Thanks for the answers.

[hanermo2]

Happy to help You.

1.
Forget it.

2.
Calibrate Your expectations.

3.
Why are there no good videos of them using ISO30 spindles and machining steel ?

--
I scratch built a machine like that.
It took 17.000 hours and about 100k€.
..

Because I was well known ..

I got employed by the best and biggest machine tool maker in the world, HAAS automation, as their general manager for sales. Spain.
I grew sales from 4 / yr to 65 / yr in 8 months.
.. removed longish detail ..

[AndyUK]

Hi Marcus,

Welcome to the forum.

Unfortunately the TL;DR is exactly what hanermo2 says - BUT, don't be discouraged, just you need to keep exploring DIY builds to get a realistic grasp of the limitations.

Start here: http://www.mycncuk.com/forums/253-DIY-Router-Build-Logs

Look for the popular threads with lots of pages and responses, grab a few beers and a blanket, settle down for the long read. You'll pick up an awful lot. Unfortunately so many people just can't be bothered to do this step before jumping ahead. All your questions above will be answered, and more.

The classic Dunning-Kruger (https://grahamsavill.wordpress.com/2018/08/20/you-dont-know-what-you-dont-know/) peak is "I want a machine that can cut aluminium and steel well, but also have a massive build area for wood and I don't want to spend much money". Show me a commercial machine that can achieve those aims for less than £500k and I'll be impressed - that should be a good hint :)

[Neale]

It's possible to build a machine that can do what you want - but you have to accept that it is a compromise. My own router has a cutting area about 1500x750 and I use it to cut anything from plastic and wood to steel. Yes, it does cut steel but with light cuts and not very fast. That probably cost the equivalent of around €3000. It's not a Haas - or even as powerful as the Chinese vertical mill I have in the workshop - but CNC means that it can do things that the manual mill cannot.

I repeat the advice in the previous reply - take a look through the build logs, think very hard about your real requirements, and start to get some ideas. Then ask questions!

[iGyros]

Thanks for your answers.
I think it is clear that the milling machine will not be perfect. I also know that steel will probably not be possible or almost not possible at all. As I said at the beginning "steel is secondary and probably not possible at first". But I hoped that some of the questions could be answered.

[JAZZCNC]

I could answer your questions but I'm going to be a little harsh and not answer because I'd be wasting my time and a worthy reply would take a lot of time. So I'm kind of going to be cruel to be kind, while saving my fingers some aching.!!

If you don't have the experience or the skills and maybe equipment to build a strudy machine, which from your questions you clearly don't, then I would think about buying an old VMC or Mill that is either dead or with an older obsolete controller and retro fitting it with modern electrics etc. This route will workout cheaper and with much higher chance of success.

Sorry if it's not what you wanted to hear but it is an honest reply with your best interests in mind.

[Colin Barron]

Hi folks,
I am Marcus from Germany (Hamburg). I decided about 3 months ago that I need a milling machine. I am still quite new to the whole subject.
Since then I have been reading and collecting ideas, but I still lack a lot of knowledge and experience. I have built a small CNC laser for "practice" to get familiar with the topic. But of course this is not comparable to a milling machine.
After that worked out quite well, I would like to tackle my actual goal.


My goals:
-I would like to build a milling machine to mill aluminum/steel parts for other projects (steel is secondary and probably not possible at first).
-I would like to build a portal milling machine to mill large pieces of wood and to mill enclosure panels.
-I haven't thought much about the accuracy yet. It should already give useful results, because I want to "improve" myself sometime and want to build a new milling machine with this one.
-I would like a machining area of about 700 mm x 1000 mm +/- 100 mm.
-My main goal is to learn about CNC machining and not to get more than 1500€ and still do something useful with the milling machine.


These are my options:
1. i first build a MPCNC because i have most of the parts lying around anyway. The design and the performance of the milling machine keeps me from doing so. I don't think I would learn as much as I hope with the milling machine. I think I will not be happy with it. Because of the price the MPCNC is still not completely out of the game (for practice).


2. i found the PrintNC project online. This is also an Open Source portal milling machine. It looks much more robust (steel frame, linear guides and ball screws). This is of course reflected in the price, but also extremely in the performance. But the videos here look really promising. Nevertheless, there are many points that bother me about the construction, e.g. due to the construction, a maximum of square tubes with 4 mm wall thickness can be used, the linear guides are screwed directly onto the steel beams (are they not too crooked?) and only one linear carriage is used on each of the guides. Some of these can be safely fixed. But then maybe I can design directly myself.

Maybe someone who knows more about the construction can answer a few questions.
- Do you notice any major errors in the design?
- What do you think about the milling machine?
- I have often read that it is better to screw the linear guide to the side of the portal, because the forces are better absorbed. Is that correct?
- Will it be a big problem that the guides are screwed directly onto the unmachined square tube?
- Is it worthwhile to mill over the steel profiles or to cast them flat with epoxy resin (I can't think of the name "liquid metal"?) or should I then simply place them directly onto another material?

Link to the PrintNC website: https://threedesign.store/gallery/
GitHub: https://github.com/threedesigns/printNC


3. I construct my own milling machine. But I still have many questions. Maybe the professionals can help me a little.

- I would like to build the milling machine similar to the PrintNC (frame made of steel square tubes). I would then go to 6.3 or 8 mm wall thickness and fill it with sand.
- Does it make sense to use steel profiles or are they unsuitable?
- Does it make sense to weld the frame or can I get a sufficiently strong connection screwed?
- When welding I have doubts, because I read about distortion and tension again and again. Is there any way I can avoid this (I have never welded before, but have a good friend who has already promised me his help). I also see a disadvantage in welding, because the subsequent alignment is very difficult.
- Do I "gain" anything from the steel profiles? I hope that the milling machine will be cheaper and at the same time much more stable or is it smarter to use the typical aluminium profiles?
- I would also have a design in mind with a fixed portal. I hope that this will provide stability. Is it worthwhile to build such a structure? I know without a drawing this question is hard to answer, but a "rule of thumb" would be enough for me. Is a milling machine with a fixed portal usually more stable or not?
- I am simply not quite sure how I can face mill the components. I think I have an understanding problem here. If I face-mill the parts on one side first, they will all lie on an uneven side, which is different for all parts. If I now turn the parts over and face-mill them from the other side, both sides are flat, but not all parts are the same, because all parts were previously on a differently inclined side. Or do I have to proceed in such a way that I do not place the components on the crooked side, but clamp them perfectly aligned?

I hope my questions don't seem too amateurish, but unfortunately I can't find much information about building with steel square tubes and if they are often old or not exactly what I want to know. Please keep in mind that I do not know that much about this topic yet. If I have written something wrong, please correct me.

Thanks for the answers.

Your best chance of success as others have said is to buy an existing machine with ball screws already fitted and fit new electronics. There are plenty of examples on the net. The more space you have the bigger and heavier the machine you can buy; bigger machines are generally cheaper because most diy people use single phase and no bigger than a Bridgeport (about 875kg).

[iGyros]

I have made plans today after all. The whole square tubes are 100 x 80 x 6.3 mm tubes. The plates on the Z axis are 25 mm flat steel. There is one thing I would like to adjust that is not in the plans yet. I will weld 10 mm of flat steel on all support surfaces and have it milled flat. These are 25 mm guides and ballscrews with 20 mm.


This is all still very rough, but I would be happy if you can tell me if I am on a real path or if there are already huge mistakes in there.

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[Clive S]

I would swap the Z motor so that it is stationary .

Like moving the ball screw to the back plate

[pippin88]

Add bracing within the tubes or at least rigidly cap the ends.

[JAZZCNC]

You are making the Z axis much heaveir than it needs to be with this arrangment by having the motor, ballscrew, bearings etc moving with it. All it's doing is creating more work for the motor and lowering performance and add's nothing to the strength.
Also I would widen the bearing and rail spacing to give more stabilty, I understand your chasing space but a few CM's makes a big difference and is worth losing sometimes.

Regards the tubes, you do realise Tube doesn't have sharp edges don't you.? At this size they will have between 8 to 12mm radius and you show the gantry ballscrew bearing at the edge and this won't work as you'll be drilling into the radius and the side wall.
Yes, small detail I know but these make a big difference and are what catch you out. If you are going to model the design make sure you model every detail because if not then at some point you will find things that don't fit as you expect and sometimes they can be very diffcult or impossible to correct without major upevil.

The gantry need bracing where the bearing box meets the gantry box and again I would widen the bearing spacing.
If you are going to weld plate to the box section then only weld it in short sections 30-40mm in length spaced 100mm apart and staggered on each side, don't fully weld the edge because it will put stresses into the tube which will release when you have the tubes machined unless you have it heat treated first.

If you don't want to go the heat treat/machined route then think about using epoxy metal putty on the surfaces and putting on a surface plate to create flat and parallel surfaces. You'll need a large surface plate but it works very well and is easy and quick. I use this method all the time and it's very accurate and strong.

[driftspin]

I have made plans today after all. The whole square tubes are 100 x 80 x 6.3 mm tubes. The plates on the Z axis are 25 mm flat steel. There is one thing I would like to adjust that is not in the plans yet. I will weld 10 mm of flat steel on all support surfaces and have it milled flat. These are 25 mm guides and ballscrews with 20 mm.


This is all still very rough, but I would be happy if you can tell me if I am on a real path or if there are already huge mistakes in there.

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29066
29068Hello iGyros,

Look like you could use my design to refine yours.

I have used 120x80x4 mm and 80x80 for the bed..

Did you already decide on 1 or 2 ballscrews on the long axis?

The linkage on those are a weak point in my design. I have no real world problems with it yet but would rethink it when done all over again.



Grtz Bert.




Verstuurd vanaf mijn SM-A505FN met Tapatalk

[iGyros]

Hello guys,
I have worked a little bit on the design again.
I also tried a plan with a fixed portal, but it would be much more complicated.


Here are a few important points that I have adapted.
- The portal is 850 mm wide.
- The travels are about 510 mm x 425 mm x 200 mm.
- Steel profiles with the dimensions 60 x 100 x 6.3 mm are planned everywhere.
- The profile for the portal has the dimensions 150 x 100 x 6.3 mm.
- I plan to use 25 mm linear guides and 1605 Ballscrews.
- Now all support surfaces are underlaid. So far I plan to use 10 mm flat steel for this.
- I made the Z axis much more massive and moved the motor to the fixed side.
- Where it is possible (and useful), I have added angles. These are made of 20 and 15 mm flat steel.
- I have planned a slot table. It consists of a large 10 mm thick steel plate and single 15 mm steel plates for the slots.


I have the following questions.
- What do you think of the Z axis? Does the reinforcement on the "fixed" plate (not on the movable side) give me something or is it just unnecessary weight?
- Do the angles bring me a serious advantage or is that unnecessary work?
- The Z axis plates are 25 mm steel and the reinforcements are 15 mm steel. Is this too thick and just unnecessary weight?
- I would like to mill the angles and the steel slotted table with the machine once it is set up. How realistic is it that I want to mill steel with the machine?
- Which steel should I use for all the components?
- With the size Nema 34 motors (for now) are sufficient?
- I am practically dependent on the 16 mm ballscrews, because I would have to mill too much with the 20 mm ballscrews and I currently have no milling machine. At work a college can facemill the all mounting surfaces, but unfortunately they can't do too much for me there. Would I have a big advantage for 20 mm ballscrews?

What do you notice about the plans? Are there any more mistakes somewhere?

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[pippin88]

You need to model your end mill / cutting bit and look at whether it will clear above your workpiece.

If you are using a vice, it will use up a lot of Z travel.

Also check how you will actually bolt the linear bearing carriages. You usually can't have them right on top of each other as you can't bolt them that way.

Overall lots of good things in your design. Bracing is good