Originally shared by Sam De La Haye
Wooden milling machine which is still under construction but getting there! Does anyone know the limitations of using plywood, when cutting metal? I was thinking using extremely shallow depth of cut and a slow feed rate. Does anyone have any experience doing this?
I can’t tell what your Y axis movement is, but that unsupported length on the bottom of the Z axis will be a problem. I assume your spindle will hang off of this?
Yes you can cut aluminum, very shallow depth of cut. I’d guess around 0.005". You can’t slow down the feed rate to be conservative. You will end up wearing your bits out quickly at best, and break them because of built up edge, due to rubbing causing dull cutting edge. Make sure you cut atleast 0.0005" of material per flute of cutter. 0.001" - 0.002" is even better.
@Alan_M Thanks for the advice! The Y axes is 2 meter long rails either side of the machine, under the table top, they are the same 25mm rails as the X and Y.
The Z axis will have the bottom aligned with the bottom of the X axis plate. Hopefully there won’t be too much defection of the bottom of the plywood!
Should have taken some better pictures! 
Would you say that cutting steel would be out of the question?
Thank again!!
I doubt you will be cutting steel.
If you want to cut steel you need a very rigid machine, and slower spindle speeds than a router does.
You are welcome to try, I would get a carbide bit, TiAlN coated, and the shortest length you can find. 0.001" depth of cut. Lowest RPM your spindle will go.
Depends on what you are cutting when you say steel. If you are talking light gauge sheet, or a very small bit at high rpm, might do fine. If you are talking about cutting large blocks, not much hope with that configuration. Basically, you are mounting your spindle on a spring. It doesn’t make for much rigidity. You would do better to reverse the z-axis and have the supported rails on the spindle side.
There will be deflection. You don’t say what in the way of steel or aluminium you want to cut - 1mm, 3mm, 10mm, 50mm?
The simple answer is yes, of course you can. That Kress will eat up 3mm and 5mm plate, but it’s going to be inaccurate to probably half a mm or more, given the lack of rigidity.
So, it depends on what you are cutting and why.
If it’s for art projects with large tolerances, go for it.
Can you be a bit detailed? I will be glad if I can help@ calldipankar@gmail.com
Thanks @Alan_M the aim was to build the bits I need for the steel version of it with this one. The accuracy of the steel version won’t depend on the accuracy of this one, its just to make my life easier as there’s a lot of 5mm steel plate to cut.
@David_Kirtley thanks for the help! I have the support rails reversed on the steel version I’m building, but wonder if like you say it would be better to swap them round. Part of the reason why I did this, is so that the stepper motor only has the linear blocks rather than the rails to lift. But for rigidity I think like you said its well worth changing!
@Mike_Thornbury really helpful information!! I will soon have access to a milling machine and lathe at work, so I just need something to do 98% of the heavy work rather than an angle grinder!
I think your best bet would be using the machine to layout cut lines, and bring the steel to someone to cut. Your wood machine would have to take around 100 passes each time around for that 5mm plate, if will even cut steel acceptably. If your bit is moving (by way of your entire machine deflecting) more than the chipload thickness, the bit will bounce off and on the material causing bad chatter, and chipped cutter teeth. This will get expensive real fast using the proper TiAlN coated carbide endmills.
You will have worse luck with regular carbide at high rpms, and HSS will burn up very fast.
You will have much better luck with aluminum, though It is going to take forever to cut and you may not be happy with the finish.
A router is barely adequate to cut metal, and if it is a wood framed router, the chance is close to 0.
Here is a wood framed machine that was able to cut steel if you want to look. http://www.cnczone.com/forums/cnc-wood-router-project-log/135232-cnc-software-forum-posts-post1237569.html#post1237569
Please prove me wrong, if you succeed post pictures. I would love to try steel on my router, but haven’t got the courage, or the bits yet.
Getting enough wood by itself into that small of an area to support the spindle is not really feasible. Your best bet would be to move to something like a piece of square metal tubing for the z-axis. A composite structure with vibration dampening infill would be even better.
Good explanation @Alan_M
Thanks @Alan_M do the great information, Especially the link! I’m looking forward to trying this all the more! More than pleased to be the Ginny pig on this one!!
@David_Kirtley brillant idea I will have a look for what I have lying around, I do have some 25mm plate aluminum which might be big enough!! Talking of dampening I’ve heard of a technique of epoxying sand, to increase a milling machines weight and I presume vibration dampening too. Has anyone tried it?
Cant wait to move forward on this thanks everyone for the help!
@David_Kirtley how’s you wood milling machine coming on is it nearly finished? Would love to see how its going!
All my projects have been on hold due to work and the stupid flu season that has had me dragging.
I will probably take the rails back from that one and start the build I was originally planning for them. Plywood/fiberglass box structures filled with fiber reinforced concrete. I had been waiting on some anchors and some other things that had been on backorder.
@Sam_De_La_Haye this may be helpful: http://blog.cnccookbook.com/2012/03/27/10-tips-for-cnc-router-aluminum-cutting-success/
@Mike_Thornbury wow!! Unbelievably helpful article! Very usefull indeed!
