Aluminium CNC build (TEP mill converted) by Craynerd

[raynerd]

I`ve been wanting a little CNC machine for the last couple of years, not specifically for anything, just to learn more about it really. I feel I`m doing well with my manual machines and want to keep machining that way. I`m learning all the time and this cnc build is just to help me learn the basics of cnc, not to take over my manual work (slightly irrelevent, as this machine won`t be up to it anyway!). I just don`t dare start from scratch and anything more complete is too expensive, as is buying a bench mill and converting. So this is a cnc build based on confidence and available funds.

I started with a TEP cnc mill. One went on ebay a while ago for about 200 and just the other day another went for £350!! I can assure you I paid only a fraction of that price for mine. These are a sturdy machine and quite well made...just a dreadful design and dreadful software which is locked onto the driver hardware!!

I was lucky enough to get hold of the original TEP software (isn`t available from anywhere!!) and it was dreadful. Imagine MSWindows Paint, no numberical input (so no saying I want a 20mm line, 10mm from the origin!!, just simple drag and click stuff!!) Then from that, tell the machine to move.

Here is the machine from purchased:





Very very bizzare design and many machine limitations:
Cons:
In my opinion the x axis should be mounted so the slides are vertical parallel, not horizontal.
No z axis, it is just a solanoid motor to raise and lower the spindle to a fixed level.
All hardware is locked so commands can only be sent from the PC interfaced by the TEP software - it won`t talk to Mach or EMC
Stepper motors are only about 50Ncm
Both axis are fixed off centre to allow space at the back for the electronics
Only 12v 5A supply.

Pros:
I had a working CNC machine as a basis
If all else failed, I strip it down and the ally bar/plate is worth more than the price I`d payed for the machine !

In truth, there is little going for this other than having a solid working basis to start from.





 

[raynerd]

First job was to strip the electronics completely from it. I will be using a TB6560 3 axis driver. I`ve heard nothing but BAD things about these, but I have one anyway and it`ll certainly get me going if I can avoid blowing it up.

I wanted to flip the X axis and although replacing the entire side piece would have been ideal, I couldn`t afford it and had some pieces suitable in stock. I raised the sides and used a plate to join them. It may need some supports bridging the sides later on.

After flipping the X, I could then mount a Z axis. I made the Z axis from a small leadscrew someone kindly gave me and the slides are olite 8mm ID bushes on 8mm silver steel rod slides. The rest is just plate bolted together. There is a problem in that I`ve used a flexible coupling but I haven`t "trapped" the leadscrew. This means that the Z axis compresses on the flexible coupling and moves the relative position of the axis - not good!! This is easy to correct but I haven`t done it yet.

Once i had the X flipped and raised and the Z built, I couldn`t help try it out... it is running of only 12v at the time and the noise from these small motors is horrific, I think the TB6560 is also to blame but since then I`ve jumped upto 24v and the noise is quieter.

At this point, the mill went back to its owner while we negotiated price. Other than electronics that we both agreed wouldn`t be needed, it was all replaced to original, thankfully, if he had seen the work I`d put into it I expect the price would have gone up!

Further updates to come: Now running on 24v from two ATX supplies in series, spindle connected, first door sign engraving done...all good fun! Issues: still not sorted the z axis flexible coupling issue. Is the Z axis height too big. Flex is the spindle.

[raynerd]

First door Sign. Actually, that is a lie, I did one for my daughter that didn`t work out quite as well and I stalled the spindle whilest pocketing it out. This was my second attempt for my niece, with a slower feed during the pocketing.



I have an issue somewhere but I`ve noticed that when the spindle is turned on, the spindle drops a significant fraction of a mm! The sign is too deep as areas that should be a thinner line are deeper than desired.  I was pleased with my first results.

Chris

[HS93]

that may be due to you energising the coils the magnets are pulled in to line moving the bell with them in down and the spindle with it. you need to find a way of getting rid of the end float, did you put a collapsible washer on the spindle ? you should not need it with the thrust bearing.

peter

[raynerd]

Pete, thanks for that tip, you were right and I never posted a reply to say so...sorry! I removed the end float by applying pressure to the main shaft while locking down the bell and it got rid the float.

An update and advice if anyone has any!...

During the last week I`ve stripped the machine to do some mods and in the last few days got it back together. However, I just can`t get my head around the fact that the movement is well out of sync! Just a simple example, say I draw two ovals concentric to one another, they will end up overlapping and even with little flats on them instead of nice curves!

The wierd thing is, I get the same results on both Mach3 and EMC2... so either I`ve got a setting wrong in the software on both or something is wrong with the TB6560 driver?

I`m sure it was working OK just last week and so after nearly a full day trying to correct it today, any thoughts or suggestions would be helpful...I`m totally out of ideas!

Chris

[Brass_Machine]

Hi Chris...

I am going to go out on a limb and suggest it is the TB6560. I had one for my CNC... That just isn't a good board. I even supposedly had one of the "good" ones. I had problem after problem. Some left me scratching my head... kinda like what is going one with you. I bit the bullet and got a C10 breakout board with some real drivers. what a world of difference! I hear even more so with some of the more expensive stuff like the geckos.

Eric

[raynerd]

Eric, I think you are very much right here in that the TB6560 is terrible.

I have another question and this might be stupid but what would something like this BOB -

give me over this LPT quick connect: http://www.routoutcnc.com/lptcon.html     

I have 3 x m452 drivers that I could borrow from other things in my workshop and I also have the LPT quick connect above. I have a 24v supply and also a 5 v supply. I believe the m452 like Arc Euro sell are opto-isolated inside the driver themselfs... so actually what is a BOB giving me extra other than perhaps a pull up resistor for inputs and maybe a relay for the spindle. Could I actually get my three drivers going with the LPT quick connect ??

Can anyone see any problems with this..... sorry if this is a dumb question. I`m just struggling to see what a BOB actually does for £50, above what my quick connect does (I have the quick connect for a project I attempted about 3 years ago and it is sat on a shelf doing nothing).

Chris

[Rob.Wilson]

Hi Chris

I am using this BOB ,,,,,,,,,,, only a few quid more http://www.zappautomation.co.uk/zp5aint-p-499.html?cPath=143 ,,,,,,, you get a true High /Low signal on the PP pins and a few other things  ,,,,,, fink thats right 

  http://www.ebay.co.uk/itm/CNC-5-Axis-Breakout-interface-Board-for-Stepper-Motor-Driver-Mill-/260948751632?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item3cc1c1f510#ht_2763wt_1110    a few quid cheaper


Rob

[raynerd]

Hi Rob, thanks for the link. I`ll make a decision tonight and get one ordered!

Another question for you cncer`s!

I`m questioning my wiring of my stepper motors: http://www.sanyo-denki.com/Data/Servo/catalogs/F2.pdf  page 53 of PDF pages but p52 at the bottom of the document page under bipolar winding. The colours represent my colours red, orange, blue and yellow. In terms of colours and A-, A+, B-, B+ - how would you guys be wiring it?

Chris

[David Jupp]

I would arbitrarily assign one coil to be A, say Orange and Blue wires - the other coil must therefore be B.
I don't thik it actually matters too much what you do after that (though good to be consistent across all drives).  I would take say the first row from the excitation order table and assign +/- based on that -> Orange A+, Blue A-, Yellow B +, Red B-.

If direction of rotaion is wrong, either change the sense of your direction control output, or swap the +/- connection on one phase only.

[raynerd]

Ok, this one is driving me bonkers and I know we have quite a few cut2d and vcarve users in here so maybe someone can help.

For the past 3 hours I`ve been trying to produce the code to cut a clock wheel:

http://www.raynerd.co.uk/images/wheel1.pdf

Nice big wheel, 2.5mm or there abouts gap between the teeth which is good because my smallest endmill is 1.95mm which I`ve selected along with a profile toolpath cutting "outside/right". However,  I keep getting an undercut on the tooth tips! Here is a picture of the preview:



Is it trying to get right into the corner of the root of the tooth and therefore the radius of the cutter is causing the undercut? If so, is there anything I can do to stop this. I know for a fact that a lot of people are using cut2d to cut wheel but none of them describe the settings they are using. Also, is there a better tool than an small endmill to be using to cut this out...I presume there must be a narrower option for smaller wheels i.e smaller gaps.

Very sorry if there is an obvious answer or way to correct this! Any help appreciated!

Chris

[philf]

Ok, this one is driving me bonkers and I know we have quite a few cut2d and vcarve users in here so maybe someone can help.

For the past 3 hours I`ve been trying to produce the code to cut a clock wheel:

http://www.raynerd.co.uk/images/wheel1.pdf

Nice big wheel, 2.5mm or there abouts gap between the teeth which is good because my smallest endmill is 1.95mm which I`ve selected along with a profile toolpath cutting "outside/right". However,  I keep getting an undercut on the tooth tips! Here is a picture of the preview:

Is it trying to get right into the corner of the root of the tooth and therefore the radius of the cutter is causing the undercut? If so, is there anything I can do to stop this. I know for a fact that a lot of people are using cut2d to cut wheel but none of them describe the settings they are using. Also, is there a better tool than an small endmill to be using to cut this out...I presume there must be a narrower option for smaller wheels i.e smaller gaps.

Very sorry if there is an obvious answer or way to correct this! Any help appreciated!

Chris

Chris,

I took your PDF and opened it in Cut2d. I used a 2mm cutter and it looked fine:



Did you join all the vectors? I did. If you selected individual lines then that may be your problem.

Cheers.

Phil.

[raynerd]

  ooops, that could be the issue.

What do you mean by join them, how do you join them? Your right, the wheel is made up of all individual small vectors. I`ve tried selecting them but don`t seem to have any option of joining them.

[John Stevenson]

Go edit show open vectors and you will see dotted lines, then go edit > Join open vectors and it tells you how many are left after the operation, should be 0.

[raynerd]

  Wish I would have read about that earlier, that explains a few strange behaviours I`ve been seeing in the gcode!

Thank you both - preview shows it is OK now and I will try cutting later today.

Chris

[John Stevenson]

To me that part of the program is worth more than the program itself.

I get loads of drawings in via DXF for laser cutting and I bring them into Cut2D, join all the vectors and export as a decent DXF, then send to the laser cutters or process in another program to go on the CNC.

It's fantastic how well things cut when you get a clean drawing.

[raynerd]

Well thanks for the advice last night - I swiped a piece of scrap hardwood from the wood yard before it closed at lunch and had a go at cutting - worked first time!

Sorry a little out of focus!

[philf]

Well thanks for the advice last night - I swiped a piece of scrap hardwood from the wood yard before it closed at lunch and had a go at cutting - worked first time!

Sorry a little out of focus!

Very nice Chris. 

How long did it take?

Phil.

[raynerd]

It took a good 20-25 minutes plunging at 2mm depths each pass, so with 7.5mm material, it took 4 passes to cut through. I was holding back on the feed speeds as my motor has stalled on me a few times, but this was before I modified the axis and was having flex on the spindle. I expect I could nearly knock 25% of that time off if I pushed the feed up.

Just a question regarding feeds and depth of cuts - I know it is very dependent on the machine, but what sort of depths of cuts would you be attempting if i wanted to attempt cutting brass on this? Do you think I could even give steel a bash or is it not worth even attempting? It is small, but pretty damn sturdy now I`ve supported that extra rail with the linear bearing.
- so I`ve been using 2mm plunges in wood with a feed of 12mm/sec. In terms of my machine, from what you can see in the vids and pics...what would you turn this down to for steel and brass with the same 1.95mm end mill. I feel that the depth of cut is in some ways more important than the feed speed - especially with my motor stalling if pushed too far.

[Swarfing]

Chris as an estimate ignoring feed and speeds you should be able to get half the diameter of the cutter in depth of cut. But a lot depends on the spindle speed, coolant and more etc.

[philf]

Chris,

Have you any idea what spindle speed you're running at?

How many flutes on the cutter and is it carbide or hss?

As you say, it depends very much on the rigidity of your machine and some trial and error is necessary.

I've emailed you a simple feeds/speeds calculator which may help.

Cheers.

Phil.

[mattinker]

To me that part of the program is worth more than the program itself.

I get loads of drawings in via DXF for laser cutting and I bring them into Cut2D, join all the vectors and export as a decent DXF, then send to the laser cutters or process in another program to go on the CNC.

It's fantastic how well things cut when you get a clean drawing.

Cut2D also runs under Wine in Linux. I just tried it!

Regards, Matthew

[John Stevenson]

Cut2D also runs under Wine in Linux. I just tried it!

Regards, Matthew

Wash your mouth out and we'll forget you wrote that. 

[mattinker]

Cut2D also runs under Wine in Linux. I just tried it!

Regards, Matthew

Wash your mouth out and we'll forget you wrote that. 

Ubuntu!
Ubuntu!
Ubuntu!
Ubuntu!
Ubuntu! Ne ne ni ne ne   

[Swarfing]

There is now a linux version of cambam.

ubuntu
ubuntu
ubuntu