Author Topic: Building Tom's "Easy Mill"  (Read 29015 times)

Davetech

  • New Member
  • *
  • Posts: 47
    • View Profile
    • Davetech's Projects
Re: Building Tom's "Easy Mill"
« Reply #15 on: July 30, 2009, 02:39:16 PM »
Received the thicker copper clad boards today.  Loaded up my control board .dxf, single stepped it up to the first lowering of the z-axis and precision-adjusted the height and turned it loose. It made a mess.

There's just not enough room between ic pads to isolation mill with a .036" tool.  I thought slop was my problem, but I've got the slop under control and it still left hardly any or no copper between cuts.

I started searching YouTube comments to try to find mention of exactly what tools others were using in their videos of them making pcb's. One guy said his tool was .2mm!  Egad! That's tiny!  I had asked the fellow on eBay that sold me these .036's if he had anything smaller and he said "I have some 1/32" (.0312"). That's the smallest router made. To mill smaller than that you will need micro-miniature end mills, which are usually not available as used tools and are quite expensive as new tools."

Then I did a search on eBay for "cnc bit pcb" and I think I've found the answer to my problem. The type of tool I was trying to use was wrong.  These I've got are called "Carbide MicroMiniature Fluted Routers" but that search turned up tools I have never seen called "PCB Engraving Bits".  They are "V" shaped bits, ending in a point, and come in different "degrees", which I assume refers to the angle of the "V".  I saw one that said it was .2mm. I don't know what part of the "V" was .2mm but I'm sure it makes sense to people who know what they are talking about, unlike myself.

So here's another subject where a faq would have been nice. would have saved me a lot of time, aggravation, and money if I had known from the start what tool to use. I have read a ton of cnc related posts but had never run across the answer to that question. 

So, here goes another $20 for what I hope are going to be the correct bits to use for isolation milling of pcb's. They have to come from Hong Kong (the ones I found, anyway) so that's a two to three week wait.  :-\




Davetech

  • New Member
  • *
  • Posts: 47
    • View Profile
    • Davetech's Projects
Re: Building Tom's "Easy Mill"
« Reply #16 on: August 02, 2009, 12:47:41 PM »


I occurred to me that I have not posted a picture of what I replaced the marbles/rails with.  Here's a picture of the present whole setup.




I haven't finished the power supply I'm building so the old AT psu is still supplying the 5 volts for the driver board but the motors are supplied by my bench supply via the red and black wire pair coming from the other side of the room.

You can see I relocated the Y axis motor. Did that a long time ago. The rails are a lot longer than my first ones. Gives me a lot more work area. I didn't have enough steel conduit to make the Y rails but I had some 1/2" rigid copper pipe. It is working just as well. The channel steel slides easily over either of them. The steel strap the Y motor was mounted on was flexing so I gorilla glued three straps together. It still bends a tiny amount but I was able to tune that backlash out with the software.

With the Y motor hanging way out there, it has a lot of leverage and if the y stage was run out close to the motor, the whole mess would try to tip forward. There's nothing holding the stages down on their rails but gravity. The X stage would tip sideways. I went out to my ammo reloading shack, got my lead furnace and made a 6 pound anchor that sits on the x stage platform. You can't see it in the picture because it is under the y stage.

I need to install some dust control because eveything in the computer room is getting coated.




Close up of the steel and copper rails. The spacers are to make up some of the height lost when the marbles were removed. Otherwise my Y lead screw would have been at an angle unless I completely redesigned the motor mount.


The power supply I'm building will have an ac supply for the RotoZip too. I'm building in a 600 watt light dimmer that will control the spindle speed.




Davetech

  • New Member
  • *
  • Posts: 47
    • View Profile
    • Davetech's Projects
Re: Building Tom's "Easy Mill"
« Reply #17 on: August 08, 2009, 10:47:34 AM »
-

Still awaiting arrival of the engraving bits. ETA - Aug 23.  Dang! 

---------------------------------------------------------------------------------------

Got the mill power supply mostly built... and changed course again!

I decided I really wanted a variable voltage supply. I remembered an old power supply I had picked up at some hamfest back in the 70's that has been sitting around gathering dust since.  It was a bench supply meant to be used while servicing tube-type equipment. It had outputs for a 6.3 volt ac filament voltage, and a plate voltage output that was variable from 0 to 300 volts dc at 100 milliamps max. 

Well, that was of no use to me... my tube days are long gone and 100 ma was not enough to run my stepper motors. But it would make a good basis upon which to build the supply I wanted.  I had never even opened the box up and was delighted to find inside a vintage, original General Radio Company Variac model 200 B in beautiful shape.




General perfected the Variac back in the 30's, got a patent on it in 1935 and copyrighted the Variac name. This was one of their early production models. It is hardly rare, but is a nice conversation piece among us electronics nerds and is very useful.

Anyway, I decided to gut the box and build in a modern, regulated, variable supply for the cnc mill, but I wanted to keep the external appearance vintage. So out came the old paper capacitors, the big selenium rectifiers, etc. I hated chopping all that up as it really was a handsomely built unit inside, very professionally done.  There was a single spdt switch on the front panel which would cause the D'Arsonval meter to read either output voltage or amperage.  I installed a stepdown power transformer after the Variac to provide isolation and to lower the voltage for the rectifier/regulator board I made with the mill. It has large traces and I was able to mill it with the bit I have.  With the Variac all the way up, the rectifier delivers 27 volts dc to the driver board.




The board just has a full-wave bridge rectifier, a smoothing capacitor, an LM7805 5 volt regulator for the driver board, and a glass 4 amp fuse. I kept the old wiring harness I chopped out and reused the wire. They made really nice wire back then.  The frosted, bayonet-mount power indicator bulb was replaced by a white led and current limiting resistor. To do this I took a bayonet-mount bulb and cracked and removed the glass with pliers, then soldered the led to the filament leads and gobbed a bit of gorilla glue to hold it in place. It shines out through the original, red plastic dome lens. I found a couple of terminal blocks in the junk box and put them to work on the board too.

I had to open up the meter and remove the internal shunt. It was only made to handle 100 ma and was as thin as thread. I gave the meter a good cleaning while it was apart and re-glued the glass to the meter face because it had turned loose over the years. I made an external shunt that calibrated the meter to use the top 0 to 500 volts scale to indicate amps; thus, 100 volts on the scale means 1 amp. Similarly, I calibrated the lower scale that used to be 0 to 100 ma to be 0 to 100 volts, so that the 25 mark means 25 volts.

On the left side of the picture, there used to be some wierd connector going through the case side. I removed it and was left with a 3/4" square hole. So I cut a piece of ABS plastic, mounted it on the inside and drilled it out to hold an bayonet ac fuse assembly that fuses the power cord as soon as it enters the box. The power cord was old and frayed. It was an electrocution / fire waiting to happen. It got replaced by the power cord from my microwave that died last fall.

The supply is now connected to the mill and is working flawlessly. But there was not room to install the light dimmer for the spindle speed control and it would have ruined the appearance anyway, so it will be in its own enclosure.

With that done, I'm building an enclosure for the linear actuator for the heliostat and while waiting for glue to dry I'm boring people by posting this stuff on the forum.

Don't miss the next exciting episode!



Gabriel

  • Administrator
  • Hero Member
  • *****
  • Posts: 651
    • View Profile
Re: Building Tom's "Easy Mill"
« Reply #18 on: August 09, 2009, 06:50:33 PM »
-

Still awaiting arrival of the engraving bits. ETA - Aug 23.  Dang! 


I know, waiting is terrible isn't it. I swear that my CNC would have been finished a month sooner if I didn't have to wait for the delivery truck. CNC machines need to be more popular so that you can just pick this stuff up at a local hardware store.

You said that you are using a light dimmer to control the spindle speed. That's something that I thought about trying myself but I decided not to because I had never heard of anyone else doing it. I didn't want to damage my router, even though I don't see how it could. How is it working out for you?

Davetech

  • New Member
  • *
  • Posts: 47
    • View Profile
    • Davetech's Projects
Re: Building Tom's "Easy Mill"
« Reply #19 on: August 25, 2009, 09:06:45 AM »
Well, actually I don't recommend using a dimmer to control anything that has its own speed control built in, like a Dremel or a RotoZip. My Dremel didn't like it at all. But my RotoZip had already developed a problem. I had not used it but a little when its speed control seemed to short out. It would only run at high speed and sliding the switch to the medium speed position didn't make any difference. So I went ahead and tried it with the dimmer, not caring if it burned out the speed control since it was shot anyway, and the motor worked okay.  The only problem was that at low speed the Rotozip had little torque. When you put a load on it, like grinding into something, it slowed the motor down easily. But at medium up to high speed it had enough torque to do work. I guess it might have its uses, but it is not a priority with me now.

Shortly after that, the RotoZip developed another problem. While I was milling some thin plywood, a scraping noise started up inside the motor and I started getting hit by tiny pieces of black plastic flying out of the cooling vents. When I took the motor apart, I found that the cooling fan had slipped down the armature shaft and was scraping on the case. A little Googling provided some answers.

I found that this was not an unusual problem with the early RotoZip models. As a matter of fact, I think it caused the RotoZip company a bit of pain and probably had something to do with the sale of the company to the Bosch Corporation, who now makes it known that they have redesigned the fan in all the newer models to prevent that problem.  I wrote to Bosch and asked them if they could recommend a fix and they basically said it was unfixable but they could offer me a replacement new model at a discount. I did; however, find a post that recommended using Loctite Bearing Cement to hold the fan in place on the shaft, but I have not gotten by an auto parts store to get some (I don't get out much).

In the meantime, my engraving bits have arrived from China. Yeaaa..!  And they are everything I had hoped they would be. I could go ahead and make the heliostat control board now... what this whole CNC journey has been about in the first place... but actually, now that I have built the controls on the picaxe prototype board, I'm more interested in concentrating on getting the heliostat working.  I'm finding that my ramp idea is not as easy to implement as it sounded. But I haven't given up on it.

@ Gabriel - BTW... I plugged your YouTube heliostat vid in the comments section of Dan Rojas' latest vid about parabolic reflector mounting with a magnet. Someone had asked if he was going to present how to make heliostat control for his mirrors or dishes and I couldn't resist. Dan wrote back "Good Video!"
 ;D

If you get any of these "V" shaped engraving bits... be careful!  They are damn sharp!  I was picking up a piece of work under the Dremel and my index finger touched the bit and it pricked me. Instinctively I jerked my hand back and that drove the bit deep into my finger! Bled like a stuck pig! So I'm nursing my finger today.



Gabriel

  • Administrator
  • Hero Member
  • *****
  • Posts: 651
    • View Profile
Re: Building Tom's "Easy Mill"
« Reply #20 on: August 25, 2009, 04:42:29 PM »
Thanks for the info!

I had one router that had the bearings go bad in it. The extra heat from the added friction actually caused the plastic on the inside of it to melt. Yikes!

Thanks also for yet another plug.  :) It's pretty cool that Dan actually commented back.


gocnc

  • Jr. Member
  • **
  • Posts: 64
    • View Profile
Re: Building Tom's "Easy Mill"
« Reply #21 on: September 29, 2009, 12:31:51 PM »
Thanks to this site we are able to better understand the concept of building such machines but still there are hurdles like finding the right parts.
the stepper motors can be found in e-bay but the other nuts and bolts are smal details that are posing problems .
still I am encouraged at the pase I am able to advance in cnc milling.
If there are web sites that sell parts like leadscrews and so on I would like to have them
Thanks.

travis77

  • Jr. Member
  • **
  • Posts: 75
    • View Profile
Re: Building Tom's "Easy Mill"
« Reply #22 on: September 29, 2009, 01:19:20 PM »
There are lots and lots of websites. This thread has a list: http://www.daddyhobby.com/forum/showthread.php?t=41674

Also other sites going through my bookmarks:
ACME Leadscrews: http://www.use-enco.com/CGI/INSRAR?PMSECT=0000000451

Parts: http://buildyourcnc.com/default.aspx

Parts: http://www.dumpstercnc.com/

More parts: http://cncrouterparts.com/index.php

Some more parts: http://www.mcmaster.com/

Electronics: http://www.kelinginc.net/index.html

If you still want more info, should read through stuff over on http://www.cnczone.com There's too much info on CNC stuff. Read though the DIY CNC routers forum.

GerardoMendez

  • Newbie
  • *
  • Posts: 1
    • View Profile
Re: Building Tom's "Easy Mill"
« Reply #23 on: August 13, 2013, 10:23:00 AM »
That RepRap page is a good pinout reference. 

>"To supply higher current, it is a good idea to connect several of the black wires together to provide ground and several of the yellow wires together to provide +12V. "

I didn't do that. Maybe that was my problem. I was using an old AT supply rated at 250 watts. Anyway, I have found that my motors work very well at 8 volts with no ballast lamps. The analog ammeter shows them drawing about 300 milliamps and they stay cool to the touch even after going through a long milling session. The heat sink on the driver card also only gets slightly warm and I have a cpu cooling fan keeping it company. So I'm just going to make a regulator board with a full wave bridge rectifier, LM7805 and LM7808 regulators, and fuses, switches, LED's, and any other bells and whistles I can think of. The LM7808 is rated at 1.5 amp so it should be able to supply the motors without a pass transistor. We will see.


Kudos on your first Instructable!  It looks great. It occured to me this morning as I sipped my morning coffee, that it simulates the way nutrients are delivered to plants by nature. When it rains, more than water is delivered to the roots. The water dissolves nutrients from the surface soil (where all the new dead stuff is) and carries them down to the roots. As we have seen time and time again, nature's way is always the best since the plants have evolved to work best in those conditions. Your "breath of fresh air" simulates a good rain. I haven't read any books on hydroponics, but your system seems to make good sense. 

My mill has undergone a lot of changes in the last few days. Mainly attempts to get more precision and eliminate backlash but also to increase the work area. The steel nuts on the lead screws are gone, replaced by plastic nuts made with your method. I used black 1/4" ABS plastic, sandwiching the lead screw so the "nut" is 1/2" thick.
 
The marbles are gone. I'm using galvanized steel electrical conduit as a rail for the channels to slide on. It seems to be working very well. I'll have pictures soon.

Right now I'm having the most trouble getting the platform perfectly level. I don't see what is causing it but the depth of the cut varies slightly on different areas of the platform and with thin pc board, cutting on both sides, there is no room for error. A cut on one side easily cuts through to a cut on the other side if there is the slightest variation. I need thicker pc board too.

hello Dave I know thread is bit and I am trying to get some changes in my Mill.. Can you share latest pics of your  Mill..