Mini Engraver

shortbus

Joined Sep 30, 2009
10,045
My thoughts exactly.

I'm having a hard time running the tacho, with a PIC16F628 and 20x2 LCD.
I thinks the LCD command set is giving me problem, and may be the 4Mhz Xtal.
Circuit uses a 2 pin one, what I have is 3 pin one.
So I think I will enable the internal oscillator.
question is will it hinder the RPM accuracy reading? :confused:
Hi R!!f@, again you are confusing me(easy to do) Why the tachometer? The PC will tell the steppers how fast to turn. The hi-low step out put from the PC (using the CAM software) will control the movement of the motors.

Different commands from the CAM software tell the machine how fast to move for different tasks that its doing. And you do that in the CAM program.

I know you are really eager to get started on this, but, and this is not meant as a put down, Your running before you can crawl. The motors should be the first thing you get, then you can figure out the drivers and power supply you need.

If your in the same boat as me you don't have a lot of extra money to waste.:rolleyes: Buying/building something now that won't work for the final machine is discouraging and uses finances that could be put into what will work:D.

Again not a put down just a different way to look at things, cary
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
I know. It's just that I like to have a working tacho. U know.
It's kinda my thing..I donno..how to explain.
After making the drivers I like to measure the RPM with the torque
Still fighting over the circuit board, this stupid F628 does not have an internal osc, or does it? :confused:
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
Got the oscillator working. problem was in the software. I was using willem pro eprom,
I donno why this happens. the F88 programed just fine but the F628 gives a different eprom dump, when checked.
So next I tried IC prog and now it works up to some extent.
I can see the LCD initialization, but the counter is not working.
just displays 00000 :mad:.
This is driving me nuts
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
Building the frame from wood is bad idea. For long term usage at least.
And doing SS or aluminum is hard and very expensive. It's more hard, the cutting, filling and grinding, since I do not have a machine shop now, it is almost impossible.
I am willing to spend together use everything that I have, what good is making if you are buying everything, better to buy a complete machine. Right?
In other words, spend as little as possible.

This situation got me thinking. I have cousin who has lazer cutter, a big one, only one this country has, my only problem was he cannot cut copper, not even the layer of the clad, so it also can't drill fiber clad boards, pretty useless to me that machine is right now.
So I cam up a brilliant idea, why not use 6mm Plastic to do the frame work. clear, white, black or whatever. Cutting is precise, finishing is perfect. it can cut virtually any way. It's strong and rigid. It will suite very well for small bed. am I right?
Why not the gears two, if teflon could be used why not plastic, it will be quieter, and I can always get a new one cheap if a gear breaks.
What do you think guys. should I go for it.

Oh! by the way, what is the best program to do the drawing and measuring stuff, u know like before building anything you can draw it and look at at with the proper measurements and stuff.
I think I have to learn how to use another program.
 

jpanhalt

Joined Jan 18, 2008
11,087
@gears, screws, nuts, etc.
These are very difficult to machine to sufficient accuracy, if you do not have the proper tools. Gears are particularly hard to make. Plastic parts, particularly for the gears, are quite practical and relatively inexpensive. You may also consider belt drives instead of gears. Notice all of the belt drives in a typical printer.

@frame, bed, etc.(structural members)
Plastic is an alternative; however, it is not free of the effects of moisture (depending on which plastic you use) and it is "plastic," as in not rigid. Many grades of aluminum are easily machined with wood working tools having carbide cutting edges. The reason carbide is needed is mostly because the cutting speeds of wood working tools are high, and cooling is difficult. I have seen 2" blocks of 2024T3 cut dry on a table saw with a carbide blade. You might consider 6061 or 6063 aluminum alloys. Some specialized alloys (e.g., mic8) are available pre-machined for your flat plate. If I had the choice of using unmodified wood working tools for a machinable aluminum alloy or a hard plastic (e.g., acrylic), I would pick the aluminum as easier to do. PVC and similar plastics are easy to machine, but are not very strong. Delrin (acetal) is easy to machine, self-lubricating, and relatively strong, but it is also expensive.

Bottom line, I would not discard wood as a material. For a first, proof-of-concept device, I would use wood and engineered wood products for the frame and structural members.

John
 

BMorse

Joined Sep 26, 2009
2,675
For one, there are no gears in the CNC, the stepper motors are directly coupled to the screw drive shaft. If I were you I would use aluminum angle, it is easy to cut by hand using a hacksaw, and you could use wood for the base and for the worktable (wooden work tables are better than metal ones in my opinion, if your tool ever makes contact with it, atleast your tool wont break) and also as Jpanhalt said, aluminum can be cut with carbide tipped wood cutting saw blades... I cut the 2 main aluminum plate risers and the rest of the aluminum plates for my machine with a cheap "toolshop" brand miter saw...


The only thing I did for my machine that you may not be able to do is the welding of the bearing guide rods onto the angle iron.... but the guides can be easily made from aluminum angle....

B. Morse
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
Aluminum angle types are limited here, I don't have much to chose from.
I am really stuck at this point, trying to figure out what to use depending on my current situation. But the problem is these days are the days that I have plenty of time to do this kind of a project.
You say that 6mm plastic is not rigid, but I have seen these acrylic plastic sheets, they are really strong and if I use aluminum angle with it I think it will make a solid frame. With bolts and nuts every where it won't be bad. I think I will try this method first, but before that I am finalizing the motors and drivers.
I'll post the specs as soon as it's done.
 

jpanhalt

Joined Jan 18, 2008
11,087
@R!f@@,

You indicated that you are relatively inexperienced in the mechanical end of things. In the US, if I could not get aluminum, I would use a hard wood, like birch or maple, for the gantry and other "stick" parts. Oak is strong and a good alternative, but will dull carbide faster than birch will. Poplar will also work. I have no idea what woods you can get. Mahogany and bamboo may also be good.

My comment about modified cutters should not be ignored, if you are working with acrylic and polycarbonate. Acrylic and polycarbonate will melt and grab the cutter or make it hog in and break the piece. There are ways around that, but if you use such plastics, be sure to practice first. Be extremely careful, if you try to hand hold a piece of plastic and drill it with anything larger than a 3mm wood bit (unmodified) or so.

John
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
@ Alberto,
I think that is about the size of the machine I had in mind, may be slightly bigger.
You have 15mm plastic, jeeeez, I never seen such thick plastics here.

@jpanhalt,
I bet I can built mechanical stuffs, it's that I do not have a work shop right now to do stuff without disturbing others and without spending on labor work.
When you said drilling plastic, I donno what you mean, my aim of the machine is mainly to drill PCB holes and may be cut copper layers like a circuit and to engrave initials on PCB. Doing plastic's is not for me, since I have access to lazer cutter and engraver. I may use a mini circular saw blade to split open battery packs and adapters that are glued together, this way I can open and close it back without leaving as much as scratch mark.
I have opened glue packs with hand, but this way they are few cut marks visible.
I know this type of cutting is a bit different but I think I can find a way to move the drill around once I got the initial setup working properly.
I have had bad experience drilling metal and thick plastics holding by hand, thank got that my hands are still OK. I want to drill straight holes in heat sinks without snapping the drill bit, but this is a heavy duty job, I will find a way to incorporate this work into this machine one way or the other.
Like I said as before, I need first a working prototype to begin with.
Modifications can be done later.

The main purpose to check the torque of the motors I have is to see whether I can have a multiple purpose drill, for drilling at low as well as high RPM, with proper torque.
Once I got the specs I know you guys can point out if they are any good, then after that I will buy or try to get another that do the job. If the drill is heavy then I will make the x axis ( am I saying this right, the axis which the drill moves, up or down )
frame stronger and get a stepper that can do the job without a hassle.

This is the whole idea.
What do you think?
 

BMorse

Joined Sep 26, 2009
2,675

BMorse

Joined Sep 26, 2009
2,675
The main purpose to check the torque of the motors I have is to see whether I can have a multiple purpose drill, for drilling at low as well as high RPM, with proper torque.
Once I got the specs I know you guys can point out if they are any good, then after that I will buy or try to get another that do the job. If the drill is heavy then I will make the x axis ( am I saying this right, the axis which the drill moves, up or down )
frame stronger and get a stepper that can do the job without a hassle.

This is the whole idea.
What do you think?

The drill motor will be on the Z axis, which moves up or down..... X moves left to right, Y moves away from you and towards you...

Steppers are not good for drill motors, you want high speed, high torque motors, like a variable speed up to 30,000 RPM dremmel, so a drill motor is not the main thing you need to worry about, it is the drive motors for the axis's..... again, I think you are over thinking the whole process and getting way ahead of your self..... need to slow down and get the sequence of processes inline...


  1. You need stepper motors, preferably at least a NEMA 23 size ones, and all 3 should be identical in size and ratings (Makes it easier to duplicate one controller for all three)
  2. Once you have the motors, it is on to the controllers and power supply.... (This way you can test the motors on the bench to make any adjustments to the drive circuit if necessary...)
  3. Then once you have step 1 and 2 done, it is on to the mechanics.... Start with the X axis, since usually this will also support the Y and Z axis weight, then build the Y axis and test that along with the X, then do the Z axis..... And you can build the frame out of anything you want, remember this is your machine and you will be the one using it. You can use aluminum angle along with some MDF wood, as long as it is sturdy and rigid....

B. Morse
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
What would I do without you guys:).
The plans shortbus showed seems good, too bad I can't buy em.

OK Bmorse, time for me to get a better drill. Wait till I show you what I found lately, I am not home right now, once back I will post a pic of that baby. ;)
 

BMorse

Joined Sep 26, 2009
2,675
The dremmel you have on post #1 of this thread is more than suitable for light jobs, you have to remember that it is not necessarily the speed and torque of the motor that is critical but also the ability of the bit you are using to remove material when cutting.

Here is what Wikipedia says:
Chip formation

Although there are many different types of milling cutter, understanding chip formation is fundamental to the use of any of them. As the milling cutter rotates, the material to be cut is fed into it, and each tooth of the cutter cuts away small chip of material. Achieving the correct size of chip is of critical importance. The size of this chip depends on several variables.

  • Surface cutting speed (Vc): This is the speed at which each tooth cuts through the material as the tool spins. This is measured either in metres per minute in metric countries, or surface feet per minute (SFM) in America. Typical values for cutting speed are 10m/min to 60m/min for some steels, and 100m/min and 600m/min for aluminum. This should not be confused with the feed rate.
  • Spindle speed (S): This is the rotation speed of the tool, and is measured in revolutions per minute (rpm). Typical values are from hundreds of rpm, up to tens of thousands of rpm.
  • Diameter of the tool (D):
  • Feed per tooth (Fz): This is the distance the material is fed into the cutter as each tooth rotates. This value is the size of the deepest cut the tooth will make.
  • Feed rate (F): This is the speed at which the material is fed into the cutter. Typical values are from 20mm/min to 5000mm/min.
  • Depth of cut: This is how deep the tool is under the surface of the material being cut (not shown on the diagram). This will be the height of the chip produced. Typically, the depth of cut will be less than or equal to the diameter of the cutting tool.
The machinist needs three values: S, F and Depth when deciding how to cut a new material with a new tool. However, he will probably be given values of Vc and Fz from the tool manufacturer. S and F can be calculated from them:
Spindle Speed Feed rate
Looking at the formula for the spindle speed, S, it can be seen that larger tools require lower spindle speeds, while small tools may be able to go at high speeds. The formula for the feed rate, F shows that increasing S or z gives a higher feed rate. Therefore, machinists may choose a tool with the highest number of teeth that can still cope with the swarf load.
So with the conventional bits I use with the dremmel, it is possible to do all that you want with just a dremmel tool.... like this bit I use for milling PCB's and engraving signs...


and I also use these types of bits which have the right shaft size to fit a dremmel standard collet for some milling, but mostly for drilling PCB's. I can also use standard high speed steel drill bits....


Here are some of the things I have done with mine, the only thing I have not done is mill metals with it (Which it is fully capable at slower feed rates) but I just don't have any coolant reservoir or pump to cool the bit while cutting...






so you have a perfectly capable drill motor right now, what you want to acquire is the flexible shaft attachment to make it easier to mount onto the Z axis...

B. Morse
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,918
The first picture is a tool bit I have never seen, mind telling me where to get those, as for the second bit set, I bought one set from ebay last year, you'll laugh to know that none of them last a minute in my hand :D.
I was checking stuff from ebay to cut plastics and stuff and also to scrape oxides off PCB when I came across them.
I found out the hard way that these bits should be mounted on a stable drill and feed rate should be stable. I used by hand and one by one snapped. :p.

I guess I'll buy a couple of sets for this machine.

You know something, the dremmel I use is too noisy, that is why I am having second thoughts on it, I like to use a quieter spindle motor.
May be I can use the flex shaft coupled with a low noise motor. Of course the motor will have a high rpm. This way the Z axis will be lighter, and I will get the benefits of a powerful spindle too. Does the shaft has any limitation, I mean the speed at which the shaft should rotate, high speed can cause it to heat up in long spin duration. I am thinking of all these situation is that I have to get all these from abroad, and the stuff here are expensive yet cheap made Chinese stuff. If one item were to get damaged due poor choice I will end up with more than a month of no service from the machine.
Would it suffice If I can get a DC motor with higher RPM?
When would the drill motor torque comes in to play, say is when drilling or using a miniature saw blade or when milling. I am not going to use to do any metal parts with this, At least I don't have any intention yet. But I want this machine to be used to mill small gears from Teflon.
I know this is separate thing to do with my current configuration, but I am hoping to implement this in a later stage once I get the hang of this machine working. I think all I need it to add another motor horizontally as in a Lath machine, but of course then I will sometimes need a stable mount for the cutting bit. Don't worry these are all ideas for now, first is to just doing plastics and PCB's :D.

I will check for nema steppers and see what I can afford for now. Of course I'll show you before I make a choice.
 

BMorse

Joined Sep 26, 2009
2,675
I fixed the Dremel directly to the Z axis without any problem and it works fine.

Alberto

Yes, I know it will work fine, plenty of people on the net doing that, but in R!f@@'s case, he is limited to the material he has and a couple of u bolts will suffice to attach the flex shaft to his machine...... I have attached a Rotozip tool to mine and it works just fine, (which by the way is bigger and heavier than a dremmel.)

B. Morse
 

BMorse

Joined Sep 26, 2009
2,675
@ R!f@@:
I purchased that milling/Engraving bit from a local machine tool shop (Production Tool Supply).... you might be able to find them on ebay or online somewhere.....

As for the dremmel being noisy, I have not seen a "quiet" CNC yet! Noise is the last thing you should worry about, any high speed spindle will make noise especially at higher RPM's and while cutting..... some people even have a shop vacuum running at the same time (some use the vacuum pressure to hold the work piece onto the work table...)

As for the the flex shaft, I have continuously ran the flex shaft for hours at a time, and I never had any issues with it over heating in any way due to friction, every once in a while I do oil it with some WD-40 lube just to make sure it does not wear out prematurely...... Preventative maintenance is a must with these machines.... you should check all motor set screws, and any thing else that could loosen up from vibration at least once every 10 to 15 hours of use.....

B. Morse
 

BMorse

Joined Sep 26, 2009
2,675
So how is the project going R!f@@?? Any progress on the motors? Just curios.... I am currently working on a new machine (not CNC though, atleast not yet) I had a gentleman contact me from Missouri that wanted me to build him a custom machine... This ought to be interesting I will post some pics of the hardware and give more details later.... right now I can not disclose anything else until the machine is complete.....

But here is a glimpse of some of the parts I have machined and built for the machine so far:

Current Phase 03_12_2010.jpg

Drive Spindle for Workpiece.jpg

Master Drive Assembly 1.jpg

Support Spindle for workpiece 2.jpg

B. Morse
 

BMorse

Joined Sep 26, 2009
2,675
So, BMorse, What is it like to not sleep? EVER?

I figure I will get enough rest when I pass away :rolleyes:.... right now life is too short to be taking naps!!;) With all the projects I do for myself and others I barely have enough time to sleep, if I did sleep l wouldn't be able to post on here:D...


B. Morse
 
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