Messages

521

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: February 19, 2014, 06:47:39 PM »

Bernard,
If your machine still has dials or an index mark, then park it some place with the dials all at zero and call that home. When you power up move all axis to zero and hit the zero all button and you are ready to go.

522

General Mach Discussion / Re: holes .2mm undersized, backlash???

« on: February 19, 2014, 06:43:22 PM »

Tools bend. It could be just tool deflection.

523

General Mach Discussion / Re: Mach as a linear indexer help

« on: February 19, 2014, 06:40:30 PM »

Mach 3 is a very good program. However it may not be the best choice for this kind of simple task.  You will be running windows on a PC. Do you have any 15 year old PCs that have never been powered down except in a power failure?  I have several PLCs that have been running continuously for 18 years!  Because that is what PLCs are made to do.

So an Automation Direct DL06 as an example, with a high speed counter module and a micro graphics terminal will cost you about $700 and you can drive a stepper, a servo, a 1 HP DC motor using a $150 controller, or a 3 phase motor from a $150 VFD for this little project.  You'd have 20 inputs and 16 outputs for safety switches, limits, selector switches, etc. Ladder logic programming gives you if/then/else timers, counters and on an on.  You do want to count how many pieces of each length you cut right?

In fact my multi-purpose CNC has one in it, along with Mach 3. I have a selector switch for the high speed router spindle or the high torque R8 spindle.  There is another one for Mill/Lathe/3d printer, another for air blow off/none/coolant, and one for Spindle On/Off/Auto with Mach 3.  There are door switches and limit switches on the axis that kill all power, and key switch to override the door switches. There are two conveniently located pushbuttons programmed as toggles for the vacuum cleaner.  Mach 3 also has inputs to the PLC. I drive the vacuum outlet, two spindles, a heated bed, a nozzle heater, and Mach 3 handles 4 axis motion.

524

General Mach Discussion / Re: Shielding

« on: February 19, 2014, 06:12:22 PM »

Bob,
Shielding is very important and the best practice is to shield everything. I also try to keep all signal wires away from power wires when I layout a panel.  AC one side, DC the other, that kind of thing.

Something to understand about grounding.  By the National Electric Code ground loops, grounding everything to everything is a good thing.  That is because the intent of power grounding is to make sure that when something faults and hundreds or thousands of amps are flowing through the grounding system, no two points you could touch will ever have a voltage difference large enough to hurt you.  All electrical equipment leaks power to ground, some very small amounts some very large. So power grounding systems will ALWAYS have current flowing through them.  I have to laugh when electronic engineers tell you that you need to have the mythical 'clean' ground!

Control grounding is very different, as what we care about is not having a signal created, distorted, or destroyed by noise.  In control grounding of devices and cable shielding you want to make sure first that there is only one ground point that connects the control grounding to the electrical power ground.  Then you must make sure that every device ground and every cable shield connects to that ground point by just one path.  This sounds simple, however what usually trips people up is that manufacturers of devices like pressure transmitters will provide a ground terminal, and internally they connected it to the metal case. So if you connect your cable shield to that terminal and to the ground point at the other end you now have two paths, one through the cabinet, one through the cable shield, which is bad.  Another touchy spot is shielded cables passing through a junction box.  It is tempting to tie the in and out shields to a ground bar that the box may have.  However in junction boxes shield wires must be insulated the same as conductors. Otherwise you create multiple ground paths.

That's it, hope that helps.

525

Tangent Corner / Re: How would you clamp this?

« on: February 18, 2014, 09:59:40 PM »

It is very easy to design a very expensive part, and quite difficult to design cheap parts.  At my last job another engineer designed a part. I looked at it and said it would be very expensive to make because it would have to be fixtured 6 times. He said "No it won't, they do it with a CNC machine".  I asked him who was going to do the part and when he told me I said "You know they have Fadal 4020 machining center, and I happened to actually have run one for 3 months and then continued doing the programming for another 6 months!"  He still didn't believe me, until he got the price.

526

General Mach Discussion / Re: Limit rapid speed from a digital input

« on: February 18, 2014, 09:48:34 PM »

Thanks guys,
That sounds good, I think.

527

General Mach Discussion / Limit rapid speed from a digital input

« on: February 17, 2014, 08:37:12 PM »

I have door switches that stop the spindle if you open the doors on the mill, to protect my grandson.  I'd really like to be able to limit the rapids to a slow speed when the doors are open too.  The machine could easily crush a hand with a quick move, but you need to reach in sometimes to locate a part. When the doors are closed the rapids should be whatever they are set for.  Is this possible?

Thanks,

528

General Mach Discussion / Re: Checking your CNC for squareness and accuracy

« on: February 17, 2014, 08:30:40 PM »

I think I have an easier way for my machine. I have 9" granite angle block accurate on 4 sides. I set it up against the X axis way, and sweep a dial indicator over it in all directions at lots of places.  Very quick and no math.  Paid $65 for the block, however they seem to cost about $1600 new!

529

Tangent Corner / Re: How would you clamp this?

« on: February 17, 2014, 08:25:04 PM »

You know, the first question I'd ask is how many are you making?  The answer for 1 is very different than for 100! For instance you could simply clamp it down from the top on one side and cut the other side and maybe the holes.  Then put clamps on the other side and finish it.  Flip it locating along the straight edge with a dial indicator and indicate the center of one hole. I have done a lot of one offs this way, and I don't have a pile of fixtures plates I'll never use again.

A very good machinist once made me a very expensive fixture that added nearly 5 dollars a part to 100 pieces. Another machinist had made a very simple fixture for $20 and did the same number of parts for about $300 less.

530

General Mach Discussion / Re: Using Mach 3 for a Rostock Delta printer

« on: February 16, 2014, 03:11:48 PM »

Tweakie,
I've been on the Reprap forum for more than a year following all the builds people have been doing. The machine I'm building is a little outside of the typical home build and I'd like more capability than the 3D printer control boards currently have. However I see that the Smoothie board may be available soon and that looks like it could be a winner.