It's my turn to be the noob

[jmytyk]

Hello everyone, I have been lurking and planning for the last few months. I have drawings roughed up. I have some electronics in the works and have been bitten by the CNC bug.

The overall scope is this:

Mechanical
25" x 49" x 5" work area (1/4 sheet sizing)
Torsion box / hybrid construction (MDF, Birch Ply)
2" Pipes for X & Y
Dumpster find Linear Bearing for Z
Acme 1/2-10 drive screw, single center drive for gantry- but optional twin drive depending on need.
210 oz/in direct drive motors for starters

Electronics:
Centent 0143 Drivers X,Y,Z
Home built 56v power supply
CNC4PC breakout board.

Computer:
Mach2 or 3 control software for starters, EMC later on.
Still up in the air for CAM software.
Solidworks / Autocad for design.

Goals.
Parts cut from MDF / PLY, 2 pass for a 3/4" would be awesome.
Parts cut from foam
Parts cuts from plastic, likely acrylic, UHMW, etc.
1000in / sec - haha just kidding, 50-75in / min would be a more reasonable goal.

Small scale funiture, R&D environmental design.

OK-- Thanks for watching. I'll try to keep up with the documentation.

[jmytyk]

Here are some quick sketches in AutoCad, there are not complete by any means.

[jmytyk]

As you can see in the above pics the design is rough, but some things to note.
The torsion box idea is being borrowed (thanks)
The EMT idea is being borowed (thanks)
The angle with skate bearings pushing in, instead of out (thanks)

I will tie the Y-Axis (short) to the gantry walls with some threaded rod run through the center of the box. It will attach to the gantry walls passing through oversized holes so that adjustments for Z-Axis perpendicularity can be made, we'll see how well this works... The rod will run the full length inside of the box.

The X-Axis (long) will be a nice thick torsion box, since it is spanning 50+ inches. As a mechanical system I know it will pull some support from the tubes, but I would like to have the frame support itself, without needing support from the tubes.

Driving the thing:
The Y-Axis (short) center driven, acme screw. The Z-Axis is still up in the air.
The X-Axis (long) will be center driven, I know there has been conversation about racking, or using 2 drives screws- I'll see how this goes- simpler is better for first time around. The if it is a problem, I could move a pair of screws to the edges and belt drive the thing.

Where have you guys seen flex points when center driving the gantry? are they flexing in the bearing blocks? or what--- thanks...

[jmytyk]

A question about step / direction and the 5vdc supply. The step and direction come off the breakout card, and originate from the computer. On my setup the 5vdc is coming from a wall-wart. do these have to be link somehow? would it be better to pull he 5vdc for the drive from the computer PS?

Also, concerning the enable in Mach2? pin 15? is this necessary, or can i run without it being attached??

Thanks_Jon

[spalm]

Hey Jon, congrats on starting your own log.

Flex and backlash come from everywhere they can find a way.

Few comments:
How are you going to attach your pipe? I would recommend lengthening it and routing holes in the end plates and gantry walls for it to pass through.

I see you have two bearing adjuster plate thingies on X. I think you only need one. These are an easy way for flex to enter the system. The less the better.

I sense that you are really worried about Z-Axis perpendicularity. I would worry more about flex and not compromise the strength of the gantry to Y connection.

About twin leadscrews. Just keep it in mind so it is not designed out. Center drive is the easiest and may work for you.

Steve

[CJL5585]

Originally Posted by jmytyk A question about step / direction and the 5vdc supply. The step and direction come off the breakout card, and originate from the computer. On my setup the 5vdc is coming from a wall-wart. do these have to be link somehow? would it be better to pull he 5vdc for the drive from the computer PS? Also, concerning the enable in Mach2? pin 15? is this necessary, or can i run without it being attached?? Thanks_Jon

The Wallwart power goes to the breakout board as in attached drawing. The step and direction signals are outputted from the CNC4PC board as follows:

Pin # ID

2 X Step
3 X Dir

4 Y Step
5 Y Dir

6 Z Step
7 Z Dir

8 Not Used
9 Not Used

THE ABOVE WILL HAVE TO BE ENTERED INTO THE MACH SOFTWARE, AS THE PINS FOR OUTPUTTING TO THE CNC4PC BOARD.


Centent 143 Drives are very good units in my opinion. I have built several systems for others using them. They are an older version of the Gecko 202 drives, and the 202 manuals can be used for reference on the 143's as they wire and operate the same externally.

I cannot give you a DEFINATE AND CONCRETE answer on Mach II, but from memory, I BELIEVE THAT IT WILL WORK WITHOUT ANY CONNECTION.

Hope this helps,
Jerry

[CJL5585]

I Forgot to mention that in the Vicor1. Dxf drawing the +5 / +12 volt supply is the one from CNC4PC. Anyway, the +5 Volts goes to the 5 volt connection on the breakout board and also to pin 10 on the Centent 143 drive. The 5V common ONLY goes to the common connection on the breakout board.

The breakout board common completes the circuit to the step/direction on the drives. No other common connections are necessary.

Jerry

[jmytyk]

So my build log isn't all that intresting yet. Life outside of the CNC world has kept me very busy. I sold my truck (03' taco xtracab, v6, 4x4, TRD) but i found a new old one (87' 'yota x-cab truck, 4x4, 22re, 5sp) only a few blocks from where i live with the goal of having some more money towards this type of stuff... so now I am back.

I know you guys say "don't spin the motor before its finished" but I could help myself, I spun them!! 3 drives, 3 spinning motors. not at all optimized by any means, but atleaset they're moving.... Electronics is my weakest link, I made a deal that if I get the electronics done, then I can start the build phase.

I'll post some pics of the frankestein mess in the morning. (3:46am right now) -reminds me of someone elses build log title - tablesaw, kids, 2am.

-Jon

[jmytyk]

In addition to spinning the motors i would like to test the electronics for limit switches. I saw in the Mach 2 manual the best way to save pins is to wire the limit switches in series

x-limit with x-home
y-limit with y-home
z-limit with z-home

I see this as straighforward, with the switches in the NC (normally closed) configuration, and attach one end to a input pin and the other to ground?

That doesn't seem right, or do I use my 5v wallwart? I posted a pic from the Mach2 Manual, what wattage is the resistor, and does it have to be a 470 Ohm specifically?

Thanks

[CJL5585]

Originally Posted by jmytyk In addition to spinning the motors i would like to test the electronics for limit switches. I saw in the Mach 2 manual the best way to save pins is to wire the limit switches in series x-limit with x-home y-limit with y-home z-limit with z-home I see this as straighforward, with the switches in the NC (normally closed) configuration, and attach one end to a input pin and the other to ground? That doesn't seem right, or do I use my 5v wallwart? I posted a pic from the Mach2 Manual, what wattage is the resistor, and does it have to be a 470 Ohm specifically? Thanks

The Resistor should be a 470 Ohm 1/8 watt unit. A higher wattage is fine. The actual wattage required is 0.053 watts.

The reason the resistor should be 470 ohms is to set the max amount of current that can flow to the computer port electronics with one of the limit switches in the open position. The 470 Ohm limits the current at 0.0106 Amps or (10.6 ma.). The max that the electronics can take is normally in the range of 16 ma (0.016 Amp). The lower threshold is somewhere around 8 ma (0.008 Amps).

The 5 Volts comes from the (+) side of the wallwart. The common (-) of the wallwart needs to connect to pins 18 - 25 on the breakout board. This might be a common connection already made on the breakout board. It varies from one BO Board to another.

Jerry

[jmytyk]

Wow, it's amazing what kind of work you can get done when you have the house all to yourself Today, limit switches wired and tested, motors "fully tested" -found one wiring problem that I need to trace down- and learning more about Mach2 - all in all a good day. Tommorow will be spent at the DMV getting plates for my new truck, i surely am looking forward to that

Here are some pics of my wiring mess. it all works- mostly

next question, motor tuning. top speed and accel settings? I am going by the sound of the motors, there is a definite limit and i can hear it. I understand that these are unloaded settings, and will change depending on everything else the motors are hooked to. Is there other methods?

How hot is "hot" for a motor- is heatsinking them a requirement?
4.6a - 2.71v motors running at drive set current of ~4.5a and 56v

Thanks everyone.

[CJL5585]

You should have the Powermax II motors wired in series if you are running them at 56 Volts DC.

They will get VERY HOT at 56 Volts in Series, and will want to melt if wired in Parallel at this voltage.

If they get too hot -- I would make some wrap-around metal heatsink fins for the motors.

I use these motors too, and plan to heatsink mine. They are wired series at 48 VDC.

Jerry