First Build All MDF Machine

[ttjarrett]

Hi All,

In a previous thread I started a week or so ago outlining a few ideas I have for an all aluminum machine I am considering building, I mentioned I had recently completed an MDF machine. I mentioned that I may start a thread on this machine, and Rod encouraged this idea as there are a couple of guys here that are interested in MDF machines.

Instead of starting a new build thread, I thought I should just point you guys in the direction of my CNC Zone thread, which is here "http://www.cnczone.com/forums/showthread.php?t=71807"

I should point out that this thread on CNC Zone is pretty threadbare (pun intended), so if you have any questions feel free to ask!

I should also point out that in my first thread here I stated that the MDF machine was finished. I would now like to retract this statement as over the last couple of days I have decided that I'm not happy with my electronics set up and have stripped it from the machine. I am now considering an electronics upgrade, but I need to explore this further.

Thanks

Toby


Editor's Note: Removed Cross forum link. (watson)

[rodm]

Hi Toby,
Thanks for taking the time to post about your machine.
A couple of photos on this thread would be good to show off your machine. Sorry if it sounds like I am demanding.

First machine always results in a bit of experimentation. I wish I knew what I do now when I started as it would have saved me a lot of trouble and money.

[Greolt]

........ over the last couple of days I have decided that I'm not happy with my electronics set up and have stripped it from the machine. I am now considering an electronics upgrade, but I need to explore this further.

Welcome aboard Toby.

Electronics. What have you got and what are you thinking?

Greg

[rodm]

Toby,
I finally got time to read your thread on the zone. That is a very impressive build and you should be really pleased with it. Oh yeah, I got your pun about being threadbare.
Greg is the bloke to discuss electronics with so run your ideas past him as it could save you a lot of time/money.

[John H]

Welcome Toby. Good to see another local into CNC.

[ttjarrett]

Hi All

Attached are a couple of pictures of my machine as it is at the moment.

The design intent for my machine was to keep it simple (which went out the window pretty quickly) and to approach the design of the machine as a 'kit'. Due to this, almost every MDF part connects to it's surrounding parts with locating tabs. This made construction of the machine seem more like assembly of the machine, which worked pretty good for me. I got all the MDF laser cut from two 2400 X 1200 X 16 sheets (that's why the edges are black and there are some smoke marks on the machine), which probably saved me about 100 hours+ of jigsaw work.

For more pictures of the evolution of my machine, check out my Zone thread.

Welcome aboard Toby.

Electronics. What have you got and what are you thinking?

Greg

Greg, at the moment I have a HobbyCNC PRO Board, three HobbyCNC 205oz/in steppers, and a homemade power supply. I have decided to go in a different direction now with the electronics purely because I'm not getting the performance I wanted from the HobbyCNC board (and I now recognise that I should have done more research to begin with).

When testing my machine, I could not get more than around 300mm/min speed from the X and Y steppers before they stalled, and only around 200mm/min from the Z stepper. This speed is far too slow considering I plan to machine, amongst other things, 3D guitar parts! I could see it taking a bloody long time to machine the full contour or a guitar neck.

I believe that the slow performance I was receiving from the HobbyCNC board was simply because the board could not kick out enough volts to the steppers to move the weight of my machine and the 'stiffish' rotation of the acme threads in it. I think this board would be more suited to a smaller/lighter machine, or a machine with ball screws. In your experience would you agree?

I now want to just 'cut my losses' and upgrade, rather than bugger around for another couple of months trying to get blood from a stone! I am considering the following set up:

a Gecko G540;

two 318oz/in Keling steppers for the X and Y axes;

one 382oz/in Keling Stepper for the Z axis;

a homemade power supply (around 50VDC, 6.7+ Amps); and

all the other things such as fuses, an e-stop, etc.

Would this set up give me more power/speed? I can easily rotate the acme screws by hand and with a cordless drill, but I am bemused that 3A stepper motors being supplied a decent amount of volts can't! Your input would be much appreciated Greg. I need guidance!

Rod, thanks for the encouragement (good suggestions aren't demanding in my book)! I feel like I'm on my way to an ok machine, but there's still a lot of work to be done!

John, hi fellow Canberrian. Are there many of us here in the Territory?

[John H]

...........
John, hi fellow Canberrian. Are there many of us here in the Territory?

Well now you are here, that makes two of us.

[Greolt]

Toby

I am not familiar with the HobbyCNC board but will do some reading.

Tell me about the motors that you have. Do you have a data sheet on them?

Amps per phase, volts, inductance at series and parallel connection.

What are you using for lead screws? And what nuts?

It may be that you would be best to keep the motors and drive them with better bipolar drives and higher voltage.

Small motors can often be made to rev faster than bigger motors with a given drive/power supply setup.

Tell me about your comfort level at building power supplies and setting up the electronics etc. Or whether plug and play is more appealing.

Greg

Oh Yeah, I am going to be away for a few days so response may be a bit slow.

[AJ240]

Well now you are here, that makes two of us.

Count me in for 3.

I am just looking around for a machine just like yours Toby.
I have a Sherline desktop CNC mill which is great for small stuff, but I am looking for something bigger to cut depron sheets for RC planes.

I would love to catch up and discuss the pros and cons of your machine before I dive in.

Anthony

[WillyInBris]

I thought I would just chime in on the G540 its very much plug and play (fantastic I am over the moon with mine) a lot of safe guards built in compared to other drivers and as your probably aware has a breakout board built in for your limits etc.

when I start the next build I will be adding another G540 to the mix.

You cant go wrong with the product the support and instructions are first rate as well as for the rest yes well Greg is Da man .

[John H]

Count me in for 3.

WhooHoo, Now we can have our own CNC BBQ days like they do in Melbourne

[ttjarrett]

Toby

I am not familiar with the HobbyCNC board but will do some reading.

Tell me about the motors that you have. Do you have a data sheet on them?

Amps per phase, volts, inductance at series and parallel connection.

What are you using for lead screws? And what nuts?

It may be that you would be best to keep the motors and drive them with better bipolar drives and higher voltage.

Small motors can often be made to rev faster than bigger motors with a given drive/power supply setup.

Tell me about your comfort level at building power supplies and setting up the electronics etc. Or whether plug and play is more appealing.

Greg

Oh Yeah, I am going to be away for a few days so response may be a bit slow.

Hi Greg,

The motors I have are no longer mine! I sold them yesterday with my HobbyCNC board. I decided to sell the board before I purchased a Gecko, and the motors made the sale much more appealing to a potential buyer. Hopefully they can get some better performance than I did (the board and motors were fine, just not suited to my machine).

This means I am starting again with a clean electronics slate!

I am using 2 start, 10tpi (5 effective tpi) lead screws on my machine with Derlin anti backlash nuts. I think this gives these screws 5.08mm pitch. Am I right there?

With the Gecko G540 unit, the motors I have (tentatively) looked at are:

two Keling KL23H2100-35-4B 318oz steppers for the X and Y axes; and

one Keling KL23H2100-30-4B 382oz stepper for the Z.

I have included two PDFs of the specs of these motors as they appear on the Keling site.

My comfort level in building a power supply and setting up the electronics is good. I’m confident that I can build everything and make it safe, but I am less confident about selecting components. There seem to be a lot of variables in even the most simple of electronic parts!

What is your opinion on these motors Greg? Are they suited to the Gecko, and would they give me good overall performance? Any suggestions will be taken as gospel!

John, you can supply the sausages!

Anthony, I would be happy to catch up and discuss my machine before you dive in! Can we wait until mine's actually making dust though?

[Greolt]

Toby

I think you may have got the second motor listed mixed up.

KL23H284-35-4B may be the one you meant. 387 oz, 3.5 amp, 2.8 mh

They would nicely match the G251s teamed up with a 50 v supply.

My first thought would be that because you are using acme screws that the greater oz/inch would be the way to go. Acme screws are not as efficient as ball screws, R&P or belts. You have more friction to overcome.

Greg

[AJ240]

Happy to help out with the electronics side. Thats what I do for a living.
Let me know if you need a hand.

Anthony

[ttjarrett]

Greg,

I think I want to go with the G540 unit (just because the BOB is included) and I only deal with building the power supply.

You were right about the motor, I was looking at the KL23H284-35-4B. I think I might just go with three of these, rather than putting smaller motors on the X and Y. I was given this advice to put smaller motors on the X and Y over at the Zone, but I can't see how larger motors on all axes could hurt.

To this end, I've worked out the numbers for the transformer for my power supply (using Bob Campbell's power supply PDF), which are as follows:

Transformer Secondary Voltage = 50/1.4

= 35.71VAC

Transformer Current Raiting = (3.5*3)*0.67

= 7.03A

At Sonar Plus (www.sonarplus.com) I've found a transformer that is able to give me 36VAC, 8.33A. This is higher than the numbers needed for the supply, but would it be suitable? Can the G540 handle slightly higher numbers (especially current) than it needs?

Sorry I keep asking you to step me through the whole process. It's a learning curve I am enjoying, but solid answers are a hard thing to find outside of asking certified forum gurus.

Anthony, any advice you have here would be much appreciated also!

I would be very interested in getting a hand with the electronics, especially in verifying what I eventally make is safe/going to work!

What are you thinking for your machine (not just electronics)? Have you done much research?

Thanks Guys

Toby