View Full Version : Large Foam Cutter

09-13-2012, 02:00 PM
I am planning to build a fairly large foam cutter using some 80/20 aluminum T-slot extrusions and other parts I have on hand. I also have some of 80/20's linear slides. I don't have much money to spend so, I was thinking that, instead of buying expensive linear rails, I would use the 80/20 extrusions as the rails and use the slides. These things slide surprisingly well and 80/20 also makes/sells "high-cycle" bearing pads for these units. http://www.8020.net/Images/Application-106.jpg I think that as slow as this thing will be, they should be sufficient. I'm not looking for absolute perfect accuracy anyway. like what would be needed for a router or mill. I would sure like some help in figuring out a few things on this.

What size stepper motors would I need?
Would a 3/4" timing belt be sufficient for the y axis?
1" belt for the x axis?
What type wire would I need?
As for a controller, I would like to maybe add a turntable later so would a 3 axis controller be fine? Or would I need 4? If I could just get the board/s, I can build the enclosure and install the components for it
I use SignWizard (Aries Graphics) to make most of my 2D vector files and have Aspire 2.5 for making 3D models and generating G-code: could Aspire run it or would I need Mac3?
I also plan to build the heat generator power supply thingy using a transformer and a potentiometer of some kind to control the heat. What size transformer and potentiometer would you recommend for a 7' or 8' wire length?

Oh yeah, as it is drawn here, the cut capacity would be about 120" x 84" x 66"H. I could cut down the height if I don't need that much, and it would most likely help prevent problems with racking. Does my design look like it would work?

09-14-2012, 04:08 PM
I reduced the height of the upright t-slot 'gantry' to 60". Aren't most foam blocks 48" high anyway? Then widened the base to 14". This would reduce the cut length to 113" but would make the uprights more stable.

What do ya think?

09-14-2012, 05:01 PM
sorry, double post

09-15-2012, 11:38 AM
Never used the type of linear guides you have chosen, but I can tell you if using bearing a nema 34 stepper with a gear box works well. Motor torque is not real critical when using gearboxes
As for as moving the axis’s with belts, why not? Chain would also be an inexpensive option.
I see 4 motors in your dwg, so you would need a 5 axis board if you are going to use a turn table
You can buy various types of wire for EPS from companies like alloy wire. Quick Google search will turn up a nice list.
As for as transformer size, that depends on the wire size. The bigger the wire the bigger the transformer.
Payne engineering sells a 30 amp SCR that’s ready to go. Don’t remember what we paid for the last one, but I don’t think it was much more than $300.00.
For a .014 nickel wire 30 amps is more than enough for 1 wire.
You are right about block size. The biggest I have ever seen is 50” thick. Any thicker the middle of the block does not fuse together well during molding.
Hope this helps

09-15-2012, 12:29 PM
Do I need gearboxes on the motors?

09-17-2012, 11:20 AM
Not necessarily
You are going to be cutting slow, prob around 20 inm for 1lb foam. The gear box will let you be closer to the middle of the motor rpm range with lot more torque. I always like to be in the middle of the rpm arrange of a motor instead at either the upper or lower range. Plus I like the extra torque.

09-17-2012, 11:26 AM
That makes sense. Sounds good. Thanks!

09-17-2012, 11:30 AM
Do I need my uprights connected at the top to counteract the tension of the wire, or do the y need to be able to move independently for taper cuts?

09-17-2012, 11:30 PM
That depends what you are trying to cut. If you are using 1 wire (tapered cuts), I would think you a good to go, But if you are looking for more of a production machine with 20 or 30 wires, then you need it really ridged. I have seen 2X3 aluminum tubing bend from trying to use too many wires.

10-01-2012, 03:17 PM
Thanks BoPierce

In light of the possibility that I might want to cut with more than one wire, I will try to design it so that a cross "gantry/brace" can be added or removed when needed. I have a few more questions...

Since my wire will be between 7 and 8' long, would this transformer/power supply work for me? If so, how many wires would it supply? LiteFuze LT-1500 1500 Watt Heavy Duty Voltage Converter Transformer Step Up/Down | eBay (http://www.ebay.com/itm/LiteFuze-LT-1500-1500-Watt-Heavy-Duty-Voltage-Converter-Transformer-Step-Up-Down-/330799485055?pt=Heavy_Duty_Voltage_Converters&hash=item4d052f907f)

I want 4 independent motors ont he x and y axes and a 5th axis so that I cna add a turntable/lathe at a later date. Would this be what I need to run the machine? or is 262 in/oz powerful enough? 5 Axis Driver Board + 24V PSU + 263 Oz-in Stepper Motor + Mach3 Software CNC Kit | eBay (http://www.ebay.com/itm/5-Axis-Driver-Board-24V-PSU-263-Oz-in-Stepper-Motor-Mach3-Software-CNC-Kit-/280976584102?pt=LH_DefaultDomain_0&hash=item416b826da6)

10-01-2012, 07:46 PM
I would think that that stepper set would be fine. You can always put some counter weight on the y axis if needed.
I not sure about the transformer. not really sure what you are trying to do. You need to use a SCR to control your voltage, Search on Ebay (Payne SCR). There is a really nice 50amp for 89.00. I might have to buy that one. It is a 240vac, but there is a little transformer on the board that can be rewired for 120vac if needed. You would need to buy a 75K ohm pot for it, but they are cheep.
I would think you could run about a dozen wires, prob more, (depending on the type of wire) with that Payne unit without a transformer.
Hope this helps

10-01-2012, 08:45 PM
Is it this one?
Are there other brands? Because I only see one like it on Ebay.

10-01-2012, 08:55 PM
I want to be able to cut through a very large block of foam to build monument signs, architectural moldings, and 3D letters . My machine will be over 10' long x 8' wide x 6' high. I'm thinking the wire length will be about 7' so it will need plenty of heat, especially if I add a few more wires for cutting miltiple sheets, moldings etc.

10-01-2012, 09:12 PM
50 amp Payne unit will do it. 1 of our cutters is 12' wide 6' high, and 16' long. we can put 40 wires (.014). we use a 150amp Payne unit and have had the same unit on it for over 15 years with no problem. we put 240vac to the Payne unit then run that thru a 2 to 1 step down transformer. this approx doubles the amps. For what you want to do I think that a 50 amp unit is more than enough.
This is the unit I was talking about: Item #300745926743

10-01-2012, 09:57 PM
Thanks Bo

10-03-2012, 02:03 PM

I found some v groove bearings to run on my home-made rails which have room for a sturdy 3/8" axle/bolt. Lot/Package of 8 V Groove Ball Bearing 3/8" CNC Rails/Slide Guide Wheel 8 pieces | eBay (http://www.ebay.com/itm/Lot-Package-of-8-V-Groove-Ball-Bearing-3-8-CNC-Rails-Slide-Guide-Wheel-8-pieces-/400326129348?pt=LH_DefaultDomain_0&hash=item5d354bf6c4)

But these are much cheaper. Do you think they would be sufficient?

20pcs 4mm 624VV V Groove Sealed Ball Bearings 0.157'' Vgroove 4 x 13 x 6mm | eBay (http://www.ebay.com/itm/150883808309?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

10-03-2012, 10:59 PM
My thinking would be in your case bigger is better. You do want to build a fairly good size cutter. I have never built a cutter with V bearings so I might not be the one to really help you on that.

10-03-2012, 11:12 PM
I think i will go with the bigger ones.

10-04-2012, 02:04 PM
If I used this kit, where would I find gearboxes to gear them down? Is this a good deal, or does anyone know of a better price somewhere? Thanks!

5 Axis Driver Board + 24V PSU + 263 Oz-in Stepper Motor + Mach3 Software CNC Kit | eBay (http://www.ebay.com/itm/350607921314?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649)

10-04-2012, 03:13 PM
Or would I be better off with these steppers........

5pcs Nema 23 stepper motor 425oz-in 3.0A FOR CNC Cutting LONGS MOTOR | eBay (http://www.ebay.com/itm/200819437754?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649)

...and would these be the right components to go with them?
CNC Router DIY Kit 5 Axis Breakout Board + 5x M542H Stepper Motor Driver 1A-4.5A | eBay (http://www.ebay.com/itm/180968754864?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649)

10-04-2012, 07:18 PM
Do a search on ebay for nema 23 Planetary Gearbox and you will find them. They cost more than the motors, but I really like to use them on my cutters. I have bought a few things from Anaheim Automation's and was sastified with them.

10-04-2012, 07:20 PM
I like to use indiviual driver boards because if one goes out and your in a bind you can just swap out the driver with another axis and your good to go.

10-04-2012, 08:11 PM
Good idea, thanks! I'll check out those gearboxes, So you think the 263 in/oz motors are strong enough if used with the gearboxes?

10-04-2012, 08:45 PM
What gear ratio do you use
and what is the holding torque on your motors?

10-08-2012, 11:30 AM
Sorry for slow response. Just got back in town. We use 20:1 gearboxes. The gear boxes in the link I saw looks good to me. The 263 oz/in motors should work fine. If the is a problem with the Y axis you can always ues counter weights, but because you are not making a large gantry and using indiviual motors on each side of your Y axis you are prob alright

10-08-2012, 11:34 AM
We use Nema 34 motors with 450 oz/in holding torque. We build our gantry with alluminum sq tube and use a counter weight on the Y axis.

10-08-2012, 12:06 PM
Are you saying I can use the 263 oz motors with the 1:20 gearboxes or without?

10-08-2012, 09:34 PM
I see no problem with the motors and gearboxes. It is all about making sure you cutter's movements (linear bearings or slides) are traveling smooth with little or no resistance. Bigger motors can allow for misaligned bearings, and other things that can cause your gantry to hang up.

11-09-2012, 11:43 AM
Well, I might have done a dumb thing, but I bought it........

Payne Engineering 18D 4 150SW Proportional Power Controller 480VAC 150Amp | eBay (http://www.ebay.com/itm/121011169539?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649&autorefresh=true)

11-09-2012, 02:52 PM
That was a steal. I didnt see that one or i would have been bidding on it. That is the only type of SCR that we use. Good Job.

11-09-2012, 03:05 PM
Cool! Thanks!

The controller is single phase, but the input is 480VAC, Will I need this transformer to step up my voltage from 240? New Old Stock General Electric Step Up Down Transformer 9T58K2810 Made in U s A | eBay (http://www.ebay.com/itm/New-Old-Stock-General-Electric-Step-Up-Down-Transformer-9T58K2810-Made-In-U-S-A-/200844549676?pt=BI_Circuit_Breakers_Transformers&hash=item2ec3449e2c)

11-09-2012, 03:24 PM
You can rewire the little transformer on the unit for 240vac. (The little transformer at the top in the 1st pic) The name plate says 480vac and that is what the little transformer is wired now. If I can remember when I get home, I will scan the wiring diagram for the transformer and post it for you. If i have a few beers (it's Friday) I might forget. Just post and remind me and I will get it to you. You will also need a 75K ohm pot to go with that unit for controlling output voltage. I will post that drawing too.

11-09-2012, 04:09 PM
Thanks Bo!

11-09-2012, 04:23 PM
I almost have everything I need to build the machine but have to stop for a few days to catch up on my work; 3D letters for a monument sign and painting the graphics on a semi trailer.
Thanks for the help so far!

11-11-2012, 10:23 PM
Here is the info I have on Payne SCR. It should work for you.

11-12-2012, 09:56 PM
Thanks a million, Bo!

Would any of these pots work? Payne Engineering 75K Potentiometer | eBay (http://www.ebay.com/itm/Payne-Engineering-75k-Potentiometer-/380206896200?pt=LH_DefaultDomain_0&hash=item588618d448)

2 Mil Spec Clarostat 738 743 75K 3W Wirewound Potentiometers Linear Taper | eBay (http://www.ebay.com/itm/2-Mil-Spec-Clarostat-738-743-75k-3W-Wirewound-Potentiometers-Linear-Taper-/200628944506?pt=LH_DefaultDomain_0&hash=item2eb66abe7a)

Allen Bradley Type J Potentiometer 75K 2 Watt | eBay (http://www.ebay.com/itm/ALLEN-BRADLEY-TYPE-J-POTENTIOMETER-75K-2-WATT-/330827197511?pt=LH_DefaultDomain_0&hash=item4d06d66c47)

11-12-2012, 11:47 PM
The first one is an OEM pot. should work perfect.

11-15-2012, 11:19 AM
Would it be feasable to install a digital readout between the potentiomer and the control uint to monitor the voltage? If so, what kind would I need?

11-15-2012, 06:08 PM
Am assuming that you want to monitor the voltage going to your wires. If so, then all you need to do is to install a voltage meter and wire it parallel with the lines going to the heated wire.

11-15-2012, 06:16 PM
Thanks Bo,
Right, voltage to the wires. What about amps? I noticed some of the 'storebought' power supplies like from Hotwire Direct, have high amps for some applications' would I need to wire an ammeter in too?

Also, how many volts will mine put out if I wire it 240 single phase?

11-15-2012, 07:27 PM

This might help you.

11-15-2012, 08:43 PM
Here's one I found on Ebay

500V 200A DC Amp Volt Combo Meter for HHO EV Car Solar Wind Glof Boat Shunt | eBay (http://www.ebay.com/itm/500V-200A-DC-Amp-Volt-Combo-Meter-for-HHO-EV-car-Solar-Wind-Glof-Boat-Shunt-/170825906905?pt=LH_DefaultDomain_0&hash=item27c6047ad9)

02-16-2013, 09:38 AM

I was at a foam supplier some years back and saw their large block cutter in action. They were using a constant current welder connected to the wires. They said they would just adjust the current depending on the number of wires.

02-16-2013, 10:39 AM

02-16-2013, 07:47 PM

I suggest that you add the Amp and Voltage meters. At least the Amp meter. for monitoring.

I control the amps to my bow wire after I find what amps is needed by using foam scrapes. You will find that the amps for cutting the foam will be the same for 100 mm to 1.5 meter length of wire but the voltage to supply the amps will vary to wire length. I found that 1 to 1.75 amps is all that is needed depending on type of foam.

I have a home built 50V supply using 2 10A transformer wire in series through a bridge for DC voltage and control by a light dimmer. I just the voltage to the transformers by the light dimmer until I have the amps that is needed for the cut.


02-16-2013, 07:53 PM
Thanks Harold!