Homemade Gravity Assisted Foam Cutter!

[weeliano]

Yes I finally did it! I have successfully replicated the gravity assisted foam hot wire cutter capable of cutting tapered wings! Here are the pictures from my very first cut! You will notice that the top surface of the wing has a bad hot groove, that was caused by the bad templates I have, the hot wire was cutting very smoothly until it got caught by an uneven ridge on the template.

The bottom cut was perfect! Now I'm using a much lower hot wire temperature to cut than my previous manual method. The resulting surface is much better than cutting manually! This is fantastic! And I didn't spend a fortune on building this device. It took me a few hours to figure out how to cut the taper and adjust the weights though, but when I finally did, the first cut was almost flawless.

My design differed from the Feathercut system in that my hot wire bow is suspended like the Utah Flyers Organization's version. http://www.utahflyers.org/ (check out the video on foam cutting! Simply amazing!)

Now all I need to do is to find out where I can buy formica sheets as this is the recommended material for making airfoil templates.









It may be crude in construction but the most important thing is that IT WORKS!

[aloev]

wow!!!

very nicely done...

[peary]

got to make myself one of these some day.

[Tony]

Congratulations. Very ingenious work. Does not matter if it looks a bit crude, the important thing is that it works and produces beautiful wings.

The next time I need to have a foam wing made, I'll know who to go to

[weeliano]

Thanks Tony! Now I need to find out where I can get formica sheets so that I can make better templates. Does anyone have any idea?

[HZM]

You probably can get scrap fomica sheet from those furniture maker.

There are a few at Eunos industrial estate, hougang defu lane, Kaki bukit also has 1

Basically you drive round, see if they can spare u some cos they had no use if it is too small a size.

Cheers

Mike

[eidja]

Formica can be obtaine from household kitchen table tops... usually contractors thow them away after cutting through a hole for cinks or hob. look around for renovating homes....

[HZM]

Any chance a video the system at work ?

It sure be interesting

Cheers

Mike

[weeliano]

I need to get another big block of blue foam to do more cutting experiments and R&D. So far the first Wing is the only cut I've made and I have to go to sleep after that , it was already 4am by the time I posted the pictures . The initial results are very promising and I believe I can tweak the set up further to get even better results. So far the only stumbling block are the airfoil templates, I need to ensure that they are super smooth so that the hot wire can slide over them smoothly and easily. The hot wire temperature can also be lowered further to reduce the shrinkage near the wing tip for tapered wings, and the benefit of having a variometer is that I can manually adjust the temperature on the fly during the cut. The current swing arm is cobbled from strips of old balsa wood, I need to make my way down to the timber wholesaler (at the junction of Jalan Syed Alwi and Townshend Road) and buy wood from their waste basket to make a better and more robust swing arm.

I'll definitely post a video of the cutting in progress. I can't cut in the day as I'll fume up the kitchen, have to do it in the evening when everyone goes to sleep!

Once perfected I can start to take orders!

[Tony]

Weeliano,

You could tidy it up a little and make a few sets for sale. I'm sure it'll be snapped up pretty quickly by modellers here.

[weeliano]

Weeliano,

You could tidy it up a little and make a few sets for sale. I'm sure it'll be snapped up pretty quickly by modellers here.

It's a good idea, but it would be too labour intensive for me, the whole machine took me 2 days of running around and R&D to get it to the current prototype stage. Also, I don't think I have the resources to build the complete set as I already have the transformer and potentiometer left over from my old manual cutter. Transformers of that size is not very common, I tried to look for one at Sim Lim Tower and found only those that are about 1/3 smaller, I'm not sure about the power rating though.

The hot wire bow also took a lot of drilling to get it right. It's a good thing I have different tools at my disposal. The pulleys are Tamiya "Engineering" toy series bought at $6 a set from a corner basement store at Sim Lim Tower. I bought 2 sets to get the larger pulleys. For the extruded aluminum bars for the adjustable pulleys, I bought them at Teck Cheong Aluminum at King George's Ave (very near Rotor). The amount of aluminum ($14.70) I bought can make about 2 x 1m sets. I bought extra foam cutting wire at 0.5 mm thickness from Art Friend at $2.50 each. Timber as mentioned in the previous posts, I got them cheap, a dollar a piece, since they are from the waste bin. Nuts, bolts and washers are bought from hardware stores. I also bought a steel hinge for the swing arm. Stationary clippers are used as the string "grabbers". Crocodile clips are used to pull the wire. Soft skin wire is used to power the the hot wire at 70 cents a metre. So you do the math, the resulting costs is very much lower than the commercial Feathercut system, but the hot wire cutter will only work as well as amount of craftsmanship you put into it !

Let me see if I got time, if anyone is interested, I'll post detailed closeup pictures of my set-up and you guys can go figure it out and build one yourself

UPDATE!!!

I have located a great place to buy 1 inch blue foam, the same size as the ones they sell at Art friend for a dollar cheaper ($8). The Shop is called Ban Heng Long Trading and they sell all sorts of Plywood, timber, veneer sheet and most important for us Polystyrene foam of different sorts! This is the exact place where I bought my timber for making the hot wire bow. I was about to pay for some timber when I looked up and saw stacks of blue and white foam, I immediately asked to buy it, it saved me a trip to Art friend, should have asked if they stock Depron as well, they sell a type of mounting board called Kapaline that looks like depron sandwiched between two hard cardboard. I also discovered that they sell Formica sheets!!! I bought a $2 sheet (32"x15") enough to make heaps of airfoil templates. I also discovered a shop located at Kelantan Road BLK 30 corner hardware store called Eng Guan, selling ball bearing pulleys for $1.40 each (there are infact nylon rollers installed for those sliding doors or windows, I had to use a screwdriver, pliers and a sharp tip soldering iron to melt the retainer to remove the roller). I have bought 4 of these to try out. I have also bought this really exquisitely made mini wood working plane for $15, beautifully made with rosewood from the same shop. This shop is quite unique in that they also sell old steel army helmets and equipment! I'll update everyone again to see if my new purchases will improve the hot wire cutter.

[weeliano]

New Improved foam cutter!

Update on the development of the Gravity foam wire cutter.

I have made some improvements to my current design, I have changed all the Tamiya pulleys into the nylon ball bearing rollers and also simplified the way to fix the pulleys on the aluminum tracts. I have managed to screw up some cuts but they are sure educational! I discovered that good quality laminate formica is very easy to cut using a sharp pair of scissors. The formica templates I used now are the best material for hot wire cutting, its able to resist the hot wire without melting. Another thing I learned is that the surface of the template must be very smooth to ensure a ridge free cut. The shape and size of the templates must be prepared with extra precision, I found out the hard way when the first set of templates I used are not shaped correctly and ended with a bad set of wings. The shape of the foam block for hot wire cutting must also be cut with extra precision; I wasted 2 blocks just because I’m impatient to try out the cutter. But once the whole set up is set up properly, it works every time! I also experimented with a much lower hot wire temperature and it causes less shrinkage near the wing tips.

Here are some of the pictures of my cutting rig closeup.

I bought 2 of these springs at 50cents each from the Eng Guan hardware store at Kelantan Road. The address can be found on the previous post. They are very good as the hot wire tensioners. I used cotton twine bought from Art friend to secure the centre as well as tie it to the hook in the kitchen ceiling.


¼ inch square nuts and bolts with washers are used to create the joint of the hot wire bow.


These are the extruded aluminum tracts I used, it consists of 2 hour glass shaped tracts and one L shaped bar all epoxied together using 5 minute epoxy. The swing arm below is secured by a steel hinge.



The plastic pulley is actually extracted from those window rollers. These come with ball-bearings. The photo show how I secure it to the tract using a 3.5mm bolt with a 5mm head. I made sure it fits into the tract before I bought it from the hardware store.



Using a hacksaw, I sawed a groove onto the end of the bolt. A washer is used to spread the force of the nut as the diameter of the pulley is too big.



Instead of using wing nuts to secure and using a previously over elaborate retaining sytem, the current method is much simpler using a wrench and screwdriver, this enables me to move the pulleys along the tract to adjust to the length of the wing I wish to cut.



Instead of running the wire through the pulleys, I thought it’s easier to set up and safer to clip it this way.



This is a heavy duty crocodile clip I used to pull the hot wire, it was bought from the basement hardware store at Sim Lim Tower. You can get these from most other stores there as well. I removed the plastic fittings and tied the polyester pulling cord to it.


After learning from the mistakes of cutting the 1st 2 pair of wings, the 3rd pair came out perfect!!!


Probably the best Tapered wings I’ve ever cut PERIOD!


The lower cutting temperature ensured a smooth cut and less shrinkage.



That’s it! I’ll post the video of the cutting machine in action when I have time.

2011 Dec Update

Seems like this post is missing quite a lot of pictures. I might update it when I rebuilt my wire cutter again.

[Tony]

The Shop is called Ban Heng Long Trading and they sell all sorts of Plywood, timber, veneer sheet and most important for us Polystyrene foam of different sorts!

Where is Ban Heng Long Trading located? I need to get plywood, timber and possibly veneer to make a custom pit box. Also, I need mounting board to mount my tools on the wall. Those panels with holes or failing which, just regular timber/ply would work.

[weeliano]

Address of Ban Heng Long Trading

The Address is

No. 11 Syed Alwi Road
#01-07 Teck Heng Long Ind. Bldg.
Singapoer 207629
Tel : 63923343
Fax : 62928685
email: banhenglong@pacfic.net.sg

[Tony]

Thanks Weeliano for the info. I was just in that neighbourhood this afternoon. Went to the nuts and bolts shop to replenish my stock. Will go to check out what kind of ply and boards they have.