[LeeWay]

I have good luck just machining one side. I use both colors. I don't expose my machines to sunshine. That may be the biggest issue.

[diyengineer]

I have good luck just machining one side. I use both colors. I don't expose my machines to sunshine. That may be the biggest issue.

I suppose as long as i dont expose it to light or heat, and store it flat, it should be ok.

[Boltz]

I've built a few fixtures out of MDF coated with System 3 boatbuiding epoxy. I let the MDF heat on an electric griddle for about 20 minutes, the heat makes it suck up the epoxy like a sponge. Then I put it back on the griddle at very low heat and the epoxy cures in about an hour and a half.

-Jim Hart

[diyengineer]

I'm trying to think of ways to get around drilling holes in my precious table. I want tooling pins to locate my fixtures, but dont want them permanent or to damage the table. any clues?

[diyengineer]

I've built a few fixtures out of MDF coated with System 3 boatbuiding epoxy. I let the MDF heat on an electric griddle for about 20 minutes, the heat makes it suck up the epoxy like a sponge. Then I put it back on the griddle at very low heat and the epoxy cures in about an hour and a half.

-Jim Hart

Jim, that sounds like it could be a good way to make really inexpensive jigs with the same performance that hdpe has for a lot less money! any pics?

[diyengineer]

HDPE utility grade black (blend of virgin and reprocessed HDPE).

48"x96" sheet:

3/8"- $102
1/2"- $137
3/4"- $205
1"- $274

Seems like the prices dropped down a bit. 3/4" use to be $250+ dollars.
(prices from Kurbell plastics, WA state)

3/4" would be adequate correct? I would think 1/2" would be too thin for a double sided jig. More than enough for a single sided jig however.

I'm going to design a "fake" widget part. something that has 4-6 pieces and attempt to make a jig out of hdpe and then hopefully learn from my mistakes and refine it until i can repeat the parts over and over. Then the concept will be sound and i should be good to go on designing something that makes some $.

[diyengineer]

http://www.cnczone.com/forums/genera...tml#post970682

[HelicopterJohn]

I haven't read the whole post but what do you intend to put on your table as a spoil board i.e 3/4 MDF. I understand you are concerned about the table base being damaged.

How are you going to attach the 3/4 MDF removable spoil board to the table?

Has your control been setup where you can home your machine in X,Y & Z axis?

What software are you using to run your machine? i.e. Mach 3

What accuracy is needed for placement of your parts and or fixtures?

Do you have a probe and probing software?

The reason I ask this is that I am in a similar junction with my Shopbot PRT 48 X 96 CNC Router. This is my plan and I believe it will work for my purposes.

My current 3/4 MDF spoil board is mounted to the frame i.e. metal table with bolts recessed into the spoil board. The former owner chose to use 1/4 X 20 Nylon bolts in case a bit should hit one of them.

I have read that someone drilled a hole pattern in the spoil board in the X and Y axis i.e. 1/4 inch holes. Then you could place removable pins in the MDF spoil board to locate your part i.e. a couple on each both the X and Y axis to square the part on the machine. Once the part is attached to the spoil board then the pins would be removed. You would know where the part is located on the table by the location of the pin hole pattern originally drilled. Then when I design a part, fixture location I first draw a rectangle which is the size of the table and draw that part at the selected location based on the drill pin hole locations drilled in the table.

In my Mach3 2010 screen set you also have the ability to do probing options and that could also be an answer to locating parts on the X and Y axis. Not sure what software you are running.

Just some information that may be of some help. I have enjoyed your thread.

John

[diyengineer]

I'm minimizing waste by using a jig made of HDPE. I have specific parts to be cut so i can make sure i will be able to resue the jig over and over as long as i can zero off its corner correctly.

The Jig is powered purely by vacuum on both sides. One side to suck to table, the other to hold down the part.

Yes, i use mach 3 and it homes using optical sensors in the x,y, and z direction (corner of table). I would like a very high accuracy. <.010 or better. I can make my channels around the part larger then they need to be to account for mis alignment and so it wont cut into my jig. say if i use a 1/4" endmill, i may place a 1/2" trence or pocket around the outside of the part and gasket so i have some room to play.

I will be buying a probe and touch off kit soon. Probably a starret last word, and this CNC4PC

Thanks for the information, hopefully i can figure it out

I haven't read the whole post but what do you intend to put on your table as a spoil board i.e 3/4 MDF. I understand you are concerned about the table base being damaged.

How are you going to attach the 3/4 MDF removable spoil board to the table?

Has your control been setup where you can home your machine in X,Y & Z axis?

What software are you using to run your machine? i.e. Mach 3

What accuracy is needed for placement of your parts and or fixtures?

Do you have a probe and probing software?

The reason I ask this is that I am in a similar junction with my Shopbot PRT 48 X 96 CNC Router. This is my plan and I believe it will work for my purposes.

My current 3/4 MDF spoil board is mounted to the frame i.e. metal table with bolts recessed into the spoil board. The former owner chose to use 1/4 X 20 Nylon bolts in case a bit should hit one of them.

I have read that someone drilled a hole pattern in the spoil board in the X and Y axis i.e. 1/4 inch holes. Then you could place removable pins in the MDF spoil board to locate your part i.e. a couple on each both the X and Y axis to square the part on the machine. Once the part is attached to the spoil board then the pins would be removed. You would know where the part is located on the table by the location of the pin hole pattern originally drilled. Then when I design a part, fixture location I first draw a rectangle which is the size of the table and draw that part at the selected location based on the drill pin hole locations drilled in the table.

In my Mach3 2010 screen set you also have the ability to do probing options and that could also be an answer to locating parts on the X and Y axis. Not sure what software you are running.

Just some information that may be of some help. I have enjoyed your thread.

John

[diyengineer]

This friday im buying the HDPE! :P

[diyengineer]

½” x 48” x 96” UG Black HDPE - $137.08

2 sheets ordered! Tomorrow ill pick them up!

[Phife]

½” x 48” x 96” UG Black HDPE - $137.08

2 sheets ordered! Tomorrow ill pick them up!

1/2" is pretty thin for a jig, are you not planning on machining grooves for your gasket?

[diyengineer]

1/2" is pretty thin for a jig, are you not planning on machining grooves for your gasket?

I am, 1/4". Just doing a tester first. Going to cut it down into smaller pieces probably 12 inches by 12 inches. First time cutting stuff on it to, so lots of learning. 2 flute should work I hppe

[diyengineer]

[ame=http://www.youtube.com/watch?v=rRo-IZC-2Kw]Cnc Rebuild Video #89 - YouTube[/ame]

Single Sided vacuum fixture. Uses 1/4-20 square nuts inset into HDPE. I can bolt the objects to the plate, or make cams that bolt down sheet for engraving, etc.

Just a tester to see how my machine will run, as well as how the vacuum gasketing works.

Solidworks 2010--> Cam Bam--> G code--> Cut Viewer--> Mach 3--> Solidworks photoview 360