Core Profiler +/- 0.05mm
Posted: Tue Aug 31, 2010 8:30 am
I've been getting good results with this +/- 0.05 mm, so feel free to give it a go. Critically, I'm sure it not as good as a CNC'd crib, but its damn close for the price. The resultant core will vary according to the hardness of the materials, so maple isn't as accurate as poplar or ash. I'm guessing this has something to do with how the core is held in place. One more thing, the picture have been pulled together from the bits left over and may not be the original pieces. They look a bit scrappy, but I hope it points you in the right direction.
You'll need to check your blade are clean and mounted correctly or you will get variable results. I replaced an old set recently and ran a quick test to check accuracy of mounting ; )
So I started by marking out the profile I wanted on a piece of mdf - 24mm x 35mm x 1800 mm, this length was enough for me. Make sure this piece is really straight - put it though the planner and it must be thick enough so that it supports itself when mounted on its side. A marking gauge (google) to mark out your profile is a must. Sorry, snowcad can't help with this. I think I marked about 15 points from tip to tip. I started at 3.51 mm, up to 11 mm and back to 3.71 mm. Remember to allow for snipe, hence the piece is longer than the core being shaped. Test mark the marking gauge in advance of actual mark and measure using a micrometer. A pencil won't be accurate enough even if it is 0.5mm lead.
Once the profile is marked, I attached uhmwpe strip to the piece of mdf and cut against a flush trim bit - the PE is attached as a guide. Use whatever plastic you have, as long as it is about 5 mm thick. I used screws, which means I drilled pilot holes, so correct any movement if the plastic moves when screwed down, no matter how small.
Cut the profile against a flush trim bit and mount the finished profile on a piece of mdf so it can go through the planner, as per the first two pic. Hot glue is good enough.
Send through the planner with a slim piece of mdf attached, as per third pic. I cut strips of 24mm mdf and the polished side was sent through the planner - so not a shown. I would suggest cutting strips from a single piece so you can be sure they are all the same length. Mount them on the form in the same position each time, so that you can be sure of accurate placement when you mount them together. Do this a few times, so you have three or four. Hot glue.
Mount three or four (depending of width) in parallel on the plank that you usually pass through the planner, as per fourth pic - this creates a crib for the first negative piece. Check your alignment and glue in place. It will look better than shown here, as these are random piece I had to hand, but don't worry if it doesn't look perfect, just make sure the glue does not get under the pieces you're mounting and it is perfectly aligned.
Put a mdf blank around the size of the planner crib on to this crib, 12mm was good enough for me and the marking shown should be on the underside when passed through the planner. I was marking points of reference which matched the core profile I wanted, so 3.5 mm @ 100 mm along, 3.71 mm @ 150 mm along and so on.
This gives you your first negative template, as per pic five. No need to make the blank too big at this stage. Check for initial accuracy of results before going further - micrometer at set points already marked. As long as the flush trim bit was mounted correctly you shouldn't have too many problems to resolve.
Remove the three or four strips and attach the negative template you have just created, pic six. I used 12 mm mdf for this. I didn't add tape at this point, but you can and next time I probably would. As you'll appreciate, its like photocopying a copy, you have to keep an eye on quality. This where the mold starts to really take shape. Unlike the photo's in my journal, you could apply tape to the right areas now will ensure you use less towards the end. You'd be adding tape at this point because the crib took too much off at a particular point and you want to put it back.
Once your closing in on the result you are looking for, attach a piece of mdf (the size you want the planner crib to be) to the negative template and pass through the planner. This creates the crib, the one you can see in my journal.
Modify with tape if necessary - blue is 0.15mm and brown is 0.07mm in my pic. The tape is nothing special, but now you are adding tape to remove areas of the core. It took eight attempts to get the results I wanted, but that's because I waited until the last minute before applying tape. All this sounds a lot, but I was adjusting by nominal amounts and taking reading to assure continuity of results and ultimately the whole process only uses around one sheet of mdf, so it's not that costly.
If you want your final crib to be without the tape, take a core from the above and attach it to the base and put a crib sized piece of mdf on top and send it though.
It total it took a day to do this the first time, but now I know how to do it, I'm thinking an afternoon. One more thing, the base in the photo's is not the base I used, it has the same final width as the planner with plastic runners either side. This ensures accuracy.
Anyone has any questions, just shout and I'll do my best to answer
You'll need to check your blade are clean and mounted correctly or you will get variable results. I replaced an old set recently and ran a quick test to check accuracy of mounting ; )
So I started by marking out the profile I wanted on a piece of mdf - 24mm x 35mm x 1800 mm, this length was enough for me. Make sure this piece is really straight - put it though the planner and it must be thick enough so that it supports itself when mounted on its side. A marking gauge (google) to mark out your profile is a must. Sorry, snowcad can't help with this. I think I marked about 15 points from tip to tip. I started at 3.51 mm, up to 11 mm and back to 3.71 mm. Remember to allow for snipe, hence the piece is longer than the core being shaped. Test mark the marking gauge in advance of actual mark and measure using a micrometer. A pencil won't be accurate enough even if it is 0.5mm lead.
Once the profile is marked, I attached uhmwpe strip to the piece of mdf and cut against a flush trim bit - the PE is attached as a guide. Use whatever plastic you have, as long as it is about 5 mm thick. I used screws, which means I drilled pilot holes, so correct any movement if the plastic moves when screwed down, no matter how small.
Cut the profile against a flush trim bit and mount the finished profile on a piece of mdf so it can go through the planner, as per the first two pic. Hot glue is good enough.
Send through the planner with a slim piece of mdf attached, as per third pic. I cut strips of 24mm mdf and the polished side was sent through the planner - so not a shown. I would suggest cutting strips from a single piece so you can be sure they are all the same length. Mount them on the form in the same position each time, so that you can be sure of accurate placement when you mount them together. Do this a few times, so you have three or four. Hot glue.
Mount three or four (depending of width) in parallel on the plank that you usually pass through the planner, as per fourth pic - this creates a crib for the first negative piece. Check your alignment and glue in place. It will look better than shown here, as these are random piece I had to hand, but don't worry if it doesn't look perfect, just make sure the glue does not get under the pieces you're mounting and it is perfectly aligned.
Put a mdf blank around the size of the planner crib on to this crib, 12mm was good enough for me and the marking shown should be on the underside when passed through the planner. I was marking points of reference which matched the core profile I wanted, so 3.5 mm @ 100 mm along, 3.71 mm @ 150 mm along and so on.
This gives you your first negative template, as per pic five. No need to make the blank too big at this stage. Check for initial accuracy of results before going further - micrometer at set points already marked. As long as the flush trim bit was mounted correctly you shouldn't have too many problems to resolve.
Remove the three or four strips and attach the negative template you have just created, pic six. I used 12 mm mdf for this. I didn't add tape at this point, but you can and next time I probably would. As you'll appreciate, its like photocopying a copy, you have to keep an eye on quality. This where the mold starts to really take shape. Unlike the photo's in my journal, you could apply tape to the right areas now will ensure you use less towards the end. You'd be adding tape at this point because the crib took too much off at a particular point and you want to put it back.
Once your closing in on the result you are looking for, attach a piece of mdf (the size you want the planner crib to be) to the negative template and pass through the planner. This creates the crib, the one you can see in my journal.
Modify with tape if necessary - blue is 0.15mm and brown is 0.07mm in my pic. The tape is nothing special, but now you are adding tape to remove areas of the core. It took eight attempts to get the results I wanted, but that's because I waited until the last minute before applying tape. All this sounds a lot, but I was adjusting by nominal amounts and taking reading to assure continuity of results and ultimately the whole process only uses around one sheet of mdf, so it's not that costly.
If you want your final crib to be without the tape, take a core from the above and attach it to the base and put a crib sized piece of mdf on top and send it though.
It total it took a day to do this the first time, but now I know how to do it, I'm thinking an afternoon. One more thing, the base in the photo's is not the base I used, it has the same final width as the planner with plastic runners either side. This ensures accuracy.
Anyone has any questions, just shout and I'll do my best to answer