DIY... making a Digital Precision Length Cutter - Page 1
Forum section: electronics / general

author: robrenz
author_rank: Super Contributor
timestamp: April 17, 2013, 02:21:36 pm
content: I frequently need to cut relatively precise lengths of wire, heat shrink, kapton tubing, etc. I have had this idea in mind and even bought the multi cutter as a starting point quite a while back. I finaly took the time to make it and thought some forum members might find the design and build interesting so I did a video. From my YouTube statistics not many people are interested in all the gory details of me making something. So I tried to make this more of a quick (35mins?) overview covering only some of the more unusual manufacturing details.

author: Balaur
author_rank: Unknown
timestamp: April 17, 2013, 03:37:34 pm
content: Hey, I've seen it and I like your approach quite a lot.Also, I will shamelessly copy your idea about adding the clamp collar and the rod to the standard stripper as I prefer those to automatic strippers. Your suggestion is very welcome.Best regards,Dan

author: SeanB
author_rank: Super Contributor
timestamp: April 17, 2013, 06:42:44 pm
content: Enjoyed that one a lot. Especially liked the wire gripper you made.

author: codeboy2k
author_rank: Super Contributor
timestamp: April 17, 2013, 07:04:21 pm
content: I'd buy oneExcellent work!And I like the long, detailed videos tooBut this was a good length.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: April 17, 2013, 07:06:40 pm
content: Please put the price and I may also buy one.

author: Balaur
author_rank: Unknown
timestamp: April 17, 2013, 07:19:16 pm
content: I'd buy one ... if you drop the Mitutoyo caliper and put a cheap one

author: ecat
author_rank: Frequent Contributor
timestamp: April 17, 2013, 07:33:03 pm
content: Excellent work, excellent and informative video

author: robrenz
author_rank: Super Contributor
timestamp: April 17, 2013, 07:40:04 pm
content: Quote from: Balaur on April 17, 2013, 07:19:16 pmI could do that but you would have to reset the zero of the unit every time you turned it on. That is the beauty of the Mitutoyo absolute calipers, they don't loose the set origin as long as a battery is in them, even if you remove the head from the beam.I would also have to think about how to make the spring gripper much more economically or just leave it off. If there is enough interest I would consider making a run of them with Hazard Fraught calipers instead. But at best I wouldGUESSit to be somewhere in the $90.00 to $150 dollar range considering roughly $40 to $50 in materials.

author: JackOfVA
author_rank: Unknown
timestamp: April 17, 2013, 08:00:54 pm
content: Very nice work Robrenz.I've never had an application requiring cutting tubing or wire to +/- 0.001 inches (0.0254mm for those Imperially challenged), but it's not uncommon to need to cut to say 1/16th or 1/32nd inch. That suggests a cheaper version with a machinist's rule instead of digital calipers for length measurement.Your spring hold down clamp reminded me of a contour gauge - but obviously with greater thickness. Again in the interest of reducing cost, I wonder if a flat plate with a bit of friction material would work - such as silicon rubber. Down force supplied by a spring and lever arrangement.I have an application that requires cutting 0.1" (2.5mm) diameter Teflon tubing to a particular length and for that I made up a simple fixture consisting of a block of aluminum with a hole drilled through, partway threaded. A screw and locking nut provide an adjustable depth stop and I cut the tubing with a razor knife slid along the face of the block with the tubing pushed in place against the depth stop.

author: robrenz
author_rank: Super Contributor
timestamp: April 17, 2013, 09:03:28 pm
content: Thanks all for the kind comments.@ JackOfVA, thanks also.I can get cheap but functional 6" digital calipers for $10 to $15 so I would probably stick with them because they also provide a free lock screw for maintaining the setting. They don't have to be super accurate.The first thing that comes to mind for the spring gripper is 1/8 x .03" Graphite/carbon fiber strips used for hobby aircraft building. they would still generally keep groups together and they won't bend lateraly to any significant degree.

author: ftransform
author_rank: Frequent Contributor
timestamp: April 18, 2013, 01:50:39 am
content: Quote from: JackOfVA on April 17, 2013, 08:00:54 pmWhat did you need to cut wires for so precisely?And god damn you put alot of work into making that. I would have used a butchers knife and a clip board.How do you hold wire down taught if you want to cut it precisely? I found my thin wires have alot of flex in them. I am waiting for the feed rollers and hydraulic cutting arm.

author: JackOfVA
author_rank: Unknown
timestamp: April 18, 2013, 12:28:19 pm
content: Not wires, but Teflon tubing and, in a few cases, brass tubing.These parts have a mechanical as well as an electrical purpose and hence have to have dimensions within reasonable tolerances.Jack

author: robrenz
author_rank: Super Contributor
timestamp: April 18, 2013, 02:12:02 pm
content: @ ftransform, I though you were asking JackOfVA those questions, if not, here are my answers.Quote from: ftransform on April 18, 2013, 01:50:39 am

author: krivx
author_rank: Frequent Contributor
timestamp: April 18, 2013, 02:17:24 pm
content: For anyone questioning the use of Mitutoyo calipers - check ebay. I bought a set similar to the one in the video for about 15euros used with a case.

author: ftransform
author_rank: Frequent Contributor
timestamp: April 18, 2013, 02:45:49 pm
content: Can it handle magnet wire? I'd imagine the steel grippers to be rough on thin insulation. Or does the deburring leave the edges round enough?

author: robrenz
author_rank: Super Contributor
timestamp: April 18, 2013, 02:51:21 pm
content: Quote from: ftransform on April 18, 2013, 02:45:49 pmI would just fold over a small piece of postit note material and stick it down on the base under the grippers. Then the magnet wire insulation would just rub on paper surface top and bottom not on any metal directly.

author: Balaur
author_rank: Unknown
timestamp: April 18, 2013, 03:02:42 pm
content: Quote from: krivx on April 18, 2013, 02:17:24 pmLucky you.The cheapest Mitutoyo Absolute I'm seeing on my side is 109 euros + delivery at Buy It Now or at least 30-40 on unfinished auctions.

author: ftransform
author_rank: Frequent Contributor
timestamp: April 18, 2013, 03:34:17 pm
content: Quote from: robrenz on April 18, 2013, 02:51:21 pma post it note is not worthy of such a machine.I think a special swiss made insert is needed. I would accept your solution if we lived in mad max.I think it should have some kind of thin molded rubber that can be fixed to the springs. Or is that too tacky.. hmm....

author: nicknails
author_rank: Regular Contributor
timestamp: April 18, 2013, 04:21:29 pm
content: Very nice build! I don't have a use for something like that, but if I did, I would definitely buy that.

author: robrenz
author_rank: Super Contributor
timestamp: April 18, 2013, 06:30:33 pm
content: Custom imported Swiss manufactured Post It note paper in the ever popular magenta.40 AWG enameled magnet wire on the left 45 AWG on the right. Tension is very nice and smooth through the paper. I tried cutting the 45 AWG on the regular multi cutter with the plastic blade anvil and it does cut it but not until after forming the wire down into the groove in the plastic and leaving a nice hockey stick shape to the end of the wire. So in this case the aluminum as a blade anvil appears to be superior.CuttingAs cut

author: ftransform
author_rank: Frequent Contributor
timestamp: April 21, 2013, 07:04:20 am
content: How many hours did that take you to fully assemble?

author: robrenz
author_rank: Super Contributor
timestamp: April 22, 2013, 02:23:59 am
content: These are guestimations, I didn't keep actual time.Caliper mod 1.5 hr.Multi cutter accurizing 2 hr.Aluminum plate, steel "T" pieces, three legs, and assembly 4 hr.Spring gripper unit comlete 12 hrs.If I was going to produce some I would start with a clean sheet design for produceability. This design version just evolved from wanting to mod an existing cutter and is not ideal.

author: BravoV
author_rank: Super Contributor
timestamp: April 22, 2013, 02:31:10 am
content: You should be banned from making this kind of posting, unless you sell it.... j/kSee .. I've ruined my keyboard again because of an extreme drooling, its all your fault.

author: robrenz
author_rank: Super Contributor
timestamp: April 22, 2013, 02:49:02 am
content: Just for the fun of it I will design the "production version" and come up with a price. I will post the design and features. If I get 10 or more to commit I would do a run of them.This is not why I did the original postbut several implied they would buy one if available so why not?