【導(dǎo)讀】其類型目前主要有：。LY型電動機驅(qū)動,梯形螺紋傳動。許通過的汽車的最大寬度為mm2100。電器和行程開關(guān)來達到控制舉升臂不超過最低、最高舉升范圍的目的。潤滑方面，這次設(shè)計還采用了吸油器自動潤滑以提高其壽命。的是，本設(shè)計還設(shè)計了鏈條斷裂自鎖裝置，即通過JR-1型繼電器的使用，國產(chǎn)車輛和進口車輛的增加，人民生活水平的提高都使汽車的普及程。為了解決這個問題，人們設(shè)計出了舉升機，它的運用極大方便了汽。車的維護，尤其是在地盤維修時，更顯其優(yōu)越性。其中尤以液動居多，機械式次之，氣動最少,且每類里又可分為。二柱式和四柱式。具體言之，液動的特點是平穩(wěn)、噪音小、力量大，缺點。是用久之后易漏油，污染工作環(huán)境。而機械式的一般多為電機驅(qū)動，螺桿。傳動，它不存在漏油問題，且自鎖保護簡單易行。價格低廉的方向發(fā)展。從剪切應(yīng)力計算螺母允許的磨損最大量?????????（假設(shè)單邊舉升臂的重量為

　　

【正文】 time consuming you can remove a couple of cubic inches of metal per minute. (limited mostly by your ability to keep the friction of cutting from overheating, and possibly melting things. This is especially important for the cutting tool, which may be severely weakened if you get it too hot, never mind near to melting), A part that is sprawling like your right crank, can take 10 minutes or more to make, pared to the small number of seconds that it takes a press to cycle. (A large press can make several parts per squish, providing even higher productivity.) They are plicated machines, full of servomechanisims, and measuring technology that can measure to () while covered in oil. A CNC machine has a minimum of 6 motors (including some to change tools, and one or more to pump oil and coolant various places). This translates to running costs that may be well over $1/minute. (The puter is not a significant part of the cost any more.) Oh yeah, strength. Well, if you cut away metal, it doesn39。t have the tightly packed surface finish of a fing. Worse, there may be inside corners that 南昌航空工業(yè)學院 2021 屆學士畢業(yè)論文 40 have a sharp junction. These are stress risers, places that cracks can start (in any metal, but aluminum is particularly sensitive to it. Titanium is even worse.) Advantages of CNC machining You can39。t use an acute inside angle on a fing, you would never be able to get the part out of the mold. So all inside corners must be wider than 90 degrees, and have radiused edges (if you had a die (mold) that tried to form a sharp corner, it would cut rather than push the metal into place. CNC doesn39。t impose such restrictions, though to get nicely radiused corners, you might have to change tools, to make the last pass. (you use a flat tool to get rid of the bulk of the metal over the flat areas, and use a round nosed tool to form the inside radius where needed.) So eliminating stress risers means more expensive machining time. Why CNC? So why CNC at all? Well its good at making small numbers of picated shapes. In fact, they are just the thing to make the molds (called tools and dies) to do your fing in. (As a result, CNC technology has in fact lowered the tooling costs associated with fing!) It got its biggest boost from the missle folks. If you only plan to build 30 of something, CNC is just the thing for parts with a plicated shape, like that landing gear strut on that fighter. The peace dividend left a bunch of shops with excess CNC capacity. Since the cost of the machine just sitting idle can easily be over half what it costs 南昌航空工業(yè)學院 2021 屆學士畢業(yè)論文 41 running full out on a billable job, it was find something for it to do, or the bank may be calling the auctioneer. They cast around for things that would get some money in to make the lease payments. Boutique bike parts and other things, where rocket science adds enough marketing appeal to overe CNC39。s inefficencies, were something these shops latched onto. (for others, take a look at golf clubs or mototcycle and car hop up parts) A press, while big and heavy is a very simple low tech machine, that has very low maintence requirements. For the most part, they are too stupid to break. The most plicated part of a press are the sensors that make sure that the operator39。s body is out of the way before it starts moving. It39。s either a single motor connected to a pump, and a big hydraulic piston, or a drop fe, a big lump of metal, with a mechanisim that picks it up, and drops it. (CLANG!!!!!). No fancy measuring gear. No puter, unless they have a robot next to it to load and unload the finished parts. Why Fe? CNC is a good pliment to fing. There are a lot of shapes that fing can’t produce .internal thread ,for instance . If you know that you will be making 50,000 a year, and its always going to be 5 holes in a 110mm circle, you program the CNC to make a fixture that holds the 5 drill bits in that circle, and has them turn in unison. Add another bit in the middle geared down to cut the puller threads, and 7 to thread the pedal hole. Its faster than the puter (which will do one or at most two holes at a time, and will spend time moving the part to the place for the next hole.) and a 南昌航空工業(yè)學院 2021 屆學士畢業(yè)論文 42 whole lot cheaper to run. Neither takes any skill on the operators part, and there may indeed be a pick and place machine that specializes in stacking parts. It isn39。t perfect, it can only do that one job. Want to change bolt circles? You have to make a new machine. It might be worth it to make it changable so it can do 17039。s and 17539。s, it might be better to just make two different machines. 南昌航空工業(yè)學院 2021 屆學士畢業(yè)論文 43 NUMERICAL CONTROL APPLICATION As with other expanding technologies ,there is a tendency to consider numerical control as a final solution to a broad range of manufacturing problems。 however,NC applicationin in certain manufacturing situations would be highly undesirable. An NC machine is most efficient used in a environment that t akes advantage of the inherent flexibility of NC .The presice level of control attributed to a numerically controlled device enables it to perform plex oprations often beyond the capability of a human operator. For these reasons ,numerical control is best suited to relatively to low volume runs of plex and varied ponents. However,NC can also be used to produce large numbers of plex ponents and/or small numbers of simple ones. Specific